Estrogenic diazenes: Heterocyclic non-steroidal estrogens of unusual structure with selectivity for estrogen receptor subtypes

Bioorganic & Medicinal Chemistry 11 (2003) 629–657

Estrogenic Diazenes: Heterocyclic Non-steroidal Estrogens of

Unusual Structure with Selectivity for Estrogen Receptor Subtypes

Usha Ghosh,^aDeshanie Ganessunker,^bViswajanani J. Sattigeri,^aKathryn E. Carlson,^a

a,

Deborah J. Mortensen,^aBenita S. Katzenellenbogen^bandJohn A. Katzenellenbogen *

^aDepartment of Chemistry, University of Illinois, Urbana, IL 61801, USA

^bDepartment of Molecular andIntegrative Physiology, University of Illinois, Urbana, IL 61801, USA

Received5 February 2002; accepted23 May 2002

Abstract—Estrogens regulate many biological functions, often acting in a tissue-selective manner. Their tissue-selective action is

believedto involve diﬀerential estrogen action through the two estrogen receptor (ER) subtypes, ER a andER b, as well as diﬀer-

ential interaction of the ligand–receptor complexes with promoters and coregulator proteins. In the latter case, selectivity is based

on the induction of speciﬁc conformations of the ligand–ER complex, conformations that are inﬂuenced by the structure of the

ligand. Estrogen pharmaceuticals having an ideal balance of tissue-selective activity are being sought for menopausal hormone

replacement, breast cancer prevention andtherapy, andother actions. To expandon the structural diversity of ER ligands that

might show such tissue selectivity, we have prepared a series of diazenes (pyrazines, pyrimidines, and pyridazines) substituted with

two to four aryl groups andvarious short-chain aliphatic substituents. All of the pyrazine andpyrimidines bindto ER, some with

high aﬃnity and with a considerable degree of preferential binding to either ERa or ERb. One pyrimidine and one pyrazine have

ERa aﬃnity preferences as high as 23 and9, respectively, andone pyrimidine has an ER b aﬃnity preference of 8. The pyridazines,

by contrast, are quite polar andhave only very low binding aﬃnity for the ER. In cell-basedtranscription assays, several of the

pyrimidines and a pyrazine were found to be considerably more agonistic on ERa than on ERb. Because these triaryl diazenes have

the largest volumes among the ER ligands so far investigated, their high aﬃnity demonstrates the ﬂexibility of the ligand binding

pocket of the ERs andits tolerance for large substituents. Thus, these novel heterocyclic ligands expandthe repertoire of chemical

structures that bindto the estrogen receptor, andthey couldprove to be useful in elucidating the biological behavior of the two ER

subtypes andin forming the basis for new estrogen pharmaceuticals having desirable tissue selectivity.

Introduction

that act positively in those tissues where estrogenic sti-

mulation is needed, but that are inactive or block

estrogen action in those tissues where stimulation poses

a risk. Such agents are being developed, and they have

been termed, appropriately, selective estrogen receptor

modulators, or SERMs.^1ꢀ3

The estrogen receptor (ER) is a ligand-regulated trans-

cription factor that mediates the action of estrogens in

many tissues. Estrogen action is requiredfor the devel-

opment andfunction of the female reproductive system,

andit plays supportive roles in cardiovascular health, in

cognitive andneuronal function, andin maintaining

bone mineral density. On the other hand, estrogenic

stimulation is a risk factor for the development and

growth of some breast cancers, andestrogen antagonists

are usedfor the prevention andtreatment of breast

cancer. Therefore, to obtain estrogen pharmaceuticals

that will provide optimal health beneﬁt for each inten-

ded medical use, it would be best to have compounds

The mechanistic basis for the tissue-selective action of

SERMs is not well understood. Part of the selectivity

might arise from diﬀerent activity that these compounds

have on the two estrogen receptors, ERa andER b;⁴

these receptor subtypes have diﬀerent tissue distribu-

tions andtranscriptional activity. ^5ꢀ7Another important

element of this selectivity is thought to arise from dif-

ferential interaction that various ligand–receptor com-

plexes have with promoter sites andwith coregulator

proteins, important mediators of transcriptional activ-

ity. Because a large variety of structurally diverse ster-

oidal and non-steroidal compounds can bind to the

*Corresponding author. Tel.: +1-217-333-6310; fax: +1-217-333-

7325; e-mail: jkatzene@uiuc.edu

PII: S0968-0896(02)00309-7

630

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

estrogen receptor, and in doing so stabilize diﬀerent

conformations of the ligand–receptor complex,^8,9it is

thought that this spectrum of ligand–receptor con-

formations is also responsible for the tissue-selective

pharmacology of estrogens.¹⁰

diazoles, namely diazenes, might also function as sui-

table core elements for ER liganddevelopment. As illu-

stratedin Figure 1, the three classes of diazenes, namely,

pyrazines, pyrimidines, and pyridazines, are all con-

ceptually relatedto the idazoles through the formal

insertion of a ring carbon at either a C–N or an N–N

bond, to go from a ﬁve-membered to a six-membered

heterocycle. In this fashion, pyrazines are analogues of

imidazoles, pyridazines are analogues of pyrazoles, and

pyrimidines are analogues of both of the diazoles.

Because of this intriguing link between ligandstructure

andthe selective pharmacology of estrogens, a great

eﬀort is being made to discover structurally novel com-

pounds that bind to ER in a manner that induces unu-

sual ligand–receptor conformations that might have

11

optimizedpharmacological proﬁles. A number of het-

The diazene core is a common feature of natural pro-

ducts and drugs. Pyridazine fungal metabolites are

known,²²andpyrazines are responsible for the ﬂavor of

many foods and are found in insect pheromones and, in

dihydro form, in luciferins.^23ꢀ25Pyrimidines, the most

widely represented class, are found in nucleic acids and

vitamin B₁, andthey form the basis of many drugs

(antimalarial, antibiotics, herbicides, anti-virals, anti-

hypertensives, etc.).²⁵

erocyclic systems have been investigatedas ‘core ele-

ments’ in the development of novel estrogens, especially

ones whose preparation might be expanded through

combinatorial synthetic methods.^12ꢀ20

15

We have investigatedameid

andheterocyclic

motifs^{12ꢀ14,16,17,19,20}that can be usedas core elements in

the development of novel estrogens. One of the more

promising core systems was the ﬁve-memberednitrogen

heterocycle, pyrazole, a member of the family of diazole

heterocycles (Fig. 1).^{11ꢀ14,16,17}Although most di- and

trisubstitutedpyrazoles were feeble ER ligansd, we

foundthat tetrasubstitutedpyrazoles have high aﬃnity

for ER, with some analogues having very high selectiv-

ity for ERa in terms of binding aﬃnity and potency as

agonists.^{11ꢀ14,16,17}Other relatively non-polar, tetra-

substitutedﬁve-memberedheterocycles or carbocycles

also provedto be goodligands (e.g., furans, thiophenes,

cyclopentadienes), some having very high selectivity for

ERa.^19ꢀ21However, certain other azole heterocycles

that were inherently more polar (e.g., imidazoles) or

aﬀorded sites for only three substituents (e.g., oxazoles,

thiazoles, isoxazoles, etc.) were less eﬀective ligands.¹²

Thus, it appearedthat the heterocyclic core performed

not just the role of an inert scaﬀoldto which the

requiredphenol andalkyl substituents couldbe

attached, but also played an integral role in the overall

binding of the complete ligand to the ER. The geometry

of the heterocycle seemedto be most important in the

scaﬀolding role, and the polarity, most important in the

integral role.

In this report, we describe the synthesis of a series of

diazenes bearing aromatic and aliphatic substituents at

sites that are patternedafter the structures of the high

aﬃnity pyrazoles. We have assayedthe binding aﬃnity

of these compounds for ERa andER b andevaluated

the transcriptional activity of some of the higher aﬃnity

analogues in a cell-basedassay. Thus, in this investiga-

tion, we have addressed several issues in the develop-

ment of ER ligands of the heterocycle core design: (a)

The role playedby the core element—geometric versus

integral, (b) the tolerance of ER to ligands of increasing

overall size, and(c) the structural basis for ER a versus

ERb selectivity. In the process, we have founddiazenes

that have high binding aﬃnity for the ERs, and in some

cases show preferential aﬃnity for ERa or for ERb, and

exhibit diﬀerent levels of agonistic activity on the two

ER subtypes.

Results

Synthesis

In considering a further expansion of this theme of

estrogens with novel heterocyclic core systems, we won-

deredwhether the six-memberedring analogues of the

In selecting substituents to place on the diazene core

motif, we were inﬂuencedby our prior work in the azole

12ꢀ14,16,17,19,20

andfuran series.

Thus, we have typically

introduced 2–3 aromatic groups (i.e., 4-hydroxylphenyl

or, in a few cases, phenyl), andwe have ﬁlledthe

remaining positions with short aliphatic substituents,

because these types of substituents gave the highest

aﬃnity compounds in the pyrazole and furan series.

Pyridazines. The pyridazines were readily synthesized by

the reaction of hydrazine with 1,4-diones (1a–d, Scheme

1). The intermediate dihydropyridazines underwent

spontaneous oxidation to the aromatic heterocycles (2a–

d) upon exposure to air, andthe methyl ether protecting

groups were readily removed. All of the 1,4-diones (1a–d)

that we usedto prepare the pyridazines 3a–d were syn-

thesizedby us earlier as precursors for estrogenic furans,

by a route involving the cross-coupling of the enolate of a

1,2-diarylethanone with an a-bromoketone.^19,20

Figure 1. Diazole (above) anddiazene (below) heterocyclic cores for

estrogen receptor ligands. The diazoles are known core motifs for ER

ligands,^{11ꢀ14,16ꢀ17}andthe diazenes are proposedcore motifs. The

substituents R₁–R₄are either aromatic (phenyl or 4-hydroxyphenyl) or

aliphatic (Me, Et, Pr, Bu, etc.).

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

631

chlorotrimethylsilane), followedby bromination of the

enediol disilyl ether product.^27,28If they were unsym-

metrical (5a–b), they were preparedby oxidation of an

a-hydroxy-ketone²⁹or selenium dioxide oxidation³⁰of

an appropriate ketone precursor. The 1,2-diamine (4)

usedwas symmetrical andcommercially available.

The pyrazines that hadiedntical substituents at the

C(2)/C(5) andC(3)/C(6) position ( 12a–e) were readily

preparedin high yieldby dimerization of an appropriate

a-aminoketone, whose synthesis via the corresponding

a-bromo (9a–e) and a-azidoketones (10a–e) is shown in

Scheme 3.³¹Again, oxidation of the dihydropyrazine

was spontaneous, andether deprotection gave the free

phenols (12a–e) in goodyields.

Pyrimidines. The most favorable route to the pyri-

midines depended on the pattern of substituents. Those

that bore the same groups at the C(2) andC(6) positions

were readily prepared by a triple condensation, invol-

32

ving a ketone andtwo equivalents of a nitrile,

as

shown in Schemes 4 and5 . Those with other patterns of

substituents were preparedfrom 1,3-diones by the route

shown in Scheme 6.

Scheme 1.

Pyrazines. The pyrazines were preparedby two routes,

depending on the pattern of aryl and alkyl substituents.

Those that bore the same substituents on the C(2) and

C(3) positions couldbe preparedas single regioisomers

in reasonable yields by the reaction of a 1,2-dione (5a–e)

with a 1,2-diamine (4), either one of which couldbe

symmetrical, followedby spontaneous oxidation of the

intermediate dihydropyrazine.²⁶Removal of the methyl

ether protecting groups gave the free phenols (7a–e,

Scheme 2).

The triple condensation approach was well suited for

the synthesis of 2,4,6-triaryl-pyrimidines (and certain

2,4-diaryl-pyrimidines, that is, those that utilized methyl

ketone precursors).³²With the alkylphenones (13a–d),

this cyclization proceeded regioselectively and in good

yield( Scheme 4), because these ketones can enolize only

in one direction. However, with the methyl alkyl

ketones (13e–f), which can form two diﬀerent enols, the

cyclization yields were considerably lower. Byproducts

If symmetrical, the 1,2-diones (5c–e), which are all

known compounds, were prepared by acyloin con-

densation from an ester precursor (in the presence of

Scheme 2.

Scheme 3.

632

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

Scheme 4.

Scheme 6.

show little preference for enolization in the two diﬀerent

directions. As a result, the cyclizations shown in Scheme

5 in most cases give 1:1 mixtures of isomeric pyrimidine

products. With the alkyl benzyl ketones (17a–b), yields

were good, and the free phenols of the triaryl-pyri-

midines (20a–b and 21a–b) were readily separable.

However, when the benzyl substitutent has a p-methoxy

substituent (17c), the vinyl triﬂate intermediate is less

reactive. When the cyclization reaction is conducted at

room temperature, only the undesired isomer (19c) was

obtained, and in low yields, suggesting that the styryl

enol triﬂate is unreactive. At reﬂux, both isomeric pyri-

midines 18c and 19c were produced, but they were

inseparable either as methyl ethers or free phenols and

thus were not studied further. With the dialkyl ketones

(17d–e), cyclization yields were lower, and both pyri-

midine isomers were produced. We were unable to

separate these diaryl-pyrimidines as methyl ethers (20d–

e) or free phenols (21d–e), but the phenols were tested

as isomeric mixtures.

Scheme 5.

Our ﬁnal approach to the pyrimidines involved the

condensation of a 2-aryl-1,3-dione (24a–g) with an aro-

matic aldehyde (25, Scheme 6). This is a well pre-

cedented reaction, and it is well suited for the synthesis

of both 2,5-diaryl and 2,4,5-triaryl pyridimines. How-

ever, the yields in the key condensation reaction are

were observed, but they were unstable and were not

isolated. All of the free phenols (16a–f) were readily

obtainedafter ether deprotection.

34

reportedto be low, andthey provedto be low in our

It provedto be a greater challenge to prepare the iso-

meric 2,5,6-triaryl-pyrimidines (and certain other

2,6-diaryl-pyrimidines) by this trimerization route

(Scheme 5), because the dialkyl ketone precursors³³

hands, as well. Nevertheless, the overall route proceeded

well, andgave products ( 27a–g), free from the isomeric

contaminants that plaguedthe alternative approach

(Scheme 5).

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

633

Binding aﬃnity

Pyrimidines (Table 1). The largest number of diazenes

we preparedwere in the pyrimiidne class. Here, we

foundthat aﬃnity for ER andselectivity for ER a versus

ERb depends in a detailed fashion on the number and

nature of substituents, andcompounds with goodbind-

ing preferences for both ERa andER b were found.

The relative binding aﬃnity of the diazenes for estro-

gen receptors was determined by a competitive radio-

metric receptor binding assay, using puriﬁed, full-

length human ERa andER b.^35,36The results of these

assays are given as relative binding aﬃnity (RBA)

values, where the aﬃnity of estradiol is considered to

be 100.

Nearly all of the pyrimidines of the triaryl group (class

I) have quite goodbinding aﬃnities for estrogen recep-

tor alpha (ERa); these include two that have high ERa

aﬃnity selectivity (entry numbers 3 and4), which peaks

at an ERa/ERb aﬃnity ratio of 23 for compound 16d

(entry number 4). It is notable that in the I-A subclass,

the higher ERa/ERb aﬃnity ratios are foundwith those

pyrimidines that have a propyl rather than an ethyl

substituent (i.e., entries 2 vs 1, or 4 vs 3) or are triphenols

rather than diphenols (i.e., 3 vs 1, or 4 vs 2). This is the

same substitution pattern that was foundto give the

highest ERa binding selectivity in both the pyrazole and

the furan series.^14,18Trends of this nature are not evi-

dent in the I-B subclass, however.

The estrogen receptor binding aﬃnities of the pyri-

midines and pyrazines are summarized in Tables 1 and

2, respectively. To assist in the analysis of the binding

data, we have classiﬁed the pyrimidines and pyrazines

according to aryl-substitution isomer class, denoted by

combinations of a Roman numeral (denoting the type

of heterocycle andnumber of aryl substituents) anda

letter (denoting the pattern of aryl substituents on the

heterocycle), as illustratedin Figure 2. Table entry

numbers are also provided for convenience.

From Fig. 2, it is apparent that we have preparedall of

the possible isomers of diarylpyrimidines (classes II-A

and II-B) andtriaryl pyrimidines (classes I-A and I-B)

that contain an N(2)-aryl group. (There are two other

diarylpyrimidine classes and one triarylpyrimidine class

that do not have an N(2)-aryl group, but we have not

exploredthese synthetically, because they require dif-

ferent synthetic methodology than we have used.) We

have preparedthe only isomeric class of triarylpyrazines

(class III) andtwo of the three possible subclasses of

diarylpyrazines (classes IV-A and IV-B).

Those pyrimidines of the diaryl classes (class II) show a

wider range of aﬃnities. In general, those from the more

symmetrical 2,5-diaryl subclass (II-B; entry numbers

16–20) have higher aﬃnity than those from the less

symmetrical 2,4-diaryl subclass (II-A; entry numbers

9–12). We have included in the II-A subclass as an

alternate subclass (II-A¹), pyrimidines that have a C(6)

benzyl rather than alkyl substituents (21a–c, entry

numbers 13–15). Two of these (21a–b, entry numbers 13

and14) are isomers of the triaryl compounds 20a–b

Table 1. Relative binding aﬃnities (RBA) of pyrimidines for estrogen receptors^a

Entry

CompdClass

X(4)

p-HO-C₆H₄

Y(5)

Z(6)

ER

a^b

0.99

3.2

4.9

4.6

4.5

4.9

5.3

ERb^b

a/b^c

b/a^c

1

2

3

4

5

6

7

8

16a

16b

16c

16d

20a

20b

27a

27b

16e

I-A

I-B

II-A

II-A⁰

II-B

C₂H₅

n-C₃H₇

C₂H₅

n-C₃H₇

C₆H₅

0.77

0.56

0.30

0.20

1.9

2.8

1.3

1.1

0.08

0.27

0.75

1.0

0.42

0.56

0.03

1.1

1.3

5.7

16.3

23

2.4

1.8

4.1

2.7

—

2.9

1.8

—

p-HO-C₆H₄

C₂H₅

p-HO–C₆H₄

C₂H₅

n-C₃H₇

C₂H₅

n-C₃H₇

CH₃

p-HO–C₆H₄

C₂H₅

4.5

9

0.21

0.19

0.57

0.54

0.16

1.6

0.06

0.50

0.04

0.93

5.1

—

10

11

12

13

14

15

16

17

18

19

20

16f

n-C₃H₇

1.4

1.3

1.9

2.6

—

20/21d

20/21e

21a

21b

21c

27c

27d

27e

C₂H₅+CH₃

CH₃

Et+n-Pr

n-Pr+n-Bu

C₆H₅–CH₂

p-OH–C₆H₄–CH₂

CH₃

C₂H₅

CH₃

—

p-HO–C₆H₄

2.2

7.5

2.7

2.1

1.0

CH₃

n-C₃H₇

C₂H₅

n-C₃H₇

CH₃

C₂H₅

0.30

2.5

11

27f

27g

—

8.1

8.2

^aRelative binding aﬃnity (RBA) values are determined by competitive radiometric binding assays (see Experimental). RBA(estradiol)=100. Under

these conditions, the K_dfor estradiol is ca. 0.3 nM on ERa and0.9 nM on ER b. Values represent the average of 2–4 determinations (CV<0.25).

^bFull length human ER expressedin baculovirus andpuriﬁed(Pan Vera Corp, Madison, WI, USA).

^cSelectivity of binding to ER subtypes. Ratios of RBA values, as indicated.

634

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

Table 2. Relative binding aﬃnity of pyrazines for estrogen receptors^a

Entry

CompdClass

X(3)

Y(5)

Z(6)

ER

a^b

1.4

ERb^b

a/b^c

b/a^c

1

2

3

4

5

6

7

8

9

10

7a

7b

7c

7d

III

—

IV-A

IV-B

p-HO-C₆H₄

C₂H₅

n-C₃H₇

p-HO–C₆H₄

C₂H₅

0.25

0.55

0.01

0.42

1.9

1.5

3.2

1.4

2.4

5.4

5.3

2.0

—

2.6

1.6

—

3.0

2.9

d

p-HO-C₆H₄

C₂H₅

n-C₃H₇

p-HO–C₆H₄

0.02

0.16

1.2

7e

n-C₃H₇

C₂H₅

n-C₃H₇

n-C₄H₉

i-C₄H₉

CH₃

—

12a

12b

12c

12d

12e

2.5

1.6

9.4

1.0

4.3

—

n-C₃H₇

n-C₄H₉

i-C₃H₇

CH₃

30

1.4

10

0.02

0.06

^aRelative binding aﬃnity (RBA) values are determined by competitive radiometric binding assays (see Experimental). RBA (estradiol)=100; under

these conditions, the K_dfor estradiol is ca. 0.3 nM on ERa and0.9 nM on ER b. Values represent the average of 2–4 determinations (CV<0.25).

^bFull length human ER expressedin baculovirus andpuriﬁed(PanVera Corp, Madison, WI, USA).

^cSelectivity of binding to ER subtypes. Ratios of RBA values, as indicated.

^dTetraarylpyrazine.

route (cf., Scheme 5). Because it provedvery diﬃcult to

separate these isomers, we testedthem as a mixture;

their aﬃnities were not suﬃciently high to warrant fur-

ther eﬀorts at isomer separation.

The ﬁve representatives of the 2,5-diarylpyrimidine

subclass (II-B) span a large aﬃnity range. There is a

general trendfor increasedaﬃnity as the number of

carbon atoms in the two alkyl substituents increase (i.e.,

in the entry number series, 17, 16, 18, 19, 20). However,

ERb aﬃnity appears to peak (entry 19) before ERa

aﬃnity (entry 20). The dimethyl analogue (27d; entry

number 17) was the ligandwith the greatest preferential

aﬃnity for ERb (ERb/ERa=7.5). It is interesting that

the highest ERb/ERa aﬃnity preference is not necessa-

rily associatedwith the highest ER b binding aﬃnity.

Pyrazines (Table 2). The aﬃnity of the pyrazines varied

considerably with the nature and orientation of the

substituents. The two triaryl members (class III; com-

pounds 7a and 7b; entry numbers 1 and2) have sig-

niﬁcant aﬃnities, with goodER a subtype aﬃnity

preference. The one tetraaryl analogue (compound 7c;

entry number 3) has remarkably low aﬃnity for both

receptors. Aside from the pyridazines (see section

below), it was the lowest aﬃnity diazine we have inves-

tigated, a result which suggests that there is a size limit

in the ER ligandbinding pocket.

Figure 2. Display of various diaryl- andtriaryl-substitutedpyrimidine

andpyrazine isomers anddesignation of structural classes andsubclasses.

As was the case with the pyrimidines (see above), the

aﬃnities of the diarylpyrazines (class IV) span a large

range andvary in a detailedmanner with changes in the

(subclass I-B; entry numbers 5 and6), andthey are

produced as byproducts during their synthesis (cf.,

Scheme 5). These two diaryl benzyl pyrimidines have

lower aﬃnity than their corresponding isomeric triaryl

isomers. It is also of note that the compounds (20d/21d

and 20e/21e, entry numbers 11 and12) were a mixture

of two structural isomers, in a roughly 1:1 ratio,

obtainedas a result of a non-regioselective synthetic

alkyl substituents. Overall, the aﬃnities of those in the

2,3-diaryl class (subclass IV-A) were rather low and

somewhat ERb selective in comparison with those in the

2,5-diaryl subclass (IV-B), whose aﬃnities are, in gen-

eral, higher anddependin an interesting way on the size

of the two alkyl substituents: Both ERa andER b aﬃ-

nity increase in the progression methyl to ethyl to pro-

pyl (entries 10, 6, and7), where they peak, andthen

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

635

decline to isobutyl and n-butyl (entries 9 and8). In fact,

the analogues with two additional propyl or iso-propyl

substituents (12b and 12d; entry numbers 7 and9,

respectively) hadthe highest aﬃnity of all of the dia-

zenes we investigated, and the analogue with two propyl

substituents (12b; entry 7) was the thirdmost selective

for ERa (ERa/ERb=9.4; for the two most ERa selec-

tive diazenes, see 16c and 16d; Table 1, entries 3 and4).

It is of note that the high aﬃnity diarylpyrazines of

subclass IV-B are isomeric with the diarylpyrimidines of

subclass II-B, yet the pyrimidines are generally ERb

selective, whereas the corresponding pyrazines are ERa

selective.

most striking with the triaryl pyrimidines of subclasses

I-A and I-B, and the diaryl pyrimidines of subclass II-A.

All of these pyrimidines have minimal eﬃcacy on ERb

andare weak on this subtype, as well (according to our

deﬁnition above). The eﬃcacy of these compounds on

ERa diﬀers, but aside from compounds 16b and 16d

(entries 1 and2), eﬃcacies are ꢁ50%. From this set,

compound 27b (entry 5), which appears to be quite

potent on ERa, was selectedfor further stuyd (see

below and Fig. 3). Its pharmacological character is

reminiscent of that of the structurally relatedpro-

pylpyrazole triol (PPT) that we have studied earlier.¹⁴

The pyrimidines of subclass II-B, which are 2,5-diaryl-

4,6-dialkyl isomers, are quite diﬀerent from the other

pyrimidine classes. They are potent on ERa andall but

compound 27d (entry 10) are highly eﬃcacious on this

ER subtype; all four of those testedare also more eﬃ-

cacious on ERb than were those of the other three clas-

ses, although the level of eﬃcacy varies from 25 to 50%.

These diﬀerences could arise from the generally greater

ERb aﬃnity that is characteristic of this class (cf., Table

1), although this is not true in every case. [Note com-

pound 27d, which has low ERb aﬃnity (Table 1, entry

17), yet has goodpotency on ER b (Table 3, entry 10)].

From this subclass, two were selectedfor further study,

compounds 27c and 27g (entries 9 and12); both are

potent on both ERs andhighly eﬃcacious on ER a, but

the ﬁrst is somewhat more agonistic on ERb than is the

second(see below and Figs 4 and5 ).

Pyridazines. The four pyridazines we investigated (3a–d)

all had exceedingly low ER binding aﬃnity, with RBA

values below the detection limit of our assay (i.e.,

<0.0008, data not shown). These diazines are by far the

most polar of the three classes of diazenes we studied.

The low aﬃnity of these polar isomers is consistent with

the behavior in the diazole series, where we found that

the more polar imidazoles had ER binding aﬃnities that

were 50–100-foldless than that of their less polar pyra-

zole isomers (see Discussion).¹²

Transcriptional activity

Basedon their ER binding aﬃnity and/or ER a versus

ERb binding selectivity, we selected a set of 19 diazine

ligands from several of the structural series to be

assayedfor their transcriptional activity through both

ER subtypes. (Because of their low aﬃnity, no pyri-

dazines were selected for this assay.) These cotransfec-

tion assays are conducted in human endometrial

carcinoma (HEC-1) cells, using expression plasmids for

human ERa or ERb andan estrogen-responsive luci-

ferase reporter gene system containing estrogen

response elements.³⁷The transcriptional activity of

these 19 compounds was initially screened with ERa

andER b at two concentrations in the agonist mode

(i.e., 10^ꢀ8and10 ^ꢀ6M of compoundalone) andat one

concentration in the antagonist mode (i.e., 10^ꢀ6M

compoundtogether with 10 ^ꢀ9M estradiol). The results

of these screening assays are summarizedin Tables 3

and4 as percent eﬃcacy relative to 10^ꢀ9M estradiol.

Pyrazines (Table 4). Seven pyrazines were assayedfor

their transcriptional activity. Those of the triaryl class

III andthe 2,3-diaryl subclass IV-A (Table 4, entries 1, 2

and4) were very weak on both ER a andER b. Those of

class 2,5-diaryl subclass IV-B (Table 4, entries 5–7),

however, were for the most part potent partial agonists

on ERa andrather potent complete or nearly complete

antagonists on ERb. It is interesting that in both the

pyrimidine and the pyrazine series, it is the 2,5-diaryl

motif that engenders high potency on ERb. From the

four compounds in subclass IV-B, we selectedcom-

pound 12b (entry 6) for further study, because this

compoundappearedto be a high potency agonist on

ERa anda high potency antagonist on ER b. In this

sense, it is reminiscent of the R,R-diethyl-tetra-

hydrochrysene compound (R,R-THC) that we have

studied earlier.^35,37

Basedon the level of eﬃcacy achievedin the agonist and

antagonist modes, the compounds were classiﬁed as

‘agonists’ (full to nearly full eﬃcacy; >80%), ‘partial

agonists’ (50–85% eﬃcacy), ‘partial antagonists’

(10–50% eﬃcacy) or ‘antagonists’ (very little eﬃcacy;

<10%). In addition, compounds that showed similar

eﬃcacy in the agonist mode at 10^ꢀ8and10 ^ꢀ6M were

considered to be ‘potent’, whereas those that failed to

reach a similar level of eﬃcacy at 10^ꢀ6M in both ago-

nist andantagonist moeds were classifedas ‘weak’.

From this initial screen, as is notedbelow, four com-

pounds were selected for full dose response assays (see

below).

Full dose–response curves for agonist and antagonist

activity with ERa andER b were run with the four

compounds, pyrimidines 27b, 27c, and 27g, andpyra-

zine 12b. As statedabove, these compounds were selec-

tedfor further study basedon a combination of their

high potency as agonists on ERa anddiﬀerences in ER a

versus ERb potency or eﬃcacy. The results of these

assays are given in Figures 3–6.

The triarylpyrimidine 27b (Fig. 3) is, as expected, weak

andvery low eﬃcacy on ER b, as was the case with the

propylpyrazole triol compound, PPT.¹⁴In the full dose

response on ERa, the level of eﬃcacy of pyrimidine 27b

is moderate, but its potency (measured as the ratio of

Pyrimidines (Table 3). In general, the 12 pyrimidines

studied in these transcription assays were more potent

andmore eﬃcacious on ER a than on ERb. This was

636

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

a

Table 3. Transcriptional eﬃcacy andpotency of pyrimidines

Entry CompdClass ^bX(4) Y(5)

Z(6)

% Eﬃcacy on ERa^c

Agonist (M)^dAntg (M)^d10^ꢀ6Pharm. char.^e

10^ꢀ810^ꢀ6

% Eﬃcacy on ERb^c

Agonist (M)^dAntg (M)^d10^ꢀ6

10^ꢀ810^ꢀ6

Pharm. char.^e

1

2

3

4

5

6

7

8

16b

16d

20b

27a

27b

16f

I-A Ar^f

I-A Ar

I-B Ar

II-A Ar

Pr

Ph

Ar

Pr

Ph

Ar

Pr

Et

Pr

12

28

26

5

33

10

50

57

52

65

75

28

87

33

72

82

65

33

70

78

60

85

80

52

92

37

80

87

Weak part. agonist

Part. antagonist

Part. agonist

Agonist

Part. agonist

Agonist

Part. agonist

Potent agonist

Part. antagonist

Potent agonist

5

3

2

3

2

30

20

30

16

17

2

3

4

3

42

48

43

25

68

58

52

67

57

55

33

85

45

60

70

30

Weak part. agonist

Weak part. antagonist

Very weak

Potent part. agonist

Part. agonist

Weak part. agonist

Potent part. antagonist

CH₃

20/21d II-A Ar Et+Me Et+Pr 17

21b II-A⁰Ar

27c

27d

27e

27g

Et

Ar

Bn

CH₃

Et

4

78

25

75

80

9

II-B Et

II-B CH₃Ar

II-B Pr

10

11

12

Ar

^aTranscriptional eﬃcacy determined in cotransfection assay in HEC-1 cells using ERa andER b expression plasmids and an estrogen regulated

reporter gene plasmid (see Experimental for details). Values are percent of the transcriptional response of estradiol at 10^ꢀ9M.

^bFor a description of compound class, see Figure 2.

^cValues are percent of the transcriptional response of estradiol at 10^ꢀ9M, andthey represent the average of triplicate determinations (CV <0.15).

^dAgonist assays are done with compound alone; antagonist assays are done with compound together with 10^ꢀ9M estradiol.

^eFor a deﬁnition of these terms, see text.

^fAr=p-HO–C₆H₄–.

a

Table 4. Transcriptional eﬃcacy andpotency of pyrimidines

b

Entry CompdClass X(3) Y(5) Z(6)

% Eﬃcacy on ERa^c

% Eﬃcacy on ERb^c

Agonist (M)^dAntg (M)^d10^ꢀ6

10^ꢀ810^ꢀ6

Pharm. char.^e

Agonist (M)^dAntg (M)^d10^ꢀ6

10^ꢀ810^ꢀ6

Pharm. char.^e

1

2

3

4

5

6

7

7a

7b

7c

7e

12a

12b

12c

III

—

Ar^gEt Ar

Ar Pr Ar

Ar Ar Ar

4

11

2

28

25

12

4

80

72

51

78

82

55

62

70

68

Weak part. agonist

Weak

Weak part. antgonist

Potent part. agonist

2

1

2

11

4

3

2

1

2

22

5

100

60

52

10

25

7

Very weak

Weak part. antagonist

Antagonist

f

IV-A Ar Pr Pr

IV-B Et Ar Et

IV-B Pr Ar Pr

IV-B Bu Ar Bu

4

76

68

28

Part. antagonist

Antagonist

2

3

13

^aTranscriptional eﬃcacy determined in cotransfection assay in HEC-1 cells using ERa andER b expression plasmids and an estrogen regulated

reporter gene plasmid (see Experimental for details). Values are percent of the transcriptional response of estradiol at 10^ꢀ9M.

^bFor a description of compound class, see Figure 2.

^cValues are percent of the transcriptional response of estradiol at 10^ꢀ9M, andthey represent the average of triplicate determinations (CV <0.15).

^dAgonist assays are done with compound alone; antagonist assays are done with compound together with 10^ꢀ9M estradiol.

^eFor a deﬁnition of these terms, see text.

^fTetraarylpyrazine.

^gAr=p-HO–C₆H₄–.

EC₅₀values) is only 0.1% that of estradiol. Thus, this

compoundis less cleanly an ER a potency selective ago-

nist than is PPT.¹⁴

ERb, they are considerably less agonistic, especially 27g,

andthey have potencies ca. 0.1% that of estraidol.

Thus, they have modest potency and eﬃcacy selectivity

for ERa.

The two diaryl pyrimidines, compounds 27c and 27g,

are both full to nearly full agonists on ERa, with

potencies ca. 1% that of estradiol (Figs 4 and5 ). On

The one diarylpyrazine (12b, Fig. 6) is quite eﬃcacious

on ERa andis almost a complete antagonist on ER b.

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

637

Figure 3. Transcription activation by ERa andER b in response to the pyrimidine compound 27b. Human endometrial cancer (HEC-1) cells were

transfectedwith expression vectors for ER a (left panel) or ERb (right panel) andan (ERE) ₂-pS2-luc reporter gene andwere treatedwith the

designated concentrations of estradiol (squares), pyrimidine (diamonds, agonist mode), or pyrimidine in the presence of 10^ꢀ9M estradiol (circles,

antagonist mode) for 24 h. Luciferase activity was normalized for b-galactosidase activity from an internal control plasmid. The maximal activity

with E₂was set at 100. Values are the meanÆSD from three separate experiments.

Figure 4. Transcription activation by ERa andER b in response to the pyrimidine compound 27c. For details, see Figure 3 legend.

Figure 5. Transcription activation by ERa andER b in response to the pyrimidine compound 27g. For details, see Figure 3 legend.

638

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

Figure 6. Transcription activation by ERa andER b in response to the pyrimidine compound 12b. For details, see Figure 3 legend.

14,19

Again, relative to estradiol, its potency on ERa is 1%

andon ER b is 0.1%. Its pharmacological character is

relatedto that of R,R-THC. However, R,R-THC was a

very eﬀective ERb-selective antagonist, being more

potent as an ERb antagonist than as an ERa agonist.^35,37

pyrazole andthe furan series of ligands.

The degree

of ERa aﬃnity andpotency selectivity of the former

ligands was much greater than the pyrimidines, how-

ever. One of the diaryl-dialkyl pyrimidine classes, the

2,5-diaryl isomers subclass II-B, also provedto have

high aﬃnity members, provided that they had alkyl

groups of appropriate size, but the 2,4-diaryl isomeric

subclass (II-A) did not. We have recently investigated

two classes of dialkyl-diaryl pyrazoles classes and found

that some of the 1,4-dialkyl-3,5-diaryl pyrazoles have

very high aﬃnity but little ERa/ERb selectivity, whereas

some 4,5-dialkyl-1,3-diaryl pyrazoles have low aﬃnity.⁴⁰

Thus, in a general sense, there is an apparent correlation

between the preferreddisposition of aryl andalkyl sub-

stituents on the pyrazole andthe pyrimidine rings.

Discussion

We have investigateda novel series of heterocycle

ligands for the estrogen receptor based on a diazene

core motif. We conceivedof these ligands by structural

analogy with various pyrazoles andimidazoles that we

have investigatedextensively in the past ( Scheme 1)¹²

andfrom which we have developedboth high aﬃnity

andhighly ER a-selective agonists^14,16andantago-

nists.^17,38,39We have developed eﬃcient synthetic routes

to the three classes of diazenes to prepare analogues

having the types of substituents (i.e., a balance of aryl

andalkyl groups) that we foundto be eﬀective in

engendering high aﬃnity binding to ERa andhigh

With respect to the relationship between the polarity of

the heterocyclic ligandcore andbinding aﬃnity, how-

ever, there is a goodparallel between the diazoles and

the diazenes. The polarity and basicity of the members

of each heterocycle class is given in Table 5.⁴¹In both

the diazoles and diazenes, those members having basic

or polar heterocyclic cores hadpoor aﬃnity, whereas

the less basic andless polar ones gave high aﬃnity

ligands. Thus, many of the pyrazoles had high aﬃnity,

as did the pyrazines, whereas imidazoles and pyri-

dazines were poor binders.¹²The pyrimidines, being of

intermediate polarity, produced a number of analogues

having goodaﬃnities.

ERa/ERb aﬃnity selectivity in the other heterocyclic

12,14,16,19

series (pyrazoles andfurans).

These synthetic

routes are generally eﬃcient andconvenient, but in cer-

tain cases we couldnot avoidproducing regioisomeric

diazenes (cf. Scheme 5).

Members of the pyrazine and pyrimidine classes of dia-

zenes were foundto have high aﬃnity for the ERs, in

some cases with preferences either for ERa or for ERb

being as high as 23- and7.5-fold, respectively. In this

This experience reaﬃrms the thought that the core

structure of ER ligands of this design plays two roles,

regard, the diazenes were diﬀerent from the pyr-

azoles^14,17,39andfurans

19,20

we studied, where, as far as

Table 5. Dipole moment andp K_aof diazenes⁴¹

we evaluated, only ERa aﬃnity preference was seen,

although others have described ERb selective com-

pounds in the pyrazole series.¹¹

Diazene class

Basicity (pK_a)

Dipole moment (m)^a

Pyridazines

Pyrimidines

Pyrazines

Imidazoles

Pyrazoles

2.3

1.3

0.65

7.0

3.95

2.10

0.00

3.70

1.92

With the pyrimidines, the substituents that gave the

highest binding aﬃnities for ERa, namely three aryl

groups andan ethyl or propyl substituent (i.e., sub-

classes I-A and I-B, Table 1), were very similar to those

that gave the highest ERa binding aﬃnities in both the

2.52

^aIn Debye units.

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

639

(a) a ‘geometric role’, through which it provides a two-

dimensional scaﬀold for the attachment of substituents

that ﬁll the subpockets of the ligandbinding zone of

ER, and(b) an ‘integral role’, through which it has an

overall eﬀect on binding aﬃnity. It is the second of these

roles that seems to be directly related to core polarity.

This is not surprising, because one wouldexpect that

more desolvation energy would be required to transfer a

ligandwith a polar-core from water to the non-polar

interior of the ER ligandbinding pocket than a ligand

having a less polar core.

antagonist activities. Most of these derivatives had quite

low aﬃnities for the ERs, although one analogue hadan

RBA value of ca. 10% on ERa andER b, andanother

showedhigher eﬃcacy on ER a than on ERb in cell

transfection studies. In all cases, selectivity for ERa was

modest.

The novel aryl diazenes that we have investigated here

have helpedus to explore further the structural deter-

minants of binding aﬃnity, potency and eﬃcacy in the

alpha andbeta subtypes of the estrogen receptor. The

additional analogues and derivatives of them that

might be preparedcouldprove to be useful probes of

the biological activity of these receptors andmight

form the basis for the development of novel estrogen

pharmaceuticals.

Although we have not foundin the idazene series

ligands having ERa binding aﬃnities quite as high as in

14,19

the pyrazole andfuran series,

some of the ligands

have aﬃnities that are at least within a factor of 3–10

equivalent to that of estradiol. This would correspond

to K_dvalues of ca. 1–3 nM.⁴²Because these substituted

di- and triaryl diazenes have among the largest volumes

of ER ligands so far investigated, their high aﬃnity

demonstrates again the ﬂexibility of the ligand binding

pocket of the ERs andits tolerance for large substituents.

This has been documented by various analyses of the

eclectic structure–aﬃnity relationships andbulk toler-

ance of the ER for substituted steroidal and non-steroidal

ligands,^42,43as well as by the varying shape of the internal

pocket of these receptors as revealedby X-ray crystal-

lography of various ligand–receptor complexes.^44ꢀ46

Experimental

Chemical synthesis

General chemical methods. All reactions using water or

air sensitive reagents were conducted under a dry inert

gas atmosphere with dry solvents. Solvents were dis-

tilledunder N

as follows: 1,2-dichloroethane, DMF,

2

DMSO, acetonitrile, pyridine, triethylamine and hexane

from CaH₂andstoredover molecular sieves. THF, di-

chloromethane, diethyl ether and toluene were obtained

dry from solvent delivery system designed by J. C.

Meyer using neutral alumina under dry Argon. All of

the reagents purchasedfrom Alrdich Chemicals and

Lancaster were usedwithout further puriﬁcation. All

reactions were monitoredby TLC, suppliedby Merck

(0.25 mm silica gel glass plates containing F-254 indi-

cator. Visualization on TLC were achievedby UV light

(254 nm), I₂vapor and phosphomolybdic acid indicator.

Flash column chromatography was performedusing

Woelm 32–63 mm silica gel packing.⁴⁷

In two series of ER ligands based on ﬁve-membered

heterocycles, namely pyrazoles andfurans, we found

that even an analogue with four aryl substituents

retainedvery high ER a binding aﬃnity (Katzen-

19

ellenbogen andHuang, unpublished).

By contrast, in

the one diazene case where we investigated this, we

foundthat a tetraaryl-pyrazine ( 7c, Table 2) was a very

poor ligand. Perhaps, with tetraaryl substitution in this

more extended six-membered ring heterocyclic core sys-

tem, we have ﬁnally exceeded the allowable ﬂexible

volume of the internal pocket of ER, at least in the

geometry provided by this pyrazine core.

¹H NMR and ¹³C NMR spectra were recorded on Var-

ian U400 or U500. NMR spectra chemical shifts (d) are

reportedin parts per million (ppm) odwnﬁeldfrom

internal tetramethylsilane or by reference to proton

resonances resulting from incomplete deuteration of

NMR solvent. NMR coupling constants are reportedin

Hertz. Electron ionization (EI) spectra were obtained

using a Finnigan-MATCH5 spectrometer at 70 eV and

Fast Atomic Bombardment (FAB) spectra were

obtainedon VG Instrument ZAB-SE mass-spectro-

meter. Elemental analysis was performedby the Micro-

analytical service Laboratory at University of Illinois,

Urbana-Champaign. Melting points (uncorrected)

were recorded on Thomas-Hoover Electrothermal

Apparatus. All compounds are chromatographically

homogenous andbiological sample purities are

checkedin two diﬀerent solvent systems by reversed

phase HPLC.

Through an analysis of the transcriptional activity of

the higher aﬃnity diazene derivatives, we have identiﬁed

ligands that show interesting selectivity for ERa and

ERb. Of the four that we studied most fully, all have

higher potency andeﬃcacy on ER a. The selectivity in

potency is modest, ca. 10-fold in terms of relative EC₅₀

values, andis less than that of the best pyrazole or furan

14,19

that we have investigatedearlier.

The compounds

that have the highest ERa eﬃcacy selectivity, being the

most agonistic on ERa andmost antagonistic on ER b,

are the pyrimidine 27g andthe pyrazine 12b (Figs 5 and

6); their eﬃcacies on ERa reach 65–80% but on ERb

are less than 10–15%. A structurally novel tetra-

hydrochrysene, termed by us R,R-THC, is also in this

pharmacological class, but is more complete andpotent

as an antagonist of ERb.³⁵

It is of note that in a recent publication by Henke et

al.,¹⁸a series of 2-amino-4,5-diarylpyridines were pre-

paredandevaluatedas ligands for the ERs, with the

aim of developing compounds that might have selective

A number of starting materials were obtainedfrom

Aldrich (1a–d, 5c–d, 8e, 13a,b,e,f, 17d,e, 22a). For the

remainder, literature references for their preparation are

given in the experimental sections.

640

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

0

General procedure A: synthesis of pyridazines

J_AA=2.44 Hz, ArH ortho to OCH₃), 7.04 (2H,

0

AA⁰XX⁰, J_AX= 8.73, J_AA=2.44 Hz, ArH ortho to

OCH₃), 7.04 (2H, AA⁰XX⁰, J_AX= 8.73, J_XX=2.44 Hz,

ArH meta to OCH₃), 7.23 (3H, m, ArH meta and para

0

A stirredsolution of 1,4-dione (55.0 mg, 0.12 mmol) in

hydrazine hydrate (5 mL) with a minimal amount of

ethanol (to dissolve dione), was heated to reﬂux over-

night. The reaction was allowedto cool to room tem-

perature andthen dilutedwith ethyl acetate (15 mL).

The solution was transferredto a separatory funnel and

the aqueous layer washedwith EtOAc. The organic

extracts were pooledandwashedwith H ₂O andsatd

NaCl. Organic extract was dried over Na₂SO₄, ﬁltered

and solvent removed under reduced pressure to yield

crude 4,5-dihydropyridazine. Flash column chromato-

graphy (1:4 EtOAc/hexanes) aﬀorded pure 4,5-dihy-

dropyridazine, which was taken up into CH₂Cl₂andleft

to pyridazine), 7.35 (2H, m, ArH ortho to pyridizine),

0

7.57 (2H, AA⁰XX⁰, J_AX= 8.76, J_XX=2.51 Hz, ArH

meta to OCH₃); ¹³C NMR (100 MHz, CDCl₃) d 13.9,

22.3, 55.2, 55.3, 113.80(2), 113.83(2), 127.69, 127.72(2),

127.9, 130.0(2), 130.4, 130.5(2), 130.7(2), 137.7, 138.8,

140.3, 158.9, 159.0, 159.9, 160.8; MS (EI, 70 eV) m/z

395.2 (M⁺).

4-Ethyl-3,6-bis(4⁰-methoxyphenyl)-5-phenylpyridazine

(2d). Dione 1d (35 mg, 0.09 mmol) was reacted, as out-

linedin general procedure A, to aﬀord 2d (21 mg, 62%

yield). ¹H NMR (500 MHz, CDCl₃) d 0.75 (3H, t,

J=7.50 Hz, CH₃CH₂), 2.63 (2H, q, J=7.48 Hz,

CH₃CH₂), 3.76 (3H, s, CH₃OAr), 3.89 (3H, s,

exposedto air overnight. Any remaining CH Cl₂was

2

removed under reduced pressure to aﬀord crude pyrid-

azine. Puriﬁcation by ﬂash column chromatography (1:1

EtOAc/hexanes) followedby recrystallization (EtOAc/

Hex) gave pure pyridazine.

CH₃OAr), 6.74 (2H, AA⁰XX⁰, J_AX

=

J_AA=2.59 Hz, ArH ortho to OCH₃), 7.04 (2H,

8.82,

0

AA⁰XX⁰, J_AX= 8.60, J_AA=2.57 Hz, ArH ortho to

OCH₃), 7.15 (2H, m, ArH ortho to pyridazine), 7.30

0

4 - Ethyl - 3,5,6 - tris(4⁰- methoxyphenyl)pyridazine (2a).

Dione 1a (40 mg, 0.092 mmol) was reacted, as outlined

in general procedure A, to aﬀord 2a (17 mg, 44% yield).

¹H NMR (400 MHz, CDCl₃) d 0.75 (3H, t, J=7.45 Hz,

CH₃CH₂), 2.63 (2H, q, J=7.45 Hz, CH₃CH₂), 3.77 (3H,

s, CH₃OAr), 3.82 (3H, s, CH₃OAr), 3.88 (3H, s,

(2H, AA⁰XX⁰, J_AX= 9.01, J_XX=2.57 Hz, ArH meta to

OCH₃), 7.35 (3H, m, ArH para and meta to pyridazine),

0

7.57 (2H, AA⁰XX⁰, J_AX= 8.76, J_XX=2.53 Hz, ArH

0

meta to OCH₃); ¹³C NMR (125 MHz, CDCl₃) d 13.9,

22.3, 55.1, 55.3, 113.2(2), 113.8(2), 127.9, 128.5(2),

129.6(2), 129.9, 130.4, 130.5(2), 131.4(2), 135.9, 138.7,

139.9, 158.0, 159.5, 159.9, 160.5; MS (EI, 70 eV) m/z

395.2 (M⁺).

CH₃OAr), 6.76 (2H, AA⁰XX⁰, J_AX

=

8.51,

J_AA=2.59 Hz, ArH ortho to OCH₃), 6.88 (2H,

0

AA⁰XX⁰, J_AX= 8.41, J_AA=2.37 Hz, ArH ortho to

0

OCH₃), 7.03 (2H, AA⁰XX⁰, J_AX= 8.74, J_AA=2.46 Hz,

0

ArH ortho to OCH₃), 7.05 (2H, AA⁰XX⁰, J_AX= ₀9.01,

General procedure B: deprotection of phenolic methyl

ethers

0

J_AX= 8.68, J_XX=2.53 Hz, ArH meta to OCH₃), 7.56

0

J_XX=2.50 Hz, ArH meta to OCH₃), 7.31 (2H, AA XX ,

0

(2H, AA⁰XX⁰, J_AX= 8.58, J_XX=2.55 Hz, ArH meta to

Boron triﬂouride–dimethylsulﬁde complex (10 mmol/

phenolic group) was added dropwise to a stirred solu-

tion 4-methoxyphenylpyrazine (1 mmol) in dichloro-

methane (5 mL) at room temperature. The reaction

mixture was stirredfor 24–36 h. Water (2 mL) was

added and the organic layer was combined with an ethyl

0

OCH₃); ¹³C NMR (125 MHz, CDCl₃) d 13.9, 22.3, 55.1,

55.2, 55.3, 113.2(2), 113.8(2), 114.0(2), 128.0, 130.1,

130.5(2), 130.6, 130.8(2), 131.4(2), 138.5, 140.2, 158.4,

159.1, 159.4, 159.9, 160.5; MS (EI, 70 eV) m/z 425.2

(M⁺).

acetate extract (10 mL), washedwith satdNaHCO

3

3,4,6 - Tris(4⁰- methoxyphenyl) - 5 - propylpyridazine (2b).

Dione 1b (55 mg, 0.12 mmol) was reacted, as outlined

in general procedure A, to aﬀord 2b (30 mg, 57% yield).

¹H NMR (400 MHz, CDCl₃) d 0.55 (3H, t, J=7.39 Hz,

CH₃CH₂CH₂), 1.14 (2H, m, CH₃CH₂CH₂), 2.58 (2H,

m, CH₃CH₂CH₂), 3.78 (3H, s, CH₃OAr), 3.83 (3H, s,

CH₃OAr), 3.89 (3H, s, CH₃OAr), 6.76 (2H, AA⁰XX⁰,

solution (5 mL) andbrine (5 mL), anddriedover anhyd

Na₂SO₄. Removal of solvent under vacuum gave the

crude product, which was puriﬁed by ﬂash column

chromatography over silica gel using hexane–ethyl ace-

tate or by direct crystallization.

4-Ethyl-3,5,6-tris(4⁰-hydroxyphenyl)pyridazine (3a). Pyr-

idazine 2a (10 mg, 0.02 mmol) was reacted, according to

0

J_AX= 8.78, J_AA=2.58 Hz, ArH ortho to OCH₃), 6.87

0

(2H, AA⁰XX⁰, J_AX= 8.81, J_AA=2.56 Hz, ArH ortho to

general procedure B, to aﬀordcrued

material was puriﬁedby recrystallization from EtOAc/

3a. The crude

OCH₃), 7.04 (4H, overlapping AA⁰XX⁰, 2ArH ortho to

and 2ArH meta to OCH₃), 7.31 (2H, AA⁰XX⁰, J_AX

=

9.00, J_XX=2.58 Hz, ArH meta to OCH₃), 7.56 (2H,

CH₂Cl₂to provide 3a (6.7 mg, 74% yield). H NMR

(500 MHz, acetone-d₆) d 0.73 (3H, t, J=7.44 Hz,

CH₃CH₂), 2.69 (2H, q, J=7.48 Hz, CH₃CH₂), 6.71 (2H,

1

0

AA⁰XX⁰, J_AX= 8.80, J_XX=2.59 Hz, ArH meta to

OCH₃).

0

AA⁰XX⁰, J_AX= 8.26, J_AA=2.73 Hz, ArH ortho to OH),

0

6.86 (2H, AA⁰XX⁰, J_AX= 8.24, J_AA=2.71 Hz, ArH

0

4-Ethyl-3,5-bis(4⁰-methoxyphenyl)-6-phenylpyridazine

(2c). Dione 1c (25 mg, 0.06 mmol) was reacted, as out-

linedin general procedure A, to aﬀord 2c (17 mg, 68%

yield). ¹H NMR (400 MHz, CDCl₃) d 0.76 (3H, t,

J=7.55 Hz, CH₃CH₂), 2.66 (2H, q, J=7.49 Hz,

CH₃CH₂), 3.81 (3H, s, CH₃OAr), 3.89 (3H, s,

ortho to OH), 7.00 (2H, AA⁰XX⁰, J_AX

0

J_AA=2.63 Hz, ArH ortho to OH), 7.07 (2H, AA XX ,

=

₀8.20,

J_AX= 8.03, J_XX=2.34 Hz, ArH meta to OH), 7.23 (2H,

0

AA⁰XX⁰, J_AX= 8.34, J_XX=2.48 Hz, ArH meta to OH),

0

7.50 (2H, AA⁰XX⁰, J_AX= 8.23, J_XX=2.45 Hz, ArH

0

meta to OH), 8.47 (1H, bs, OH), 8.55 (1H, bs, OH), 8.65

(1H, bs, OH); ¹³C NMR (125 MHz, acetone-d₆) d 13.7,

CH₃OAr), 6.85 (2H, AA⁰XX⁰, J_AX

=

8.84,

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

641

23.2, 115.6(2), 116.2(2), 116.3(2), 127.0, 128.5, 128.7,

131.5(2), 131.8(2), 132.4(2), 142.0, 143.8, 158.4, 158.9,

159.3, 158.5, 161.3; MS (EI, 70 eV) m/z 383.1 (M⁺);

HRMS calcdfor C ₂₄H₂₀N₂O₃: 383.139568, found:

383.139800.

A stirredsolution of the a-diketone (1 mmol) and 1,2-

bis-diamine (1 mmol) in glacial acetic acid (2 mL) was

reﬂuxed for 4–5 h under dry air. After the completion of

reaction, the reaction mixture was cooled, water (5 mL)

was added, and the mixture was extracted with ethyl

acetate (2 Â 10 mL). The organic phase was washed

3,5,6 - Tris(4⁰- hydroxyphenyl) - 4 - propylpyridazine (3b).

Pyridazine 2b (20 mg, 0.05 mmol) was reacted, accord-

ing to general procedure B, to aﬀordcrude 3b. The

crude material was puriﬁed by recrystallization from

with brine (5 mL) andrdiedover anhydNa

₂SO₄.

Removal of the solvent under vacuum gave the crude

product, which was puriﬁed by ﬂash column chromato-

graphy over silica gel using hexane–ethyl acetate or

crystallization.

1

EtOAc/CH₂Cl₂to provide 3b (13 mg, 74% yield). H

NMR (500 MHz, acetone-d₆) d 0.52 (3H, t, J=7.38 Hz,

CH₃CH₂CH₂), 1.16 (2H, m, CH₃CH₂CH₂), 2.63 (2H,

m, CH₃CH₂CH₂), 6.70 (2H, AA⁰XX⁰, J_AX= 8.73,

2-Ethyl-3,5,6-tri-(4⁰-methoxyphenyl)pyrazine (6a). The

reaction of the a-diketone 5a (71 mg, 0.37 mmol; pre-

0

29,48,49

0

J_AA=2.47 Hz, ArH ortho to OH), 6.86 (2H, AA XX ,

paredaccording to literature methods

with the

0

J_AX= 8.55, J_AA=2.42 Hz, ArH ortho to OH), 7.00

0

diamine 4 (100 mg, 0.37 mmol) in glacial acetic acid,

following the general procedure B, furnished the corre-

sponding pyrazine 6a (90 mg, 58%). Mp 127 ^ꢂC; ¹H

NMR (CDCl₃, 500 MHz). d 7.64 and7.01 (4H,

(2H, AA⁰XX⁰, J_AX= 8.52, J_AA=2.47 Hz, ArH ortho to

OH), 7.05 (2H, AA⁰XX⁰, J_AX= 8.54, J_XX=2.43 Hz,

0

ArH meta to OH), 7.23 (2H, AA⁰XX⁰, J_AX= 8.75,

0

J_AX= 8.68, J_XX=2.42 Hz, ArH meta to OH), 8.44 (1H,

0

AA⁰XX⁰, J_AX=8.84 Hz and J_AA=2.21 Hz), 7.51 and

0

J_XX=2.45 Hz, ArH meta to OH), 7.49 (2H, AA XX ,

0

6.85 (4H, AA⁰XX⁰, J_AX=8.84 Hz and J_AA=2.03 Hz)

0

bs, OH), 8.54 (1H, bs, OH), 8.63 (1H, bs, OH); MS (EI,

70 eV) m/z 397.2 (M⁺); MS (CI, 130 eV) m/z 399.2

(M⁺+H); HRMS calcdfor C ₂₅H₂₃N₂O₃: 399.170868,

found: 399.169900.

and7.49 and6.83 (4H, AA ⁰XX⁰, J_AX=8.84 Hz and

0

J_AA=2.02 Hz) [aromatic], 3.88 (3H, s), 3.82 (3H, s) and

3.81 (3H, s) [3ÂOCH₃], 3.00 (2H, q, J=7.55 Hz, CH₂)

and1.33 (3H, t, J=7.55 Hz, CH₃); ¹³C NMR (CDCl₃,

125 MHz). d 159.89, 159.75, 159.64, 151.84, 149.35,

148.25, 147.66, 131.59, 131.26, 131.05, 131.0, 130.56,

113.75, 113.69, 113.58, 55.34, 55.24, 55.22, 27.80 and

13.30. MS (EI, 70 eV). m/z 427 (M+1, 28%), 426 (M⁺,

100); HRMS: calcdfor C ₂₇H₂₆N₂O₃: 426.1943, found:

426.1939. Analysis: for C₂₇H₂₆N₂O₃+0.4 EtOAc: calcd

C, 74.39; H, 6.37; N, 6.07, foundC, 74.86; H, 6.09; N,

6.35.

4-Ethyl-3,5-bis(4⁰-hydroxyphenyl)-6-phenylpyridazine

(3c). Pyridazine 2c (10 mg, 0.025 mmol) was reacted,

according to general procedure B, to aﬀordcrude 3c.

The crude material was puriﬁed by recrystallization

from EtOAc/CH₂Cl₂to provide 3c (7 mg, 55% yield).

¹H NMR (500 MHz, CDCl₃) d 0.75 (3H, t, J=7.58 Hz,

CH₃CH₂), 2.716 (2H, q, J=7.52 Hz, CH₃CH₂), 6.83

(2H, AA⁰XX⁰, J_AX= 8.61, J_AA=2.41 Hz, ArH ortho to

0

OH), 7.01 (2H, AA⁰XX⁰, J_AX= 8.58, J_AA=2.44 Hz,

2-n-Propyl-3,5,6-tri-(4⁰-methoxyphenyl)pyrazine (6b).

The reaction of the a-diketone 5b (15 mg, 0.073 mmol;

preparedaccording to a literature known method ³⁰with

the diamine, 4 (20 mg, 0.073 mmol) in glacial acetic acid,

following the general procedure B, furnished the corre-

0

ArH ortho to OH), 7.07 (2H, AA⁰XX⁰, J_AX= 8.583,

0

J_XX=2.42 Hz, ArH meta to OH), 7.22.27 (3H, over-

lapping m, ArH meta and para to pyridazine), 7.37 (2H,

m, ArH ortho to pyridazine), 7.51 (2H, AA⁰XX⁰, J_AX

=

8.42, J_XX=2.49 Hz, ArH meta to OH); ¹³C NMR

(125 MHz, CDCl₃) d 13.2, 22.1, 115.2(2), 115.3(2),

126.7, 127.6(2), 127.8, 129.6, 130.0(2), 130.7(2),

131.1(2), 138.4, 139.2, 140.2, 157.3, 158.0, 158.8, 160.9.

sponding pyrazine 6b (20 mg, 63%). H NMR (CDCl₃,

0

1

0

500 MHz). d 7.63 and7.01 (4H, AA XX⁰, J_AX=8.29 Hz

and J_AA=1.47 Hz), 7.50 and6.85 (4H, AA ⁰XX⁰,

0

J_AX=8.29 Hz and J_AA=1.65 Hz) and7.48 and6.82

0

(4H, AA⁰XX⁰, J_AX=8.29 Hz and J_AA=1.66 Hz) [aro-

matic], 3.88 (3H, s), 3.82 (3H, s) and3.81 (3H, s)

4-Ethyl-3,6-bis(4⁰-hydroxyphenyl)-5-phenylpyridazine

(3d). Pyridazine 2d (12 mg, 0.03 mmol) was reacted,

according to general procedure B, to aﬀordcrude 3d.

The crude material was puriﬁed by recrystallization

from EtOAc/CH₂Cl₂to provide 3d (8 mg, 60% yield).

¹H NMR (500 MHz, CDCl₃) d 0.72 (3H, t, J=7.48 Hz,

CH₃CH₂), 2.64 (2H, q, J=7.54 Hz, CH₃CH₂), 6.684

[3ÂOCH₃], 2.95 (2H, A₃MM⁰XX⁰, J_XM=7.74 Hz and

J_XX=1.65 Hz, Ar–CH₂), 1.82 (2H, A₃MM⁰XX⁰,

0

J_XM=7.74 Hz and J_AM=7.37 Hz, CH₂CH₃) and0.95

(3H, t, J=7.37 Hz, CH₃); ¹³C NMR (CDCl₃, 125 MHz).

d 164.51, 159.84, 159.74, 159.64, 150.84, 149.60, 148.19,

147.60, 131.59, 131.54, 131.31, 131.05, 130.99, 130.60,

113.74, 113.69, 113.57, 55.33, 55.24, 55.21, 36.53, 22.36

and14.07. MS (EI, 70 eV). m/z 441 (M+1, 14%), 440

(M⁺, 50), 135 (100); HRMS: calcdfor C ₂₈H₂₈N₂O₃:

440.2099, found: 440.2095.

(2H, AA⁰XX⁰, J_AX= 8.79, J_AA=2.51 Hz, ArH ortho to

0

OH), 7.00 (2H, AA⁰XX⁰, J_AX= 8.74, J_AA=2.43 Hz,

0

ArH ortho to OH), 7.21 (2H, AA⁰XX⁰, J_AX= 9.00,

0

J_XX=2.46 Hz, ArH meta to OH), 7.62 (2H, m, ArH

ortho to pyridazine), 7.34.41 (3H, overlapping m, ArH

para and meta to pyridazine), 7.50 (2H, AA⁰XX⁰, J_AX

=

2,3,5,6 - Tetra - (4⁰- methoxyphenyl) - pyrazine (6c). The

reaction of 4,4⁰-dimethoxybenzil (5c, 27 mg, 0.1 mmol)

with meso-1,2-bis-(4-methoxyphenyl)-ethylenediamine

(4, 27.2 mg, 0.1 mmol) in glacial acetic acid(2 mL),

according to the general procedure C, after careful ﬂash

column chromatography (10% EtOAc–hexane) over

silica gel andcrystallization with ethyl acetate–hexane,

0

8.88, J_XX=2.52 Hz, ArH meta to OH), 8.46 (1H, bs,

OH), 8.65 (1H, bs, OH).

General procedure C: synthesis of 2,3-bis-alkyl-5,6-bis-

arylpyrazines and 2,3,5,6-tetraarylpyrazines

642

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

gave the pyrazine 6c (39 mg, 76%) as a solid. Mp

275–276 ^ꢂC; H NMR (CDCl₃, 500 MHz) d 7.63 (8H,

2-n-Propyl-3,5,6-tri-(4⁰-hydroxyphenyl)pyrazine (7b).

Deprotection of the pyrazine 6b (10 mg, 0.02 mmol)

using BF₃SMe₂(89 mg, 0.68 mmol), according to the

general procedure B, furnishedthe phenolic pyrazine 7b

(8 mg, 89%). Mp 239 ^ꢂC; ¹H NMR ((CD₃)₂CO,

400 MHz). d 7.50 and6.92 (4H, A ₂X₂, J=8.30 Hz), 7.37

and6.76 (4H, A ₂X₂, J=8.55 Hz) and7.37 and6.73 (4H,

A₂X₂, J=8.79 Hz) [aromatic], 7.33 (1H, s), 7.22 (1H, s)

and7.18 (1H, s) [3 ÂOH], 2.90 (2H, t, J=7.33 Hz,

Ar–CH₂), 1.75 (2H, A₃MM⁰XX⁰, J_MX=7.33 Hz,

1

AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 6.88 (8H,

.

0

AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 3.85 (12H, s, 4

0

Â OMe); ¹³C NMR (CDCl₃, 125 MHz) d 159.86,

146.81, 131.28, 131.07, 113.66 and55.24. MS (EI, 70 eV)

m/z 504 (M⁺3%), 69 (100%); Analysis for

C₃₂H₂₈N₂O₄, calcdC, 76.17; H, 5.59; N, 5.55, foundC,

76.13; H, 5.56; N, 5.58.

2,3-Bis-ethyl-5,6-bis-(4⁰-methoxyphenyl)-pyrazine (6d).

The reaction of 3,4-hexanedione (5d, 45 mg, 0.37 mmol)

with meso-1,2-bis-(4-methoxyphenyl)-ethylenediamine

(4, 100 mg, 0.37 mmol) in glacial acetic acid(5 mL),

according to the general procedure C, after careful ﬂash

column chromatography (15% EtOAc–hexane) over

silica gel, gave the pyrazine 6d (101 mg, 79%) as a solid.

J_AM=7.56 Hz, J_MM=3.12 Hz, CH₂CH₃) and0.89 (3H,

0

t, J=7.32 Hz, CH₃); ¹³C NMR ((CD₃)₂CO, 100 MHz).

d 157.70, 157.57, 149.60, 149.12, 147.54, 147.19, 130.87,

130.51, 114.88, 114.71, 36.11, 21.71 and13.31. MS (EI,

70 eV). m/z 399 (M+1, 29%), 398 (M+, 100); HRMS:

calcdfor C ₂₄H₂₀N₂O₃: 398.1630, found: 398.1621.

Mp 78–79 ^ꢂC; H NMR (CDCl₃, 500 MHz) d 7.43 (4H,

2,3,5,6 - Tetra - (4⁰- hydroxyphenyl) - pyrazine (7c). The

reaction of 2,3,5,6-tetra-(4⁰-methoxyphenyl)-pyrazine

(6c, 253 mg, 0.5 mmol) with BF₃SMe₂(2.0 mL,

1

AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 6.83 (4H,

0

AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 3.81 (6H, s, 2

.

0

Â OMe), 2.92 (4H, q, J=7.50 Hz, 2 Â CH₂CH₃) and

1.37 (6H, t, J=7.50 Hz, 2 Â CH₂CH₃); ¹³C NMR

(CDCl₃, 125 MHz) d 159.49, 152.69, 148.01, 131.88,

130.92, 113.59, 55.19, 27.12 and13.01. MS (EI, 70 eV)

m/z 348 (M⁺100%), 333 (18%); HRMS calcdfor

C₂₂H₂₄N₂O₂, 348.1838, found: 348.1845.

20 mmol) in dry dichloromethane (10 mL), according to

the general procedure B, after crystallization with

methanol, gave the pyrazine 7c (201 mg, 90%) as a

solid. HPLC purity (reversed phase, C18) in two sol-

vents is: MeOH–H₂O (60:40) 100% andCH CN–H₂O

3

(40:60) 100%; mp >360 ^ꢂC; ¹H NMR (acetone-d₆,

500 MHz) d 8.59 (4H, s, 4 Â OH), 7.51 (8H, AA⁰XX⁰,

2,3-Bis-propyl-5,6-bis-(4⁰-methoxyphenyl)-pyrazine (6e).

The reaction of 4,5-octanedione (5e, 58 mg, 0.37 mmol;

preparedaccording to a literature method ²⁶) with meso-

1,2-bis-(4-methoxyphenyl)-ethylenediamine (4, 100 mg,

0.37 mmol) in glacial acetic acid(5 mL), according to

the general procedure C, after careful ﬂash column

chromatography (15% EtOAc–hexane) over silica gel,

gave the pyrazine 6e (111 mg, 80%) as a solid. Mp

71–72 ^ꢂC; ¹H NMR (CDCl₃, 500 MHz) d 7.40 (4H,

0

J_AX=8.79 and J_AA=2.14 Hz), 6.80 (8H, AA XX ,

J_AX=8.79 and J_AA=2.14 Hz); ¹³C NMR (acetone-d₆,

0

125 MHz) d 158.78, 147.33, 131.94, 131.21 and115.88.

MS (FAB, ZAB) m/z 449 (M⁺31%), 154 (100%);

HRMS calcdfor

448.1425.

C ₂₈H₂₀N₂O₄, 448.1423, found:

2,3-Bis-ethyl-5,6-bis-(4⁰-hydroxyphenyl)-pyrazine (7d).

The reaction of 2,3-bis-ethyl-5,6-bis-(4⁰-methoxy-

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 6.83 (4H,

phenyl)-pyrazine (6d, 80 mg, 0.23 mmol) with BF₃SMe₂

.

0

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 3.80 (6H, s, 2

(0.48 mL, 4.6 mmol) in dry dichloromethane (5 mL),

according to the general procedure B, after ﬂash column

chromatography (30% EtOAc–hexane) over silica gel,

gave the pyrazine 7d (70 mg, 95%) as a solid. Mp 241–

242 ^ꢂC; HPLC purity (reversedphase, C18) in two sol-

0

Â OMe), 2.86 (4H, t, J=7.40 Hz, 2 Â CH₂CH₂CH₃),

1.83 (4H, quint, J=7.40 Hz, 2 Â CH₂CH₂CH₃) and1.05

(6H, t, J=7.40 Hz, 2 Â CH₂CH₂CH₃); ¹³C NMR

(CDCl₃, 125 MHz) d 159.49, 151.93, 147.98, 131.86,

130.91, 113.59, 55.21, 35.99, 22.29 and14.19. MS (EI,

70 eV) m/z 376 (M⁺62%), 348 (100%); HRMS calcd

for C₂₄H₂₈N₂O₂, 376.2151, found: 376.2149.

vents is: MeOH–H₂O (70:30) 99.4% andCH CN–H₂O

3

1

(50:50) 99.12%; H NMR (acetone-d₆, 500 MHz) d 8.47

(2H, s, 2 Â OH), 7.35 (4H, AA⁰XX⁰, J_AX=8.79 and

0

J_AA=2.14 Hz), 6.76 (4H, AA XX , J_AX=8.79 and

2 - Ethyl - 3,5,6 - tri - (4⁰- hydroxyphenyl)pyrazine (7a).

Deprotection of the pyrazine 6a (65 mg, 0.15 mmol)

.

using BF₃SMe₂(595 mg, 4.58 mmol), according to the

J_AA=2.14 Hz), 2.89 (4H, q, J=7.50 Hz, 2 Â CH₂CH₃)

0

and1.32 (6H, t, J=7.50 Hz, 2 Â CH₂CH₃); ¹³C NMR

(acetone-d₆, 125 MHz) d 158.39, 152.77, 148.70, 131.88,

115.72, 27.35 and12.89. MS (EI, 70 eV) m/z 320 (M⁺

100%), 75 (92%); HRMS calcdfor C ₂₀H₂₀N₂O₂,

320.1525, found: 320.1519.

general procedure B, furnishedthe phenolic pyrazine 7a

(55 mg, 96%). Mp 250 ^ꢂC; ¹H NMR ((CD₃)₂CO,

500 MHz). d 8.61 (3H, s, 3ÂOH), 7.59 and6.97 (4H,

AA⁰XX⁰, J_AX=8.81 Hz and J_AA=2.02 Hz), 7.44 and

0

6.80 (4H, AA⁰XX⁰, J_AX=8.81 Hz and J_AA=2.02 Hz)

2,3-Bis-propyl-5,6-bis-(4⁰-hydroxyphenyl)-pyrazine (7e).

0

and7.40 and6.78 (4H, AA ⁰XX⁰, J_AX=8.81 Hz and

The reaction of 2,3-bis-propyl-5,6-bis-(4⁰-methoxy-

.

phenyl)-pyrazine (6e, 85 mg, 0.23 mmol) with BF₃SMe₂

0

J_AA=2.02 Hz) [aromatic], 2.96 (2H, q, J=7.52 Hz,

CH₂) and1.29 (3H, t, J=7.52 Hz, CH₃); ¹³C NMR

((CD₃)₂CO, 125 MHz). d 158.69, 158.53, 158.44,

151.63, 149.85, 148.60, 148.24, 131.85, 131.52, 131.45,

131.41, 130.90, 115.86, 115.72, 115.69, 28.24 and13.33.

MS (EI, 70 eV). m/z 385 (M+1, 27%), 384 (M⁺, 100);

(0.48 mL, 4.6 mmol) in dry dichloromethane (5 mL),

according to the general procedure B, after ﬂash column

chromatography (30% EtOAc–hexane) over silica, gave

the pyrazine 7e (70 mg, 89%) as a solid. Mp 175–176 ^ꢂC;

HPLC purity (reversedphase, C18) in two solvents is:

HRMS: calcdfor

384.1469.

C

₂₄H₂₀N₂O₃: 384.1474, found:

MeOH–H₂O (80:20) 98.3% andCH CN–H₂O (60:40)

3

99.9%; ¹H NMR (acetone-d₆, 500 MHz) d 8.49 (2H, s, 2

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

643

Â

OH), 7.34 (4H, AA⁰X₀X⁰, J_AX=8.79 and

51–52 ^ꢂC; ¹H NMR (CDCl₃, 400 MHz) d 8.03 (2H,

0

J_AA=2.14 Hz), 2.84 (4H, t, J=7.50 Hz,

AA⁰XX⁰, J_AX=9.00 and J_AA=2.19 Hz), 6.97 (2H,

0

J_AA=2.14 Hz), 6.77 (4H, AA XX , J_AX=8.79 and

0

AA⁰XX⁰, J_AX=9.00 and J_AA=2.19 Hz), 5.12 (1H, dd,

0

2

Â

CH₂CH₂CH₃), 1.81 (4H, quint, J=7.50 Hz, 2 Â

J=6.84 and6.59 Hz, CH(Br)CH₂), 3.90 (3H, s, OMe),

2.28.08 (2H, m, CH₂CH₂CH₂CH₃), 1.53.35 (4H, m,

CH₂CH₂CH₃) and1.02 (6H, t,

J=7.40 Hz, 2 Â

CH₂CH₂CH₃); ¹³C NMR (acetone-d₆, 125 MHz) d

158.36, 151.94, 148.64, 131.85, 131.79, 115.66, 36.25,

22.55 and14.36. MS (EI, 70 eV) m/z 348 (M⁺46%),

320 (100%); HRMS calcdfor C ₂₂H₂₄N₂O₂, 348.1837,

found: 348.1837.

CH₂CH₂CH₂CH₃) and0.94 (3H, t,

J=7.08 Hz,

CH₂CH₂CH₃); MS (EI, 70 eV) m/z 286 (M⁺H 0.65%),

284 (0.66%), 135 (100%).

2-Bromo-1-(4⁰-methoxyphenyl)-4-methylpentan-1-one

(9d). Bromine (0.1.06 mL, 20 mmol) was added drop-

0

wise to a stirredsolution of 1-(4 -methoxyphenyl)-4-

General procedure D: synthesis of ꢀ-bromoketone

methylpentan-1-one (8d, 4.12 g, 20 mmol; for prepara-

tion, see ref 14) in diethyl ether (50 mL) and glacial

acetic acid (2 mL), according to the general procedure

D. Solvent removal gave the a-bromoketone 9d (5.3 g,

93%) as an oil; ¹H NMR (CDCl₃, 400 MHz) d 8.01 (2H,

Bromine (1 mmol) was added dropwise to a stirred

solution of ketone (1 mmol) in diethyl ether (5 mL) and

glacial acetic acid(0.2 mL) at room temperature. After

the reaction was complete, water (5 mL) was added. The

organic layer was combinedwith an ether extract

(10 mL), washedwith 10% sodium thiosulfate solution

(5 mL) andbrine (5 mL), anddriedover anhydNa ₂SO₄.

The solvent was removedunder vacuum andthe pro-

duct was puriﬁed by crystallization.

AA⁰XX⁰, J_AX=9.00 and J_AA=1.96 Hz), 6.95 (2H,

0

AA⁰XX⁰, J_AX=9.00 and J_AA=1.96 Hz), 5.18 (1H, dd,

0

J=6.59 and6.58 Hz, CH(Br)CH₂), 3.89 (3H, s, OMe),

2.12.98 (2H, m, CH₂CH(CH₃)₂), 1.86 (1H, septet,

J=6.59 and7.32 Hz, CH CH(CH₃)₂) and 0.96 (6H, dd,

2

J=6.59 and3.66 Hz, CH2CH2 (CH₃)₂); MS (EI, 70 eV)

m/z 286 (M⁺0.34%), 284 (0.34%), 135 (100%).

2-Bromo-1-(4⁰-methoxyphenyl)-butan-1-one (9a). To a

stirredsolution of 1-(4 ⁰-methoxyphenyl)-butan-1-one

(8a, 0.8 g, 4.4 mmol; for preparation, see ref 14) in d i-

ethyl ether (25 mL) andglacial acetic acid(0.5 mL) was

added dropwise bromine (0.3 mL, 4.5 mmol), according

to the general procedure D. Crystallization from hex-

ane, gave the a-bromoketone 9a (0.9 g, 80%) as a solid.

2-Bromo-1-(4⁰-methoxyphenyl)-propan-1-one (9e). Bro-

mine (1.55 mL, 30 mmol) was added dropwise to a stir-

0

redsolution of 1-(4 -methoxyphenyl)-propan-1-one (8e,

5.0 g, 30 mmol) in diethyl ether (60 mL) and glacial ace-

tic acid(2 mL), according to the general procedure D.

Crystallization from hexane gave the a-bromoketone 9e

Mp 45–46 ^ꢂC; H NMR (CDCl₃, 500 MHz) d 8.03 (2H,

1

AA⁰XX⁰, J_AX=9.00 and J_AA=1.96 Hz), 6.98 (2H,

(5.9 g, 81%) as a solid. Mp 66 ^ꢂC; H NMR (CDCl₃,

1

0

AA⁰XX⁰, J_AX=9.00 and J_AA=1.96 Hz), 5.06 (1H, dd,

400 MHz)

0

d

J_AA=1.96 Hz), 6.98 (2H, AA XX , J_AX=8.79 and

8.03 (2H, AA⁰XX⁰, J_AX=8.79 and

0

J_AA=1.96 Hz), 5.29 (1H, q, J=6.84 Hz, CH(Br)CH₃),

J=6.5 and6.5 Hz, CH(Br)CH₂), 3.90 (3H, s, OMe),

2.24 (1H, dq, J=6.6 and7.3 Hz, CH(Br) CH_ABCH₃),

2.14 (1H, dq, J=6.6 and7.3 Hz, CH(Br) CH_ABCH₃),

and1.09 (3H, t, J=7.33 Hz, CH₂CH₂CH₃); MS (EI,

70 eV) m/z 258 (M+H, 2.24%), 256 (2.30%), 135

(100%).

0

3.90 (3H, s, OMe) and1.89 (3H, ,d

J=6.59 Hz,

CH(Br)CH₃); MS (EI, 70 eV) m/z 244 (M⁺2.30%), 242

(2.47%), 135 (100%).

General procedure E: synthesis of ꢀ-azidoketone

2-Bromo-1-(4⁰-methoxyphenyl)-pentan-1-one (9b). Bro-

mine (0.6 mL, 10 mmol) was added dropwise o a stirred

solution of 1-(4⁰-methoxyphenyl)-pentan-1-one (8b,

1.92 g, 10 mmol; for preparation, see ref 14) in diethyl

ether (50 mL) andglacial acetic acid(2 mL), according

to the general procedure D. Crystallization from hexane

gave the a-bromoketone 9b (2.0 g, 74%) as a solid. Mp

48–49 ^ꢂC; ¹H NMR (CDCl₃, 500 MHz) d 8.01 (2H,

Sodium azide (3 mmol) was added to a stirred solution

of a-bromoketone (1 mmol) in dry DMF (5 mL) at

room temperature, under nitrogen atmosphere. The

reaction was complete after stirring for 10 h. Water

(5 mL) was added and the aqueous phase extracted with

ether (10 mL). The organic phase was washedwith brine

(5 mL) anddriedover anhydNa ₂SO₄. Removal of sol-

vent under vacuum gave the crude product that was

puriﬁedby ﬂash column chromatography over silica gel

using hexane–ethyl acetate.

AA⁰XX⁰, J_AX=9.00 and J_AA=1.96 Hz), 6.95 (2H,

0

AA⁰XX⁰, J_AX=9.00 and J_AA=1.96 Hz), 5.11 (1H, dd,

0

J=6.5 and6.5 Hz, CH(Br)CH₂), 3.88 (3H, s, OMe),

2.19.08 (2H, m, CH₂CH₂CH₃), 1.57.40 (2H, m,

CH₂CH₂CH₃) and0.98 (3H, t,

J=7.33 Hz,

2-Azido-1-(4⁰-methoxyphenyl)-butan-1-one (10a). NaN₃

(0.97 g, 15 mmol) was added to a stirred solution of

bromo-1-(4⁰-methoxyphenyl)-butan-1-one (9a, 1.28 g,

4.9 mmol) in DMF (20 mL), according to the general

procedure E, after ﬂash column chromatography over

silica gel using 15% ethyl acetate/hexane, gave a-azido-

CH₂CH₂CH₃); MS (EI, 70 eV) m/z 271 (M⁺0.05%),

135 (100%).

2-Bromo-1-(4⁰-methoxyphenyl)-hexan-1-one (9c). To a

stirredsolution of 1-(4 ⁰-methoxyphenyl)-hexan-1-one

(8c, 1.3 g, 6.3 mmol; for preparation, see ref 14 in diethyl

ether (30 mL) and glacial acetic acid (1.0 mL) was added

dropwise bromine (0.4 mL, 6.3 mmol), according to the

general procedure D. Crystallization from hexane gave

the a-bromoketone 9c (1.6 g, 89%) as a solid. Mp

1

ketone 10a (0.98 g, 92%) as an oil. H NMR (CDCl₃,

500 MHz)

0

d

7.95 (2H, AA⁰XX⁰, J_AX=9.00 and

J_AA=1.96 Hz), 6.98 (2H, AA XX , J_AX=9.00 and

0

J_AA=1.96 Hz), 4.89 (1H, dd, J=5.13 Hz, CH(Br)CH₂),

0

3.90 (3H, s, OMe), 2.06.85 (2H, m, CH(Br)CH_ABCH₃),

644

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

and1.09 (3H, t, J=7.33 Hz, CH₂CH₂CH₃); MS (EI,

70 eV) m/z 271 (M⁺ꢀN₂1.2%), 135 (100%).

General procedure F: synthesis of 2,5-bis-alkyl-3,6-bis-

arylpyrazines. A solution of the a-azidoketone (1 mmol)

andPh P (1.2 mmol) in dry THF (5 mL) was stirred for

3

2-Azido-1-(4⁰-methoxyphenyl)-pentan-1-one (10b). NaN₃

(0.75 g, 10 mmol) was added to a stirred solution of

2-bromo-1-(4⁰-methoxyphenyl)-pentan-1-one (9b, 1.0 g,

3.7 mmol) in DMF (15 mL), according to the general

procedure E, after ﬂash column chromatography over

silica gel using 15% ethyl acetate/hexane, gave a-azido-

0.5 h under dry air. Water (0.4 mL) was added and stir-

ring continuedovernight. THF andwater were removed

with a toluene azeotrope. Hexane (2Â10 mL) was added

andthe precipitatedPh ₃P¼O was removedby ﬁltration

andwashing with 10% ethyl acetate/hexane. Solvent

was removedunder vacuum, andethanol (10 mL) and

acetic acid (0.2 mL) were added. The mixture was

reﬂuxed for 4 h, cooled, and water (5 mL) was added.

The mixture was extractedwith ethyl acetate (2 Â10 mL)

andthe organic phase was washedwith brine (5 mL)

1

ketone 10b (0.83 g, 96%) as an oil. H NMR (CDCl₃,

500 MHz)

0

d

7.95 (2H, AA⁰XX⁰, J_AX=9.00 and

J_AA=1.96 Hz), 6.99 (2H, AA XX , J_AX=9.00 and

0

J_AA=1.96 Hz), 4.55 (1H, dd, J=5.43 Hz, CH(N₃)CH₂),

0

3.91 (3H, s, OMe), 1.91.82 (2H, m, CH₂CH₂CH₃),

1.61.47 (2H, m, CH₂CH₂CH₃) and1.00 (3H, t,

J=7.33 Hz, CH₂CH₂CH₃); MS (EI, 70 eV) m/z 205

(M⁺ꢀN₂1.3%), 135 (100%).

andrdiedover anhydNa

₂SO₄. Removal of solvent

under vacuum gave the crude product, which was puri-

ﬁedby ﬂash column chromatography over silica gel

using hexane-ethyl acetate or directly by crystallization.

2-Azido-1-(4⁰-methoxyphenyl)-hexan-1-one (10c). NaN₃

(1.03 g, 16 mmol) was added to a stirred solution of

2-bromo-1-(4⁰-methoxyphenyl)-hexan-1-one (9c, 1.5 g,

5.3 mmol) in DMF (20 mL), according to the general

procedure E, after ﬂash column chromatography over

silica gel using 15% ethyl acetate/hexane, gave a-azido-

2,5-Bis-ethyl-3,6-bis-(4⁰-methoxyphenyl)-pyrazine (11a).

The reaction of 2-azido-1-(4⁰-methoxyphenyl)-butan-1-

one (10a, 1.1 g, 5 mmol) andPh P (1.45 g, 5.5 mmol) in

3

dry THF (15 mL) followed by hydrolysis, dimerization

and oxidation according to the general procedure F,

after ﬂash column chromatography (15% EtOAc–hex-

ane) over silica gel, gave the pyrazine 11a (0.7 g, 80%)

as a solid. Mp 127–128 ^ꢂC; ¹H NMR (CDCl₃, 500 MHz)

1

ketone 10c (1.25 g, 95%) as an oil. H NMR (CDCl₃,

400 MHz)

0

d

7.92 (2H, AA⁰XX⁰, J_AX=9.00 and

J_AA=2.19 Hz), 6.96 (2H, AA XX , J_AX=9.00 and

0

J_AA=2.19 Hz), 4.51 (1H, dd, J=4.88 and5.13 Hz,

0

d 7.58 (4H, AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz),

0

7.02 (4H, AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 3.88

0

CH(Br)CH₂), 3.90 (3H, s, OMe), 1.93.78 (2H, m,

CH₂CH₂CH₂CH₃), 1.58.27 (4H, m, CH₂CH₂CH₂CH₃)

and0.91 (3H, t, J=7.33 Hz, CH₂CH₂CH₃); MS (EI,

70 eV) m/z 206 (M⁺ꢀN₃0.55%), 135 (100%).

(6H, s, 2 Â OMe), 2.94 (4H, q, J=7.50 Hz, 2 Â

CH₂CH₃) and1.28 (6H, t, J=7.50 Hz, 2 Â CH₂CH₃);

¹³C NMR (CDCl₃, 125 MHz) d 159.80, 151.85, 150.09,

131.54, 130.39, 113.80, 55.35, 27.78 and13.56. MS (EI,

70 eV) m/z 348 (M⁺100%), 333 (18%); HRMS calcd

for C₂₂H₂₃N₂O₂, 347.1757, found: 347.1759.

2-Azido-1-(4⁰-methoxyphenyl)-4-methylpentan-1-one

(10d). NaN₃(1.95 g, 30 mmol) was added to a stirred

solution of 2-bromo-1-(4⁰-methoxyphenyl)-4-methyl-

pentan-1-one (9d, 2.85 g, 10 mmol) in DMF (20 mL),

according to the general procedure E, after ﬂash column

chromatography over silica gel using 15% ethyl acetate/

hexane, gave a-azidoketone 10d (2.10 g, 87%) as an oil.

¹H NMR (CDCl₃, 400 MHz) d 8.01 (2H, AA₀⁰XX⁰₀,

2,5 - Bis - propyl - 3,6 - bis - (4⁰- methoxyphenyl) - pyrazine

(11b). The reaction of 2-azido-1-(4⁰-methoxyphenyl)-

pentan-1-one (10b, 0.5 g, 2.15 mmol) andPh P (0.62 g,

3

2.4 mmol) in dry THF (10 mL) followed by hydrolysis,

dimerization and oxidation according to the general

procedure F, after ﬂash column chromatography (15%

EtOAc–hexane) over silica gel, gave the pyrazine 11b

(334 mg, 82%) as a solid. Mp 116–117 ^ꢂC; ¹H NMR

(CDCl₃, 500 MHz) d 7.56 (4H, AA⁰XX⁰, J_AX=8.79 and

0

J_AX=9.00 and J_AA=1.96 Hz), 6.95 (2H, AA XX ,

0

J_AX=9.00 and J_AA=1.96 Hz), 4.54 (1H, dd, J=4.15

and10.0 Hz, CH(Br)CH₂), 3.88 (3H, s, OMe), 1.92.84

(1H, m, CH(N₃)CH_ABCH(CH₃)₂), 1.79 (1H, septet,

J=8.79 and4.15 Hz, CH(N ₃)CH_ABCH(CH₃)₂), 1.65

0

J_AA=2.14 Hz), 7.01 (4H, AA XX , J_AX=8.79 and

0

J_AA=2.14 Hz), 3.88 (6H, s, 2 Â OMe), 2.87 (4H, t,

(1H, septet, J=8.79 and4.15 Hz, CH CH(CH₃)₂), 1.04

2

J=7.40 Hz, 2 Â CH₂CH₂CH₃), 1.75 (4H, quint,

J=7.40 Hz, 2 Â CH₂CH₂CH₃) and0.90 (6H, t,

J=7.40 Hz, 2 Â CH₂CH₂CH₃); ¹³C NMR (CDCl₃,

125 MHz) d 159.73, 150.77, 150.28, 132.63, 131.57,

130.40, 114.18, 113.77, 55.31, 36.50, 22.56 and14.02.

MS (EI, 70 eV) m/z 376 (M⁺65%), 348 (100%); HRMS

calcdfor C ₂₄H₂₇N₂O₂, 375.2072, found: 375.2072.

(3H, dd, J=6.59 and3.66 Hz, CH ₂CH₂(CH₃)₂) and0.98

(3H, dd, J=6.59 and3.66 Hz, CH ₂CH₂(CH₃)₂); MS

(EI, 70 eV) m/z 205 (M⁺ꢀN₃0.21%), 135 (100%).

2-Azido-1-(4⁰-methoxyphenyl)-propan-1-one (10e). NaN₃

(1.95 g, 30 mmol) was added to a stirred solution of

2-bromo-1-(4⁰-methoxyphenyl)-propan-1-one (9e, 2.43 g,

10 mmol) in DMF (20 mL), according to the general pro-

cedure E, after ﬂash column chromatography over silica

gel using 15% ethyl acetate/hexane, gave a-azidoketone

10e (1.68 g, 86%) as an oil. ¹H NMR (CDCl₃, 400 MHz) d

2,5-Bis-butyl-3,6-bis-(4⁰-methoxyphenyl)-pyrazine (11c).

The reaction of 2-azido-1-(4⁰-methoxyphenyl)-hexan-1-

one (10c, 1.0 g, 4.01 mmol) andPh ₃P (1.17 g, 4.45 mmol)

in dry THF (15 mL) followed by hydrolysis, dimeriza-

tion and oxidation according to the general procedure

F, after ﬂash column chromatography (15% EtOAc–

hexane) over silica gel, gave the pyrazine 11c (0.66 g,

78%) as a solid. Mp 102–103 ^ꢂC; ¹H NMR (CDCl₃,

7.95 (2H, AA⁰XX⁰, J_AX=9.00 and J_AA=1.96 Hz), 6.95

0

(2H, AA⁰XX⁰, J_AX=8.79 and J_AA=1.96 Hz), 4.66 (1H, q,

0

J=7.08 Hz, CH(Br)CH₃), 3.88 (3H, s, OMe) and1.56 (3H,

d, J=7.08 Hz, CH(Br)CH₃); MS (EI, 70eV) m/z 163

(M⁺ꢀN₂0.17%), 135 (100%).

500 MHz)

d

7.56 (4H, AA⁰XX⁰, J_AX=8.79 and

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

645

0

13.10. MS (EI, 70 eV) m/z 320 (M⁺61.7%), 319

(57.3%), 57 (100%); HRMS calcdfor C ₂₀H₁₉N₂O₂,

319.1443, found: 319.1443.

0

J_AA=2.14 Hz), 7.02 (4H, AA XX , J_AX=8.79 and

0

J_AA=2.14 Hz), 3.88 (6H, s, 2 Â OMe), 2.89 (4H, t,

J=7.40 Hz, 2 Â CH₂CH₂CH₂CH₃), 1.73.67 (4H, m, 2

Â CH₂CH₂CH₂CH₃), 1.31 (4H, quint, J=7.50 and

14.79 Hz,

2

Â

CH₂CH₂CH₃) and0.86 (6H, t,

2,5-Bispropyl-3,6-bis-(4⁰-hydroxyphenyl)-pyrazine (12b).

J=7.50 Hz, 2 Â CH₂CH₂CH₃); ¹³C NMR (CDCl₃,

125 MHz) d 159.78, 150.97, 150.23, 131.54, 130.44,

113.80, 55.35, 34.25, 31.49, 22.61 and13.89. MS (EI,

70 eV) m/z 404 (M⁺7%), 362 (53%), 121 (100%);

The reaction of 2,5-bis-propyl-3,6-bis-(4⁰-methoxy-

.

phenyl)-pyrazine (11b, 377 mg, 1 mmol) with BF₃SMe₂

(0.23 mL, 20 mmol) in dry dichloromethane (5 mL),

according to the general procedure B, after crystal-

lization with MeOH–acetone, gave the pyrazine 12b

(289 mg, 83%) as a solid. Mp 272–274 ^ꢂC; HPLC purity

HRMS calcdfor

404.2466.

C ₂₆H₃₂N₂O₂, 404.2464, found:

(reversedphase, C18) in two solvents is: MeOH–H O

2

2,5-Bis-isopropyl-3,6-bis-(4⁰-methoxyphenyl)-pyrazine

(11d). The reaction of 2-azido-1-(4⁰-methoxyphenyl)-4-

methylpentan-1-one (10d, 2.47 g, 10 mmol) andPh ₃P

(2.80 g, 12 mmol) in dry THF (20 mL) followed by

hydrolysis, dimerization and oxidation according to the

general procedure F, after ﬂash column chromato-

graphy (15% EtOAc–hexane) over silica gel, gave the

pyrazine 11d (1.7 g, 84%) as a solid. Mp 108–109 ^ꢂC; ¹H

(70:30) 99.3% andCH ₃CN–H₂O (50:50) 99.8%; ¹H

NMR (acetone-d₆, 500 MHz) d 8.61 (2H, s, 2ÂOH),

7.54 (4H, AA⁰XX⁰, J_AX=8.58 and J_AA=1.93 Hz), 6.97

0

(4H, AA⁰XX⁰, J_AX=8.54 and J_AA=1.93 Hz), 2.87 (4H,

0

t, J=7.28 Hz, 2 Â CH₂CH₂CH₃), 1.76 (4H, quint,

J=7.50 and7.28 Hz, 2 Â CH₂CH₂CH₃) and0.87 (6H, t,

J=7.50 Hz, 2 Â CH₂CH₂CH₃); ¹³C NMR (acetone-d₆,

125 MHz) d 158.61, 150.83, 150.78, 131.48, 131.33,

115.85, 37.13, 22.79 and14.27. MS (EI, 70 eV) m/z 348

(M⁺60%), 347 (47%), 320 (100%); HRMS calcdfor

C₂₂H₂₃N₂O₂, 347.1757, found: 347.1757.

NMR (CDCl₃, 500 MHz) d

0

J_AX=8.79 and J_AA=2.14 Hz), 7.02 (4H, AA XX ,

7.56 (4H, AA⁰₀XX₀⁰,

0

J_AX=8.79 and J_AA=2.14 Hz), 3.89 (6H, s, 2 Â OMe),

2.86 (4H, d, J=7.07 Hz, 2 Â CH₂CH(CH₃)₂), 2.19 (2H,

septet, J=6.66 and13.72 Hz, 2 Â CH₂CH(CH₃)₂)) and

0.89 (12H, d, J=6.65 Hz, 2 Â CH₂CH(CH₃)₂); ¹³C

NMR (CDCl₃, 125 MHz) d 159.75, 150.64, 149.93,

130.62, 133.80, 55.33, 42.90, 28.48 and22.29. MS (EI,

70 eV) m/z 404 (M⁺17%), 362 (48%), 84 (100%);

2,5-Bis-butyl-3,6-bis-(4⁰-hydroxyphenyl)-pyrazine (12c).

The reaction of 2,5-bis-butyl-3,6-bis-(4⁰-methoxy-

phenyl)-pyrazine (11c, 90 mg, 0.22 mmol) with

.

BF₃SMe₂(0.48 mL, 4.4 mmol) in dry dichloromethane

(5 mL), according to the general procedure B, after

crystallization with ethyl acetate–hexane, gave the pyr-

azine 12c (67 mg, 81%) as a solid. Mp 242–243 ^ꢂC;

HPLC purity (reversedphase, C18) in two solvents is:

MeOH–H₂O (75:25) 100% andCH ₃CN–H₂O (75:25)

HRMS calcdfor

404.2466.

C ₂₆H₃₂N₂O₂, 404.2464, found:

2,5 - Bis - methyl - 3,6 - bis - (4⁰- methoxyphenyl) - pyrazine

(11e). The reaction of 2-azido-1-(4⁰-methoxyphenyl)-

propan-1-one (10e, 1.0 g, 5 mmol) andPh ₃P (1.6 g,

6 mmol) in dry THF (10 mL) followed by hydrolysis,

dimerization and oxidation according to the general

procedure F, after crystallization of crude, gave the

pyrazine 11e ( 0.61 g, 75%) as a solid. Mp 190–191 ^ꢂC;

¹H NMR (CDCl₃, 500 MHz) d 7.62 (4H, AA₀⁰XX⁰₀,

1

100%; H NMR (acetone-d₆, 500 MHz) d 8.62 (2H, s,

2ÂOH), 7.53 (4H, AA⁰XX⁰, J_AX=8.58 and

0

J_AA=1.93 Hz), 6.96 (4H, AA XX , J_AX=8.58 and

0

J_AA=1.93 Hz), 2.89 (4H, t, J=7.72 Hz, 2 Â CH₂CH₂

CH₂CH₃), 1.75.67 (4H, m, 2 Â CH₂CH₂CH₂CH₃), 1.31

(4H, quint, J=7.50 and14.79 Hz, 2 Â CH₂CH₂CH₃)

and0.84 (6H, t, J=7.50 Hz, 2 Â CH₂CH₂CH₃); ¹³C

NMR (acetone-d₆, 125 MHz) d 158.61, 151.02, 150.76,

131.46, 131.34, 115.84, 34.77, 31.80, 23.16 and14.13.

MS (EI, 70 eV) m/z 376 (M⁺7%), 375 (9%), 334

(100%); HRMS calcdfor C ₂₄H₂₇N₂O₂, 375.2072,

found: 375.2074.

0

J_AX=9.00 and J_AA=2.14 Hz), 7.04 (4H, AA XX ,

0

J_AX=9.00 and J_AA=2.14 Hz), 3.89 (6H, s, 2 Â OMe)

and2.66 (6H, s, 2 Â CH₃); ¹³C NMR (CDCl₃,

125 MHz) d 159.87, 150.18, 147.49, 131.23, 130.39,

113.84, 55.35 and22.79. MS (EI, 70 eV) m/z 320 (M⁺

100%), 319 (81%), 135 (55%); HRMS calcdfor

C₂₀H₁₉N₂O₂, 319.1446, found: 319.1446.

2,5-Bis-isopropyl-3,6-bis-(4⁰-hydroxyphenyl)-pyrazine

(12d). The reaction of 2,5-bis-isopropyl-3,6-bis-(4⁰-

methoxyphenyl)-pyrazine (11d, 405 mg, 1 mmol) ) with

2,5-Bis-ethyl-3,6-bis-(4⁰-hydroxyphenyl)-pyrazine (12a).

The reaction of 2,5-bis-ethyl-3,6-bis-(4⁰-methoxy-

BF₃SMe₂(2.6 mL, 20 mmol) in dry dichloromethane

.

phenyl)-pyrazine (11a, 697 mg, 2 mmol) with BF₃SMe₂

(10 mL), according to the general procedure B, after

crystallization with acetone-hexane gave the pyrazine

12d (321 mg, 85%) as a solid. Mp 277–278 ^ꢂC; HPLC

purity (reversedphase, C18) in two solvents is:

MeOH–H₂O (75:25) 100% andCH ₃CN–H₂O (60:40)

(0.42 mL, 40 mmol) in dry dichloromethane (10 mL),

according to the general procedure B, after crystal-

lization with MeOH–acetone gave the pyrazine 12a

(535 mg, 86%) as a solid. Mp >300 ^ꢂC (dec.); HPLC

purity (reversedphase, C18) in two solvents is: MeOH–

H₂O (70:30) 99.6% andCH ₃CN–H₂O (40:60) 100%; ¹H

NMR (DMSO-d₆, 500 MHz) d 9.78 (2H, s, 2ÂOH), 7.47

1

100%; H NMR (acetone-d₆, 500 MHz) d 8.61 (2H, s, 2

Â

OH), 7.53 (4H, AA⁰X₀X⁰, J_AX=8.58 and

0

J_AA=1.93 Hz), 2.83 (4H, d, J=7.29 Hz,

0

J_AA=1.93 Hz), 6.97 (4H, AA XX , J_AX=8.58 and

(4H, AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 6.89 (4H,

2

Â

0

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 2.84 (4H, q,

CH₂CH(CH₃)₂), 2.19 (2H, septet, J=6.66 and13.51 Hz,

2 Â CH₂CH(CH₃)₂) and0.79 (12H, d, J=6.65 Hz, 2 Â

CH₂CH(CH₃)₂)); ¹³C NMR (acetone-d₆, 125 MHz) d

158.58, 151.14, 150.07, 131.61, 131.43, 115.85, 115.77,

0

J=7.50 Hz, 2 Â CH₂CH₃) and1.19 (6H, t, J=7.50 Hz,

2 Â CH₂CH₃); ¹³C NMR (DMSO-d₆, 125 MHz) d

157.83, 150.76, 149.32, 130.39, 129.14, 115.08, 27.14 and

646

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

43.79, 28.78 and22.66. MS (EI, 70 eV) m/z 376 (M⁺

33%), 375 (31%), 334 (100%); HRMS calcdfor

C₂₄H₂₇N₂O₂, 375.2072, found: 375.2072.

AA⁰XX⁰, J_AX=9.04 Hz and J_AA=2.20 Hz, C-2 aryl H),

0

7.64 and7.04 (4H, AA ⁰XX⁰, J_AX=8.79 Hz and

0

J_AA=2.20 Hz, C-4 aryl H), 7.40.50 (5H, m, phenyl),

3.90 (3H, s) and3.86 (3H, s) [2 ÂOCH₃], 2.82 (2H,

CH₂CH₂CH₃), 1.19 (2H, A₃MM⁰XX⁰, J_MX=7.81 Hz,

2,5-Bis-methyl-3,6-bis-(4⁰-hydroxyphenyl)-pyrazine (12e).

The reaction of 2,5-bis-methyl-3,6-bis-(4⁰-methox-

yphenyl)-pyrazine (11e, 200 mg, 0.62 mmol) ) with

A₃MM⁰XX⁰,

J_XM=7.81 Hz

and

0

J_XX=1.95 Hz,

0

J_AM=7.33 Hz and J_MM=2.20 Hz, CH₂CH₂CH₃) and

0.59 (3H, t, J=7.33 Hz, CH₃); ¹³C NMR (CDCl₃,

100 MHz). d 167.11, 166.58, 161.39, 160.01, 139.88,

132.23, 130.57, 130.28, 129.77, 128.74, 128.58, 128.23,

127.29, 113.66, 113.56, 55.31, 55.27, 30.33, 23.09 and

13.89. MS (EI, 70 eV). m/z 411 (M+1, 29%), 410 (M⁺,

87), 381 (100); HRMS: calcdfor C ₂₇H₂₆N₂O₂: 410.1994,

found: 410.1988. Analysis: for C₂₇H₂₆N₂O₂: calcdC,

79.00; H, 6.38; N, 6.82, foundC, 78.69; H, 6.59; N, 6.97.

.

BF₃SMe₂(1.3 mL, 12.6 mmol) in dry dichloromethane

(10 mL), according to the general procedure B, after

crystallization with acetone–hexane, gave the pyrazine

12e (160 mg, 88%) as a solid. Mp >360 (dec.) ^ꢂC;

HPLC purity (reversedphase, C18) in two solvents is:

MeOH–H₂O (70:30) 99.14% andCH CN–H₂O (60:40)

3

1

100%; H NMR (DMSO-d₆, 500 MHz) d 9.73 (2H, s, 2

Â OH), 7.51 (4H, AA⁰XX⁰, J=8.58 Hz), 6.87 (4H,

AA⁰XX⁰, J=8.58 Hz) and2.54 (6H, s, 2 Â CH₃); ¹³C

NMR (DMSO-d₆, 125 MHz) d 157.82, 149.24, 146.63,

130.49, 129.03, 115.01 and22.67. MS (EI, 70 eV) m/z

292 (M⁺97%), 291 (100%), 91 (24%); HRMS calcdfor

C₁₈H₁₆N₂O₂, 292.1212, found: 292.1211.

5 - Ethyl - 2,4,6 - tri - (4⁰- methoxyphenyl)pyrimidine (15c).

The reaction of 4⁰-methoxy-butyrophenone (13c, which

is the same compoundas 8a) (178 mg, 1 mmol) with

anisonitrile (14) (293 mg, 2.2 mmol) andTf O (310 mg,

2

1.1 mmol), according to the general procedure G, furn-

ished the corresponding pyrimidine 15c (300 mg, 73%)

General procedure G: synthesis of pyrimidines from vinyl

triﬂates. Triﬂic anhydride (1.1 mmol) was added drop-

wise over 10 min at RT under nitrogen atmosphere to a

stirredsolution of the ketone (1 mmol) andanisonitrile

(14, 2.2 mmol) in dry 1,2-dichloroethane (5 mL). The

as a solidwhich was contaminatedwith

unreactedanisonitrile. A portion of the sample was then

recrystallizedusing hexane–CH ₂Cl₂as solvent. Mp

ꢃ10% of

ꢂ

1

147 C; H NMR (CDCl₃, 500 MHz). d 8.49 and6.96

0

reaction mixture was stirredfor 24 h, andsatdNaHCO

(4H, AA⁰XX⁰, J_AX=8.95 Hz and J_AA=1.95 Hz, C-2

3

0

solution (5 mL) was added. The organic phase was

washedwith brine (5 mL) andrdiedover anhyd

Na₂SO₄. Solvent was removedunder vacuum andthe

product puriﬁed by ﬂash column chromatography over

silica gel using hexane–ethyl acetate.

aryl H), 7.63 and7.03 (8H, AA XX⁰, J_AX=8.66 Hz, C-4

andC-6 aryl H), 3.89 (6H, s) and3.86 (3H, s) [3 ÂOCH₃],

2.89 (2H, q, J=7.55Hz, CH₂) and0.79 (3H, t, J=7.55Hz,

CH₃); ¹³C NMR (CDCl₃, 125 MHz). d 166.47, 161.41,

160.81, 132.30, 130.70, 130.27, 129.97, 113.70, 113.58,

55.32, 55.28, 21.67 and14.37. MS (EI, 70 eV). m/z 427

(M+1, 5%), 426 (M⁺, 19), 133 (100); HRMS: calcdfor

C₂₇H₂₆N₂O₃: 426.1943, found: 426.1940.

2,4-Di-(4⁰-methoxyphenyl)-5-ethyl-6-phenylpyrimidine

(15a). The reaction of butyro-phenone (13a) (148 mg,

1 mmol) with anisonitrile (14) (293 mg, 2.2 mmol) and

Tf₂O (310 mg, 1.1 mmol), according to the general pro-

cedure G, furnished the corresponding pyrimidine 15a

(300 mg, 78%) as white solidwhich as recrystallized

5-n-Propyl-2,4,6-tri-(4⁰-methoxyphenyl)pyrimidine (15d).

The reaction of 4⁰-methoxy-valerophenone (13d, which

is the same compoundas 8b) (192 mg, 1 mmol) with

anisonitrile (14) (293 mg, 2.2 mmol) andTf O (310 mg,

2

1.1 mmol), according to the general procedure G, furn-

ished the corresponding pyrimidine 15d (306 mg, 72%)

using hexane–CH₂Cl₂as solvent. Mp 132 ^ꢂC; H NMR

1

(CDCl₃, 500 MHz). d 8.48 and6.95 (4H, AA ⁰XX⁰,

0

J_AX=8.96 Hz and J_AA=2.02 Hz, C-2 aryl H), 7.63 and

0

7.03 (4H, AA⁰XX⁰, J_AX=8.78 Hz and J_AA=2.02 Hz, C-

as a solidwhich was contaminatedwith

unreactedanisonitrile. A portion of the sample was then

recrystallizedusing hexane–CH ₂Cl₂as solvent. Mp

ꢃ10% of

4 aryl H), 7.45.55 (5H, m, phenyl), 3.89 (3H, s) and3.86

(3H, s) [2ÂOCH₃], 2.85 (2H, q, J=7.50 Hz, CH₂) and

0.78 (3H, t, J=7.50 Hz, CH₃); ¹³C NMR (CDCl₃,

125 MHz). d 166.91, 166.38, 161.38, 160.79, 159.99,

139.75, 132.04, 130.54, 130.17, 129.72, 128.69, 128.62,

128.53, 128.19, 113.62, 113.51, 55.19, 55.14, 21.49 and

14.35. MS (EI, 70 eV). m/z 397 (M+1, 19%), 396 (M⁺,

ꢂ

1

135 C; H NMR (CDCl₃, 400 MHz). d 8.49 and6.95

(4H, AA⁰XX⁰, J_AX=9.03 Hz and J_AA=1.95 Hz, C-2

0

aryl H), 7.62 and7.03 (8H, AA XX⁰, J_AX=8.79 Hz and

0

J_AA=1.95 Hz, C-2 andC-4 aryl H), 3.90 (6H, s) and

3.86 (3H, s) [3ÂOCH₃], 2.84 (2H, A₃MM⁰XX⁰,

0

74), 395 (100); HRMS: calcdfor

C

₂₆H₂₄N₂O₂:

J_XM=7.81Hz and J_XX=1.95 Hz, CH₂CH₂CH₃), 1.16

396.1838, found: 396.1832. Analysis: for C₂₆H₂₄N₂O₂:

calcdC, 78.76; H, 6.10; N, 7.07, foundC, 78.37; H,

6.11; N, 6.74.

(2H, A₃MM⁰XX⁰, J_MX=7.81 Hz, J_AM=7.57Hz and

0

J_MM=2.20 Hz, CH₂CH₂CH₃) and0.59 (3H, t,

J=7.57Hz, CH₃); ¹³C NMR (CDCl₃, 125MHz). d

166.51, 162.99, 162.71, 161.29, 159.91, 133.86, 132.29,

130.59, 130.23, 129.65, 127.10, 114.63, 113.73, 113.58,

55.41, 55.24, 55.20, 30.29, 22.92 and13.84. MS (EI, 70eV).

m/z 441 (M+1, 16%), 440 (M⁺, 58), 369 (100). HRMS:

calcdfor C ₂₈H₂₈N₂O₃: 440.2099, found: 440.2094.

2,4-Di-(4⁰-methoxyphenyl)-6-phenyl-5-n-propylpyrimidine

(15b). The reaction of valero-phenone (13b) (162 mg,

1 mmol) with anisonitrile (14) (293 mg, 2.2 mmol) and

Tf₂O (310 mg, 1.1 mmol), according to the general pro-

cedure G, furnished the corresponding pyrimidine 15b

(400 mg, quantitative) as white solidwhich as recrys-

5-Ethyl-2,6-bis-(4⁰-methoxyphenyl)-4-methylpyrimidine

(15e). The reaction of 2-pentanone (172.26 mg, 2 mmol)

with anisonitrile (14, 585 mg, 4.4 mmol) andTf ₂O

ꢂ

1

tallizedusing hexane–CH Cl₂as solvent. Mp 128 ; H

2

NMR (CDCl₃, 400 MHz). d 8.51 and6.97 (4H,

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

647

(620 mg, 2.2 mmol), according to the general procedure

G, gave the corresponding pyrimidine (15e) after ﬂash

column chromatography (15% EtOAc–hexane) over

silica gel. Residual anisonitrile was removed by distilla-

tion, andcrystallization of the remainder from ethanol

2,4-Di-(4⁰-hydroxyphenyl)-6-phenyl-5-n-propylpyrimidine

(16b). Deprotection of the pyrimidine 15b (100 mg,

.

0.25 mmol) using BF₃SMe₂(490 mg, 3.77 mmol),

according to the general procedure B, furnishedthe

phenolic pyrimidine 16b (88 mg, 95%). Mp 189 ^ꢂC; H

1

ꢂ

1

gave 15e (220 mg, 33%) as a solid. Mp 114–115 C, H

NMR (CDCl₃, 500 MHz)

NMR (CDCl₃+(CD₃)₂CO, 400 MHz). d 8.28 and6.78

8.43 (2H, AA⁰₀XX₀⁰,

(4H, AA⁰XX⁰, J_AX=8.79 Hz and J_AA=1.95 Hz, C-2

0

d

0

J_AX=9.00 and J_AA=2.00 Hz), 7.53 (2H, AA₀XX₀,

aryl H), 8.07 (1H, br s) and7.97 (1H, br s) [2 ÂOH], 7.49

(2H, dd, J=8.06 and1.71 Hz) and7.30.40 (3H, m)

[phenyl], 7.43 and6.86 (4H, AA ⁰XX⁰, J_AX=8.55 Hz and

0

J_AX=9.00 and J_AA=2.00 Hz), 7.01 (2H, AA₀XX₀,

0

J_AX=9.00 and J_AA=2.00 Hz), 6.96 (2H, AA XX ,

0

J_AX=9.00 and J_AA=2.00 Hz), 3.88 (3H, s, OMe), 3.86

0

J_AA=1.95 Hz, C-4 aryl H), 2.69 (2H, A₃MM XX ,

0

(3H, s, OMe), 2.72 (2H, q, J=7.50 Hz, CH₂CH₃), 2.67

(3H, s, CH₃) and1.14 (3H, t, J=7.50 Hz, CH₂CH₃);

¹³C NMR (CDCl₃, 125 MHz) d 166.23, 164.99, 161.41,

160.93, 160.07, 132.07, 130.93, 130.26, 129.68,129.35,

113.73, 113.71, 55.42, 55.38, 22.47, 21.68 and14.24.

MS (EI, 70 eV) m/z 334 (M⁺, 68%), 333 (100%);

J_XM=7.81 Hz and J_XX=1.95 Hz, CH₂CH₂CH₃), 1.03

(2H, A₃MM⁰XX⁰, J_MX=7.81 Hz, J_AM=7.57 Hz and

J_MM=2.44 Hz, CH₂CH₂CH₃) and0.45 (3H, t,

0

J=7.57 Hz, CH₃); ¹³C NMR (CDCl₃+(CD₃)₂CO,

100 MHz). d 166.75, 166.63, 160.61, 158.68, 157.28,

139.69, 131.07, 130.14, 129.63, 129.51, 128.51, 127.93,

126.82, 114.97, 30.07, 22.77 and13.57. MS (EI, 70 eV).

m/z 383 (M+1, 20%), 382 (M⁺, 75), 353 (100). HRMS:

calcdfor C ₂₅H₂₂N₂O₂: 382.1681, found: 382.1674.

Analysis: for C₂₅H₂₂N₂O₂₊0.4 EtOAc: calcdC, 76.49;

H, 6.08; N, 6.74, foundC, 76.18; H, 5.58; N, 6.71.

HRMS calcdfor

334.1671.

C ₂₁H₂₂N₂O₂, 334.1681, found:

2,6-Bis-(4⁰-methoxyphenyl)-4-methyl-5-propylpyrimidine

(15f). The reaction of 2-hexanone (200 mg, 2 mmol)

with anisonitrile (14, 585 mg, 4.4 mmol) andTf ₂O

(620 mg, 2.2 mmol), according to the general procedure

G, gave the corresponding pyrimidine (15f) after ﬂash

column chromatography (15% EtOAc–hexane) over

silica gel. Residual anisonitrile was removed by distilla-

tion, andcrystallization of the remainder from ethanol

5 - Ethyl - 2,4,6 - tri - (4⁰- hydroxyphenyl)pyrimidine (16c).

Deprotection of the pyrimidine 15c (165 mg, 0.4 mmol)

.

using BF₃SMe₂(1.4 g, 11.41 mmol), according to the

general procedure B, furnishedthe phenolic pyrimidine

16c (145 mg, 97%). Mp 276 ^ꢂC; ¹H NMR

(CDCl₃+(CD₃)₂CO, 400 MHz). d 8.13 and6.63 (4H,

A₂X₂, J=8.54 Hz, C-2 aryl H), 8.10 (2H, s) and8.04

ꢂ

1

gave 15f (238 mg, 34%) as a solid. Mp 89–90 C, H

NMR (CDCl₃, 500 MHz)

d

8.42 (2H, AA⁰₀XX₀⁰,

0

J_AX=9.00 and J_AA=2.00 Hz), 7.52 (2H, AA₀XX₀,

(1H, s) [3ÂOH], 7.27 and6.71 (8H, A X₂, J=8.54 Hz,

2

0

J_AX=9.00 and J_AA=2.00 Hz), 7.00 (2H, AA₀XX₀,

C-4 andC-6 aryl H), 2.65 (2H, q, J=7.33 Hz, CH₂) and

0.50 (3H, t, J=7.33 Hz, CH₃); ¹³C NMR

(CDCl₃+(CD₃)₂CO, 100 MHz). d 166.3, 160.54, 158.53,

157.18, 131.24, 130.57, 130.14, 129.64, 128.23, 115.26,

114.99, 21.47 and14.08. MS (EI, 70 eV). m/z 385

(M+1, 15%), 384 (M⁺, 62), 383 (100); HRMS: calcd

for C₂₄H₂₀N₂O₃: 384.1474, found: 384.1477.

0

J_AX=9.00 and J_AA=2.00 Hz), 6.95 (2H, AA XX ,

0

J_AX=9.00 and J_AA=2.00 Hz), 3.88 (3H, s, OMe),

3.86 (3H, s, OMe), 2.69.65 (2H, m, CH₂CH₂), 2.64

(3H, s, CH₃), 1.53.45 (2H, m, CH₂CH₃) and0.88

(3H, t, J=7.50 Hz, CH₂CH₃); ¹³C NMR (CDCl₃,

125 MHz) d 166.29, 165.22, 161.45, 160.85, 160.05,

132.17, 130.87, 130.33, 129.68,129.72, 128.09, 113.75,

113.71, 55.43, 55.39, 30.60, 23.19 and14.29. MS (EI,

70 eV) m/z 348 (M⁺, 100%), 333 (38%), 319 (98%);

5-n-Propyl-2,4,6-tri-(4⁰-hydroxyphenyl)pyrimidine (16d).

Deprotection of the pyrimidine 15d (60 mg, 0.14 mmol)

.

using BF₃SMe₂(486 mg, 3.74 mmol), according to the

general procedure B, furnishedthe phenolic pyrimidine

16d (45 mg, 84%). Mp 264 ^ꢂC; ¹H NMR

(CDCl₃+(CD₃)₂CO, 400 MHz). d 8.29 and6.78 (4H,

A₂X₂, J=8.55 Hz, C-2 aryl H), 7.99 (2H, s) and7.90

HRMS calcdfor

348.1840.

C

₂₂H₂₄N₂O₂, 348.1838, found:

2,4-Di-(4⁰-hydroxyphenyl)-5-ethyl-6-phenylpyrimidine

(16a). Deprotection of the pyrimidine 15a (125 mg,

.

0.33 mmol) using BF₃SMe₂(640 mg, 4.89 mmol),

(1H, s) [3ÂOH], 7.42 and6.86 (8H, A X₂, J=8.18 Hz,

2

according to the general procedure B, furnish_ꢂedthe

C-4 andC-6 aryl H), 2.73 (2H, t, J=8.06 Hz, Ar–CH₂),

1.03 (2H, A₃MM⁰XX⁰, J_AM=7.08 Hz, J_MX=7.81 Hz,

CH₂CH₃) and0.45 (3H, t, J=7.33 Hz, CH₃); ¹³C NMR

((CD₃)₂CO, 125 MHz). d 167.69, 161.33, 160.47, 158.94,

132.34, 131.69, 131.36, 130.63, 130.47, 127.67, 115.93,

115.83, 31.24, 23.42 and14.12. MS (EI, 70 eV). m/z 399

(M+1, 25%), 398 (M⁺, 27), 369 (100); HRMS: calcd

for C₂₅H₂₂N₂O₃: 398.1630, found: 398.1639. Analysis:

for C₂₅H₂₂N₂O₃+ 0.4 EtOAc+0.3 CH₂Cl₂: calcdC,

70.36; H, 5.66; N, 6.10, foundC, 70.62; H, 5.25; N, 6.10.

1

phenolic pyrimidine 16a (110 mg, 95%). Mp 197 C; H

NMR ((CD₃)₂CO, 400 MHz). d 8.19 and6.70 (4H,

AA⁰XX⁰, J_AX=8.54 Hz and J_AA=1.46 Hz, C-2 aryl H),

0

8.10 (2H, br s, 2ÂOH), 7.41 (2H, dd, J=8.06 and

1.46 Hz) and7.20.30 (3H, m) [phenyl], 7.35 and6.78

0

(4H, AA⁰XX⁰, J_AX=8.55 Hz and J_AA=1.46 Hz, C-4

aryl H), 2.65 (2H, q, J=7.33 Hz, CH₂) and0.57 (3H, t,

J=7.32 Hz, CH₃); ¹³C NMR (CDCl₃, 125 MHz). d

166.54, 166.30, 160.58, 158.63, 157.23, 139.47, 130.79,

129.98, 129.53, 129.40, 128.33, 128.22, 128.19, 127.86,

114.89, 21.21 and13.99. MS (EI, 70 eV). m/z 369

(M+1, 17%), 368 (M⁺, 71), 367 (100); HRMS: calcd

for C₂₄H₂₀N₂O₂: 368.1525, found: 368.1516. Analysis:

for C₂₄H₂₀N₂O₂₊0.2 EtOAc: calcdC, 77.16; H, 5.64; N,

7.26, foundC, 77.10; H, 5.55; N, 7.11.

5-Ethyl-2,6-bis-(4⁰-hydroxyphenyl)-4-methylpyrimidine

(16e). The reaction of 5-ethyl-2,6-bis-(4⁰-methoxy-

phenyl)-4-methylpyrimidine (15e, 90 mg, 0.27 mmol)

with BF₃SMe₂(0.56 mL, 5.4 mmol) in dry dichloro-

methane (10 mL), according to the general procedure B,

.

648

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

after ﬂash column chromatography (45% EtOAc–hex-

ane) over silica gel, gave the pyrimidine 16e (78 mg,

94%) as a solid. HPLC purity (reversed phase, C18) in

two solvents is: MeOH–H₂O (70:30) 99.8% and

compound(5.4 g, 82%) as an oil. ¹H NMR (CDCl₃,

400 MHz) d 7.32.28 (3H, m, Ph), 7.25.24 (2H, m, Ph),

3.77 (2H, s, CH₂Ph), 3.60 (3H, s, OCH₃) and3.19 (3H,

s, CH₃); MS (EI, 70 eV) m/z 179 (M⁺, 8%), 118 (33%),

91 (100%).

CH₃CN–H₂O (40:60) 100%. Mp 160–161 ^ꢂC; H NMR

1

(acetone-d₆, 500 MHz) d 8.66 (2H, s, OH), 8.35 (2H,

AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 7.47 (2H,

N-Methoxy-N-methyl-4⁰-methoxyphenylacetamide. Pyri-

dine (20.0 mL, 0.25 mol) was added dropwise to a stirred

solution of 4-methoxyphenylacetyl chloride (20.0 g,

0.11 mol) and N-methoxy-N-methyl ammonium chlor-

ide (13.0 g, 0.13 mol) in CH₂Cl₂(150 mL), according to

the general procedure H. Solvent removal gave the title

compound(23.0 g, 100%) as an oil. ¹H NMR (CDCl₃,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 6.96 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 6.91 (2H,

0

AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 2.75 (2H, q,

0

J=7.50 Hz, CH₂CH₃), 2.60 (3H, s, CH₃) and1.13 (3H,

t, J=7.50 Hz, CH₂CH₃); ¹³C NMR (acetone-d₆,

125 MHz) d 166.80, 165.92, 161.35, 160.35, 158.83,

131.87, 131.11, 130.68, 130.38, 129.86, 115.88, 115.75,

22.51, 22.07 and14.31. MS (EI, 70 eV) m/z 306 (M⁺,

59%), 305 (100%); HRMS calcdfor C ₁₉H₁₈N₂O₂,

306.1368, found: 306.1368.

500 MHz)

0

d

7.24 (2H, AA⁰XX⁰, J_AX=9.00 and

J_AA=2.00 Hz), 6.88 (2H, AA XX , J_AX=9.00 and

0

J_AA=2.00 Hz), 3.83 (3H, s, OMe), 3.82 (2H, s, CH₂),

0

3.65 (3H, s, OCH₃) and3.22 (3H, s, CH ); ¹³C NMR

3

(CDCl₃, 125 MHz) d 130.34, 113.96, 161.33, 55.26 and

38.46. MS (EI, 70 eV) m/z 209 (M⁺, 10%), 148 (20%),

121 (100%).

2,6-Bis-(4⁰-hydroxyphenyl)-4-methyl-5-propylpyrimidine

(16f). The reaction of 2,6-bis-(4⁰-methoxyphenyl)-

4-methyl-5-propylpyrimidine (15f, 70 mg, 0.20 mmol)

.

with BF₃SMe₂(0.42 mL, 4.0 mmol) in dry dichloro-

General procedure I: preparation of 1-aryl-alkan-2-ones

(17a–e)

methane (5 mL), according to the general procedure B,

after careful ﬂash column chromatography (45%

EtOAc–hexane) over silica gel, gave the pyrimidine 16f

(58 mg, 91%) as a solid. HPLC purity (reversed phase,

C18) in two solvents is: MeOH–H₂O (70:30) 98.9% and

CH₃CN–H₂O (40:60) 99.4%. Mp 110–111 ^ꢂC, ¹H NMR

(acetone-d₆, 500 MHz) d 8.63 (2H, s, OH), 8.32 (2H,

Grignard’s reagent (1.2 mol) was added dropwise at 0 ^ꢂC

to a stirredsolution of N-methoxy-N-methyl-arylamide

(1 mol) in THF (8 mL). After the addition, the reaction

was stirredfor 3 h, andfor 1 h at rt, andthen poured

over cooled6 N HCl andextractedwith diethyl ether.

The organic phase was washedwith brine anddried

over anhydNa SO₄. Solvent removal andﬂash column

2

chromatography (EtOAc–hexane) over silica gel gave

corresponding ketone as an oil.

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 7.42 (2H,

0

AA⁰XX⁰, J_AX=8.58 and J_AA=2.14 Hz), 6.92 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 6.86 (2H,

0

AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 2.69.65 (2H,

0

m, CH₂CH₂), 2.55 (3H, s, CH₃), 1.50.45 (2H, m,

CH₂CH₃) and0.88 (3H, t, J=7.20 Hz, CH₂CH₃); ¹³C

NMR (acetone-d₆, 125 MHz) d 166.95, 166.09, 161.32,

160.34, 158.76, 131.95, 131.14, 130.65, 130.36, 128.52,

115.87, 115.73, 31.05, 23.61, 22.66 and14.39. MS (EI,

70 eV) m/z 320 (M⁺, 59%), 319 (32%), 291 (100%);

1-Phenyl-pentan-2-one (17a). n-PrMgBr (30 mL,

0.038 mol, preparedfrom C H₇Br andMg in ether) was

3

added dropwise to a stirred solution of N-methoxy-N-

methyl-phenylacetamide (5.0 g, 0.027 mol) in THF

(30 mL) at 0 ^ꢂC, according to the general procedure I.

Flash column chromatography (10% EtOAc–hexane),

over silica gel, gave ketone 17a (2.88 g, 64%) as an oil.

¹H NMR (CDCl₃, 400 MHz) d 7.34.19 (5H, m, Ph), 3.67

(2H, s, CH₂Ph), 2.42 (2H, t, J=7.33 Hz, CH₂CH₂), 1.58

(2H, quint, J=7.33 and7.57 Hz, CH ₂CH₂CH₃) and

0.86 (3H, t, J=7.57 Hz, CH₃); ¹³C NMR (CDCl₃,

100 MHz) d 208.68, 134.61, 129.63, 128.91, 127.17,

50.39, 44.12, 17.39 and13.85. MS (EI, 70 eV) m/z 162

(M⁺, 16%), 91 (47%), 71 (100%).

HRMS calcdfor

320.1522.

C ₂₀H₂₀N₂O₂, 320.1524, found:

General procedure H: preparation of N-methoxy-N-

methylacetamide

Pyridine (2.2 mol) was added dropwise at 0 ^ꢂC to a stir-

redsolution of acidchloride (1 mol) and N-methoxy-N-

methylammonium chloride (1.2 mol) in CH₂Cl₂

(10 mL). After the addition of pyridine, the reaction was

stirred at rt for 1 h, then water (5 mL) was added. The

organic phase was washedwith 2 N HCl (5 mL) fol-

1-(4⁰-Methoxyphenyl)-butan-2-one (17b). EtMgBr (3M)

(40.0 mL, 0.12 mol) was added dropwise to a stirred

solution of N-methoxy-N-methyl-4⁰-methoxyphenyl-

acetamide (20.9 g, 0.10 mol) in THF (80 mL) at 0 ^ꢂC,

according to the general procedure I. Flash column

chromatography (10% EtOAc–hexane) over silica gel

gave 17b (14.5 g, 81%) as an oil. ¹H NMR (CDCl₃,

lowedby satdNaHCO

over anhydNa SO₄. Solvent removal gave the corre-

soln andbrine, at 0 ^ꢂC dried

3

2

sponding amides.

N - Methoxy - N - methyl - phenylacetamide. Pyridine

(7.0 mL, 0.08 mol) was added dropwise to a stirred

solution of phenylacetyl chloride [prepared from phenyl-

acetic acidandoxalyl chloride (5.72 g, 0.037 mol)] and

400 MHz)

0

d

7.12 (2H, AA⁰XX⁰, J_AX=8.79 and

J_AA=2.00 Hz), 6.85 (2H, AA XX , J_AX=8.79 and

0

J_AA=2.00 Hz), 3.79 (3H, s, OMe), 3.61 (2H, s, CH₂Ar),

0

N-methoxy-N-methylammonium

chloride

(4.0 g,

2.45 (2H, q, J=7.2 Hz, CH₂) and1.02 (3H, t, J=7.2 Hz,

CH₃); ¹³C NMR (CDCl₃, 100 MHz) d 130.44, 126.58,

114.17, 55.32, 48.98, 35.09 and7.86. MS (EI, 70 eV) m/z

178 (M⁺, 10%), 135 (5%), 121 (100%).

0.041 mol) in CH₂Cl₂(50 mL), according to the general

procedure H. Solvent removal and ﬂash column

chromatography with 15% EtOAc/hexane gave the title

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

649

1-(4⁰-Methoxyphenyl)-pentan-2-one (17c or 22b).

n-PrMgBr (30 mL, 0.038 mol, preparedfrom C ₃H₇Br

and Mg in ether) was added dropwise to a stirred solu-

pyrimidine (19b). The reaction of 1-phenylpentan-2-one

(3b) (324 mg, 2 mmol) with anisonitrile (14, 585 mg,

4.4 mmol) andTf O (620 mg, 2.2 mmol), according to

2

tion

of

N-methoxy-N-methyl-4⁰-methoxyphenyl-

the general procedure G, gave the corresponding pyri-

midines 18b and 19b in aꢃ1:1 ratio. Careful ﬂash col-

umn chromatography (15% EtOAc–hexane) over silica

gel andcrystallization from ethanol gave the ﬁrst

requiredisomeric pyrimidine ( 18b) (280 mg, 34%), fol-

lowedby the pyrimidine ( 19b) (260 mg, 32%, as solids.

2,6-Bis-(4⁰-methoxyphenyl)-5-phenyl-4-propylpyrimidine

acetamide (6.0 g, 0.028 mol) in THF (30 mL) at 0 ^ꢂC,

according to the general procedure I. Flash column

chromatography (10% EtOAc–hexane) over silica gel

gave 17c (3.8 g, 71%) as an oil. ¹H NMR (CDCl₃,

400 MHz)

0

d

7.12 (2H, AA⁰XX⁰, J_AX=8.79 and

J_AA=1.95 Hz), 6.87 (2H, AA XX , J_AX=8.79 and

0

(18b). Mp 107–108 ^ꢂC; H NMR (CDCl₃, 500 MHz) d

1

0

J_AA=1.95 Hz), 3.81 (3H, s, OMe), 3.63 (2H, s, CH₂Ar),

8.56 (2H, AA⁰XX⁰, J_AX=8.79 and J_AA=1.95 Hz),

0

2.43 (2H, q, J=7.33 Hz, CH₂CH₂), 1.57 (2H, quint,

J=7.33 and7.57 Hz, CH ₂CH₂CH₃) and0.88 (3H, t,

J=7.57 Hz, CH₃and1.02 (3H, t, J=7.2 Hz, CH₃); ¹³C

NMR (CDCl₃, 100 MHz) d 208.91, 158.53, 130.35,

126.37, 114.04, 55.21, 49.20, 43.68,17.15 and13.61. MS

(EI, 70 eV) m/z 192 (M⁺, 15%), 135 (55%), 121 (100%).

7.40.30 (5H, m, Ph), 7.15 (2H, AA⁰XX⁰, J_AX=9.00 and

0

J_AA=1.95 Hz), 6.72 (2H, AA XX , J_AX=8.79 and

0

J_AA=1.95 Hz), 7.00 (2H, AA₀XX₀, J_AX=9.00 and

0

J_AA=1.95 Hz), 3.89 (3H, s, OMe), 3.76 (3H, s, OMe),

2.64 (2H, t, J=7.57 Hz, CH₂CH₂CH₃), 1.77 (2H, quint,

J=7.57 Hz, CH₂CH₂CH₃and0.89 (3H, t, J=7.39 Hz,

CH₂CH₂CH₃); ¹³C NMR (CDCl₃, 125 MHz) d 168.95,

162.71, 162.19, 161.54, 159.89, 137.39, 131.53, 131.29,

130.98, 130.30, 129.82, 128.85, 128.50, 127.31, 113.66,

113.06, 55.29, 55.11, 37.33, 21.88 and14.02. MS (EI,

70 eV) m/z 410 (M⁺,38%), 409 (33%), 381(100%);

4-Ethyl-2,6-bis-(4⁰-methoxyphenyl)-5-phenylpyrimidine

(18a) and 4-benzyl-2,6-bis-(4⁰methoxyphenyl)-5-methyl-

pyrimidine (19a). The reaction of 1-phenylbutan-2-one

(17a) (148 mg, 1 mmol) with anisonitrile (14, 293 mg,

2.2 mmol) andTf O (310 mg, 1.1 mmol), according to

2

the general procedure G, gave the corresponding pyri-

midines 18a and 19a in the ratio of ꢃ1:1. Careful ﬂash

column chromatography (15% EtOAc–hexane) over

silica gel andcrystallization from ethanol gave the ﬁrst

requiredpyrimidine ( 18a) 148 mg, 37%), followedby

the isomeric pyrimidine (19a) 156 mg, 39%), as solids. 4-

Ethyl-2,6-bis-(4⁰-methoxyphenyl)-5-phenylpyrimidine

HRMS calcdfor C ₂₇H₂₅N₂O₂, 409.1915, found:

409.1910. Analysis for C₂₇H₂₆N₂O₂, calcdC,78.99; H,

6.39; N, 6.83, foundC, 78.86; H, 6.32; N, 6.93. 4-Ben-

zyl-5-ethyl-2,6-bis-(4⁰methoxyphenyl)-pyrimidine (19b).

Mp 102–103 ^ꢂC; ¹H NMR (CDCl₃, 500 MHz) d 8.44

(2H, AA⁰XX⁰, J_AX=8.82 and J_AA=1.95 Hz), 7.53 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=1.95 Hz), 7.40.22 (5H,

0

(18a). Mp 130–131 ^ꢂC; H NMR (CDCl₃, 500 MHz) d

m, Ar), 7.00.93 (4H, m, Ar), 4.28 (2H, s, CH₂Ph), 3.87

(3H, s, OMe), 3.86 (3H, s, OMe), 2.73 (2H, q, J=7.57 Hz,

CH₂CH₃) and1.02 (3H, t, J=7.57 Hz); ¹³C NMR

(CDCl₃, 125 MHz) d 167.21, 166.02, 161.39, 160.93,

159.96, 138.59, 132.05, 130.86, 130.09, 129.69, 129.39,

128.97, 128.44, 126.41, 113.64, 55.32, 55.31, 41.38, 21.10

and14.69. MS (EI, 70 eV) m/z 410 (M⁺,73%), 409

(100%); HRMS calcdfor C ₂₇H₂₅N₂O₂, 409.1915, found:

409.1908. Analysis for C₂₇H₂₆N₂O₄, calcdC,78.99; H,

6.39; N, 6.83, foundC,78.46; H, 6.16; N, 6.80.

1

8.57 (2H, AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 7.39

0

(2H, AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 7.38.31

0

(3H, m), 7.16 (2H, AA⁰XX⁰, J_AX=9.00 and

0

J_AA=2.14 Hz), 6.73 (2H, AA XX , J_AX=9.00 and

0

J_AA=2.14 Hz), 7.02 (2H, AA₀XX₀, J_AX=9.00 and

0

J_AA=2.14 Hz), 3.89 (3H, s, OMe), 3.76 (3H, s, OMe),

2.70 (2H, q, J=7.50 Hz, CH₂CH₃) and1.24 (3H, t,

J=7.50 Hz, CH₂CH₃); ¹³C NMR (CDCl₃, 125 MHz) d

170.00, 162.63, 162.32, 161.55, 159.92, 137.36, 131.55,

131.24, 130.96, 130.23, 129.83, 128.57, 128.53, 127.35,

113.67, 113.67, 113.08, 55.32, 55.14, 28.83 and12.85.

MS (EI, 70 eV) m/z 396 (M⁺, 52%), 395 (100%);

4-(4⁰-Methoxybenzyl)-2,6-di-(4⁰-methoxyphenyl)-5-me-

thylpyrimidine

(19c).

The

reaction

(17c) (210 mg,

of

HRMS calcdfor C ₂₆H₂₃N₂O_2,395.1759, found:

395.1760. Analysis for C₂₆H₂₄N₂O₂, calcdC,78.75; H,

1-(4⁰methoxyphenyl)butan-2-one

1.18 mmol) with anisonitrile (14) (346 mg, 2.59 mmol)

6.10; N, 7.07, foundC,78.56; H, 6.06; N, 7.10. 4-Benzyl-

2,6-bis-(4⁰methoxyphenyl)-5-methylpyrimidine

andTf O (366 mg, 1.3 mmol), according to the general

2

(19a).

Mp 127–128 ^ꢂC; ¹H NMR (CDCl₃, 500 MHz) d 8.51

procedure G, furnished the corresponding pyrimidines

18c and 19c (21%). Column chromatography over silica

gel furnishedﬁrst the requiredisomer, 18c in only trace

amounts (andvery much contaminatedwith the

unreactedanisonitrile ( 14), followedby the isomer, the

benzyl pyrimidine 19c (105 mg, 21%) as a solid. Mp

(2H, AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 7.62 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 7.37.31 (4H,

0

m), 7.26.24 (1H, m), 7.01 (4H, AA⁰XX⁰, J_AX=9.00, 8.79

0

and J_AA=2.14 Hz), 4.28 (2H, s, CH₂Ph), 3.90 (3H, s,

OMe), 3.89 (3H, s, OMe) and2.32 (3H, s, CH ); ¹³C

218 ^ꢂC; H NMR (CDCl₃, 500 MHz). d 8.49 and6.99

1

3

NMR (CDCl₃, 125 MHz) d 167.69, 165.25, 161.36,

160.95, 160.16, 137.89, 131.56, 130.86, 129.62, 128.94,

128.49, 126.42, 122.97, 113.64, 113.53, 55.33, 55.31,

42.36 and15.36. MS (EI, 70 eV) m/z 396 (M⁺, 57%), 395

(100%); HRMS calcdfor C ₂₆H₂₃N₂O₂, 395.1759, found:

395.1763; Analysis for C₂₆H₂₄N₂O₄, calcdC,78.75; H,

6.10; N, 7.07, foundC,78.61; H, 6.05; N, 7.18.

(4H, A₂X₂, J_AX=8.48 Hz, C-2 aryl H), 7.59 and6.99

(4H, A₂X₂, J_AX=8.11 Hz, C-6 aryl H), 7.27 and6.85

(4H, A₂X₂, J_AX=8.11 Hz, C-4 aryl H), 4.20 (2H, s,

CH₂Ar), 3.87 (6H, s) and3.78 (3H, s) [3 ÂOCH₃] and

2.30 (3H, s, CH₃); ¹³C NMR (CDCl₃, 100 MHz). d

167.96, 165.13, 161.28, 160.84, 160.08, 158.12, 131.51,

130.80, 130.64, 129.84, 129.55, 113.81, 113.58, 113.45,

55.27, 55.17, 41.43 and15.31. MS (EI, 70 eV). m/z 427

(M+1, 4%), 426 (M⁺, 13), 133 (100); HRMS: calcdfor

C₂₇H₂₆N₂O₃: 426.1943, found: 426.1939.

2,6-Bis-(4⁰-methoxyphenyl)-5-phenyl-4-propylpyrimidine

(18b) and 4-benzyl-5-ethyl-2,6-bis-(4⁰methoxyphenyl)-

650

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

4,5 - Bis - ethyl - 2,6 - bis - (4⁰- methoxyphenyl) - pyrimidine

(18d) and 2,6-bis-(4⁰-methoxyphenyl)-5-methyl-4-propyl-

pyrimidine (19d). The reaction of 3-hexanone (200 mg,

2 mmol) with anisonitrile (14, 585 mg, 4.4 mmol) and

Tf₂O (620 mg, 2.2 mmol), according to the general pro-

cedure F, gave after ﬂash column chromatography

(10% EtOAc–hexane) over silica gel an inseparable

mixture of isomeric pyrimidines 18d and 19d (298 mg,

43%) as solids. Mp 109–110 ^ꢂC; ¹H NMR (CDCl₃,

(acetone-d₆, 400 MHz) d 8.64 (2H, s, OH), 8.50 (2H,

AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 7.39.32 (5H,

0

m, Ph), 7.24 (2H, AA⁰XX⁰, J_AX=8.79 and

0

J_AA=2.14 Hz), 6.68 (2H, AA XX , J_AX=9.00 and

0

J_AA=2.14 Hz), 6.97 (2H, AA₀XX₀, J_AX=8.79 and

0

J_AA=2.14 Hz), 2.63 (2H, q, J=7.50 Hz, CH₂CH₃) and

1.21 (3H, t, J=7.50 Hz, CH₂CH₃); ¹³C NMR (acetone-

d₆, 100 MHz) d 170.41, 163.68, 162.91, 160.62, 158.82,

138.41, 132.45, 131.13, 130.69, 130.63, 129.36, 129.22,

128.19, 115.97, 115.25, 29.22 and12.96. MS (EI, 70 eV)

m/z 368 (M⁺, 61%), 367 (100%); HRMS calcdfor

C₂₄H₂₀N₂O₂, 367.1446, found: 367.1442.

500 MHz)

0

d

8.48 (2H, AA⁰XX⁰, J_AX=9.00 and

J_AA=2.14 Hz), 7.62 and7.54 (2H, AA XX , J_AX=8.78

0

and J_AA=1.93 Hz), 7.05.00 (2H, m, Ar), 6.99.96 (2H,

0

m, Ar), 3.90, 3.89 and3.88 (6H, s, OMe), 2.93 and2.75

(2H, q, J=7.5 Hz,CH₂CH₃), 2.86 (2H, t, J=7.5 Hz,

CH₂CH₂), 2.35 (3H, s, CH₃), 1.92 (2H, quint,

J=7.5 Hz, CH₂CH₂CH₃), 1.45 (3H, t, J=7.5 Hz,

CH₂CH₃) and1.15.09 (6H, overlapping t, J=7.50 Hz,

4-Benzyl-2,6-bis-(4-⁰hydroxyphenyl)-5-methylpyrimidine

(21a). The reaction of 4-benzyl-2,6-bis-(4⁰-methoxy-

phenyl)-5-methylpyrimidine (19a, 80 mg, 0.20 mmol)

.

with BF₃SMe₂(0.42 mL, 4.0 mmol) in dry dichloro-

1

CH₂CH₃); ratio of two isomers by H NMR is (65:35).

methane (5 mL), according to the general procedure B,

after ﬂash column chromatography (35% EtOAc–hex-

ane) over silica gel, gave the pyrimidine 21a (70 mg,

95%) as a solid. HPLC purity (reversed phase, C18) in

two solvents is: MeOH–H₂O (75:25) _ꢂ99.9% and

CH₃CN–H₂O (60:40) 99.9%. Mp 115–116 C; ¹H NMR

(acetone-d₆, 400 MHz) d 8.67 (2H, s, OH), 8.40 (2H,

¹³C NMR (CDCl₃, 125 MHz) d 170.14, 169.47, 165.09,

164.49, 161.23, 160.76, 160.08, 159.88, 132.26, 131.87,

131.15, 130.83, 130.12, 129.60, 129.54, 128.66, 122.41,

113.66, 113.58, 113.53, 55.33, 55.31, 55.28, 37.39, 27.60,

21.11, 20.99, 15.12, 14.89, 14.18 and12.83. MS (EI,

70 eV) m/z 348 (M⁺, 10%), 347 (17%), 135 (100%);

AA⁰XX⁰, J_AX=8.79 and J_AA=1.95 Hz), 7.56 (2H,

0

HRMS calcdfor

347.1762.

C

₂₂H₂₃N₂O₂, 347.1759, found:

AA⁰XX⁰, J_AX=8.79 and J_AA=1.95 Hz), 7.36 (2H,

0

AA⁰XX⁰, J_AX=7.60 Hz), 7.29 (2H, AA⁰XX⁰, J_AX=7.30

4-Butyl-2,6-bis-(4⁰-methoxyphenyl)-5-methylpyrimidine

(18e) and 2,6-bis-(4⁰-methoxyphenyl)-4-ethyl-5-propyl-

pyrimidine (19e). The reaction of 3-heptanone (228 mg,

2 mmol) with anisonitrile (14) (585 mg, 4.4 mmol) and

Tf₂O (620 mg, 2.2 mmol), according to the general pro-

cedure F, gave after ﬂash column chromatography

(15% EtOAc–hexane) over silica gel an inseparable

mixture of pyrimidi_ꢂnes 18e and 19e (445 mg, 61%) as

and J_AA=1.95 Hz), 7.20 (1H, AA XX , J_AX=7.30 Hz),

0

6.79.91 (4H, AA⁰XX⁰, J_AX=9.00, 8.79 and

0

J_AA=2.14 Hz), 4.27 (2H, s, CH₂Ph) and2.32 (3H, s,

CH₃); ¹³C NMR (acetone-d₆, 100 MHz) d 168.66,

166.23, 161.53, 160.37, 159.06, 139.15, 131.84, 131.36,

130.69, 130.39, 129.78, 129.26, 127.13, 123.58, 123.21,

115.89, 115.67, 42.66 and15.59. MS (EI, 70 eV) m/z 368

(M⁺, 67%), 367 (100%); HRMS calcdfor C ₂₄H₂₀N₂O₂,

367.1446, found: 367.1443.

1

solids. Mp 109–110 C, H NMR (CDCl₃, 500 MHz) d

8.50 (2H, AA⁰XX⁰, J_AX=8.79 Hz), 7.62 and7.54 (2H,

AA⁰XX⁰, J_AX=8.58 and8.36 Hz), 7.05.98 (4H, m, Ar),

3.90, 3.89 and3.88 (6H, s, OMe), 2.90.85 (2H, m,

CH₂CH₃and CH₂CH₂CH₃), 2.35 (3H, s, CH₃), 1.55_.46

(2H, m, CH₂CH₂CH₃), 1.45 (3H, t, J=7.5 Hz,

CH₂CH₃), 1.04 (3H, t, J=7.50 Hz, CH₂CH₃) and0.94

(3H, t, J=7.50 Hz, CH₂CH₃); ratio of two isomers by

¹H NMR is (59:41). ¹³C NMR (CDCl₃, 125 MHz) d

170.51, 169.77, 165.52, 164.77, 161.54, 161.52, 161.07,

161.04, 160.36, 160.12, 132.63, 132.14, 131.43, 131.37,

131.11, 130.46, 129.87, 129.83, 127.62, 122.62, 113.86,

113.80, 55.59, 55.57, 55.55, 35.47, 30.23, 27.99, 24.10,

23.04, 15.38, 14.51, 14.31 and13.11. MS (EI, 70 eV) m/z

62 (M⁺, 50%), 361 (55%), 320 (70%), 84 (100%);

2,6-Bis-(4⁰-hydroxyphenyl)-5-phenyl-4-propylpyrimidine

(20b). The reaction of 2,6-bis-(4⁰-methoxyphenyl)-5-

phenyl-4-propylpyrimidine (18b, 150 mg, 0.36 mmol)

.

with BF₃SMe₂(0.76 mL, 7.2 mmol) in dry dichloro-

methane (5 mL), according to the general procedure B,

after careful ﬂash column chromatography (30%

EtOAc–hexane) over silica gel, gave the pyrimidine 20b

(125 mg, 89%) as a solid. HPLC purity (reversed phase,

C18) in two solvents is: MeOH–H₂O (75:25) 100% and

CH₃CN–H₂O (60:40) 99.9%. Mp 208–209 ^ꢂC; ¹H NMR

(acetone-d₆, 500 MHz) d 8.69 (2H, s, OH), 8.49 (2H,

AA⁰XX⁰, J_AX=9.00 and J_AA=2.40 Hz), 7.40.32 (5H, m,

0

Ph), 7.23 (2H, AA⁰XX⁰, J_AX=9.00 and J_AA=2.4 Hz),

0

6.97 (2H, AA⁰XX⁰, J_AX=8.79 and J_AA=1.95 Hz), 6.67

0

HRMS calcdfor

361.1919.

C ₂₃H₂₅N₂O₂, 361.1916, found:

(2H, AA⁰XX⁰, J_AX=8.79 and J_AA=1.95 Hz), 2.62 (2H,

0

t, J=7.57 Hz, CH₂CH₂CH₃), 1.73 (2H, quint,

J=7.57 Hz, CH₂CH₂CH₃and0.85 (3H, t, J=7.32 Hz,

CH₂CH₂CH₃); ¹³C NMR (acetone-d₆, 125 MHz) d

169.39, 163.79, 162.83, 160.65, 158.85, 138.46, 132.49,

131.23, 131.15, 130.69, 130.66, 129.56, 129.34, 128.19,

116.00, 115.26, 37.94, 22.32 and14.27. MS (EI, 70 eV)

m/z 382 (M⁺, 51%), 381 (53%), 353(100%); HRMS

calcdfor C ₂₅H₂₁N₂O₂, 381.1603, found: 381.1604.

4-Ethyl-2,6-bis-(4⁰-hydroxyphenyl)-5-phenylpyrimidine

(20a). The reaction of 4-ethyl-2,6-bis-(4⁰-methoxy-

phenyl)-5-phenylpyrimidine (18a, 60 mg, 0.15 mmol)

.

with BF₃SMe₂(0.32 mL, 3.0 mmol) in dry dichloro-

methane (5 mL), according to the general procedure B,

after ﬂash column chromatography (35% EtOAc–hex-

ane) over silica gel, gave the pyrimidine 20a ( 50 mg,

89%) as a solid. HPLC purity (reversed phase, C18) in

two solvents is: MeOH–H₂O (75:25) 100% and

CH₃CN–H₂O (60:40) 99.9%. Mp 107 ^ꢂC, ¹H NMR

4-Benzyl-5-ethyl-2,6-bis-(4⁰-hydroxyphenyl)-pyrimidine

(21b). The reaction of 4-benzyl-5-ethyl-2,6-bis-

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

651

(4⁰methoxyphenyl)-pyrimidine (19b, 90 mg, 0.21 mmol)

CH₂CH₃); ratio of two isomers by H NMR is (65.15:

34.85). ¹³C NMR (acetone-d₆, 125 MHz) d 170.71,

170.04, 166.24, 165.47, 161.45, 161.33, 160.28, 158.99,

158.75, 132.07, 131.85, 131.63, 131.08, 130.94, 130.87,

129.32, 123.16, 115.86, 115.74, 115.66, 37.81, 28.03,

21.59, 21.48, 15.32, 15.26, 14.35, 12.99 and12.94. MS

(EI, 70 eV) m/z 320 (M⁺, 47%), 319 (100%), 291 (75%);

1

.

with BF₃SMe₂(0.43 mL, 4.2 mmol) in dry dichloro-

methane (5 mL), according to the general procedure B,

after careful ﬂash column chromatography (30%

EtOAc–hexane) over silica gel, gave the pyrimidine 21b

(78 mg, 93%) as a solid. HPLC purity (reversed phase,

C18) in two solvents is: MeOH–H₂O (75:25) 100% and

CH₃CN–H₂O (60:40) 99.4%. Mp 197–198 ^ꢂC; ¹H NMR

(acetone-d₆, 500 MHz) d 8.68 (2H, s, OH), 8.36 (2H,

HRMS calcdfor

319.1441.

C

₂₀H₁₉N₂O₂319.1446, found:

AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 7.47 (2H,

0

AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 7.40.38 (2H,

4-Butyl-2,6-bis-(4⁰-hydroxyphenyl)-5-methylpyrimidine

(20e) and 2,6-bis-(4⁰-hydroxyphenyl)-4-ethyl-5-propylpyri-

midine (21e). The reaction of 4-butyl-2,6-bis-(4⁰-meth-

0

m, Ar), 7.22.19 (1H, m, Ar), 6.96 (2H, AA⁰₀XX₀⁰,

0

J_AX=8.79 and J_AA=2.14 Hz), 6.90 (2H, AA XX ,

0

(19e,

0

J_AX=8.79 and J_AA=2.14 Hz), 4.29 (2H, s, CH₂Ph),

oxyphenyl)-5-methylpyrimidine (18e) and2,6-bis-(4

methoxyphenyl)-4-ethyl-5-propylpyrimidine

-

2.80 (2H, q, J=7.50 Hz, CH₂CH₃) and1.00 (3H, t,

J=7.50 Hz); ¹³C NMR (acetone-d₆, 125 MHz) d 168.18,

167.16, 161.55, 160.45, 158.83, 139.81, 131.88, 131.05,

130.62, 130.46, 129.99, 129.84, 129.84, 129.21, 127.13,

115.93, 115.77, 41.75, 21.65 and14.90. MS (EI, 70 eV)

m/z 382 (M⁺, 42%), 381 (77%), 73 (100%); HRMS

calcdfor C ₂₅H₂₁N₂O₂, 381.1603, found: 381.1607.

.

300 mg, 0.83 mmol) with BF₃SMe₂(1.64 mL,

16.6 mmol) in dry dichloromethane (15 mL), according

to the general procedure B, after careful ﬂash column

chromatography (30% EtOAc–hexane) over silica gel,

gave an inseparable mixture of pyrimidines 20e and 21e

(244 mg, 88%) as solids. HPLC purity (reversed phase,

C18) in two solvents showedthat the pyrimidine iso-

4-(4⁰-Hydroxybenzyl)-2,6-di-(4⁰-hydroxyphenyl)-5-me-

thylpyrimidine (21c). Deprotection of the pyrimidine

mers

(65.95+33.89=98.9%) andCH ₃CN–H₂O (40:60)

are

separable.

MeOH–H₂O

(70:30)

19c (22 mg, 0.052 mmol) using BF₃SMe₂(20 mg,

1.55 mmol), according to the general procedure B,

(66.25+33.48=99.4%). Mp 96–98 ^ꢂC, H NMR (ace-

1

.

tone-d₆, 500 MHz) d 8.67, 8.65, 8.64 and8.63 (2H, s,

furnishedthe phenolic pyrimidine

21c (18 mg, 91%).

OH), 8.38 (2H, AA⁰XX⁰, J_AX=8.79 Hz), 7.56 and7.45

Mp 252 ^ꢂC; H NMR ((CD₃)₂CO, 400 MHz). d 8.679

(1H, s), 8.677 (1H, s) and8.17 (1H, s) [3 ÂOH], 8.40 and

6.92 (4H, A₂X₂, J=8.55 Hz, C-2 aryl H), 7.55 and6.95

(4H, A₂X₂, J=8.55 Hz, C-6 aryl H), 7.19 and6.77 (4H,

A₂X₂, J=8.55 Hz, C-4 aryl H), 4.16 (2H, s, CH₂Ar) and

2.33 (3H, s, CH₃); ¹³C NMR ((CD₃)₂CO, 100 MHz). d

169.13, 166.04, 161.41, 160.31, 159.00, 156.76, 131.81,

131.34, 130.69, 130.35, 129.61, 123.42, 116.05, 115.87,

115.63, 41.86 and15.54. MS (EI, 70 eV). m/z 385

(M+1, 17%), 384 (M⁺, 69), 383 (100); HRMS: calcd

for C₂₄H₁₉N₂O₃(Mꢀ1). 383.1396, found: 383.1393.

(2H, AA⁰XX⁰, J_AX=8.58 and J_AA=2.14 Hz), 6.92.90

1

0

(2H, m, Ar), 2.92.85 (4H, m, CH₂CH₃and

CH₂CH₂CH₃), 2.73.70 (2H, m, CH₂CH₂CH₃), 2.36

(3H, s, CH₃), 1.86.80 (2H, m, CH₂CH₂CH₃), 1.53.47

(4H, m, CH₂CH₂CH₂CH₃), 1.38 and0.86 (3H, t,

J=7.50 Hz, CH₂CH₃andCH CH₂CH₃) and0.86 (3H,

2

t, J=7.50 Hz, CH₂CH₂CH₂CH₃); ratio of two isomers

by ¹H NMR is (60.56:39.44). ¹³C NMR (acetone-d₆,

125 MHz) d 170.81, 170.26, 166.41, 165.49, 161.44,

161.33, 160.35, 160.29, 159.02, 158.74, 132.19, 131.86,

131.64, 131.13, 130.94, 130.87, 130.35, 127.97, 123.11,

115.88, 115.79, 115.74, 115.68, 115.59, 35.60, 28.16,

24.37, 23.33, 15.32, 15.25, 14.31 and13.02. MS (EI,

70 eV) m/z 62 (M⁺, 50%), 361 (55%), 320 (70%), 84

(100%); HRMS calcdfor C ₂₁H₂₁N₂O₂, 333.1603,

found: 333.1609.

4,5-Bis-ethyl-2,6-bis-(4⁰-hydroxyphenyl)-pyrimidine (20d)

and 2,6-bis-(4⁰-hydroxyphenyl)-5-methyl-4-propylpyrimi-

dine (21d). The reaction of 4,5-bis-ethyl-2,6-bis-(4⁰-

0

methoxyphenyl)-pyrimidine (18d) and2,6-bis-(4 -meth-

oxyphenyl)-5-methyl-4-propylpyrimidine (19d, 220 mg,

.

0.63 mmol) with BF₃SMe₂(1.23 mL, 12.6 mmol) in dry

General procedure J: preparation of p-nitrophenyl esters

dichloromethane (15 mL), according to the general pro-

cedure B, after careful ﬂash column chromatography

(40% EtOAc–hexane) over silica gel, gave an insepar-

able mixture of pyrimidines 20d and 21d (180 mg, 89%)

as solids. HPLC purity (reversed phase, C18) in two

solvents showedthat the pyrimidine isomers are separ-

able. MeOH–H₂O (70:30) (65.95+33.89=98.9%) and

CH₃CN–H₂O (40:60) (66.25+33.48=99.4%). Mp

104–106 ^ꢂC, ¹H NMR (acetone-d₆, 500 MHz) d 8.66

(2H, s, OH), 8.38 (2H, AA⁰XX⁰, J_AX=9.00 and

The acid chloride (1 mmol) was added dropwise at 0 ^ꢂC

to a stirredsolution of p-nitrophenol (1 mmol) andpyri-

dine (1.5 mmol) in dichloromethane (5 mL). Stirring was

continued for 3 h and water (5 mL) was added. The

organic phase was washedwith 2 N HCl, brine and

dried over anhyd Na₂SO₄. Solvent removal andcrystal-

lization from dry ether gave the corresponding ester.

4 - Nitrophenyl - 4⁰- methoxybenzoate (23a). p - Anisoyl

chloride (5.10 g, 30 mmol) was added dropwise to a

stirredsolution of p-nitrophenol (4.17 g, 30 mmol) and

pyridine (3.6 mL, 45 mmol) in dichloromethane

(100 mL), according to the general procedure J. Crys-

tallization from dry ether gave the ester 23a (8.0 g,

0

J_AA=2.14 Hz), 7.57 and7.46 (2H, ₀AA₀XX , J_AX=8.79

0

and J_AA=1.93 Hz), 6.96 (2H, A₀A X₀X , J_AX=8.79 and

0

J_AA=1.93 Hz), 6.90 (2H, AA XX , J_AX=8.79 and

0

J_AA=2.14 Hz),

2.90

and2.76

(2H,

q,

J=7.50 Hz,CH₂CH₃), 2.83 (2H, t, J=7.50 Hz,

CH₂CH₂), 2.35 (3H, s, CH₃), 1.88 (2H, quint,

J=7.50 Hz, CH₂CH₂CH₃), 1.39 and1.09 (3H, t,

J=7.50 Hz, CH₂CH₃) and1.05 (3H, t, J=7.50 Hz,

98%). Mp 165 ^ꢂC, H NMR (CDCl₃, 400 MHz) d 8.34

1

(2H, AA⁰XX⁰, J_AX=9.00 Hz), 8.19 (2H, AA⁰XX⁰,

J_AX=8.79 Hz), 7.40 (2H, AA⁰XX⁰, J_AX=9.00 Hz), 6.92

652

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

(2H, AA⁰XX⁰, J_AX=9.00 Hz), 3.86 (3H, s, OMe); MS

(EI, 70 eV) m/z 273 (M⁺, 27%), 135 (100%).

4 mmol) and dibenzo-18-crown-6-ether (20 mg) dis-

solved in THF (20 mL) was added dropwise to a stirred

mixture of NaH (320 mg, 8 mmol, 60% dispersion

washedwith dry hexane) and4-nitrophenyl 4 ⁰-methoxy-

benzoate (23a, 1.1 g, 4.2 mmol) in THF (20 mL) under

dry inert atmosphere, according to the general proce-

dure K. Crystallization from ethyl acetate gave 24a

(525 mg, 42%). Mp 145–146 ^ꢂC, ¹H NMR (CDCl₃,

4-Nitrophenylacetate (23b). Acetyl chloride (7.8 g,

0.10 mol) was added dropwise to a stirred solution of

p-nitrophenol (14.0 g, 0.11 mol) andpyriidne (10 mL,

0.13 mol) in dichloromethane (60 mL), according to

the general procedure J. Crystallization from dry

ether gave the ester 23b (14 g, 76%). Mp 78–79 ^ꢂC,

¹H NMR (CDCl₃, 400 MHz) d 8.23 (2H, AA₀⁰XX⁰₀,

400 MHz)

0

d

7.92 (2H, AA⁰XX⁰, J_AX=8.79 and

0

J_AA=1.95 Hz), 7.25 (2H, AA₀XX₀, J_AX=8.79 and

0

J_AA=1.95 Hz), 6.91 (4H, AA XX , J_AX=9.00 and

J_AX=9.00 Hz and J_AA=2.14 Hz), 7.24 (2H, AA XX ,

0

J_AA=1.22 Hz), 5.62 (1H, s, CHAr), 3.85 (3H, s, OMe),

J_AX=9.00 Hz and J_AA=2.14 Hz) and2.31 (3H, s,

CH₃); MS (EI, 70 eV) m/z 181 (M⁺, 75%), 139

(100%).

3.79 (3H, s, OMe), 2.63 (1H, dq, J=7.33 and3.66 Hz,

CH_ABCH₃), 2.51 (1H, dq, J=7.33 and3.66 Hz,

CH_ABCH₃) and1.06 (3H, t, J=7.33 Hz, CH₃); ¹³C

NMR (CDCl₃, 100 MHz) d 206.29, 193.93, 163.69,

159.20, 131.19, 130.39, 128.98, 125.79, 114.38, 113.87,

66.12, 55.47, 55.20, 35.32 and7.86. MS (EI, 70 eV) m/z

312 (M⁺, 28%), 135 (100%). HRMS calcdfor

C₁₉H₂₀O₄, 312.1365, found: 312.1365. Analysis for

C₁₉H₂₀O₄, calcdC,73.06; H, 6.45; foundC,72.74; H,

6.40.

4-Nitrophenylpropionate (23c). Propionyl chloride

(14.0 g, 0.15 mol) was added dropwise to a stirred solu-

tion of p-nitrophenol (23.1 g, 0.16 mol) andpyriidne

(20 mL, 0.24 mol) in dichloromethane (100 mL),

according to the general procedure J. Crystallization

from dry ether gave the ester 23c (27.0 g, 93%). Mp

63–64 ^ꢂC, ¹H NMR (CDCl₃, 400 MHz) d 8.27 (2H,

AA⁰XX⁰, J_AX=9.00 Hz and J_AA=2.14 Hz), 7.27 (2H,

0

AA⁰XX⁰, J_AX=9.00 Hz and J_AA=2.14 Hz), 2.63 (2H,

1,2-Bis-(4⁰-methoxyphenyl)-hexane-1,3-dione (24b). 1-(4⁰-

Methoxyphenyl)-pentan-2-one (22c, 960 mg, 5 mmol;

0

q, J=7.50 Hz, CH₂CH₃) and1.28 (3H, t, J=7.50 Hz,

CH₂CH₃); MS (EI, 70 eV) m/z 195 (M⁺, 4%), 57

(100%).

50

preparedaccoridng to a literature metho)d

and

dibenzo-18-crown-6-ether (25 mg) dissolved in THF

(20 mL) were added dropwise to a stirred mixture of

NaH (400 mg, 10 mmol, 60% dispersion washed with

dry hexane) and 4-nitrophenyl 4⁰-methoxybenzoate

(23a, 1.63 g, 6 mmol) in THF (20 mL) under dry inert

atmosphere, according to the general procedure K.

Flash column chromatography over silica gel using 15%

ethyl acetate/hexane andcrystallization with ethyl ace-

tate gave 24b (570 mg, 35%). Mp 107–109 ^ꢂC, ¹H NMR

(CDCl₃, 500 MHz) d 7.90 (2H, AA⁰XX⁰, J_AX=9.00 and

4-Nitrophenyl-n-butanoate (23d). n-Butanoyl chloride

(10.6 g, 0.10 mol) was added dropwise to a stirred solu-

tion of p-nitrophenol (14.0 g, 0.11 mol) andpyriidne

(10 mL, 0.13 mol) in dichloromethane (60 mL), accord-

ing to the general procedure J. Removal of solvent

under vacuum and product puriﬁcation by ﬂash column

chromatography over silica gel using 10% ethyl acetate

1

in hexane gave the ester 23d (20.1 g, 99%) as an oil. H

NMR (CDCl₃, 400 MHz)

0

8.29 (2H, AA⁰₀XX₀⁰,

J_AX=9.00 Hz and J_AA=1.95 Hz), 2.60 (2H, q,

J_AA=2.14 Hz), 7.23 (2H, AA₀XX₀, J_AX=9.00 and

0

d

J_AX=9.00 Hz and J_AA=1.95 Hz), 7.28 (2H, AA XX ,

0

J_AA=2.14 Hz), 6.88 (4H, AA XX , J_AX=9.00 and

0

J_AA=2.14 Hz), 5.58 (1H, s, CHAr), 3.83 (3H, s, OMe),

J=7.33 Hz, CH₂CH₂CH₃), 1.82 (2H, quint, J=7.33 Hz,

CH₂CH₂CH₃) and1.07 (3H, t, J=7.33 Hz, CH₂CH₃);

MS (EI, 70 eV) m/z 209 (M⁺, 2%), 71 (100%).

3.79 (3H, s, OMe), 2.57 (1H, dq, J=7.72 and2.78 Hz,

CH_ABCH₂), 2.47 (1H, dq, J=7.72 and2.78 Hz,

CH_ABCH₂), 1.63.55 (2H, m, CH₂CH₂CH₃) and0.86

(3H, t, J=7.50 Hz, CH₃); ¹³C NMR (CDCl₃, 125 MHz)

d 205.64, 193.92, 163.75, 159.27, 131.21, 130.46, 129.10,

125.73, 114.41, 113.91, 66.36, 55.48, 55.22, 43.90, 17.12

and13.53. MS (EI, 70 eV) m/z 326 (M⁺, 13%), 256 (20),

139 (100%). HRMS calcdfor C ₂₀H₂₂O₄, 326.1518,

found: 326.1515. Analysis for C₂₀H₂₂O₄, calcdC, 73.60;

H, 6.79; foundC, 73.34; H, 6.25.

General procedure K: synthesis of 1,3-diones

Ketone (1 mmol) anddibenzo-18-crown-6-ether (5 mg)

dissolved in THF (2 mL) was added dropwise over

10 min at rt to a stirredmixture of NaH (2 mmol, 60%

dispersion washed with dry hexane) and ester

(1.2 mmol) in THF (5 mL) under dry inert atmosphere.

The reaction mixture was reﬂuxedfor 3–4 h andreac-

tion progress was monitoredby TLC. The reaction

mixture was cooled, poured over cool 10% HCl (10 mL)

with stirring, andextractedwith ethyl acetate. The

3-(4⁰-Methoxyphenyl)-hexane-2,4-dione (24c). 4-Methoxy-

phenylacetone (22a, 5.0 g, 0.03 mol) andidbenzo-18-

crown-6-ether (150 mg) dissolved in THF (50 mL) was

added dropwise to a stirred mixture of NaH (23c, 2.4 g,

0.06 mol, 60% dispersion washed with dry hexane) and

4-nitrophenyl propionate (6.9 g, 0.035 mol) in THF

(50 mL) under dry inert atmosphere, according to gen-

eral procedure K. Flash column chromatography over

silica gel using 10% ethyl acetate/hexane gave 24c (3.5 g,

organic layer was washedwith water, satdNaHCO

soln, brine (5 mL) andrdiedover anhydNa

3

₂SO₄.

Removal of solvent under vacuum gave the crude pro-

duct that was puriﬁed by ﬂash column chromatography

over silica gel using hexane–ethyl acetate or was directly

crystallized.

1

52%) as oil. H NMR (CDCl₃, 500 MHz) d 16.85 (1H,

s, OH), 7.08 (2H, AA⁰XX⁰, J_AX=8.79 and

1,2 - Bis - (4⁰- methoxyphenyl) - pentane - 1,3 - dione (24a).

J_AA=2.14 Hz), 6.93 (2H, AA XX , J_AX=8.79 and

0

J_AA=2.14 Hz), 3.85 (3H, s, OMe), 2.17 (2H, q,

0

1-(4⁰-Methoxyphenyl)-butan-2-one

(22b,

712 mg,

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

653

1

J=7.50 Hz CH₂CH₃), 1.88 (3H, s, Me), and1.03 (3H, t,

J=7.50 Hz, CH₂CH₃); ¹³C NMR (CDCl₃, 125 MHz) d

196.02, 189.55, 158.88, 132.21, 130.36, 128.81,114.47,

114.12, 113.95, 113.66, 55.19, 30.19, 23.65 and9.39. MS

(EI, 70 eV) m/z 220 (M⁺, 98%), 191 (64%), 163 (100%).

HRMS calcdfor C ₁₃H₁₆O₃; 220.1106, found: 220.1106.

(2.2 g, 67%) as an oil. H NMR (CDCl₃, 400 MHz) d

16.68 (1H, s, OH), 7.32.07 (2H, m, Ar), 6.94.82 (2H, m,

Ar), 6.12 and5.62 (1H, s, C HAr Z/E isomers), 3.83,

3.80, 3.79 and3.78 (3H, s, OMe Z/E isomers of keto

andenol), 2.79.26 (2H, qd,

J=7.56 and3.41 Hz,

CH_ABCH₃of Z/E isomers), 2.13 (2H, q, J=7.56 Hz,

CH₂CH₃), 1.25.05 (3H, m, CH_ABCH₃) and1.02 (3H, t,

J=7.56 Hz, CH₂CH₃); ¹³C NMR (CDCl₃, 100 MHz) d

217.88, 194.44, 158.83, 149.83, 132.29, 130.34, 129.79,

129.41, 128.52, 127.50, 127.49, 127.14, 117.72, 114.12,

114.07, 113.71, 113.68, 113.62, 113.24, 75.85, 55.19,

55.17, 39.21, 29.87, 27.79, 27.31, 26.29, 23.18, 1135, 9.62

and9.06. MS (EI, 70 eV) m/z 234 (M⁺, 22%), 178

(81%), 121 (100%). HRMS calcdfor C ₁₄H₁₈O₃,

234.1256, found: 234.1261.

3-(4⁰-Methoxyphenyl)-pentane-2,4-dione (24d). 4-Meth-

oxyphenylacetone (22a, 5.0 g, 0.03 mol) anddibenzo-18-

crown-6-ether (150 mg) dissolved in THF (50 mL) was

added dropwise to a stirred mixture of NaH (2.4 g,

0.06 mol, 60% dispersion washed with dry hexane) and

4-nitrophenyl acetate (23b, 6.0 g, 0.033 mol) in THF

(50 mL) under dry inert atmosphere, according to the

general procedure K. Flash column chromatography

over silica gel using 10% ethyl acetate/hexane gave 24d

(3.5 g, 57%) as a solid. Mp 70 ^ꢂC, H NMR (CDCl₃,

4 - (4⁰- Methoxyphenyl) - octane - 3,5 - dione (24g). 1 - (4⁰-

Methoxyphenyl)-butan-2-one (22b, which is the same

compoundas 17c; 2.5 g, 0.014 mol) andidbenzo-18-

crown-6-ether (70 mg) dissolved in THF (20 mL) was

added dropwise to a stirred mixture of NaH (1.12 g,

0.028 mol, 60% dispersion washed with dry hexane) and

4-nitrophenylbutanoate (23d, 3.7 g, 0.016 mol) in THF

(25 mL) under dry inert atmosphere, according to the

general procedure K. Flash column chromatography

over silica gel using 10% ethyl acetate/hexane gave 24g

1

400 MHz) d 16.67 (1H, s, OH), 7.08 (2H, AA⁰₀XX₀⁰,

0

J_AX=8.79 and J_AA=2.14 Hz), 6.92 (2H, AA XX ,

0

J_AX=8.79 and J_AA=2.14 Hz), 3.84 (3H, s, OMe) and

1.89 (3H, s, Me); ¹³C NMR (CDCl₃, 100 MHz) d

191.18, 158.83, 132.07, 130.31, 129.03, 114.55, 114.11,

55.19 and24.09. MS (EI, 70 eV) m/z 206 (M⁺, 100%),

164 (98%), 121 (84%). HRMS calcdfor C ₁₂H₁₄O₃;

206.0937, found: 206.0938. Analysis for C₁₂H₁₄O₃, calcd

C,69.88; H, 6.84; foundC,70.22; H, 6.89.

1

(3.0 g, 89%) as an oil. H NMR (CDCl₃, 400 MHz) d

3-(4⁰-Methoxyphenyl)-heptane-2,4-dione (24e). 4-Meth-

oxyphenylacetone (22a, 5.0 g, 0.03 mol) anddibenzo-18-

crown-6-ether (150 mg) dissolved in THF (50 mL) was

added dropwise to a stirred mixture of NaH (2.4 g,

0.06 mol, 60% dispersion washed with dry hexane) and

4-nitrophenyl butanoate (23c, 6.5 g, 0.033 mol) in THF

(50 mL) under dry inert atmosphere, according to the

general procedure K. Flash column chromatography

over silica gel using 10% ethyl acetate/hexane gave 24e

16.76 (1H, s, OH), 7.08 (2H, AA⁰XX⁰, J_AX=8.79 and

0

J_AA=2.19 Hz), 3.85, 3.82 and3.79 (3H, s, OMe, Z/E

0

J_AA=2.19 Hz), 6.92 (2H, AA XX , J_AX=8.79 and

0

isomers of keto andenol), 2.14 (2H, q, J=7.33,

CH₂CH₃), 2.09 (2H, t, J=7.33 Hz, CH₂CH₂CH₃), 1.54

(2H, quint, J=7.33 and7.57 Hz, CH ₂CH₂CH₃), 1.57

(3H, t, J=7.57 Hz, CH₂CH₃) and0.86 (3H, t,

J=7.57 Hz, CH₂CH₂CH₃); ¹³C NMR (CDCl₃,

100 MHz) d 196.22, 192.01, 158.79, 132.39, 128.58,

114.04, 113.77, 113.65, 55.21, 37.83, 30.37, 19.03, 13.81

and9.45. MS (EI, 70 eV) m/z 248 (M⁺, 100%), 219

1

(6.2 g, 88%) as an oil, H NMR (CDCl₃, 400 MHz) d

16.77 (1H, s, OH), 7.32.96 (2H, m, Ar), 6.94.82 (2H, m,

Ar), 6.19 and5.90 (1H, s, C HAr Z/E isomers), 3.85,

3.82 and3.80 (3H, s, OMe, Z/E isomers of keto and

enol), 2.79.26 (2H, dt, J=7.32 and5.37 Hz,

CH_ABCH₂CH₃, Z/E isomers), 2.07 and1.88 (3H, s,

CH₃, Z/E isomers), 1.77.51 (2H, quint, J=7.32 Hz,

CH₂CH₂CH_3,Z/E isomers) and1.04.82 (3H, over-

lapping t, J=7.32 Hz, CH₂CH₃, Z/E isomers); ¹³C

NMR (CDCl₃, 100 MHz) d 193.69, 191.35, 171.26,

158.79, 158.36, 146.65, 144.78, 132.25, 130.33, 129.86,

129.36, 128.84, 127.15, 118.03, 115.79, 114.39, 114.06,

113.70, 113.66, 55.19, 55.16, 38.16, 36.29, 36.19, 24.24,

20.57, 18.86, 18.44, 18.27, 17.11, 13.77 and13.62. MS

(EI, 70 eV) m/z 234 (M⁺, 73%), 191 (47%), 164 (100%).

HRMS calcdfor C ₁₄H₁₈O₃, 234.1256, found: 234.1252.

(60%), 178 (70%). HRMS calcdfor

248.1412, found: 248.1411.

C ₁₅H₂₀O₃,

General procedure L: synthesis of pyrimidines from 1,3-

diones

Glacial acetic acid(0.2 mL), followedby anhydammo-

nium acetate (0.8 g, 10 mmol) at rt was added to a stir-

redsolution of the 1,3io-dne (1 mmol) and

p-anisaldehyde (25, 1 mmol) in dry DMSO (2 mL). The

reaction mixture was heatedto 80–90 ^ꢂC under dry air

atmosphere for 10–12 h. Dichloromethane (10 mL) and

water (5 mL) were added to the cooled reaction mixture.

The organic phase was washedwith brine (5 mL) and

dried over anhyd Na₂SO₄. Solvent was removedunder

vacuum and the crude product was puriﬁed by ﬂash

column chromatography over silica gel using hexane–

ethyl acetate.

4-(4⁰-Methoxyphenyl)-heptane-3,5-dione (24f). 1-(4⁰-Meth-

oxyphenyl)-butan-2-one (22b, which is the same com-

poundas 17c; 2.5 g, 0.014 mol) anddibenzo-18-crown-6-

ether (70 mg) dissolved in THF (20 mL) was added

dropwise to a stirred mixture of NaH (1.12 g, 0.028 mol,

60% dispersion washed with dry hexane) and 4-nitro-

phenyl propionate (23c, 3.2 g, 0.016 mol) in THF

(25 mL) under dry inert atmosphere, according to the

general procedure K. Flash column chromatography

over silica gel using 10% ethyl acetate/hexane gave 24f

4-Ethyl-2,5,6-tris-(4⁰-methoxyphenyl)-pyrimidine (26a).

The reaction of 1,2-bis-(4⁰-methoxyphenyl)-pentane-1,3-

dione (24a, 200 mg, 0.64 mmol) with p-anisaldehyde (25,

87 mg, 0.64 mmol) in dry DMSO (2 mL), glacial acetic

acid(0.15 mL) andanhydammonium acetate (0.5 g,

6.5 mmol), according to the general procedure L, after

654

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

careful ﬂash column chromatography (10% EtOAc–

hexane) over silica gel andcrystallization from ethanol,

gave the pyrimidine 26a (48 mg, 18%) as solids. Mp

28.64, 23.32 and12.82. MS (EI, 70 eV) m/z 334 (M⁺,

82%), 333 (100%); HRMS calcdfor C ₂₁H₂₂N₂O₂,

333.1603, found: 333.1602.

152–153 ^ꢂC; H NMR (CDCl₃, 400 MHz) d 8.58 (2H,

1

AA⁰XX⁰, J_AX=9.00 and J_AA=2.19 Hz), 7.43 (2H,

4,6-Bis-methyl-2,5-bis-(4⁰-methoxyphenyl)-pyrimidine

(26d). The reaction of 3-(4⁰-methoxyphenyl)-pentane-

2,4-dione (24d, 2.06 g, 10 mmol) with p-anisaldehyde

(25, 1.36 mg, 10 mmol) in dry DMSO (15 mL), glacial

acetic acid(2 mL) andanhydammonium acetate (8 g,

0.11 mol), according to the general procedure L, after

careful ﬂash column chromatography (10% EtOAc–

hexane) over silica gel andcrystallization from ethanol,

gave the pyrimidine 26d ( 160 mg, 5%) as a solid. Mp

0

AA⁰XX⁰, J_AX=9.00 and J_AA=2.19 Hz), 7.06 (2H,

0

AA⁰XX⁰, J_AX=9.00 and J_AA=2.19 Hz), 6.92 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=2.19 Hz), 6.83 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=2.19 Hz), 6.77 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=1.95 Hz), 3.91 (3H, s,

0

OMe), 3.86 (3H, s, OMe), 3.81 (3H, s, OMe), 2.71 (2H,

q, J=7.50 Hz, CH₂CH₃) and1.27 (3H, t, J=7.50 Hz,

CH₂CH₃); ¹³C NMR (CDCl₃, 100 MHz) d 170.32,

162.77, 162.09, 161.45, 159.80, 158.76, 131.52, 131.37,

131.28, 130.99, 129.77, 129.32, 128.16, 113.99, 113.63,

113.08, 55.31, 55.19, 55.15, 28.83 and12.89. MS (EI,

70 eV) m/z 426 (M⁺, 87%), 425 (100%); HRMS calcd

for C₂₇H₂₆N₂O₃, 426.1943, found: 426.1931.

120–121 ^ꢂC; H NMR (CDCl₃, 500 MHz) d 8.43 (2H,

1

AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 7.11 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 6.99 (4H,

0

AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 3.88 (3H, s,

0

OMe), 3.87 (3H, s, OMe) and2.31 (6H, s, 2 ÂCH₃); ¹³C

NMR (CDCl₃, 125 MHz) d 164.76, 161.99, 161.46,

159.06, 130.81, 130.59, 130.18, 129.65, 129.28, 114.25,

113.76, 55.31, 55.26 and23.26. MS (EI, 70 eV) m/z 320

(M⁺100%), 146 (30%); HRMS calcdfor C ₂₀H₂₀N₂O₂,

320.1525, found: 320.1519.

4-Propyl-2,5,6-tris-(4⁰-methoxyphenyl)-pyrimidine (26b).

The reaction of 1,2-bis-(4⁰-methoxyphenyl)-hexane-1,3-

dione (24b, 240 mg, 0.73 mmol) with p-anisaldehyde (25,

100 mg, 0.73 mmol) in dry DMSO (2 mL), glacial acetic

acid(0.15 mL) andanhydammonium acetate (0.6 g,

8 mmol), according to the general procedure L, after

careful ﬂash column chromatography (10% EtOAc–

hexane) over silica gel andcrystallization from ethanol,

gave the_ꢂpyrimidine 26b (70 mg, 22%) as a solid. Mp

2,5-Bis-(4⁰-methoxyphenyl)-6-methyl-4-propylpyrimidine

(26e). The reaction of 3-(4⁰-methoxyphenyl)-heptane-

2,4-dione (24e, 2.34 g, 10 mmol) with and p-anisalde-

hyde (25, 1.36 mg, 10 mmol) in dry DMSO (15 mL),

glacial acetic acid(2 mL) andanhydammonium acetate

(8 g, 0.11 mol), according to the general procedure L,

after careful ﬂash column chromatography (10%

EtOAc–hexane) over silica gel andcrystallization from

ethanol gave the pyrimidine 26e (300 mg, 9%) as a solid.

Mp 136–137 ^ꢂC; ¹H NMR (CDCl₃, 500 MHz) d 8.47

1

130–131 C; H NMR (CDCl₃, 500 MHz) d 8.56 (2H,

AA⁰XX⁰, J_AX=9.00 and J_AA=1.93 Hz), 7.41 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=1.94 Hz), 7.05 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 7.00 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=1.93 Hz), 6.89 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=1.95 Hz), 6.76 (2H,

0

AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 3.88 (3H, s,

(2H, AA⁰XX⁰, J_AX=8.79 and J_AA=1.93 Hz), 7.12 (2H,

0

AA⁰XX⁰, J_AX=8.58 and J_AA=1.93 Hz), 7.01 (4H,

0

OMe), 3.86 (3H, s, OMe), 3.85 (3H, s, OMe), 2.65 (2H,

t, J=7.50 Hz, CH₂CH₂), 1.78 (2H, quint, J=7.5 and

7.3 Hz, CH₂CH₂CH₃) and0.91 (3H, t, J=7.30 Hz,

CH₂CH₃); ¹³C NMR (CDCl₃, 100 MHz) d 169.33,

162.91, 162.02, 161.49, 159.85, 158.78, 131.54, 131.47,

131.38, 131.06, 129.79, 129.41, 128.52, 113.98, 113.66,

113.10, 55.13, 55.14, 37.33, 21.90 and14.05. MS (EI,

70 eV) m/z 440 (M⁺, 65%), 412 (100%); HRMS calcd

for C₂₈H₂₈N₂O₃, 440.2097, found: 440.2097.

AA⁰XX⁰, J_AX=8.58 and J_AA=2.14 Hz), 3.90 (3H, s,

0

OMe), 3.89 (3H, s, OMe), 2.54 (2H, t, J=7.50 Hz,

CH₂CH₂CH₃), 2.34 (3H, s, CH₃), 1.74 (2H, quint,

J=7.50 Hz, CH₂CH₂CH₃) and0.89 (3H, t, J=7.50 Hz,

CH₂CH₃); ¹³C NMR (CDCl₃, 125 MHz) d 167.79,

164.92, 162.01, 161.39, 158.98, 131.05, 130.41. 130.36,

129.66, 129.18, 114.10, 113.72, 55.31, 55.25, 37.15,

23.40, 21.84 and14.00. MS (EI, 70 eV) m/z 348 (M⁺

45%), 320 (100%); HRMS calcdfor C ₂₂H₂₄N₂O₂,

348.1838, found: 348.1828. Analysis for C₂₂H₂₄N₂O₂,

calcdC,75.83; H, 6.94; N, 8.04, foundC,75.85; H, 6.95;

N, 7.89.

4-Ethyl-2,5-bis-(4⁰-methoxyphenyl)-6-methylpyrimidine

(26c). The reaction of 3-(4⁰-methoxyphenyl)-hexane-

1,3-dione (24c, 1.1 g, 5 mmol) with p-anisaldehyde (25,

680 mg, 5 mmol) in dry DMSO (10 mL), glacial acetic

acid(1 mL) andanhydammonium acetate (4 g,

4,6 - Bis - ethyl - 2,5 - bis - (4⁰- methoxyphenyl) - pyrimidine

(26f). The reaction of 4-(4⁰-methoxyphenyl)-heptane-

3,5-dione (24f, 1.17 g, 5 mmol) with p-anisaldehyde (25,

680 mg, 5 mmol) in dry DMSO (10 mL), glacial acetic

acid(1 mL) andanhydammonium acetate (4 g,

53 mmol), according to the general procedure L, after

careful ﬂash column chromatography (10% EtOAc–

hexane) over silica gel andcrystallization from ethanol,

gave the pyrimidine 26c (65 mg, 4%) as a solid. Mp

132–133 ^ꢂC; H NMR (CDCl₃, 500 MHz) d 8.48 (2H,

53 mmol), according to the general procedure L, after

careful ﬂash column chromatography (10% EtOAc–

hexane) over silica gel andcrystallization from ethanol,

gave the_ꢂpyrimidine 26f (170 mg, 10%) as a solid. Mp

1

AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 7.13 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=1.93 Hz), 7.01 (4H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 3.90 (3H, s,

0

1

OMe), 3.89 (3H, s, OMe), 2.59 (2H, q, J=7.50 Hz,

CH₂CH₃), 2.32 (3H, s, CH₃) and1.27 (3H, t,

J=7.50 Hz, CH₂CH₃); ¹³C NMR (CDCl₃, 125 MHz) d

168.87, 164.85, 162.12, 161.42, 159.03, 131.04, 130.29,

130.05, 129.67, 129.13, 114.16, 113.72, 55.31, 55.25,

142–143 C; H NMR (CDCl₃, 500 MHz) d 8.52 (2H,

AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz), 7.14 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=1.93 Hz), 7.01 (4H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 3.90 (3H, s,

OMe), 3.89 (3H, s, OMe), 2.56 (4H, q, J=7.72 Hz,

0

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

655

2ÂCH₂CH₃) and1.22 (6H, t, J=7.72 Hz, 2ÂCH₂CH₃);

¹³C NMR (CDCl₃, 125 MHz) d 168.98, 162.25, 161.38,

158.98, 131.29, 130.47, 130.37, 129.69, 129.51, 128.94,

114.04, 113.68, 55.31, 55.24, 28.72 and12.86. MS (EI,

70 eV) m/z 348 (M⁺15%), 347 (28%), 121 (100%);

column chromatography (30% EtOAc–hexane) over

silica gel, gave the pyrimidine 27b (98 mg, 90%) as a

solid. HPLC purity (reversed phase, C18) in two sol-

vents is: MeOH–H₂O (70:30) 100% andCH CN–H₂O

3

(40:60) 100%. Mp 170–171 ^ꢂC; H NMR (acetone-d₆,

1

HRMS calcdfor

347.1761.

C

₂₂H₂₄N₂O₂, 347.1761, found:

500 MHz) d 8.58 (3H, s, OH), 8.48 (2H, AA⁰₀XX₀⁰,

0

J_AX=8.79 and J_AA=2.14 Hz), 7.37 (2H, AA₀XX₀,

0

J_AX=8.79 and J_AA=1.94 Hz), 7.05 (2H, AA₀XX₀,

6-Ethyl-2,5-bis-(4⁰-methoxyphenyl)-4-propylpyrimidine

(26g). The reaction of 4-(4⁰-methoxyphenyl)-octan-3,5-

dione (24g, 2.48 g, 10 mmol) with p-anisaldehyde (25,

1.36 mg, 10 mmol) in dry DMSO (15 mL), glacial acetic

acid(2 mL) andanhydammonium acetate (8 g,

J_AX=8.57 and J_AA=2.14 Hz), 6.97 (2H, AA₀XX₀,

0

J_AX=8.79 and J_AA=2.14 Hz), 6.87 (2H, AA₀XX₀,

0

J_AX=8.57 and J_AA=2.14 Hz), 6.69 (2H, AA XX ,

0

J_AX=9.00 and J_AA=2.14 Hz), 2.63 (2H, t, J=7.50 Hz,

CH₂CH₂), 1.75 (2H, quint, J=7.5 and7.3 Hz,

CH₂CH₂CH₃) and0.87 (3H, t, J=7.30 Hz, CH₂CH₃);

¹³C NMR (acetone-d₆, 125 MHz) d 169.82, 163.95,

162.52, 160.52, 158.75, 157.60, 132.49, 132.30, 131.41,

130.82, 130.59, 129.49, 129.08, 116.29, 115.29, 115.96,

115.23, 37.93, 22.36 and14.31. MS (EI, 70 eV) m/z 398

(M⁺, 55%), 397 (43%), 370 (100%); HRMS calcdfor

C₂₅H₂₁N₂O₃, 397.1552, found: 397.1553.

0.11 mol), according to the general procedure L, after

careful ﬂash column chromatography (10% EtOAc

–hexane) over silica gel andcrystallization from ethanol,

gave the pyrimidine 26g (220 mg, 6%) as a solid. Mp

120–121 ^ꢂC; H NMR (CDCl₃, 500 MHz) d 8.42 (2H,

1

AA⁰XX⁰, J_AX=8.79 and J_AA=1.93 Hz), 7.13 (2H,

0

AA⁰XX⁰, J_AX=8.58 and J_AA=1.93 Hz), 7.02.79 (4H,

m, Ar), 3.90 (3H, s, OMe), 3.89 (3H, s, OMe), 2.53 (2H,

0

q, J=7.40 Hz, CH₂CH₃), 2.52 (2H, t, J=7.50 Hz,

CH₂CH₂CH₃),

4-Ethyl-2,5-bis-(4⁰-hydroxyphenyl)-6-methylpyrimidine

(27c). The reaction of 4-ethyl-2,5-bis-(4⁰-methoxy-

phenyl)-6-methylpyrimidine (26c, 80 mg, 0.24 mmol)

1.74

(2H,

quint,

J=7.50 Hz,

CH₂CH₂CH₃), 1.21 (3H, t, J=7.40 Hz, CH₂CH₃) and

0.89 (3H, t, J=7.50 Hz, CH₂CH₂CH₃); ¹³C NMR

(CDCl₃, 125 MHz) d 169.03, 167.89, 162.12, 161.36,

158.95, 131.29, 130.52, 130.36, 129.85, 129.68, 128.99,

113.99, 113.67, 55.31, 55.23, 37.24, 28.78, 21.87, 14.02

and12.84. MS (EI, 70 eV) m/z 362 (M⁺62%), 334

(100%); HRMS calcdfor C ₂₃H₂₆N₂O₂, 362.1994, found:

362.1989. Analysis for C₂₃H₂₆N₂O₂, calcdC,76.21; H,

7.23; N, 7.73, foundC,76.18; H, 7.22; N, 7.69.

.

with BF₃SMe₂(0.85 mL, 8.4 mmol) in dry dichloro-

methane (10 mL), according to general the procedure,

after careful ﬂash column chromatography (30%

EtOAc–hexane) over silica gel, gave the pyrimidine 27c

(65 mg, 89%) as a solid. HPLC purity (reversed phase,

C18) in two solvent is: MeOH–H₂O (70:30) 100% and

CH₃CN–H₂O (40:60) 100%. Mp 178–179 ^ꢂC; H NMR

1

(acetone-d₆, 500 MHz) d 8.62 (2H, s, OH), 8.42 (2H,

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 7.12 (2H,

0

4-Ethyl-2,5,6-tris-(4⁰-hydroxyphenyl)-pyrimidine (27a).

AA⁰XX⁰, J_AX=8.79 and J_AA=1.93 Hz), 7.00 (4H,

0

The reaction of 4-ethyl-2,5,6-tris-(4⁰-methoxyphenyl)-

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 2.54 (2H, q,

0

.

pyrimidine (26a, 60 mg, 0.14 mmol) with BF₃SMe₂

J=7.50 Hz, CH₂CH₃), 2.23 (3H, s, CH₃) and1.17 (3H,

t, J=7.50 Hz, CH₂CH₃); ¹³C NMR (acetone-d₆,

125 MHz) d 169.29, 165.51, 162.49, 160.49, 157.89,

131.25, 131.06, 130.71, 130.52, 128.65, 116.48, 115.94,

23.42 and12.99. MS (EI, 70 eV) m/z 306 (M⁺, 45%),

305 (100%); HRMS calcdfor C ₁₉H₁₇N₂O₂, 305.1289,

found: 305.1289.

(0.43 mL, 4.2 mmol) in dry dichloromethane (5 mL),

according to the general procedure B, after careful ﬂash

column chromatography (30% EtOAc–hexane) over

silica gel, gave the pyrimidine 27a (78 mg, 93%) as a

solid. HPLC purity (reversed phase, C18) in two sol-

vents: MeOH–H₂O (70:30) 100% andCH ₃CN–H₂O

(40:60) 100%. Mp 234–235 ^ꢂC; H NMR (acetone-d₆,

1

500 MHz) d 8.59 (3H, bs, OH), 8.48 (2H, AA⁰₀XX₀⁰,

4,6-Bis-methyl-2,5-bis-(4⁰-hydroxyphenyl)-pyrimidine

(27d). The reaction of 4,6-bis-methyl-2,5-bis-(4⁰-meth-

oxyphenyl)-pyrimidine (26d, 120 mg, 0.38 mmol) with

0

J_AX=9.00 and J_AA=2.14 Hz), 7.38 (2H, AA₀XX₀,

0

J_AX=8.79 and J_AA=2.14 Hz), 7.04 (2H, AA₀XX₀,

.

0

J_AX=8.57 and J_AA=2.14 Hz), 6.96 (2H, AA₀XX₀,

BF₃SMe₂(0.78 mL, 7.6 mmol) in dry dichloromethane

0

J_AX=9.00 and J_AA=2.14 Hz), 6.87 (2H, AA₀XX₀,

(10 mL), according to the general procedure B, after

careful ﬂash column chromatography (30% EtOA-

c–hexane) over silica gel, gave the pyrimidine 27d

(102 mg, 92%) as a solid. HPLC purity (reversed phase,

C18) in two solvent is: MeOH–H₂O (60:40) 99.86% and

0

J_AX=8.57 and J_AA=2.14 Hz), 6.70 (2H, AA XX ,

0

J_AX=9.00 and J_AA=2.14 Hz), 2.66 (2H, q, J=7.50 Hz,

CH₂CH₃) and1.21 (3H, t, J=7.50 Hz, CH₂CH₃); ¹³C

NMR (acetone-d₆, 125 MHz) d 170.92, 163.88, 162.64,

160.57, 158.79, 157.68, 132.50, 132.25, 131.38, 130.82,

130.60, 129.19, 129.06, 116.35, 115.97, 115.25, 29.29 and

13.01. MS (EI, 70 eV) m/z 384 (M⁺, 75%), 383 (100%),

135 (34%); HRMS calcdfor C ₂₄H₂₀N₂O₃, 384.1474,

found: 384.1475.

CH₃CN–H₂O (40:60) 100%. Mp 195–196 ^ꢂC; H NMR

1

(acetone-d₆, 500 MHz) d 8.63 (2H, s, OH), 8.39 (2H,

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 7.13 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 6.97 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 6.92 (2H,

0

AA⁰XX⁰, J_AX=9.00 and J_AA=2.14 Hz) and2.25 (6H, s,

0

4-Propyl-2,5,6-tris-(4⁰-hydroxyphenyl)-pyrimidine (27b).

2ÂCH₃); ¹³C NMR (acetone-d₆, 125 MHz) d 165.25,

162.23, 160.50, 157.89, 131.53, 131.14, 130.50, 128.87,

116.51, 115.94 and23.33. MS (EI, 70 eV) m/z 292 (M⁺

100%), 132 (42%), 291 (28%); HRMS calcdfor

C₁₈H₁₅N₂O₂, 291.1133, found: 291.1133.

The reaction of 4-propyl-2,5,6-tris-(4⁰-methoxyphenyl)-

.

pyrimidine (26b, 120 mg, 0.27 mmol) with BF₃SMe₂

(0.83 mL, 8.1 mmol) in dry dichloromethane (10 mL),

according to the general procedure B, after careful ﬂash

656

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

2,5-Bis-(4⁰-hydroxyphenyl)-6-methyl-4-propylpyrimidine

(27e). The reaction of 2,5-bis-(4⁰-methoxyphenyl)-6-

methyl-4-propylpyrimidine (26e, 200 mg, 0.57 mmol)

¹³C NMR (acetone-d₆, 125 MHz) d 169.61, 168.43,

162.59, 160.50, 157.89, 133.15, 131.48, 130.94, 130.86,

130.53, 128.39, 116.92, 116.38, 116.29, 115.95, 115.85,

37.85, 37.85, 29.24, 22.34, 14.27 and12.99. MS (EI, 70eV)

m/z 334 (M⁺19%), 284 (55%), 58 (100%); HRMS calcd

for C₂₁H₂₂N₂O₂, 334.1681, found: 334.1672.

.

with BF₃SMe₂(1.15 mL, 11.4 mmol) in dry dichloro-

methane (10 mL), according to the general procedure B,

after careful ﬂash column chromatography (30%

EtOAc–hexane) over silica gel, gave the pyrimidine 27e

(168 mg, 92%) as a solid. HPLC purity (reversed phase,

C18) in two solvent is: MeOH–H₂O (70:30) 99.19% and

CH₃CN–H₂O (50:50) 99.76%. Mp 140–141 ^ꢂC; ¹H

NMR (acetone-d₆, 500 MHz) d 8.69 (1H, s, OH), 8.54

(1H, s, OH), 8.40 (2H, AA⁰₀XX⁰₀, J_AX=9.00 and

Biological methods

General biological methods. Cell culture media were

purchasedfrom Gibco BRL (GrandIsland, NY, USA).

Calf serum was obtainedfrom Hyclone Laboratories,

Inc. (Logan, UT, USA), andfetal calf serum was pur-

chasedfrom Atlanta Biologicals (Atlanta, GA, USA).

The luciferase assay system was from Promega (Madi-

son, WI, USA). The expression vector for human ERa

(pCMV5-hERa) was constructedpreviously as descri-

bed.⁵¹The expression vector pCMV5-ERb was con-

structedby inserting the cDNA encoding the full length

human ERb (530 residues;⁷into the BamHI site of

pCMV5. The estrogen responsive reporter plasmidwas

(ERE)₂-pS2-Luc, andwas constructedby inserting the

(ERE)₂-pS2 fragment from (ERE)₂-pS2-CAT into the

MluI/BglII sites of pGL3-Basic vector (Promega, Madi-

son, WI, USA). The plasmidpCMV b (Clontech, Palo

Alto, CA, USA), which contains the b-galactosidase gene,

was usedas an internal control for transfection eﬃciency.

0

J_AA=2.14 Hz), 7.10 (2H, AA₀XX₀, J_AX=8.58 and

0

J_AA=2.14 Hz), 6.96 (4H, AA₀XX₀, J_AX=8.58 and

0

J_AA=2.14 Hz), 6.94 (4H, AA XX , J_AX=8.79 and

0

J_AA=2.14 Hz), 2.51 (2H, t, J=7.72 Hz, CH₂CH₂CH₃),

2.24 (3H, s, CH₃), 1.71 (2H, quint, J=7.72 Hz,

CH₂CH₂CH₃) and0.84 (3H, t, J=7.72 Hz, CH₂CH₃);

¹³C NMR (acetone-d₆, 125 MHz) d 168.18, 165.59,

162.37, 160.50, 157.88, 131.42, 131.32, 130.71, 130.51,

128.69, 116.44, 115.94, 37.73, 23.49, 22.33 and14.25.

MS (EI, 70 eV) m/z 320 (M⁺32%), 319 (25%), 291

(100%); HRMS calcdfor C ₂₀H₁₉N₂O₂, 319.1447,

found: 319.1447.

4,6-Bis-ethyl-2,5-bis-(4⁰-hydroxyphenyl)-pyrimidine (27f).

The reaction of 4,6-bis-ethyl-2,5-bis-(4⁰-methoxy-

phenyl)-pyrimidine (26f, 150 mg, 0.36 mmol) with

.

BF₃SMe₂(0.68 mL, 6.7 mmol) in dry dichloromethane

Hormone binding assays. Binding aﬃnities of each com-

poundfor ER a andER b were determined in a radio-

metric competitive binding assay, using [³H]estradiol as

tracer and hydroxylapatite to adsorb ligand–receptor

complex.^14,36Receptor preparations were human ERa

andER b, expressedin baculovirus andpuriﬁed(Pan-

Vera, Madison, WI, USA). Values given represent the

mean of 2–3 repeat determinations which have a coeﬃ-

cient of variation of 0.3.

(10 mL), according to the general procedure B, after

careful ﬂash column chromatography (30% EtOAc–

hexane) over silica gel, gave the pyrimidine 27f (130 mg,

92%) as a solid. HPLC purity (reversed phase, C18) in

two solvent is: MeOH–H₂O (70:30) 100% and

CH₃CN–H₂O (40:60) 100%. Mp 203–204 ^ꢂC; H NMR

1

(acetone-d₆, 500 MHz) d 8.63 (2H, s, OH), 8.44 (2H,

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 7.11 (2H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 7.01 (4H,

0

AA⁰XX⁰, J_AX=8.79 and J_AA=2.14 Hz), 2.53 (4H, q,

Cell culture and transient transfections. Human endo-

metrial cancer (HEC-1) cells were maintainedin culture

as described.³⁷Transfection of HEC-1 cells in 24-well

plates useda mixture of 0.35 mL of serum-free IMEM

medium and 0.15 mL of HBSS containing 5 mL of lipo-

fectin (Life Technologies, Rockville, MD, USA), 1.6 mg

of transferrin (Sigma, St. Louis, MO, USA), 0.5 mg of

pCMVb-galactosidase as internal control, 1 or 2 mg

of the reporter gene plasmid, 100 or 250 ng of ER

expression vector, andcarrier DNA to a total of

3 mg DNA per well. The cells were incubatedat

37 ^ꢂC in a 5% CO₂containing incubator for 6 h. The

medium was then replaced with fresh medium con-

taining the desired concentrations of ligands. Repor-

ter gene activity was assayedat 24 h after ligand

addition. Luciferase activity, normalized for the

internal control b-galactosidase activity, was assayed

as described.³⁷

0

J=7.72 Hz, 2ÂCH₂CH₃) and1.17 (6H, t, J=7.72 Hz,

2ÂCH₂CH₃); ¹³C NMR (acetone-d₆, 125 MHz) d 169.51,

162.69, 160.47, 157.87, 131.39, 130.86, 130.55, 130.52,

128.33, 116.39, 115.93, 29.17 and12.99. MS (EI, 70 eV)

m/z 320 (M⁺43%), 319 (100%); HRMS calcdfor

C₂₀H₁₉N₂O₂, 319.1446, found: 319.1440.

6-Ethyl-2,5-bis-(4⁰-hydroxyphenyl)-4-propylpyrimidine

(27g). The reaction of 6-ethyl-2,5-bis-(4⁰-methox-

yphenyl)-4-propylpyrimidine (26g, 400 mg, 1.1 mmol)

.

with BF₃SMe₂(2.2 mL, 22 mmol) in dry dichloro-

methane (10 mL), according to the general procedure B,

after careful ﬂash column chromatography (30%

EtOAc–hexane) over silica gel, gave the pyrimidine 27g

(330 mg, 89%) as a solid. HPLC purity (reversed phase,

C18) in two solvent is: MeOH–H₂O (70:30) 99.91% and

CH₃CN–H₂O (40:60) 99.90%. Mp 160–161 ^ꢂC; ¹H

NMR (acetone-d₆, 500 MHz) d 8.70 (1H, s, OH), 8.55

(1H, s, OH), 8.43 (2H, AA⁰₀XX⁰₀, J_AX=8.79 and

0

J_AA=1.93 Hz), 7.09 (2H, AA XX , J_AX=8.58 and

Acknowledgements

0

J_AA=2.14 Hz), 6.99.92 (4H, m, Ar), 2.55.48 (4H, m,

CH₂CH₃and CH₂CH₂CH₃), 1.70 (2H, quint,

J=7.50 Hz, CH₂CH₂CH₃), 1.65 (3H, t, J=7.50 Hz,

CH₂CH₃) and0.84 (3H, t, J=7.50 Hz, CH₂CH₂CH₃);

We are grateful for support of this research through

grants from the National Institutes of Health [PHS

5R37 DK15556 (J.A.K.) and5R01 CA19118 (B.S.K.)]

U. Ghosh et al. / Bioorg. Med. Chem. 11 (2003) 629–657

657

andthe US Army Breast Cancer Research Program

[DAMD17-97-1-7076 (J.A.K.)]. NMR spectra were

obtainedin the Varian OxfordInstrument Center for

Excellence in NMR Laboratory. Funding for the

instrumentation was provided in part from the W.M.

Keck Foundation, the National Institutes of Health

(PHS 1 S10 RR104444-01) andthe National Science

Foundation (NSF CHE 96-10502). Mass spectra were

obtainedon instruments supportedby grants form the

National Institute of General Medical Sciences (GM

27029), the National Institutedof Health (RR 01575),

andthe National Science Foundation (PCM 8121494).

21. Mull, E. S.; Sattigeri, V. J.; Rodriguez, A. L.; Katze-

nellenbogen, J. A. Bioorg. Med. Chem. 2002, 10, 381.

22. Ralph, G.; Yongle, G.; Axel, Z.; Zengxiang, C.; Petra, H.;

Wilfred, K. A. J. Antibiot. 1988, 41, 595.

23. De Clerg, E.; Walker, R. T. Pharma. Ther. 1985, 26, 1.

24. Wood, K. V.; Lam, Y. A.; McElroy, W. D. J. Biolumin.

Chemilumin. 1989, 4, 289.

25. Joule, J. A.; Smith, G.; Mills, K. Heterocyclic Chemistry,

3rd Ed.; Chapman and Hall: London, 1995.

26. Vinot, N.; Pinson, J. Bull. Soc. Chim. Fr. 1968, 4970.

27. Ruhlmann, K.; Poredda, S. J. Prakt. Chem. 1960, 12, 18.

28. Strating, J.; Reiﬀers, S.; Wynberg, H. Synthesis 1971, 4,

211.

29. Kawada, K.; Gross, R. S.; Watt, D. S. Synth. Commun.

1989, 19, 777.

References and Notes

30. Miyashita, M.; Hara, S.; Yoshikoshi, A. J. Org. Chem.

1987, 52, 2602.

1. Grese, T. A.; Dodge, J. A. Curr. Pharm. Des. 1998, 4, 71.

2. McDonnell, D. P. Trends Endo. Metab. 1999, 10, 301.

3. Katzenellenbogen, B. S.; Katzenellenbogen, J. A. Breast

Cancer Res. 2000, 2, 335.

4. Pettersson, K.; Gustafsson, J. A. Annu. Rev. Physiol. 2001,

63, 165.

31. Heathcock, C. H.; Smith, S. C. J. Org. Chem. 1994, 59,

6828.

32. Martinez, A. G.; Fernandez, A. H.; Jimenez, F. M.;

Fraiale, A. G.; Subramanian, L. R. J. Org. Chem. 1992, 57,

1627.

33. Nahm, S.; Weinreb, S. M. Tetrahedron Lett. 1981, 22,

3815.

34. Weis, A. L.; Rosenbach, V. Tetrahedron Lett. 1981, 22,

1453.

35. Meyers, M. J.; Sun, J.; Carlson, K. E.; Katzenellenbogen,

B. S.; Katzenellenbogen, J. A. J. Med. Chem. 1999, 42, 2456.

36. Carlson, K. E.; Choi, I.; Gee, A.; Katzenellenbogen, B. S.;

Katzenellenbogen, J. A. Biochemistry 1997, 36, 14897.

37. Sun, J.; Meyers, M. J.; Fink, B. E.; Rajendran, R.; Kat-

zenellenbogen, J. A.; Katzenellenbogen, B. S. Endocrinology

1999, 140, 800.

38. Huang, Y. R.; Katzenellenbogen, J. A. Org. Lett. 2000, 2,

2833.

39. Sun, J.; Huang, Y. R.; Harrington, W. R.; Sheng, S.;

Katzenellenbogen, B. S.; Katzenellenbogen, J. A. Endocrinol-

ogy 2002, 143, 941.

5. Mosselman, S.; Polman, J.; Dijkema, R. FEBS 1996, 392,

49.

6. Kuiper, G. G. J. M.; Enmark, E.; Pelto-Huikko, M.; Nils-

˚

son, S.; Gustafsson, J.A. Proc. Natl. Acad. Sci. U.S.A. 1996,

93, 5925.

7. McInerney, E. M.; Weis, K. E.; Sun, J.; Mosselman, S.;

Katzenellenbogen, B. S. Endocrinology 1998, 139, 4513.

8. McDonnell, D. P.; Clemm, D. L.; Hermann, T.; Goldman,

M. E.; Pike, J. W. Mol. Endocrinol. 1995, 9, 659.

9. Paige, L. A.; Christensen, D. J.; Gron, H.; Norris, J. D.;

Gottlin, E. B.; Padilla, K. M.; Chang, C.; Ballas, L. M.;

Hamilton, P. T.; McDonnell, D. P.; Fowlkes, D. M. Proc.

Natl. Acad. Sci. U.S.A. 1999, 96, 3999.

10. Katzenellenbogen, J. A.; O’Malley, B. W.; Katze-

nellenbogen, B. S. Mol. Endocrinol. 1996, 10, 119.

11. Lin, X.; Huebner, V. Curr. Opin. Drug Discov. Dev. 2000,

3, 383.

40. Nishiguchi, G. A.; Rodriguez, A. L.; Katzenellenbogen, J.

A. Bioorg. Med. Chem. Lett. 2002, 12, 947.

41. Eicher, T.; Hauptmann, S. The Chemistry of Heterocycles;

Georg Thieme: Stuttgart, New York, 1995.

42. Anstead, G. M.; Carlson, K. E.; Katzenellenbogen, J. A.

Steroids 1997, 62, 268.

12. Fink, B. E.; Mortensen, D. S.; Stauﬀer, S. R.; Aron, Z. D.;

Katzenellenbogen, J. A. Chem. Biol. 1999, 6, 205.

13. Stauﬀer, S. R.; Katzenellenbogen, J. A. J. Combinat.

Chem. 2000, 2, 318.

14. Stauﬀer, S. R.; Coletta, C. J.; Tedesco, R.; Sun, J.; Kat-

zenellenbogen, B. S.; Katzenellenbogen, J. A. J. Med. Chem.

2000, 43, 4934.

15. Stauﬀer, S. R.; Katzenellenbogen, J. A. Bioorg. Med.

Chem. 2000, 8, 1293.

43. Gao, H.; Katzenellenbogen, J. A.; Garg, R.; Hansch, C.

Chem. Rev. 1999, 99, 723.

44. Pike, A. C.; Brzozowski, A. M.; Hubbard, R. E.; Bonn,

T.; Thorsell, A. G.; Engstrom, O.; Ljunggren, J.; Gustafsson,

J.; Carlquist, M. EMBO J. 1999, 18, 4608.

16. Stauﬀer, S. R.; Huang, Y. R.; Coletta, C. J.; Tedesco, R.;

Katzenellenbogen, J. A. Bioorg. Med. Chem. 2001, 9, 141.

17. Stauﬀer, S. R.; Huang, Y. R.; Aron, Z. D.; Coletta, C. J.;

Sun, J.; Katzenellenbogen, B. S.; Katzenellenbogen, J. A.

Bioorg. Med. Chem. 2001, 9, 151.

18. Henke, B. R.; Drewry, D. H.; Jones, S. A.; Stewart, E. L.;

Weaver, S. L.; Wiethe, R. W. Bioorg. Med. Chem. Lett. 2001,

11, 1939.

19. Mortensen, D. S.; Rodriguez, A. L.; Carlson, K. E.; Sun,

J.; Katzenellenbogen, B. S.; Katzenellenbogen, J. A. J. Med.

Chem. 2001, 44, 3838.

20. Mortensen, D. S.; Rodriguez, A. L.; Sun, J.; Katze-

nellenbogen, B. S.; Katzenellenbogen, J. A. Bioorg. Med.

Chem. Lett. 2001, 11, 2521.

45. Brzozowski, A. M.; Pike, A. C.; Dauter, Z.; Hubbard,

¨

R. E.; Bonn, T.; Engstrom, O.; Ohman, L.; Greene, G. L.;

¨

Gustafsson, J.-A.; Carlquist, M. Nature 1997, 389, 753.

46. Shiau, A. K.; Barstad, D.; Loria, P. M.; Cheng, L.;

Kushner, P. J.; Agard, D. A.; Greene, G. L. Cell 1998, 95, 927.

47. Still, W. C.; Kahn, M.; Mitra, A. J. Org. Chem. 1978, 43,

2923.

48. Jenkins, S. S. J. Am. Chem. Soc. 1934, 56, 682.

49. Numazawa, M.; Nagaoka, M. J. Org. Chem. 1982, 47,

4024.

50. Strohmeier, J.; von Angerer, E. Arch. Pharm. (Weinheim)

1985, 318, 421.

51. Wrenn, C. K.; Katzenellenbogen, B. S. J. Biol. Chem.

1993, 268, 24089.

Article Doi

Estrogenic diazenes: Heterocyclic non-steroidal estrogens of unusual structure with selectivity for estrogen receptor subtypes

DOI: 10.1016/S0968-0896(02)00309-7

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