Nonpeptidic HIV protease inhibitors possessing excellent antiviral activities and therapeutic indices. PD 178390: A lead HIV protease inhibitor

Article abstract of DOI:10.1016/S0968-0896(99)00215-1

With the insight generated by the availability of X-ray crystal structures of various 5,6-dihydropyran-2-ones bound to HIV PR, inhibitors possessing various alkyl groups at the 6-position of 5,6-dihydropyran-2-one ring were synthesized. The inhibitors pos

Full text of DOI:10.1016/S0968-0896(99)00215-1

Bioorganic & Medicinal Chemistry 7 (1999) 2775±2800
Nonpeptidic HIV Protease Inhibitors Possessing Excellent
Antiviral Activities and Therapeutic Indices.
PD 178390: A Lead HIV Protease Inhibitor
J. V. N. Vara Prasad, a,* Frederick E. Boyer, a John M. Domagala, a
Edmund L. Ellsworth, a Christopher Gajda, a Harriet W. Hamilton, a Susan E. Hagen, a
Larry J. Markoski, a Bruce A. Steinbaugh, a Bradley D. Tait, a Christine Humblet, a
Elizabeth A. Lunney, a Alexander Pavlovsky, a John R. Rubin, a Donna Ferguson, b
Neil Graham, b Tod Holler, b Donald Hupe, b Carolyn Nouhan, b Peter J. Tummino, b
A. Urumov, b Eric Zeikus, b Greg Zeikus, b Stephen J. Gracheck, c James M. Saunders, c
Steven VanderRoest, c Joanne Brodfuehrer, d K. Iyer, d M. Sinz, d Sergei V. Gulnik e
and John W. Erickson e
aDepartment of Chemistry, Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Company, 2800 Plymouth Road,
Ann Arbor, MI 48105, USA
bDepartment of Biochemistry, Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Company, 2800 Plymouth Road,
Ann Arbor, MI 48105, USA
cDepartmentofInfectious Diseases, Parke-DavisPharmaceuticalResearch, DivisionofWarner-LambertCompany, 2800PlymouthRoad,
Ann Arbor, MI 48105, USA
dDepartment of PDM, Parke-Davis Pharmaceutical Research, Division of Warner-Lambert Company, 2800 Plymouth Road, Ann Arbor,
MI 48105, USA
eStructure Biochemistry Program, NCI-Frederick Cancer Research and Development Center, PRI/Dyncorp, Frederick, MD 21702,
USA
Received 22 March 1999; accepted 9 July 1999
AbstractÐWith the insight generated by the availability of X-ray crystal structures of various 5,6-dihydropyran-2-ones bound to
HIV PR, inhibitors possessing various alkyl groups at the 6-position of 5,6-dihydropyran-2-one ring were synthesized. The inhibi-
tors possessing a 6-alkyl group exhibited superior antiviral activities when compared to 6-phenyl analogues. Antiviral ecacies were
further improved upon introduction of a polar group (hydroxyl or amino) on the 4-position of the phenethyl moiety as well as the
polar group (hydroxymethyl) on the 3-(tert-butyl-5-methyl-phenylthio) moiety. The polar substitution is also advantageous for
decreasing toxicity, providing inhibitors with higher therapeutic indices. The best inhibitor among this series, (S)-6-[2-(4-amino-
phenyl)-ethyl]-(3-(2-tert-butyl-5-methyl-phenylsulfanyl)-4-hydroxy-6-isopropyl-5,6-dihydro-pyran-2-one (34S), exhibited an EC50
of 200 nM with a therapeutic index of >1000. More importantly, these non-peptidic inhibitors, 16S and 34S, appear to o€er little
cross-resistance to the currently marketed peptidomimetic PR inhibitors. The selected inhibitors tested in vitro against mutant HIV
PR showed a very small increase in binding anities relative to wild-type HIV PR. Cmax and absolute bioavailability of 34S were
higher and half-life and time above EC95 were longer compared to 16S. Thus 34S, also known as PD 178390, which displays good
antiviral ecacy, promising pharmacokinetic characteristics and favorable activity against mutant enzymes and CYP3A4, has been
chosen for further preclinical evaluation. # 1999 Elsevier Science Ltd. All rights reserved.
Key words: HIV protease inhibitors; nonpeptidic HIV protease inhibitors; aspartic protease inhibitors; antivirals; anti-HIV agents.
* Corresponding author. Tel.: +1-734-622-2866; fax: +1-734-622-7879; e-mail: varaprj@aa.wl.com
0968-0896/99/$ - see front matter # 1999 Elsevier Science Ltd. All rights reserved.
PII: S0968-0896(99)00215-1

2776
J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
Introduction
inhibitors not cross-resistant with existing agents is still
important.
Reverse transcriptase (RT) and protease (PR) inhibitors
are the current antiretroviral therapy choices for the
treatment of human immunode®ciency virus type 1
(HIV-1) infection.1 These two targets play a crucial role
in viral replication. The highly promising results of recent
clinical trials with protease inhibitors in combination
with RT inhibitors provide hope that antiretroviral
therapy may succeed in signi®cantly delaying the onset
of progression to AIDS.2 Each of the currently mar-
keted protease inhibitors3,4 can cause adverse e€ects
and interact with other common medications.5,6 Clinical
data obtained with these drugs as monotherapy not
only showed alarming resistance to HIV PR inhibitors
but also clinical isolates exhibited phenotypical cross-
resistance to the known marketed drugs.7±9 Peptide
derived HIV PR inhibitors often have low bioavailability,
poor pharmacokinetics and several stereocenters.10
However, nonpeptidic HIV-1 PR inhibitors that have
been identi®ed so far are still complex in structure and/
or possess low antiviral activities11,12 with the exception
of DuPont±Merck's cyclic ureas and Pharmacia-
Upjohn's pyran-2-ones.13,14 Thus, research towards iden-
tifying simple, potent, low molecular weight HIV-1 PR
Our e€orts towards the discovery of potent nonpeptidic
inhibitors began with I, originating from a mass screen-
ing of our chemical collection.15 Further SAR led to
inhibitor II, possessing no chiral center but occupying
only three inner pockets of the enzyme.16 Introduction
of a chiral center by quaternizing the 6-position of 4-
hydroxy-pyran-2-one ring led to structure III, whose
substituents occupy the inner four pockets of the
enzyme.17 X-ray crystal structures11,12,17 of pyran-2-
ones and 5,6-dihydropyran-2-ones (e.g. II and III)
bound to HIV PR show that the enolic hydroxyl group
forms hydrogen-bonding interactions with Asp25 and/
or Asp125 residues of the enzyme. More interestingly,
all these inhibitors displace water-301 (unique to HIV
PR18) with the lactone moiety. These inhibitors are
primarily optimized for enzymatic binding and indeed
showed excellent binding anity to HIV PR. Preliminary
results concerning 6-alkyl-5,6-dihydropyran-2-ones were
described in recent communications.19,20 This paper will
discuss in more detail the design, synthesis, structure±
activity relationships (SAR), experimental details
and pharmacokinetics of 6-alkyl-5,6-dihydropyran-2-one

J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
2777
series. The considerations used for the selection of PD
178390 as a lead compound for preclinical development
will also be discussed.
enzyme, respectively, complementing the key hydrogen
bonding interactions from the core template as descri-
bed above, while the 3-(2-isopropyl-5-methylphenythio)
moiety occupies the S2 and S1 pockets of the enzyme.
Even though analogues of III exhibited excellent inhi-
bitory activities against HIV PR, they showed poor
antiviral activities. We found that the 5,6-dihydropyran-
2-one analogues with more lipophilic groups (for e.g.
III) were binding to the human serum albumin in
>98% (Table 1).20 Moreover, some of these analogues
0
0
Design
The X-ray crystal structure of III bound to HIV PR
showed that 6-position substituents (the phenyl and
phenethyl moieties) occupy the S1 and S2 pockets of the
Table 1. Dihydropyran-2-one analoguesa and their physical properties, HIV PR binding anities and antiviral activities
Entry
R1
R2
R3
Mp (ꢀC)
Molecular formulab
Elements IC50
EC50
TC50 Therapeutic
indexe
analyzed (nM)c (mM)
(mM)
.
C30H32O4S1 0.75 H2O
.
C25H30O4S1 0.13 H2O
1
2
3
4
5
6
7
8
4-OH
4-OH
4-OH
4-OH
4-OH
4-OH
4-OH Cyclopropyl
4-OH Cyclopentyl
4-OH Cyclohexyl
4-OH
4-OH
4-OH
4-OH
4-OH
4-OH
4-OH
4-OH
4-OH Cyclopropyl
4-OH Cyclobutyl
4-OH Cyclopentyl
4-OH Cyclohexyl
4-OH
4-OH
4-OH Cyclohexyl
4-OH
4-OH
4-OH
4-OH
4-OH
4-OH
4-OH Cyclopropyl
4-OH Cyclopentyl
4-NH2
4-NH2 Isopropyl
4-NH2 Isobutyl
4-NH2 Cyclohexyl
Phenyl
Methyl
n-Propyl
n-Butyl
n-Pentyl
Isopropyl
H
H
H
H
H
H
H
H
H
199±201
130±131
105±107
59±61
73±75
88±90
92±94
88±90
82±87
93±95
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
CH
HPLC
CH
HPLC
CH
CH
CH
CH
CHN
CHN
CHN
CHN
CH
CH
CH
CH
CH
CH
11
>69
69
66
66
23
27
55
66
54
1
7
9
1
1
29
13
9
11
9.5 9.4
7.8
>23
.
C27H34O4S1 0.3 H2O
19
30
C28H36O4S1
29H38O4S1
C
C27H34O4S1 0.31 H2O
C27H32O4S1
18.4d >27
.
4.6
8.0
7.2
33
338
21.6
4.3
2.6
4.1
5.9
3.6
3.3
1.0
2.2
3.1
2.5
6.5
0.03d
2.9
6.8
1.9
5.0
5.9
4.1
NDf
4.7 >100
2.5 >100
1.0
0.9
0.6
0.6 >100
1.5 >100
1.6 >100
0.8 >100
0.6 >100
0.5
>7
1.6
3.1
.
C29H36O4S1 0.1 H2O
9
C30H38O4S1
.
24H28O4S1 0.36 H2O
45
ND
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
H
Phenyl
H
C
196±199(d) C31H34O5S1 0.5 H2O
Ð
.
CH2OH
CH2OH
CH2OH
CH2OH
CH2OH
CH2OH
CH2OH
CH2OH
CH2OH
CH2OH
CH2OH
OH
>21
>40
100
70
.
C26H32O5S1 0.37 H2O
.
C28H36O5S1 0.5 H2O
C29H38O5S1
C30H40O5S1
.
C28H36O5S1 0.5 H2O
C29H38O5S1
C28H34O5S1
.
C29H36O5S1 0.57 H2O
.
C30H38O5S1 0.2 H2O
.
C31H40O5S1 0.84 H2O
Methyl
n-Propyl
n-Butyl
n-Pentyl
Isopropyl
Isobutyl
143±145
127±129
128±130
100±102
175±178
108±110
152±154
99±102
117±119
138±139
117±119
117±118
100±103
203±205
88±90
100
63
32
53
>182
>67
>63
>125
>167
156
1
41
24
>29
15
16
12
1
44
>55
65
25
75
7
66
73
.
C25H30O5S1 014 H2O
Methyl
Isopropyl
OH
OH
C27H34O5S1
.
30H38O5S1 0.28 H2O
C
.
Methyl
Methyl
n-Propyl
n-Butyl
n-Pentyl
Isopropyl
OCH2CH2OH
OCH2CH2O CH2O CH3
OCH2CH2OH
OCH2CH2OH
OCH2CH2OH
OCH2CH2OH
OCH2CH2OH
OCH2CH2OH
CH2OH
CH2OH
CH2OH
CH2OH
H
C27H34O6S1 0.75 H2O
C29H38O7S1
3.4 >100
20
6
4.6
4.3
1.7
68
70
21
9
.
C29H38O6S1 0.5 H2O
C30H40O6S1
.
C31H42O6S1 0.2 H2O
92±94
83±85
99±100
90±92
6.4
2.9
2.8
3.8
2.8
3.1
2.7
2.9
3.2
1.1
6.5
2.2
1.1d
6.8
2.6
>9
1.5
.
C29H38O6S1 1.0 H2O
66
1.6 >88.5
.
C29H36O6S1 0.8 H2O
168±170
113±115
218±221(d) C31H35O4N1S1 0.7 H2O
C31H40O6S1
1.2
3.7
0.5 >100
0.8 >100
1.4
15
2.5
0.6
1.8
78
94
.
Phenyl
.
C28H37O4N1S1 0.7 H2O
.
C29H39O4N1S1 0.6 H2O
C31H41O4N1S1
139±141
168±170
214±216
64±65
173±174
95±96
87±89
200
>125
57
4
26
118
37
80
59
66
65
66
20
87
.
C27H34O3S1 0.17 H2O
H
H
H
H
H
H
Isopropyl
Phenyl
Isopropyl
Isopropyl
Phenyl
.
C31H34O4 0.3 H2O
C28H36O4S1
CH2OH
CH2OH
OH
.
26H34O4S1 0.7 H2O
C
C32H36O5S1 0.2 H2O
.
OCH2CH2OH
OCH2CH2OH
179±182
86±88
>20
1.3
1
67
.
C29H38O6S1 0.7 H2O
Isopropyl
a
All the compounds reported are racemic mixtures.
Water content was not experimentally determined.
Values are the average of at least two determinations measured at pH 6.2.
Ki values measured at pH 6.2.
Ratio of TC50 and EC50.
ND: not determined.
b
c
d
e
f

2778
J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
were also found to decrease their IC50 to HIV PR as
well as their antiviral EC50 with the addition of human
serum albumin. Therefore, it was reasoned that one
probable explanation for the lack of antiviral activity
with these compounds could be due to their anity to
bind to protein (antiviral assay uses 10% fetal calf
serum). Hence, we focussed on the design and synthesis
of compounds with reduced lipophilicity for enhance-
ment in antiviral activity. Analysis of the X-ray struc-
ture of III bound to HIV PR suggested that aliphatic
groups might be substituted in the place of the phenyl
ring at the 6-position; we have already shown that ali-
phatic groups are also well tolerated in the 4-hydroxy
pyran-2-one series (IV).21 We speculated that our com-
pounds of type III could maintain good selectivity
against HIV PR due to the fact that signi®cant binding
is contributed by displacement of water-301.16 Various
polar functionalities were also introduced on the 3-(2-
isopropyl-5-methylphenylthio) moiety to increase
hydrophobicity and aqueous solubility compared to III.
methyl ketones in the presence of alkali at room tem-
perature.22 The unsaturated ketones were converted to
saturated ketones by hydrogenation of the double
bond using Raney nickel or 5% Pd/BaSO4 (Scheme 2).
Alternatively, the ketones were synthesized by the reac-
tion of the corresponding Weinreb amide with the
appropriate Grignard reagent (Scheme 3).23 Thiotosy-
lates used in this study were synthesized as described
previously.19,20,24
Enantiomerically pure 6,6-disubstituted-5,6-dihydro-
pyran-2-ones were synthesized via resolution of the cor-
responding b-hydroxy acid (VIII) as shown in Scheme
4. The ketone, VII, was condensed with the anion
derived from tert-butyl acetate (or benzyl acetate), and
then saponi®ed (or hydrogenolysis in the case of benzyl
ester) to yield VIII. Compound VIII on treatment with
0.55 equivalent of (S)-a-methylbenzylamine gave the
corresponding salt, which was crystallized from EtOAc/
hexanes to furnish VIII-(S)-a-methylbenzylamine salt in
>95% diastereomeric purity. Free acid (S)-VIII was
liberated from the salt by treatment with 3 N hydro-
chloric acid. Compound (S)-VIII was elaborated to its
b-keto ester, (S)-IX, via a two step protocol, viz., con-
version of carboxylate with CDI to the corresponding
imidazole followed by treatment with the magnesium
salt of ethyl malonate. Compound (S)-IX, on treatment
with sodium hydroxide, cyclized to 5,6-dihydropyran-2-
one, (S)-X. Similarly (R)-X was prepared employing
(R)-a-methylbenzylamine in the resolution procedure.
(S)-X and (R)-X, on treatment with the corresponding
thiotosylates as described in step 3, Scheme 1, a€orded
the 5,6-dihydropyran-2-one analogues (16S, 16R, 34S,
34R, 39S and 39R) of at least 95% optical purity.
Chemistry
The compounds described in this paper were synthe-
sized in a convergent fashion, by coupling the appro-
priately 6,6-disubstituted 5,6-dihydropyran-2-one (VI)
with the corresponding thiotosylate in the presence of
potassium carbonate in DMF (Scheme 1).17 The 6,6-
disubstituted 5,6-dihydropyran-2-ones were synthesized
by the condensation of the dianion derived from methyl
acetoacetate with the corresponding ketone, followed by
cyclization in the presence of a base, usually sodium
hydroxide (Scheme 1).
The ketones used above were synthesized either by the
Claisen±Schmidt reaction (Scheme 2) or via Weinreb's
methodology (Scheme 3). The Claisen±Schmidt reac-
tion was performed by the condensation of the corre-
sponding aldehydes with the appropriately substituted
Biological Assays
The compounds were tested for their inhibition of pur-
i®ed recombinant HIV PR using the peptide substrate
Scheme 1. Reaction conditions: 1. NaH, n-BuLi, THF, followed by ketone addition; 2. NaOH; 3. Corresponding thiotosylate, K2CO3, DMF.
Scheme 2. Reaction conditions: 1. Ba(OH)2, EtOH; 2. Raney nickel or 5% Pd/BaSO4 20±50 psi, hydrogen; 3. di-tert-Butyl carbonate, CH2Cl2.

J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
2779
.
Scheme 3. Reaction conditions: 1. Benzyl bromide, K2CO3, acetone; 2. LiOH; 3. SOCl2; 4. (OMe)NHMe HCl, pyridine, CH2Cl2; 5. Corresponding
Grignard reagent, THF.
Scheme 4. Reaction conditions: 1. LDA, tert-butyl acetate (or benzyl acetate), 78ꢀC, addition of ketone; 2. LiOH (10% Pd/C, H2 in the case of
benzyl ester); 3. S-a-Methylbenzylamine, crystallizations; 4. 1 N HCl; 5. CDI; 6. Magnesium salt of ethyl malonate; 7. 0.1 N NaOH; 8. 20% Pd/C,
H2; 9. K2CO3, DMF, corresponding thiosulfonate; 10. NaOH, DMSO/H2O.
His-Lys-Ala-Arg-Val-Leu-Phe(p-NO2)-Glu-Ala-Nleu-Ser
(Bachem Bioscience) at pH 6.2.25 The enzyme cleaves
the Leu-Phe(p-NO2) bond of the substrate; the sub-
strate and products were separated by reversed-phase
HPLC, absorbance being measured at 220 nm.26 All the
compounds reported in this paper were also tested for
anti-HIV activity at Southern Research Institute27 in an
in vitro cell culture assay with HIV-IIIB infected human
lymphocyte derived CEM cells using the XTT cyto-
pathic method. EC50 indicates the concentration of the
drug which provides 50% protection against HIV. TC50
is the concentration of the drug which elicits cytotoxi-
city in 50% of uninfected cells. Therapeutic index is
de®ned as TC50/EC50. The physical properties, enzyme
binding anity and antiviral activities of the com-
pounds are shown in Tables 1 and 2.

2780
J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
Table 2. Chiral dihydropyran-2-one analoguesa and their physical properties, HIV PR binding anities and antiviral activities
Entry
Mp (ꢀC)
Molecular formulab
Elements
analyzed
Rotation in degrees
(c, solvent)
Ki
(nM)c
EC50
(mM)
EC90
(mM)
TC50
(mM)
Therapeutic
index
.
28H36O5S1 0.5 H2O
16
176±178
205±207
201±203
139±141
121
128
95±96
>108d
>108d
C
C28H36O5S1 0.5 H2O
CH
CH
CH
CHN
CHN
CHN
CH
CH
CH
Ð
+35.6 (0.55, abs. EtOH)
37.2 (0.66, abs. EtOH)
Ð
+70.8 (1, MeOH)
ND
Ð
+61.58 (1, MeOH)
60.4 (1, MeOH)
0.17
0.09
31
0.43
0.11
25
ND
0.09
160
0.57
0.46
17
0.5
0.2
19.8
0.6
0.33
4.37
1
1
5.9
1
1
10.6
1
>100
>100
>100
>100
210
210
65
68
69
>200
>200
>6
>200
1050
10.6
118
.
16S
16R
34
34S
34R
39
.
28H36O5S1 0.5 H2O
C
C29H37N1O4S1 0.5 H2O
.
.
29H37N1O4S1 0.5 H2O
C
C28H37N1O4S1
C
28H36O4S1
C28H36O4S1
C28H36O4S1
39S
39R
1
NDe
340
16
a
The ratio of enantiomers is at least >95:<5.
Water content was not experimentally determined.
Ki values measured at pH 6.2.
E€ervesces at that temperature.
ND: not determined.
b
c
d
e
Results and Discussion
molecule. Speci®cally, a hydroxymethyl group sub-
stituted at the 4-position could form a hydrogen bond
with Asp129 (NH). In addition, an OCH2CH2OH
substituent at this site could interact with the side chain
of Asp129 or Asp130, or with solvent. Thus, 5,6-di-
hydropyran-2-ones with a hydroxyl-containing group at
the 4-position of the 3-(2-tert-butyl-5-methylphenylthio)
moiety were synthesized and their biological activities
were evaluated.
Dihydropyran-2-ones having various alkyl groups at the
6-position
Initial studies were focussed on probing the S1 pocket of
the enzyme by varying alkyl groups of di€erent steric
requirements at the 6-position of the dihydropyran-2-
one ring. In all these dihydropyran-2-one analogues, the
4-hydroxyphenethyl group was kept constant at the 6-
position of the dihydropyran-2-one template. This sub-
stituent had been shown to be optimal for occupying
the S2 pocket of the enzyme.28 The 3-(2-isopropyl-5-
Hydroxymethyl analogues
0
methylphenylthio) group, which occupies the S1 as well
0
In this series, the 3-(2-tert-butyl-4-hydroxylmethyl-5-
methylphenylthio) group was kept constant at the 3-
position of the 5,6-dihydropyran-2-one and the alkyl
group at the 6-position was varied (Table 1). It is inter-
esting to note that the 6-phenyl analogue containing a
hydroxymethyl group on the 3-(tert-butyl-5-methyl-
phenylthio) moiety 11 showed better antiviral activity
(4.7 mM versus >69 mM) compared to des-hydroxy-
methyl analogue 1 even though their binding anities
were similar. However, the methyl analogue 12 exhib-
ited a modest enhancement in binding anity with the
enzyme relative to 2 but a fourfold enhancement in
antiviral activity was observed. Also noteworthy is that
compound 12 exhibited less cytotoxicity when com-
pared to 2 (TC50: >100 mM versus 69 mM). Other
hydroxymethyl analogues, 13±21, showed either similar
or slightly enhanced IC50s when compared to the des-
hydroxymethyl analogues in enzymatic assays. Most
importantly, all these compounds showed much better
antiviral activities compared to their des-hydroxymethyl
analogues 3±9.
as S2 pockets of the enzyme, was used at the C-3
position of the dihydropyran-2-one. Substitution of the
6-phenyl group (1) by a methyl group led to 2. Surpris-
ingly in vitro binding anity to HIV PR is maintained.
Furthermore, there is an increase in antiviral activity by
>sevenfold (EC50: 9.4 mM versus >69 mM for 2 and 1,
respectively).
Extending the methyl group to n-propyl, n-butyl and
n-pentyl led to 5,6-dihydropyran-2-ones 3±5. All these
analogues except the n-propyl analogue 3 showed both
lower enzymatic anities and antiviral activities when
compared to 2. The isopropyl analogue 6 exhibited a
twofold increase in binding anity to HIV PR, whereas
its antiviral activity was increased by ®vefold compared
to 2. Cycloalkyl substituents at C-6 (7±9) were also
active and comparable to 2. When an alkyl group is
removed from the above 5,6-dihydropyran-2-ones to
give 10, its binding anity to HIV PR is reduced by 36-
fold. In summary, relative to the phenyl analogue 1
these structure±activity studies showed that the isopro-
pyl group conferred the greatest boost in anti-HIV
activity (by 36-fold).
Phenolic analogues
Replacement of the hydroxymethyl group by a phenol
gave the derivatives 22±24. Although these compounds
showed good binding anity to HV PR, their antiviral
activities decreased when compared to the correspond-
ing hydroxymethyl derivatives (22 versus 12, 23 versus
16 and 24 versus 21) and are somewhat similar to com-
pounds not substituted at this position (22 versus 2, 23
versus 6 and 24 versus 9).
Dihydropyran-2-ones having polar functionality on the
3-(2-tert-butyl-5-methylphenylthio) moiety
Further analysis of the X-ray structure of III bound
to HIV PR indicates that substituting at the 4-position
of the thiophenyl group might a€ord binding to
Asp129 and/or Asp130 either directly or through a water

J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
2781
Dihydropyran-2-ones containing a 4-OCH2CH2OH
moiety on the 3-(2-tert-butyl-5-methylphenylthio) moiety
removed from the molecule, for example inhibitor 37
(EC50: 15 mM;) versus 6 (EC50: 1.9 mM) or 16 (EC50:
0.6 mM) or 39 (EC50: 0.6 mM) or 40 (EC50: 1.8 mM).
However, we could not ®nd any quantitative correlation
between antiviral activity and calculated or measured
log Ps, which shows that there could be several other
factors for increased antiviral activities.
In this series, the hydroxyl group was extended outward
by two atoms relative to the hydroxymethyl series. The
resulting derivatives containing hydroxyethyl ethers at
the 4-position of (2-tert-butyl-5-methylphenylthio) moi-
ety (25, 27±32) showed HIV PR binding anity below
10 nM. Antiviral activities of these analogues were gen-
erally less than corresponding hydroxymethyl analogues
(25 versus 12, 27 versus 13, 28 versus 14, 29 versus 15,
30 versus 16, 31 versus 18 and 32 versus 20). When the
terminal hydroxyl group was protected as the MOM
ether 26, a threefold loss of enzymatic binding anity
was observed, but the antiviral activity was comparable
to the hydroxyl derivative 25.
Chiral 5,6-dihydropyran-2-ones
Given the good therapeutic indices of several racemic
5,6-dihydropyran-2-ones (16, 34 and 39), the optically
pure 5,6-dihydropyran-2-ones were synthesized (Scheme
4). Their enzymatic binding anities and antiviral
activities are shown in Table 2. The (S)-enantiomers
16S, 34S and 39S showed a better binding anity to
HIV PR relative to their (R)-enantiomers. Chiral 5,6-
dihydropyran-2-ones 34S and 39S exhibited a twofold
increase in antiviral activity relative to 34 and 39,
respectively.
Dihydropyran-2-ones containing a 6-isopropyl-6-
(4-aminophenethyl) moiety at the 6-position of the ring
In this series, the 4-hydroxyl group on the phenethyl
moiety at C-6 was replaced with 4-amino. The resulting
inhibitor 34 exhibited binding anity to HIV PR, anti-
viral activity and therapeutic index all comparable to
the 4-hydroxylphenethyl analogue 16. As before, the
inhibitor containing an isopropyl group at the 6-position
(34) exhibited better binding anity and greater anti-
viral activity when compared to its 6-phenyl analogue
33. Increasing the size of the 6-position alkyl group
from isopropyl to cyclohexyl (36) decreased the antiviral
activity compared to 34, though both showed similar
binding anity to HIV PR.
X-ray crystal structure of the 6-[(4-amino)phenethyl]-6-
isopropyl analogue (34S) bound to WT HIV PR
The X-ray crystallographic structure of 34S bound to
HIV PR was determined at 2.0 A resolution. In general,
the inhibitor binds in the active site in a manner pre-
viously described for this series of compounds.9,10,13 The
5,6-dihydropyran-2-one ring spans between the catalytic
dyad and the ¯ap region, and the substituents on the
5,6-dihydropyran-2-one ring occupy the S1=S01 and
S2=S02 sites (Fig. 1).
Beyond the core binding, the aniline in the S2 pocket
can form a weak hydrogen bond with the Asp30 (CO)
and also interacts through a water molecule with the
Asp30 side chain (Fig. 2). In comparing the activity
of the aniline inhibitor 34S (Ki=0.11 nM) with the
compound having an unsubstituted phenethyl group at
P2 (39S Ki=0.09 nM), no gain in enzyme binding is
realized with the NH2 substitution. Thus, the weak
interaction of the amino group observed in the X-ray
structure does not appear to contribute to overall
improved binding, which is inconsistent with the
experimental ®ndings.
Dihydropyran-2-ones containing a 6-isopropyl-6-phenethyl
moiety at the 6-position of the ring
In order to test the contribution of the polar group (4-
hydroxyl or 4-amino) present on the 6-phenylethyl ring
towards biological activity in the above series, the hy-
droxyl/amino group was removed and the isopropyl
group was kept constant at P1. As seen previously, the
5,6-dihydropyran-2-ones containing 6-position alkyl
groups exhibited superior antiviral activities compared
to 6-position phenyl analogues (38 versus 39 and 41
versus 42). These unsubstituted analogues displayed
similar binding anities to HIV PR compared to their
4-hydroxyl (37 versus 6, 39 versus 16, 40 versus 23, 42
versus 30) or 4-amino counterparts (34 versus 39), a
result which infers that the 4-hydroxyl or 4-amino
group on the phenethyl moiety may not be contributing
signi®cantly to the binding of the enzyme. Interestingly,
these des-hydroxy or des-amino derivatives exhibited
similar antiviral activities, though their cytotoxicities
are somewhat higher. Thus, the polar group at the 4-
position of the phenethyl group confers a reduction of
cytotoxicity, which in turn produces improved ther-
apeutic indices.
On the prime side, the hydroxymethyl group at the 4-
position of the thiophenyl ring forms a hydrogen bond
with Asp129 (NH), as expected. Surprisingly, however,
in the corresponding series having
a 4-hydroxy-
phenethyl group at P2, the incorporation of the hydroxy-
methyl substituent does not result in a binding anity
gain (6 versus 16). In an X-ray structure of HIV pro-
tease bound with an inhibitor in which the 4-position of
the thiophenyl ring is not substituted (data not shown),
a water molecule is present, which binds to Asp129
(NH) and Asp130 (NH). The free energy in binding 6
with the hydroxymethyl group at the 4-position may be
equalled by the free energy in binding the analogous
derivative with no 4-position substituent and a water
molecule. In general, polar groups attached para to the
sulfur on the thiophenyl ring did provide improved
enzyme binding.
The above SAR demonstrates that the addition of polar
groups to the initial 5,6-dihydropyran-2-ones (for e.g.
III) indeed increased the antiviral activities of these
compounds. Even among 6-isopropyl series there is a
decrease in antiviral activity when polar groups are

2782
J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
Figure 1. X-ray crystal structure of compound 37S bound to HIV PR overlaid with the bound structure of A74704 (blue).
Figure 2. Interatomic distances of compound 37S binding to HIV PR as derived from X-ray crystal structure. Distances are measured between
heavy atoms.
Comparison of 16S and 34S to PNU-140690
However, n-propyl and phenethyl groups in PNU-140690
occupy S2 and S1 pockets of the enzyme, respectively.
This orientation contrasts with 16S and 34S, wherein
the small alkyl group (isopropyl) occupies the S1 pocket
of the enzyme and 4-substituted phenethyl group occu-
pies S2 pocket. This result clearly demonstrates that
di€erent enantiomers are most active in these two series
of HIV PR inhibitor,31,32 despite the common core.
Recently, Pharmacia-Upjohn has reported on a related
series of 5,6-dihydropyran-2-ones (PNU-140690), which
occupies ®ve pockets of the enzyme.29,30 It is interesting
to note that PNU-140690 (V) contains n-propyl and
phenethyl groups at the 6-position of the 5,6-dihydro-
pyran-2-one ring, somewhat similar to 16S and 34S.

J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
2783
Table 3. Dihydropyran-2-one analogues and their Ki values tested against subsite mutants of HIV PR in vitro
Enzyme
Pockets of the enzyme
Fold increase in Ki for inhibitorsa,b
1
16
21
16S
34S
WT
V32I
V82F
I84V
V32I/I84V
V82F/I84V
V82A
D30N
G48V/L90M
Ð
S2, S2
1 (0.95)
8.3
12
11
52
2.5
Ð
Ð
Ð
1 (0.069)
4.3
2.2
3.3
13
3.6
Ð
Ð
1 (0.062)
17
26
20
40
9.3
Ð
Ð
Ð
1 (0.016)
3.3
1.1
1.8
6.9
<3.0
4.3
4.3
1 (0.028)
1.9
2.5
2.6
14
5.3
1.3
1.2
0.8
0
0
0
0
S1, S1 , S3, S3
0
S1, S1
0
S1, S1 , S2, S2
0
0
0
S1, S1 , S2, S2 , S3, S3
0
0
S1, S1 , S3, S3
0
S2, S2
Ð
18.6
a
The assays were done at pH 6.2 and Ki values are the average of at least four runs.
Actual Ki values are given in parentheses.
b
Activity against HIV PR mutants
substitutions enhance bioavailability of this class of
protease inhibitors.36,37 Mice were dosed 25 mg/kg
orally by gavage and in some cases subcutaneously. The
compounds were dosed PO in a vehicle of either (A)
20% 0.1 N NaOH/80% PEG 400, (B) 40% 0.05 N
NaOH/30% PEG 400/30% methylcellulose (MC), (C)
20% 0.1 N NaOH/80% of 0.5% MC (D), or 10%
ethanol/15% PEG 400/75% water. For subcutaneous
dosing the vehicle was 10% DMSO/PBS. The results are
shown in Table 4. Among the vehicles used it appears
that 20% 0.1 N NaOH/80% of 0.5% MC is preferred.
The inhibitors containing 6-alkyl-6-hydroxyphenethyl
derivatives showed Cmax values of 3±9 mM and half-lives
of 0.5±2 h. Among 6-position alkyl analogues, isopropyl
and cyclopentyl analogues (16, 34) showed good drug
concentrations, whereas cyclohexyl analogue (21)
exhibited poor drug plasma concentrations. Encoura-
ging to note is that the enantiomerically pure inhibitors
16S and 34S showed similar or slightly better drug
concentrations in plasma relative to their racemic ana-
logues 16 and 34, respectively. Thus 5,6-dihydropyran-
2-one inhibitors 16S and 34S, which showed excellent
therapeutic indices, also showed good pharmacokinetic
A major problem in the development of antiviral
therapies for AIDS has been the emergence of drug
resistance.8,9,33 The various classes of PR inhibitors
possessing di€erent binding interactions could poten-
tially lead to di€erent resistance patterns. Selected 5,6-
dihydropyran-2-ones with various substituents at the
6-position were evaluated for their inhibitory activity
against various mutant enzymes in vitro.34 Preliminary
results are shown in Table 3.
Mutations at amino acids 82 and 84, which contribute
0
to the formation of S1, S1 pockets of the enzyme, could
a€ect binding anities of the inhibitors with varying P1
groups relative to the WT. When the size of P1 group
was increased from isopropyl (16) to phenyl (1) or cyclo-
hexyl (21) there is a decrease in binding anities with the
V82F and I84V mutant enzymes. The same three 5,6-
dihydropyran-2-ones were then assayed against HIV PR
containing a mutation at amino acid 32, which contributes
to the formation of the S2 pocket. A similar trend was
observed in that the larger alkyl groups at C-6 conferred a
greater loss of potency. It was unclear why there is 17-fold
increase in inhibitory activity with 21, since all these inhi-
0
bitors contains similar P2 or P2 groups. Obviously, com-
Table 4. Pharmacokinetic parameters of selected dihydropyran-2-one
analogues in micea
pound 21 might bind with the wild type enzyme itself in a
slightly di€erent fashion compared to 16 and 1.31,32 Inhi-
bitors 16S and 34S were also tested against all these panels
of mutant enzymes. The decrease in inhibitory activities
was within 14-fold including V32I and V32I/I84V
mutants. It is important to note that V82I and I84V
are clinically known mutants with the existing drugs.35
Entry Vehicleb Cmax (mM) tmax (h) t1/2 (h) AUC (mg h/mL)
11
A
B
A
A
A
B
C
D
A
A
B
A
C
C
C
C
5.03
5.7
3.63
4.37
2.8
2
1
1.8
3.7
ND
3.4
2
2.43
2.0
5.4
ND
ND
3.1
0.9
ND
2.9
0.3
2.2
27.3
34.9
ND
28.6
24
20.1
37.3
40
ND
ND
12.1
0.8
ND
27.8
5.5
12
14
16
0.5
0.5
2
0.5
0.5
1
7.0
17.3
Selectivity
9.0
6.63
5.77
6.04
0.4
When 5,6-dihydropyran-2-ones 16S and 34S were tested
against other human aspartic proteases (renin, human
cathepsin D, recombinant cathepsin E, native gastricsin
and recombinant human pepsin) these agents showed a
selectivity index for HIV PR>5000.
18
19
2
0.5
0.5
0.5
0.5
0.5
0.5
0.5
21
1.0
16S
16R
34S
19.61
8.55
26.49
81.8
Pharmacokinetic studies of dihydropyran-2-ones varying
6-position alkyl groups
a
Dose: 25 mg/kg.
A: 20% 0.1 N NaOH/80% PEG 400; B: 40% 0.05 N NaOH/30%
b
5,6-Dihydropyran-2-ones containing various 6-position
alkyl groups were dosed in mice to determine which
PEG 400/30% methylcellulose; C: 20% 0.1 N NaOH/80% 0.5%
methylcellulose; D: 10% ethanol/15% PEG 400/75% water.

2784
J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
properties with 42% (63% as sodium salt) bioavail-
ability in mice.
Conclusions
With the insight generated by the availability of X-ray
crystal structures of various 5,6-dihydropyran-2-ones
bound to HIV PR, inhibitors possessing various alkyl
groups at the 6-position of 5,6-dihydropyran-2-one ring
were synthesized. The inhibitors possessing a 6-alkyl
group exhibited superior antiviral activities when com-
pared to 6-position phenyl analogues. Antiviral e-
cacies were further improved upon introduction of a
polar group (hydroxyl or amino) on the 4-position of
the phenethyl moiety as well as the polar group (hydroxy-
methyl) on the 3-(tert-butyl-5-methyl-phenylthio) moi-
ety. The polar substitution is also advantageous for
decreasing toxicity, providing inhibitors with higher
therapeutic indices. The best inhibitor among this series,
34S, exhibited an EC50 of 200 nM with a therapeutic
index of >1000. The inhibitor 34S was found to
decrease its EC50 by only twofold when 40% of human
serum albumin was added to in vitro antiviral test.
Thus, the addition of hydrophilic groups to the initial
5,6-dihydropyran-2-ones (for e.g. III) indeed decreased
protein binding. These results show that the decrease in
protein binding may be at least one factor for increased
antiviral activities. More importantly, these non-pepti-
dic inhibitors, 16S and 34S, appear to o€er little cross-
resistance to the currently marketed peptidomimetic
PR inhibitors. The selected inhibitors tested in vitro
against mutant HIV PR showed a very small increase in
binding anities relative to wild-type HIV PR. Cmax
and absolute bioavailability of 34S were higher and
half-life and time above EC95 were longer compared to
16S. Thus 34S (PD 178390, CI-1029), which displays
good antiviral ecacy, promising pharmacokinetic
characteristics and favorable activity against mutant
enzymes and CYP3A4, has been chosen for further
preclinical evaluation.
Since 16S and 34S showed favorable pharmacokinetics,
they were evaluated in rats and dog at 10 mg/kg dose.
The results are shown in Table 5. Although both inhi-
bitors exhibited favorable pharmacokinetic character-
istics, the inhibitor containing the 4-amino group on the
phenethyl moiety (34S) gave a better Cmax, half-life and
bioavailability relative to 16S. Theoretically, the amino
group could confer higher solubility in the low pH
environment of the upper GI tract, thereby resulting in
improved pharmacokinetics.
Cytochrome P-450 inhibition of selected HIV-protease
inhibitors
One of the problems associated with the current mar-
keted HIV PR drugs is their potential for drug±drug
interactions. Several peptide-derived HIV PR inhibitors
are known or suspected inhibitors of cytochrome P-450
isozyme CYP3A4.38,39 Since CYP3A4 is the most
abundant P-450 metabolic enzyme, the likelihood of
interactions between these peptidic protease inhibitors
and other drugs metabolized by the cytochrome P-450
pathway is high. Ritonavir also inhibits other cyto-
chrome P-450 isozymes, most notably CYP2D6 and
CYP2C9.40 Thus it is useful to ascertain the possible
inhibition pro®le of the present nonpeptidic inhibitors
described here against cytochrome P-450 isozymes.
Inhibitors 16S and 34S were tested against individual
cytochrome P-450 isozymes, and the data are shown in
Table 6. These two compounds do not inhibit CYP3A4
and CYP2D6 or CYP2C9 isozymes up to 10 mM con-
centration, but inhibition was observed at 100 mM con-
centration. These encouraging results suggest that these
inhibitors might show fewer drug interactions with
drugs known to be metabolized by these three cyto-
chrome P-450 isozymes.
Experimental
Biological assays. For the determination of IC50 values,
the HPLC assay used was described previously. The
®nal pH of the assay was set to 6.2.16 Southern
Research Institute as described earlier23 performed
antiviral and toxicity assays. The probe substrates used
to determine the inhibitory activities against CYP3A4,
CYP2D6 and CYP2C9 were testosterone, bufurolol and
tolbutamide, respectively. The samples were analyzed
using HPLC-UV or ¯uorescence.
Table 5. Pharmacokinetic parameters of selected dihydropyran-2-
ones in doga
Entry Cmax
(mM)
t1/2
(h)
AUC
(mg h/mL)
Hours above Bioavailability
the EC95
(%)
16S
34S
32
72
1.9
3.7
10
69
4
7
16
42
a
Dose: 10 mg/kg, capsule or solution bu€ered to pH 7.4, NaOH.
Chemical synthesis. Melting points (mp) were deter-
mined in open capillary tubes on a Hoover mp appa-
ratus and are uncorrected. Infrared (IR) spectra were
determined in KBr pellets on a Nicolet FT IR SX-20
spectrophotometer. Proton magnetic resonance (NMR)
spectra were recorded on Varian 300 and 400 spectro-
meters and chemical shifts are reported in d units rela-
tive to internal standard, trimethylsilane. All mass
spectra (MS) were obtained on a Finnigan 4500 GC±MS
or VG analytical 7070E/F spectrometer. Robertson
Microlit Laboratories, Inc. performed elemental analyses;
Table 6. P-450 inhibition of selected dihydropyrones (% of inhibition
of individual isozymesa)
Entry
3A4
2D6
2C9
1 mM 10 mM 100 mM 1 mM 10 mM 100 mM 1 mM 10 mM 100 mM
16S
34S
9
4
14
16
36
30
5
3
9
16
33
33
0
2
14
12
50
59
a
Measures change of isozyme substrate/products in the presence/
absence of inhibitor.

J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
2785
NJ and all compounds gave analytical results of ‹0.4%
of theoretical values. All alkyl lithiums and Grignard
reagents used were from commercial sources and used
as is. During work up, the organic layer was dried over
anhyd MgSO4. Flash column chromatography or med-
ium pressure chromatography was performed using
silica gel 32-63, 60A and concentrations were performed
in vacuo at 10±30 mmHg.
5.01 (s, 2H), 6.89 (d, 2H), 7.08 (d, 2H), 7.31 (t, 1H),
7.32±7.42 (m, 4H).
3-(4-Benzyloxy-phenyl)-1-cyclobutyl-propan-1-one. The
title compound was prepared as described in the general
procedure using cyclobutyl methyl ketone (15.0 g, 153
mmol), 4-benzyloxybenzaldehyde (32.4 g, 153 mmol),
Ba(OH)2 (3.0 g) and 95% EtOH (400 mL). The reaction
was kept under re¯ux for 16.5 h. The crude product was
subjected to ¯ash silica gel chromatography (CH2Cl2:
MeOH=99:1 eluent) and then rechromatographed
(hexane:EtOAc:CH2Cl2=90:5:5 to 85:7.5:7.5 eluents)
to a€ord 3.25 g of product, 3-(4-benzyloxy-phenyl)-1-
cyclobutyl-prop-2-en-1-one. The unsaturated ketone
(3.16g, 10.8 mmol) was subjected to hydrogenation
conditions using 1.0 g of 5% Pd/BaSO4 in 100 mL of
THF at room temperature. The crude product was
puri®ed by ¯ash silica gel chromatography (CH2Cl2:
MeOH=99:1 to 98:2) to a€ord 3.1 g of a gummy solid.
Isolated yield: 80%. 1H NMR (400 MHz, CDCl3): d
1.7±2.3 (m, 6H), 2.6±2.7 (t, 2H), 2.8±2.9 (t, 2H), 3.1±3.3
(m, 1H), 5.1 (s, 2H), 6.8±6.9 (d, 2H), 7.1±7.2 (d, 2H),
7.3±7.5 (m, 5H); MS-APCI (m/z): 293.
Synthesis of aldehyde/ketones (VII): (a) via
Claisen±Schmidt reaction
General procedure. To the corresponding benzaldehyde
(1 equiv) taken in EtOH, the appropriate ketone (1±2
equiv) and Ba(OH)2 (barium hydroxide octahydrate
heated to 200ꢀC under high vacuum for 4 h to remove
water) or sodium hydroxide were added. The reaction
was stirred at room temperature overnight. Initially all
the reactants were soluble and as the reaction pro-
gressed, a precipitate was observed. The reaction mix-
ture was diluted with EtOAc and dilute HCl was added
until acidic. The organic layer was separated and the
aqueous layer was extracted with EtOAc and dried. The
crude product (purity >90%) was subjected to ¯ash
silica gel chromatography (10±15% EtOAc in hexanes)
to a€ord analytically pure product. The pure unsatu-
rated ketone thus obtained was subjected to hydro-
genation conditions at room temperature at 20±50 psi of
hydrogen using 5% palladium on barium sulfate or
Raney nickel as a catalyst. The catalyst was ®ltered o€
and the resulting ketone recrystallized or puri®ed by
¯ash silica gel chromatography.
3-(4-Benzyloxy-phenyl)-1-cyclohexyl-propan-1-one. The
title compound was prepared according to the general
procedure using 4-benzyloxybenzaldehyde (29.3 g,
138 mmol), cylohexyl methyl ketone (17.4 g, 138 mmol),
Ba(OH)2 (3.2 g) and 95% EtOH (300 mL). The reaction
was re¯uxed for 8 h. The crude product, 3-(4-benzyloxy-
phenyl)-1-cyclohexyl-prop-2-en-1-one (25.9 g, 84 mmol),
was subjected to hydrogenation using 5% Pd/BaSO4
(1 g) in THF (60 mL). The crude product was subjected
to ¯ash silica gel chromatography (CH2Cl2:MeOH=
99:1 to 98:2 eluents) to a€ord 20.5 g of a gummy solid.
1H NMR (400 MHz, CDCl3): d 01.1±1.9 (m, 10H), 2.2±
2.4 (m, 1H), 2.68±2.74 (m, 2H), 2.79±2.85 (m, 2H), 5.04
(s, 2H), 6.8±6.9 (d, 2H), 7.1±7.2 (d, 2H), 7.3±7.5 (m,
5H); MS-CI (m/z): 322.
1-(4-Benzyloxy-phenyl)-4-methyl-pentan-3-one. The title
compound was prepared according to the general pro-
cedure using 4-benzyloxybenzaldehyde (42.5 g, 200.0
mmol), 400 mL of EtOH, 3-methyl-2-butanone (34.4 g,
400.0 mmol) and Ba(OH)2 (7.0 g). The crude product
(purity >90%) was subjected to ¯ash silica gel chro-
matography (10±15% EtOAc in hexanes) to a€ord
analytically pure product. Isolated yield: 80%. The
unsaturated ketone, 1-(4-benzyloxy-phenyl)-4-methyl-
pent-1-ene-3-one, was subjected to hydrogenation con-
ditions using Raney nickel in THF at 25 psi to a€ord
1-(4-tert-Butyoxycarbonyl-amino-phenyl)-4-methyl-pentan-
3-one. The title compound was prepared according to
the general procedure using 4-nitrobenzaldehyde
(22.5 g, 150 mmol), 3-methyl-2-butanone (30 mL), 1%
NaOH (25 mL) and 100 mL of THF. The reaction was
stirred at room temperature for 48 h and then kept
under re¯ux for 6 h. The solution was cooled and con-
centrated; the residue was partitioned between water
and Et2O. The organic layer was washed with brine,
dried and concentrated. The crude product was puri®ed
by ¯ash silica gel chromatography (25% EtOAc in hex-
anes eluent) to a€ord 4-methyl-1-(4-nitro-phenyl)pent-
1
the pure title compound. Isolated yield: 95%. H NMR
(400 MHz, CDCl3): d 0.86 (d, 6H), 2.08 (m, 1H), 2.64 (t,
2H), 2.77 (t, 2H), 5.0 (s, 2H), 6.83 (d, 2H), 7.07 (d, 2H),
7.28 (t, 1H), 7.31±7.44 (m, 4H).
4-Benzyloxy-phenethyl cyclopropyl ketone. The title
compound was prepared according to the general pro-
cedure
using
4-benzyloxybenzaldehyde
(50.0 g,
1
235.6 mmol), 250 mL of EtOH, cyclopropyl methyl
ketone (83.26 g, 353.4 mmol) and Ba(OH)2 (7.0 g). The
crude product (purity ꢁ90%; 50 g) was subjected to
hydrogenation conditions using 5% Pd/BaSO4 in THF
(500 mL) at 48 psi to a€ord the title compound. The
crude compound was subjected to ¯ash chromato-
graphy (10±15% of EtOAc in hexanes as eluents). The
compound thus obtained was stirred in EtOH solvent
overnight, and the solid obtained was ®ltered and dried.
Isolated yield: 50%. 1H NMR (400 MHz, CDCl3): d
0.81 (m, 2H), 1.0 (m, 2H), 1.86 (m, 1H), 2.81 (m, 4H),
1-ene-3-one. Isolated yield: 40%. H NMR (400 MHz,
CDCl3): d 1.16 (d, 6H), 2.86 (m, 1H), 6.67 (d, 1H), 6.89
(d, 1H), 7.58 (d, 1H), 8.21 (d, 1H); MS-CI (m/z): 220.
To 4-methyl-1-(4-nitro-phenyl)pent-1-ene-3-one (5.9 g,
26.9 mmol) taken in 100 mL of THF was added Pd/
BaSO4 (0.5 g) and shaken in a hydrogen atmosphere of
51 psi for 34 min. The crude material dissolved in
200 mL of THF was treated with di-tert-butyl carbonate
(5.2 g, 26.9 mmol) and stirred at 55ꢀC for 24 h, followed
by 72 h at room temperature. The reaction mixture was
concentrated and the residue was partitioned between

2786
J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
EtOAc and water. The organic layer was separated,
dried and concentrated. The crude material was puri®ed
by ¯ash silica gel chromatography (25% EtOAc in hex-
(s, 9H), 1.62 (m, 1H), 1.74 (m, 4H), 2.25 (m, 1H), 2.67
(m, 2H), 2.70 (m, 2H), 6.36 (brs, 1H), 7.05 (d, 2H), 7.21
(d, 2H); MS-CI (m/z): 331.
1
anes eluent). Isolated yield: 95%. H NMR (400 MHz,
DMSO): d 0.91 (s, 6H), 1.40 (s, 9H), 2.53 (m, 1H), 2.68
(m, 2H), 2.62 (m, 2H), 7.00 (d, 2H), 7.26 (d, 2H), 9.16
(brs, 1H); MS-CI (m/z): 291.
Synthesis of aldehyde/ketones (VII): (b) via Weinreb
amide methodology
Benzyl ester of 3-(4-benzyloxyphenyl) propionic acid. 3-
(4-Hydroxyphenyl)propionic acid (15.0 g, 90.3 mmol)
was dissolved in 300 mL of acetone and treated with
anhyd K2CO3 (25.0 g) and benzyl bromide (33.8 g,
198.6 mmol). The reaction was kept under re¯ux for
18 h, cooled to room temperature and concentrated.
The residue was taken in water and extracted with
EtOAc (3Â200 mL). The organic layer was washed with
brine and dried to furnish the title compound. 1H NMR
(400 MHz, CDCl3): d 2.61 (t, 2H), 2.89 (t, 2H), 5.0 (s,
2H), 5.08 (s, 2H), 6.86 (d, 2H), 7.07 (d, 2H), 7.22±7.42
(m, 10H).
1-(4-tert-Butoxycarbonyl-amino-phenyl)-5-methyl-hexan-
3-one. The title compound was prepared according to
the general procedure using 4-nitrobenzaldehyde (13.5 g,
90 mmol), 4-methyl-2-pentanone (16 mL, 130 mmol),
1% NaOH (20 mL) and 80 mL of THF. The reaction
was stirred at the room temperature for 48 h. The reac-
tion mixture was concentrated and the residue was par-
titioned between water and Et2O. The organic layer was
washed with brine, dried and concentrated. The crude
product was crystallized from EtOH to a€ord 5-methyl-
1-(4-nitro-phenyl)hex-1-ene-3-one. Isolated yield: 10%.
1H NMR (400 MHz, CDCl3): d 0.95 (d, 6H), 2.16±2.26
(m, 1H), 2.52 (d, 2H), 6.80 (d, 1H), 7.52 (d, 1H), 7.66 (d,
2H), 8.22 (d, 2H); MS-CI (m/z): 234. 5-Methyl-1-(4-
nitro-phenyl)hex-1-ene-3-one was subjected to hydro-
genation conditions using 0.5 g of Pd/BaSO4 . The crude
material (2.1 g, 10 mmol) taken in 100 mL of THF was
added to di-tert-butyl carbonate (2.6 g, 12 mmol) and
stirred at 50ꢀC for 16 h. The reaction mixture was con-
centrated and the residue was partitioned between
EtOAc and water. The organic layer was separated,
dried and concentrated. The crude material was puri®ed
by ¯ash silica gel chromatography (25% EtOAc in hex-
3-(4-Benzyloxyphenyl)propionic acid. To the crude
benzyl ester of 3-(4-benzyloxyphenyl)propionic acid in
THF (100 mL) was added 3 N lithium hydroxide
(180.5 mmol) and MeOH (50 mL). The reaction was
stirred at room temperature overnight. The solvents
were evaporated and the residue was acidi®ed with 3 N
HCl. The product was extracted with 1:1 EtOAc and
CH2Cl2 (3Â300 mL), dried and concentrated to give a
1
solid. Isolated yield: 65% (overall 2 steps). H NMR
(400 MHz, DMSO-d6): d 2.42 (t, 2H), 2.67 (t, 2H), 5.0
(s, 2H), 6.86 (d, 2H), 7.07 (d, 2H), 7.27 (t, 1H), 7.31±
7.39 (m, 4H).
1
anes eluent). Isolated yield: 80%. H NMR (400 MHz,
DMSO): d 0.76 (d, 6H), 1.41 (s, 9H), 1.94 (m, 1H), 2.22
(d, 2H), 2.62 (m, 4H), 7.00 (d, 2H), 7.27 (d, 2H), 9.16
(brs, 1H); MS-CI (m/z): 305.
3-(4-Benzyloxy-phenyl)-N-methoxy-N-methyl propion-
amide. To the 3-(4-benzyloxyphenyl)propionic acid
(15.0 g, 58.6 mmol) was added thionyl chloride
(150 mL). The reaction mixture was kept under re¯ux
for 5 h, and thionyl chloride was evaporated. The resi-
due was taken in 10 mL of CH2Cl2 and cooled to 0ꢀC.
To it were added N,O-dimethylamine hydrochloride
(7.1 g, 73.3 mmol) followed by 30 mL of pyridine. The
reaction was stirred at room temperature for 18 h and
quenched with 3 N HCl. The product was extracted into
EtOAc (3Â200 mL). The combined organic layers were
washed with saturated NaHCO3 solution, dilute HCl,
brine and dried. The residue was puri®ed by ¯ash silica
gel chromatography (10±20% EtOAc in hexanes as elu-
ents). Isolated yield: 82%. 1H NMR (400 MHz, CDCl3):
d 2.66 (t, 2H), 2.86 (t, 2H), 3.14 (s, 3H), 3.55 (s, 3H), 5.0
(s, 2H), 6.86 (d, 2H), 7.11 (d, 2H), 7.29 (t, 1H), 7.33±
7.42 (m, 4H).
1-(4-Boc-amino-phenyl)-4-cyclohexyl-pentan-3-one. The
title compound was prepared according to the general
procedure using 4-nitrobenzaldehyde (7.6 g, 50 mmol),
acetyl cyclohexane (6.9 g, 55 mmol), Ba(OH)2 (2.5 g) and
100 mL of 95% EtOH. The reaction mixture was stirred
at room temperature for 1 h. The reaction mixture was
poured into dilute HCl and extracted with EtOAc
(2Â150 mL). The organic layer was separated, washed
with brine, dried and concentrated. The crude product
was crystallized from EtOH to give 4-cyclohexyl-1-(4-
nitro-phenyl)but-1-ene-3-one. Isolated yield: 32%. 1H
NMR (400 MHz, CDCl3): d 1.18±1.44 (m, 5H), 1.67 (m,
1H), 1.82 (m, 2H), 1.89 (m, 2H), 2.61 (m, 1H), 6.88 (d,
1H), 7.56 (d, 1H), 7.66 (dd, 2H), 8.21 (dd, 2H); MS-CI
(m/z): 260. To 4-cyclohexyl-1-(4-nitro-phenyl)-but-1-ene-
3-one (4.0 g, 15.4 mmol) taken in 50 mL of MeOH was
added 0.4 g of 5% Pd/BaSO4 and shaken in a hydrogen
atmosphere of 52 psi for 14 h. The crude material (3.6 g,
15.4 mmol) taken in 200 mL of THF was added to di-
tert-butyl carbonate (4.0 g, 18.3 mmol) and stirred at
55ꢀC for 6 h, followed by 16 h at room temperature. The
reaction mixture was concentrated and the residue was
partitioned between EtOAc and water. The organic
layer was separated, dried and concentrated. The crude
material was puri®ed by ¯ash silica gel chromatography
(33% EtOAc in hexanes eluent). Isolated yield: 65%.
1H NMR (400 MHz, DMSO): d 1.10±1.31 (m, 5H), 1.47
3-(4-Benzyloxyphenyl)propionaldehyde. To 3-(4-benzyl-
oxy-phenyl)-N-methoxy-N-methyl propionamide (5.0 g,
16.8 mmol) taken in THF (150 mL) was added LAH
(0.6 g, 16.8 mmol) in portions. The reaction was stirred
at room temperature for 1 h. The reaction was quenched
with water and diluted with dilute HCl and EtOAc. The
organic layer was separated and dried to furnish the title
1
compound. Isolated yield: 85%. H NMR (400 MHz,
CDCl3): d 2.75 (t, 2H), 2.89 (t, 2H), 5.07 (s, 2H), 6.89
(d, 2H), 7.11 (d, 2H), 7.32 (t, 1H), 7.33±7.47 (m, 4H);
9.8 (s, 1H).

J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
2787
4-Benzyloxy-phenethyl propyl ketone. To 3-(4-benzyl-
Synthesis of 5,6-dihydropyran-2-ones
oxy-phenyl)-N-methoxy-N-methyl propionamide (10.0 g,
33.6 mmol) in THF (100 mL) was added 2 M n-propyl
magnesium bromide (33.6 mL) in THF dropwise at
room temperature. The reaction was stirred at room
temperature for 16 h, and then quenched with 1 N HCl.
The product was extracted into EtOAc (3Â200 mL),
dried and concentrated. The crude product was puri®ed
by ¯ash silica gel chromatography (20% EtOAc in hex-
anes) to give the pure title compound. Isolated yield:
General procedure. Methyl acetoacetate was added
dropwise to a slurry of hexane washed NaH in dry THF
at 0ꢀC and the reaction stirred at 0ꢀC (15 min to 3 h).
n-Butyl lithium was then added at 0ꢀC and the reaction
stirred at 0ꢀC (15 min to 24 h). A solution of the requisite
ketone (1 equiv) in THF was added, and the reaction
mixture was stirred at 0ꢀC to room temperature for
15 min to 24 h. To the reaction mixture was added
AcOH (or dilute HCl or saturated NH4Cl) with stirring,
and the THF was removed on a rotary evaporator. The
viscous reaction mixture was partitioned between H2O
and EtOAc. After separation of the layers, the aqueous
layer was again extracted with EtOAc; the combined
organic layers were dried and concentrated. The inter-
mediates were either puri®ed by ¯ash silica gel chroma-
tography or taken on crude. The aldol intermediate was
dissolved in THF (1 vol) and treated with 9±10 volumes
of NaOH (0.1±1.0 N). The reaction was stirred from 1
to 24 h at room temperature. The reaction mixture was
acidi®ed to pH 4±5 using HCl (0.1±6 N) or acetic acid.
On occasions the product could be isolated by ®ltration.
Alternatively the acidi®ed extracts were extracted with
EtOAc. The organic extracts were combined, dried and
concentrated. Puri®cation was accomplished by tritura-
tion from Et2O or ¯ash silica gel chromatography. The
pure 5,6-dihydropyran-2-one thus obtained was sub-
jected to hydrogenation conditions at room temperature
at 20±50 psi of hydrogen using 20% Pd/C as a catalyst.
The catalyst was ®ltered o€ and the resulting 5,6-di-
hydropyran-2-one was puri®ed by ¯ash silica gel chro-
matography or by crystallization.
1
99%. H NMR (400 MHz, CDCl3): d 0.86 (t, 3H), 1.53
(m, 2H), 2.33 (t, 2H), 2.66 (t, 2H), 2.81 (t, 2H), 5.0 (s,
2H), 6.86 (d, 2H), 7.06 (d, 2H), 7.25±7.42 (m, 5H).
4-Benzyloxy-phenethyl n-butyl ketone. The reaction was
performed as described for 4-benzyloxy-phenethyl ethyl
ketone, using 3-(4-benzyloxy-phenyl)-N-methoxy-N-
methyl propionamide (8.5 g, 28.5 mmol), 2 M n-butyl
magnesium chloride (21.4 mL, 42.8 mmol) and 100 mL
of THF. The crude product was puri®ed by ¯ash silica
gel chromatography (20% ethyl acetate in hexanes) to
1
give the title compound. Isolated yield: 59%. H NMR
(400 MHz, CDCl3): d 0.86 (t, 3H), 1.27 (m, 2H), 1.34
(m, 2H), 2.33 (d, 2H), 2.64 (d, 2H), 2.78 (t, 2H), 5.0 (s,
2H), 6.85 (d, 2H), 7.06 (d, 2H), 7.25 (t, 1H), 7.31±7.42
(m, 4H).
4-Benzyloxy-phenethyl isopropyl ketone. The reaction
was performed as described for 4-benzyloxy-phenethyl
ethyl ketone, using 3-(4-benzyloxy-phenyl)-N-methoxy-
N-methyl propionamide (8.0 g, 26.9 mmol), 2 M iso-
propyl magnesium chloride (20.1 mL, 40.3 mmol) and
200 mL of THF. The crude product was puri®ed by
¯ash silica gel chromatography (20% EtOAc in hex-
anes) to give the title compound. Isolated yield: 72%.
1H NMR (400 MHz, CDCl3): d 0.86 (d, 6H), 2.08 (m,
1H), 2.64 (t, 2H), 2.77 (t, 2H), 5.0 (s, 2H), 6.83 (d, 2H),
7.07 (d, 2H), 7.28 (t, 1H), 7.31±7.44 (m, 4H).
4-Hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-5,6-dihydro-
pyran-2-one. The title compound was prepared accord-
ing to the general procedure using 3-(4-benzyloxy-
phenyl)propionaldehyde (4.0 g, 16.8 mmol), methyl
acetoacetate (5.9 g, 50.4 mmol), NaH (1.2 g, 50.4 mmol)
and n-butyl lithium (1.64 M, 30.7 mL, 50.4 mmol). The
intermediate aldol was cyclized using 0.2 N NaOH
(378 mL) and THF (37.8 mL). Isolated yield: 50%.
Debenzylation was carried out using 20% Pd/C in THF
(65 mL) and MeOH (10 mL). The compound was pur-
i®ed by ¯ash silica gel chromatography (20±70% EtOAc
in hexanes as eluents) a€ording the title compound.
4-Benzyloxy-phenethyl isobutyl ketone. The reaction
was performed as described for 4-benzyloxy-phenethyl
ethyl ketone, using 3-(4-benzyloxy-phenyl)-N-methoxy-
N-methyl propionamide (5.0 g, 16.8 mmol), 2 M iso-
butyl magnesium chloride (12.6 mL, 25.2 mmol) and
100 mL of THF. The crude product was puri®ed by
¯ash silica gel chromatography (20% EtOAc in hex-
anes) to give the title compound. Isolated yield: 62%.
1H NMR (400 MHz, CDCl3): d 0.86 (d, 6H), 2.08 (m,
1H), 2.22 (d, 2H), 2.64 (t, 2H), 2.77 (t, 2H), 5.0 (s, 2H),
6.83 (d, 2H), 7.07 (d, 2H), 7.28 (t, 1H), 7.31±7.44 (m,
4H).
1
Isolated yield: 80%. H NMR (400 MHz, DMSO-d6): d
1.81 (m, 2H), 2.27 (dd, 1H), 2.39 (dd, 1H), 2.47 (m, 1H),
2.58 (m, 1H), 4.2 (m, 1H), 4.89 (s, 1H), 6.61 (d, 2H),
6.94 (d, 2H), 9.11 (s, 1H); MS-APCI (m/z): 235.
4-Hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-6-methyl-5,6-
dihydro-pyran-2-one. The title compound was prepared
according to the general procedure using 4-t-butyl-
dimethylsilyloxy-phenethyl methyl ketone (16.9 g,
60.9 mmol), methyl acetoacetate (21.2 g, 182.7 mmol),
NaH (4.39 g, 182.7 mmol) and n-butyl lithium (1.6 M,
114.2 mL, 182.7 mmol). The intermediate aldol was
cyclized using 0.2 N NaOH (1370 mL) and THF
(137 mL). The compound was puri®ed by ¯ash silica gel
chromatography (20±70% EtOAc in hexanes as eluents)
4-Benzyloxy-phenethyl cyclopentyl ketone. The reaction
was performed as described for 4-benzyloxy-phenethyl
ethyl ketone, using 3-(4-benzyloxy-phenyl)-N-methoxy-
N-methyl propionamide (5.0 g, 16.8 mmol), 2 M cyclo-
pentyl magnesium chloride (12.6 mL, 25.2 mmol) and
300 mL of THF. The crude product was puri®ed by
¯ash silica gel chromatography (20% EtOAc in hex-
anes) to give the title compound. Isolated yield: 50%.
1H NMR (400 MHz, CDCl3): d 1.44±1.77 (m, 8H), 2.69
(t, 2H), 2.77 (m, 3H), 5.0 (s, 2H), 6.86 (d, 2H), 7.07 (d,
2H), 7.28 (t, 1H), 7.33±7.42 (m, 4H).
1
a€ording the title compound. Isolated yield: 80%. H
NMR (400 MHz, DMSO-d6): d 1.31 (s, 3H), 1.8 (m,

2788
J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
2H), 2.31 (d of ABX q, 1H), 2.42±2.5 (m, 2H), 2.54 (d of
ABX q, 1H), 4.92 (s, 1H), 6.61 (d, 2H), 6.92 (d, 2H),
9.14 (brs, 1H).
6-Cyclopropyl-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-
5,6-dihydro-pyran-2-one. The title compound was pre-
pared according to the general procedure using 4-ben-
zyloxy-phenethyl cyclopropyl ketone (4.5 g, 16.1 mmol),
methyl acetoacetate (4.7 g, 40.2 mmol), NaH (1.0 g,
40.2 mmol) and n-butyl lithium (1.64 M, 24.5 mL,
40.2 mmol). The intermediate aldol was cyclized using
0.2 N NaOH (362 mL) and THF (36 mL). The com-
pound was puri®ed by ¯ash silica gel chromatography
(20±80% EtOAc in hexanes as eluents) a€ording 6-[2-
(4-benzyloxy-phenyl)-ethyl]-4-hydroxy-6-cyclopropyl-5,6-
dihydro-pyran-2-one. Isolated yield: 55%. Debenzyl-
ation was carried out using 20% Pd/C (0.5 g) in THF
(100 mL) in the presence of hydrogen atmosphere. The
crude product was puri®ed by ¯ash silica gel chromato-
graphy (20±70% EtOAc in hexanes as eluents). Isolated
3-Hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-6-n-propyl-5,6-
dihydro-pyran-2-one. The title compound was prepared
according to the general procedure using 4-benzyloxy-
phenethyl n-propyl ketone (10.0 g, 35.5 mmol), methyl
acetoacetate (10.3 g, 88.7 mmol), NaH (2.1 g, 88.7 mmol)
and n-butyl lithium (1.64 M, 54.1 mL, 88.7 mmol). The
intermediate aldol was cyclized using 0.2 N NaOH
(799 mL) and THF (80 mL). After evaporation of sol-
vents the residue was triturated from Et2O/hexanes to
a€ord 6-[2-(4-benzyloxy-phenyl)-ethyl]-6-n-propyl-4-hy-
droxy±5,6-dihydro-pyran-2-one. Isolated yield: 85%.
Debenzylation was carried out using 20% Pd/C (0.5 g)
in THF (150 mL), MeOH (100 mL) in the presence of
hydrogen atmosphere. The crude product on trituration
with Et2O/hexanes gave the pure product. Isolated
yield: 93%. 1H NMR (400 MHz, CDCl3): d 0.82 (t, 3H),
1.25 (m, 2H), 1.58 (m, 2H), 1.77 (q, 2H), 2.4 (m, 2H),
4.89 (s, 1H), 6.6 (d, 2H), 6.92 (d, 2H), 9.08 (s, 1H).
1
yield: 80%. H NMR (400 MHz, CDCl3): d 0.32 (m,
1H), 0.42 (m, 3H), 2.14 (m, 1H), 1.89 (m, 2H), 2.36 (d,
1H), 2.55 (m, 3H), 4.89 (s, 1H), 6.61 (d, 2H), 6.94 (d,
2H), 9.11 (s, 1H).
6-Cyclobutyl-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-
5,6-dihydro-pyran-2-one. The title compound was pre-
pared as described in the general procedure using
methyl acetoacetate (2.4 g, 20.4 mmol), NaH (60% dis-
persion in oil, 0.9 g, 21.4 mmol), 1.6 M n-butyl lithium in
hexanes (13.0 mL, 20.9 mmol), 3-(4-benzyloxy-phenyl)-
1-cyclobutyl-propan-1-one (3.0 g, 10.2 mmol) and THF
(200 mL). After addition of the ketone, the reaction was
stirred for 2 h at 0ꢀC. The crude product was subjected
to hydrogenolysis using 0.2 g of 20% Pd/C in THF
(100 mL) at room temperature. To the crude product, 5-
cyclobutyl-5-hydroxy-7-(4-hydroxy-phenyl)-3-oxo-hep-
tanoic acid methyl ester, in THF (25 mL), was added
0.2 N NaOH (250 mL). The reaction was stirred for 2 h
at room temperature. Puri®cation was accomplished by
¯ash silica gel chromatography (CH2Cl2:MeOH=98:2
eluent) to give 2.4 g of the desired product as a solid.
1H NMR (400 MHz, CDCl3): d 1.7±2.1 (m, 7 H), 2.2±
2.3 (m, 1 H), 2.5±2.7 (t, 2 H), 2.6±2.7 (m, 3 H), 3.42 (s, 2
H), 4.61 (s, 1H), 6.75 (d, 2 H), 6.98 (d, 2 H); MS-
APCI (m/z): 289.
6-n-Butyl-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-5,6-
dihydro-pyran-2-one. The title compound was prepared
according to the general procedure using 4-benzyloxy-
phenethyl butyl ketone (4.0 g, 13.51 mmol), methyl
acetoacetate (6.3mL, 54.1 mmol), NaH (1.3g, 54.1 mmol)
and n-butyl lithium (1.64 M, 33mL, 54.1mmol). The
intermediate aldol was cyclized using 0.2 N NaOH
(304 mL) and THF (30 mL). The compound was pur-
i®ed by ¯ash silica gel chromatography (20±80% EtOAc
in hexanes as eluents) a€ording 6-[2-(4-benzyloxy-phen-
yl)-ethyl]-6-butyl-4-hydroxy-5,6-dihydro-pyran-2-one.
Isolated yield: 35%. Debenzylation was carried out
using 20% Pd/C (0.15 g) in THF (75 mL) in the presence
of hydrogen atmosphere. The crude product was pur-
i®ed by ¯ash silica gel chromatography (20±70% EtOAc
1
in hexanes as eluents). Isolated yield: 83%. H NMR
(400 MHz, CDCl3): d 0.8 (t, 3H), 1.2 (m, 4H), 1.61 (m,
2H), 1.81 (m, 2H), 2.42 (obscured by DMSO peak, 4H),
4.89 (s, 1H), 6.61 (d, 2H), 6.9 (d, 2H), 8.08 (s, 1H).
6-Isobutyl-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-5,6-
dihydro-pyran-2-one. The title compound was prepared
according to the general procedure using 4-benzyloxy-
phenethyl isobutyl ketone (15.0 g, 50.7 mmol), methyl
acetoacetate (14.7 g, 126.8 mmol), NaH (3.0 g, 126.8 mmol)
and n-butyl lithium (1.64 M, 77.3 mL, 126.8 mmol). The
intermediate aldol was cyclized using 0.2 N NaOH
(1141 mL) and THF (114 mL). The compound was pur-
i®ed by ¯ash silica gel chromatography (20±80% EtOAc
in hexanes as eluents) a€ording 6-[2-(4-benzyloxy-phen-
yl)-ethyl]-4-hydroxy-6-isobutyl-5,6-dihydro-pyran-2-one.
Isolated yield: 35%. Debenzylation was carried out
using 20% Pd/C (0.5 g) in THF (100 mL) in the pre-
sence of hydrogen atmosphere. The crude product was
puri®ed by ¯ash silica gel chromatography (20±70%
6-Cyclopentyl-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-
5,6-dihydro-pyran-2-one. The title compound was pre-
pared according to the general procedure using 4-benzyl-
oxy-phenethyl cyclopentyl ketone (5.0g, 16.24 mmol),
methyl acetoacetate (4.7 g, 40.6 mmol), NaH (1.0 g,
40.48 mmol) and n-butyl lithium (1.64 M, 24.7 mL,
40.58 mmol). The intermediate aldol was cyclized using
0.2 N NaOH (365 mL) and THF (37 mL). The com-
pound was puri®ed by ¯ash silica gel chromatography
(20±80% EtOAc in hexanes as eluents) a€ording 6-[2-
(4-benzyloxy-phenyl)-ethyl]-6-cyclopentyl-4-hydroxy-5,6-
dihydro-pyran-2-one. Isolated yield: 75%. Debenzyl-
ation was carried out using 20% Pd/C (1.0 g) in THF
(100 mL) in the presence of hydrogen atmosphere. The
crude product was puri®ed by ¯ash silica gel chromato-
graphy (20±70% EtOAc in hexanes as eluents). Isolated
1
EtOAc in hexanes as eluents). Isolated yield: 90%. H
1
NMR (400 MHz, CDCl3): d 0.83 (d, 3H), 0.86 (d, 3H),
1.61 (dd, 1H), 1.5 (dd, 1H), 1.69 (m, 2H), 1.83 (m, 1H),
2.42 (obscured by DMSO peak, 3H), 2.55 (d, 1H), 4.92
(s, 1H), 6.64 (d, 2H), 6.92 (d, 2H), 9.11 (s, 1H).
yield: 90%. H NMR (400 MHz, CDCl3): d 1.14±1.77
(m, 8H), 1.8 (m, 2H), 2.25 (m, 1H), 2.36±2.53 (obscured
by DMSO peak, 4H), 4.92 (s, 1H), 6.61 (d, 2H), 6.89 (d,
2H), 9.11 (s, 1H).

J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
2789
1
6-Cyclohexyl-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-
5,6-dihydro-pyran-2-one. The title compound was pre-
pared according to the general procedure using methyl
acetoacetate (11.6 g, 99.9 mmol), NaH (60% dispersion
in mineral oil) (4.19 g, 105 mmol), 1.6 M n-butyl lithium in
hexanes (64.0 mL, 102 mmol), 3-(4-benzyloxy-phenyl)-1-
cyclohexyl-propan-1-one (16.1 g, 49.9mmol) and 550 mL
of THF. After addition of the ketone, the reaction was
stirred for 2 h at 0ꢀC, then 1 h at room temperature. The
reaction was quenched with AcOH (12 mL) and worked
up in the usual manner. The crude product was sub-
jected to hydrogenolysis using 2.0 g of 20% Pd on car-
bon in 400 mL of THF at room temperature. The crude
product was carried on without puri®cation. To the 5-
cyclohexyl-5-hydroxy-7-(4-hydroxy-phenyl)-3-oxo-hep-
tanoic acid methyl ester taken in THF (100 mL) was
added 0.2 N NaOH (900 mL). The reaction was stirred
for 3 h at room temperature and then worked up as
usual. Puri®cation was accomplished by ¯ash silica gel
chromatography (CH2Cl2:MeOH=99:1 to 98:2) to give
13.0 g of the desired product as a solid. 1H NMR
(400 MHz, CDCl3): d 1.0±1.9 (m, 12H), 1.9±2.1 (m, 1H),
2.5±2.7 (m, 3H), 2.8 (d, 1H), 3.4 (s, 2H), 6.75 (d, 2H),
7.05 (d, 2H).
product. H NMR (400 MHz, CDCl3): d 0.86 (t, 6H),
1.40 (s, 9H), 1.48±1.53 (m, 1H), 1.59±1.64 (m, 1H),
1.71±1.75 (m, 1H), 1.82±1.88 (m, 2H), 2.36 (d, 1H), 2.54
(d, 1H), 4.92 (s, 1H), 7.01 (d, 2H), 7.29 (d, 2H), 9.18
(brs, 1H), 11.31 (brs, 1H); MS-CI (m/z): 389.
6-[2-(4-(tert-Butoxycarbonylamino)-phenyl)-ethyl]-6-cyclo-
hexyl-4-hydroxy-5,6-dihydro-pyran-2-one. The title com-
pound was prepared according to the general procedure
using methyl acetoacetate (2.8 g, 23.7 mmol), NaH (60%
dispersion in oil) (1.1 g, 27.5 mmol), 1.5 M n-butyl
lithium in hexanes (19.0 mL, 28.5 mmol), 1-(4-tert-
butoxycarbonyl-amino-phenyl)-3-cyclohexyl-hexan-3-one
(3.1 g, 9.5 mmol) and THF (175 mL). After addition of
the ketone, the reaction was stirred for 30 min at 5ꢀC,
then 1 h at room temperature. The reaction was quen-
ched with AcOH (5 mL) and worked up in the usual
manner. To the crude product taken in THF (60 mL)
was added 1.0 N NaOH (600 mL). The reaction was
stirred for 1.5 h at room temperature and then worked
up as usual. Puri®cation was accomplished by ¯ash
silica gel chromatography (EtOAc:hexanes=1:1) to
1
give 2.9 g of the desired product. H NMR (400 MHz,
CDCl3): d 1.02±1.25 (m, 5H), 1.46 (s, 9H), 1.64 (m, 1H),
1.73 (m, 5H), 1.87 (m, 2H), 2.31 (d, 1H), 2.55 (m, 2H),
2.61 (d, 1H), 4.96 (brs, 1H), 7.04 (d, 2H), 7.33 (d, 2H),
9.22 (s, 1H).
6-[2-(4-(tert-Butoxycarbonylamino)-phenyl)-ethyl]-4-hy-
droxy-6-isopropyl-5,6-dihydro-pyran-2-one. The title
compound was according to the general procedure
using methyl acetoacetate (5.7 g, 49 mmol), NaH (60%
dispersion in oil), (2.1 g, 52.5 mmol), 1.5 M n-butyl
lithium in hexanes (36.0 mL, 54 mmol), 1-(4-tert-butoxy-
carbonyl-amino-phenyl)-4-methyl-pentan-3-one (5.7 g,
19.5 mmol) and 2000 mL of THF. After addition of the
ketone, the reaction was stirred for 2 h at 0ꢀC, then 1 h
at room temperature. The reaction was quenched with
AcOH (15 mL) and worked up in the usual manner. To
the crude product taken in THF (130 mL) was added
1.0 N NaOH (1300 mL). The reaction was stirred for 3 h
at room temperature and then worked up as usual.
Puri®cation was accomplished by ¯ash chromatography
(CHCl3:MeOH=99:1 to 98:2) to give 5.7 g of the
Synthesis of chiral 5,6-dihydropyran-2-ones
(RS)-3-Hydroxy-3-(2-phenethyl)-4-methyl-pentanoic acid
(VIII, X=H). A 3-L 3-neck ¯ask with mechanical
stirrer was charged with diisopropylamine (86.1 g,
851.0 mmol) in 320 mL THF and cooled to 15ꢀC.
n-Butyl lithium (1.6 N, 531.9 mL, 851.0 mmol) was
added dropwise over 30±40 min. After 30 additional min
the reaction was cooled to 40ꢀC and t-butylacetate
(98.9 g, 851.0 mmol) in THF (240 mL) was added drop-
wise over 45 min. The reaction mixture was stirred an
additional 30 min. Phenethyl isopropyl ketone (III) in
400 mL THF was added dropwise to the reaction mixture
over 15 min followed by 30 min additional stirring.
The cooling bath temperature was raised to 15 to
20ꢀC and then the reaction quenched slowly with
ꢁ1500 mL of 3 N HCl. The reaction mixture was
extracted with EtOAc; the organic phase was washed
with brine, dried, ®ltered and concentrated to yield
130 g of oil. This material was used without further
1
desired product. H NMR (400 MHz, CDCl3): d 0.83±
0.87 (m, 6H), 1.40 (s, 9H), 1.83 (m, 2H), 2.07 (m, 1H),
2.25 (d, 1H), 2.50 (d, 1H), 2.54 (m, partially obscured by
DMSO, 2H), 4.91 (s, 1H), 6.98 (d, 2H), 7.28 (d, 2H),
9.17 (brs, 1H); MS-CI (m/z): 375.
6-[2-(4-(tert-Butoxycarbonylamino)-phenyl)-ethyl]-6-iso-
butyl-4-hydroxy-5,6-dihydro-pyran-2-one. The title com-
pound was prepared according to the general procedure
using methyl acetoacetate (2.3 g, 19.4 mmol), NaH (60%
dispersion in oil) (0.9 g, 21.4 mmol), 1.5 M n-BuLi in
hexanes (14.0 mL, 21 mmol), 1-(4-tert-butoxycarbonyl-
amino-phenyl)-5-methyl-hexan-3-one (2.7 g, 8.84 mmol)
and THF (120 mL). After addition of the ketone, the
reaction was stirred for 2 h at 0ꢀC, then 1 h at room
temperature. The reaction was quenched with AcOH
(5 mL) and worked up in the usual manner. To the
crude product taken in THF (50 mL) was added 1.0 N
NaOH (500 mL). The reaction was stirred for 3 h at
room temperature and then worked up as usual. Pur-
i®cation was accomplished by ¯ash chromatography
(CHCl3:MeOH=95:5) to give 1.5 g of the desired
1
puri®cation. H NMR (300 MHz, CDCl3): d 0.94±0.98
(dd, 6H), 1.48 (s, 9H), 1.74±1.85 (m, 2H), 1.87±1.96 (m,
1H), 2.40 (d, 1H), 2.52 (d, 1H), 2.64±2.73 (m, 2H), 3.92
(s, 1H), 7.16±7.21 (m, 3H), 7.26±7.34 (m, 2H). To the
(RS)-3-hydroxy-3-(2-phenethyl)-4-methyl-pentanoic
acid tert-butyl ester (124.4g, 425.5 mmol) in MeOH
(1400 mL) LiOH (35.7 g, 851.0 mmol) in deionized water
(140 mL) was added. The reaction was heated at re¯ux
overnight. The reaction mixture was allowed to cool to
room temperature and concentrated. The residue was
dissolved in water and extracted twice with EtOAc. The
combined organic phases were washed with brine, dried,
®ltered and concentrated to give 79 g (78.6% isolated
yield) of a white solid. The isolated material was used
without further puri®cation. 1H NMR (300 MHz,

2790
J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
CDCl3): d 0.96±1.00 (dd, 6H), 1.80±1.90 (m, 2H), 1.92±
2.10 (m, 1H), 2.62±2.74 (m, 4H), 7.17±7.21 (m, 3H),
7.26±7.32 (m, 2H).
(R)-3-Hydroxy-3-(2-phenethyl)-4-methyl-pentanoic acid
(R-VIII, X=H). The mother liquor from the chiral
resolution of the (S) enantiomer of the b-hydroxyacid
(58.0 g, 245.4 mmol) was dissolved in 600 mL EtOAc
and treated with (R)-a-methylbenzylamine (22.0 g,
181.6 mmol). The reaction mixture was stirred rapidly
until a solid precipitate began to form, then heated to
re¯ux until all solids dissolved. The reaction mixture
was allowed to cool slowly to room temperature and
stand overnight. The reaction mixture was cooled to
0ꢀC in an ice bath for several hours. The material was
diluted with cold EtOAc: the solids were ®ltered o€ and
washed with cold EtOAc and Et2O to yield 40.0 g of
white solid. The solid was dissolved in 1 N HCl
(ꢁ1000 mL) and extracted twice with EtOAc. The com-
bined organic layers were washed again with 1 N HCl,
followed by brine, dried, ®ltered and concentrated to
yield 27.1 g of a clear oil which solidi®es slowly to a
white solid on standing. Chiral HPLC analysis (Chir-
alcel OD 0.46 cm fÂ25 cm chiral column, eluting with
97.5% hexanes/2.5% isopropanol +0.1% formic acid
at a rate of 1 mL/min) of the isolated material showed
that it contained 96% (R)/4% (S) of enantiomers.
(S)-3-Hydroxy-3-(2-phenethyl)-4-methyl-pentanoic acid
(S-VIII, X=H). To the b-hydroxyacid (VIII) (15.0 g,
63.5 mmol) in EtOAc (155 mL) was added 0.55 equiv of
(S)-a-methylbenzylamine (4.2 g, 34.9 mmol). The reac-
tion mixture was rapidly stirred until a solid precipitate
began to form. The reaction ¯ask was then placed on a
steam bath and heated to re¯ux until homogeneous
solution was obtained. The reaction mixture was
allowed to cool slowly to room temperature and stand
overnight. The resulting solids were cooled to 0ꢀC in an
ice bath for several hours. The material was diluted with
cold EtOAc, and the solid was ®ltered o€ and washed
with cold EtOAc and Et2O to yield 7.7 g of white solid.
The solid was dissolved in 500 mL 1 N HCl and then
extracted twice with EtOAc. The combined organic
phases were washed again with 1 N HCl and brine,
dried, ®ltered and concentrated to yield 5.0 g of a clear
oil which solidi®es to a white solid on standing. Chiral
HPLC analysis (Chiralcel OD 0.46 cm fÂ25 cm chiral
column, eluting with 97.5% hexanes / 2.5% isopropanol
+0.1% formic acid at a rate of 1 mL/min) of the iso-
lated material showed that it contained 96% (S)/4% (R)
of the enantiomers.
(R)-5-Hydroxy-5-(2-phenethyl)-3-keto-6-methyl-heptanoic
acid, ethyl ester (R-IX, X=H). To the R-b-hydroxy-
acid (R-VIII, 26.9 g, 113.83 mmol) in THF (500 mL),
carbonyldiimidazole (40.6, 250.4 mmol) was added.
After stirring the reaction mixture at room temperature
for 4 h magnesium ethyl malonate (32.8 g, 113.8 mmol)
was added and the resulting gummy suspension was
stirred overnight. The reaction mixture was poured into
1 N HCl and extracted with EtOAc. The organic phase
was washed with saturated NaHCO3 followed by brine,
dried, ®ltered and concentrated. The resulting residue
after ¯ash silica gel chromatography (20% EtOAc in
(S)-5-Hydroxy-5-(2-phenethyl)-3-keto-6-methyl-heptanoic
acid, ethyl ester (S-IX, X=H). To the b-hydroxyacid
(S-VIII) (10.1 g, 42.5 mmol) dissolved in THF (190 mL)
was added carbonyldiimidazole (15.2, 93.6 mmol). After
stirring at room temperature for 4 h magnesium ethyl
malonate (12.3 g, 42.5 mmol) was added and the result-
ing gummy suspension was stirred at room temperature
overnight. The reaction mixture was poured into 1 N
HCl and extracted with EtOAc. The organic phase was
washed with saturated NaHCO3 followed by brine, ®l-
tered and concentrated. The resulting residue was pur-
i®ed by ¯ash silica gel chromatography (15% EtOAc in
hexanes as eluent) to yield 4.7 g oil. 1H NMR (300 MHz,
CDCl3): d 0.93±0.97 (dd, 6H), 1.26 (t, 3H), 1.79±1.85
(m, 2H), 1.93±2.00 (m, 1H), 2.64±2.68 (m, 2H), 2.72 (d,
1H), 2.83 (d, 1H), 3.48 (s, 2H), 4.19 (q, 2H) 7.15±7.20
(m, 3H), 7.26±7.31 (m, 2H).
1
hexanes as eluent) yielded 15.6 g of an oil. H NMR
(300 MHz, CDCl3): d 0.93±0.97 (dd, 6H), 1.26 (t, 3H),
1.79±1.85 (m, 2H), 1.93±2.00 (m, 1H), 2.64±2.68 (m,
2H), 2.72 (d, 1H), 2.83 (d, 1H), 3.48 (s, 2H), 4.19 (q,
2H), 7.15±7.20 (m, 3H), 7.26±7.31 (m, 2H).
(R)-4-Hydroxy-6-isopropyl-6-(2-phenethyl)-5,6-dihydro-
pyran-2-one (R-X, X=H). To the b-ketoester (R-IX)
(15.6 g, 50.9 mmol) in THF (140 mL), 0.1 N NaOH
(1400 mL) was added and the resulting milky solution
was stirred at room temperature overnight. The reaction
¯ask was cooled to 0ꢀC and the reaction mixture was
acidi®ed with 1 N HCl to ꢁpH 3±4 and extracted twice
with EtOAc. The combined organic phases were washed
with brine, dried, ®ltered and concentrated. The result-
ing oil was dissolved in Et2O and hexanes were added
with cooling of the ¯ask in an ice water bath to give a
white solid. The solid was ®ltered o€ and washed with
hexanes to a€ord 9.7 g (73% isolated yield) of the
desired dihydropyrone as a white solid. 1H NMR
(300 MHz, DMSO-d6): d 0.88±0.92 (dd, 6H), 1.81±1.99
(m, 2H), 2.07±2.16 (m, 1H), 2.31 (d of ABX q, 1H),
2.52±2.63 (m, 3H), 4.967 (s, 1H), 7.13±7.17 (m, 3H),
7.23±7.28 (m, 2H), 11.36 (br s, 1H).
(S)-4-Hydroxy-6-isopropyl-6-(2-phenethyl)-5,6-dihydro-
pyran-2-one (S-X, X=H). To the above b-ketoester
(S-VII) (4.7 g, 15.3 mmol) in THF (42 ml) 0.1 N NaOH
(420 mL) was added and the resulting milky solution
was stirred at room temperature overnight. The reaction
¯ask was cooled to 0ꢀC in an ice bath, acidi®ed with 1 N
HCl to ꢁpH 3 and extracted twice with EtOAc. The
combined organic phases were washed with brine, dried,
®ltered and concentrated. The resulting residue was
puri®ed by ¯ash silica gel chromatography (3% MeOH
in CH2Cl2 as eluent) to a€ord 3.43 g (86% isolated
yield) of the target compound as a clear oil which soli-
di®es slowly to a solid on standing. 1H NMR (300 MHz,
DMSO-d6): d 0.88±0.92 (dd, 6H), 1.83±1.94 (m, 2H),
2.07±2.16 (m, 1H), 2.31 (d of ABX q, 1H), 2.54±2.63 (m,
3H), 4.96 (s, 1H), 7.13±7.18 (m, 3H), 7.23±7.28 (m, 2H),
11.36 (br s, 1H).
(RS)-3-Hydroxy-3-[2-(4-tert-butoxycarbonylamino-phen-
yl)ethyl]-4-methyl-pentanoic acid (VIII, X=NHBoc). A

J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
2791
solution of diisopropylamine (125 mL, 893 mmol) in dry
THF (450 mL) was cooled to 20ꢀC under nitrogen,
treated dropwise with n-butyl lithium (338 mL,
811 mmol), and stirred at 30 to 10ꢀC for 30 min. A
solution of benzyl acetate (121.7 g, 810 mmol) in dry
THF (300 mL) was added dropwise to the LDA solu-
tion; the anion was stirred at 20ꢀC for 1 h and then
52 mmol) in 500 mL dry THF was added carbonyldi-
imidazole (16.9 g, 104 mmol). After stirring the reaction
mixture at room temperature for 2 h, magnesium ethyl
malonate (37.2 g, 130 mmol) was added and the result-
ing gummy suspension was stirred overnight. The reac-
tion mixture was poured into NH4Cl solution and
extracted with EtOAc. The organic phase was washed
with saturated NaHCO3 followed by brine, dried, ®l-
tered and concentrated. The resulting crude product
was used further without any puri®cation. Isolated
yield: 100%. To the crude b-ketoester in THF (100 mL),
0.1 N NaOH (1000 mL) was added and the resulting
solution was stirred at room temperature overnight. The
reaction mixture was acidi®ed with saturated ammoni-
um phosphate solution to ꢁpH 6 and extracted four
times with EtOAc. The combined organic phases were
washed with brine, dried, ®ltered and concentrated. The
resulting solid (13.4 g, 82% isolated yield, and overall
cooled to
78ꢀC. A solution of 1-(4-tert-butoxy-
carbonyl-amino-phenyl)-4-methyl-pentan-3-one in dry
THF (300 mL) was added all at once. The reaction
mixture was stirred at 78 to 40ꢀC for 3 h. The reac-
tion was quenched by adding AcOH (70 mL) and was
allowed to warm to room temperature. The reaction
mixture was diluted with water and EtOAc, the organic
layer was separated, washed with brine, dried and con-
1
centrated. H NMR (400 MHz, CDCl3): d 0.90 (t, 6H),
1.48 (s, 9H), 1.68±1.75 (m, 2H), 1.86±1.90 (m, 1H),
2.47±2.62 (m, 4H), 5.07 (s, 2H), 6.50 (brs, 1H), 7.02 (d,
2H), 7.20±7.33 (m, 2H). The crude product, 3-hydroxy-
3-[2-(4-tert-butoxycarbonylamino-phenyl)ethyl]-4-meth-
yl-pentanoic acid, benzyl ester thus obtained (208 g)
taken in THF (1000 mL) was treated with 20% Pd/C
(5 g) and shaken in a hydrogen atmosphere (51 psi) at
room temperature for 7 h. The catalyst was ®ltered o€
and the ®ltrate was concentrated to about 200 mL. The
solution was poured into 10% KOH (1200 mL), stirred
vigorously for 30 min and partitioned with toluene
(300 mL). The organic layer was acidi®ed to pH 5.2 with
acetic acid. The product was extracted with EtOAc
(2Â200 mL), and the organic layer was washed with
brine, dried and concentrated to give 84 g of a solid. IR
1
two steps) was pure and used further as such. H NMR
(300 MHz, CDCl3): d 1.01 (d, 6H), 1.50 (s, 9H), 1.71±
1.83 (m, 1H), 1.94±2.15 (m, 2H), 2.56±2.73 (m, 3H), 2.77
(d, 1H), 6.50 (s, 1H), 7.06 (d, 2H), 7.27 (d, 2H).
(R)- and (S)-3-Hydroxy-3-[2-(4-tert-butoxycarbonylamino-
phenyl)ethyl]-4-methyl-pentanoic acid (VIIIR and VIIIS,
X=NHBoc). Racemic 3-hydroxy-3-[2-(4-benzyloxy-
carbonylamino-phenyl)ethyl]-4-methyl-pentanoic acid,
benzyl ester (10g) was subjected to HPLC using chiral AD
column at a ¯ow rate of 9±11 mL/min and 250 mg per
injection. The S (peak 1) and R (peak 2) enantiomers
obtained were concentrated separately and triturated
with Et2O/hexanes to obtain solid. The S enantiomer
(4.2 g) was 96:4 (S/R), whereas R enantiomer (4.2 g) was
>99:<1 (S/R) based on chiral HPLC. In the next step,
(R)-3-hydroxy-3-[2-(4-benzyloxycarbonylamino-phenyl)-
ethyl]-4-methyl-pentanoic acid, benzyl ester (4.2 g) was
dissolved in THF (100 mL) and stirred in the presence
of Pd/C (0.5 g) under hydrogen atmosphere. The (R)-3-
hydroxy-3-[2-(amino-phenyl)ethyl]-4-methyl-pentanoic
acid obtained was concentrated and used further with-
out any puri®cation. Isolated yield: quantitative. To the
crude amino acid (2.2 g, 8.71 mmol) in THF (50 mL)
was added di-tert-butyl carbonate (2.0 g, 9.2 mmol) in
THF (20 mL). The reaction was stirred at 70ꢀC for 24 h,
followed by room temperature for three days. Solvents
were removed and triturated with Et2O/hexanes to a
solid. Isolated yield: quantitative.
1
(KBr): 3389, 1703 cm 1; H NMR (300 MHz, DMSO-
d6): d 0.81±0.83 (m, 6H), 1.41 (s, 9H), 1.60±1.71 (m, 2H),
1.73±1.80 (m, 1H), 2.34 (q, 2H), 2.48 (m, 2H), 6.99 (d,
2H), 7.27 (d, 2H), 9.16 (brs, 1H); MS-APCI (m/z): 350.
(S)-3-Hydroxy-3-[2-(4-tert-butoxycarbonylamino-phenyl)-
ethyl]-4-methyl-pentanoic acid (S-VIII, X=NH-Boc).
To the b-hydroxyacid (VIII, X=NH-Boc) (85.0 g,
242 mmol) taken in 600 mL EtOAc was added 0.55
equiv of (S)-a-methylbenzylamine (18.7 mL, 145 mmol).
The reaction mixture was heated to re¯ux under vigor-
ous stirring until homogeneous solution was obtained.
The reaction mixture was allowed to cool slowly to
room temperature and stand overnight. The resulting
solid (99:1 S/R, 20 g) was ®ltered and washed with
EtOAc/Et2O. The mother liquor was concentrated to
obtain 7.3 g (97:3 S/R) of solid, which was ®ltered. The
solid was dissolved in 500 mL 1 N HCl and then
extracted thrice with EtOAc. The combined organic
phases were washed again with 1 N HCl, followed by
brine, dried, ®ltered and concentrated to yield a solid.
Isolated (yield: 96%) material was >97:3 (S/R) based
on chiral HPLC analysis (Chiralcel OD 0.46cm fÂ25cm
chiral column, eluting with 97.5% hexanes/2.5% i-PrOH
(R)-6-[2-(4-(tert-Butoxycarbonylamino)-phenyl)-ethyl]-4-
hydroxy-6-isopropyl-5,6-dihydro-pyran-2-one (R-X, X=
NH2). To
a solution of R-b-hydroxyacid (3.0 g,
8.6 mmol) in 50 mL dry THF was added carbonyldiimi-
dazole (2.8 g, 17.1 mmol). After stirring the reaction
mixture at room temperature for 3 h, magnesium ethyl
malonate (5.0 g, 17.1 mmol) was added and the resulting
gummy suspension was stirred overnight. The reaction
mixture was poured into NH4Cl solution and extracted
with EtOAc. The organic phase was washed with satu-
rated NaHCO3 followed by brine, dried, ®ltered and
concentrated. The resulting crude product was used
further without any puri®cation. Isolated yield: 88%.
To the crude b-ketoester in THF (25 mL), 0.1 N NaOH
(250 mL) was added and the resulting solution was
1
+0.1% formic acid at a rate of 1 mL/min.). H NMR
(300 MHz, CDCl3): d 0.9 (d, 3H), 0.92 (d, 3H), 1.48 (s, 9H),
1.66±1.81 (m, 2H), 1.92 (m, 1H), 2.40 (d, 1H), 2.52 (d, 1H),
2.56±2.63 (m, 2H), 6.67 (s, 1H), 7.09 (d, 2H), 7.23 (d, 2H).
(S)-6-[2-(4-(tert-Butoxycarbonylamino)-phenyl)-ethyl]-4-
hydroxy-6-isopropyl-5,6-dihydro-pyran-2-one (S-X, X=
NH2). To a solution of S-b-hydroxyacid (18.3 g,

2792
J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
stirred at room temperature for 4 h. The reaction mixture
was acidi®ed with saturated ammonium chloride solution
to ꢁpH 6.5 and extracted four times with EtOAc. The
combined organic phases were washed with brine, dried,
®ltered and concentrated. The resulting solid (2.2 g, 77%
isolated yield) was pure and used further as such.
hydroxy-phenyl)-ethyl-5,6-dihydropyran-2-one (0.1 g,
0.2 mmol), 2-tert-butyl-4-5-methylphenyl-p-toluenethio-
sulfonate (0.1 g, 0.2 mmol), K2CO3 (0.1 g) and DMF
(2 mL). Isolated yield: 63%. IR (KBr): 3420, 2960, 1683,
1
1600, 1515, 1385, 1250, 1046, 697 cm 1; H NMR (400
MHz, DMSO-d6): d 0.93 (t, 3H, J=6.99 Hz), 1.36 (m,
2H), 1.47 (s, 9H), 1.76 (m, 2H), 1.94 (m, 2H), 2.03 (s,
3H), 2.53 (m, 2H), 2.8 (d of ABX, 1H, J=17.36 Hz),
2.92 (d of ABX, 1H, J=17.36), 6.66 (d, 2H, J=
8.44 Hz), 6.77 (s, 1H), 6.83 (d, 1H, J=7.96 Hz), 6.99 (d,
2H, J=8.44 Hz), 7.17 (d, 1H, J=7.96 Hz), 9.19 (s, 1H);
MS-APCI (m/z): 455, 437.
Examples
General procedure. To the appropriate 5,6-dihydropyran-
2-one (1 equiv) taken in DMF (1±12 mL per mmol of
dihydropyrone), K2CO3 (4±8 equiv) was added followed
by the appropriate thiotosylate reagent (1.1±1.5 equiv).
The reaction was stirred at room temperature (2.5 h to
overnight). The reaction was diluted in a mixture of
EtOAc and either 1 N HCl or saturated aqueous NH4Cl.
The layers were separated and the aqueous layer was
extracted again with EtOAc. The combined organic
extracts were washed with brine, dried, concentrated
and puri®ed by ¯ash silica gel chromatography. The ®nal
compounds, 2±12, 29 and 40, were puri®ed using 20%
EtOAc in hexanes to 60% EtOAc in hexanes as eluents.
Compounds 13±28, 30±35, 41±45 were puri®ed using 20%
EtOAc in hexanes to 80% EtOAc in hexanes as eluents.
6-Butyl-(3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phe-
nylsulfanyl)-6-[2-(4-hydroxy-phenyl)-ethyl]-5,6-dihydro-
pyran-2-one (4). The title compound was prepared
according to the general procedure using 6-butyl-4-hy-
droxy-6-([2-4-hydroxyphenyl)ethyl]-5,6-dihydropyran-2-
one (0.2 g, 0.7 mmol), 2-tert-butyl-5-methylphenyl-p-
toluenethiosulfonate (0.3 g, 0.8 mmol), K2CO3 (0.3 g)
and DMF (3 mL). Isolated yield: 70%. IR (KBr): 3384,
2956, 1598, 1515, 1249, 1046 cm 1; 1H NMR (400 MHz,
DMSO-d6): d 0.89 (t, 3H, J=6.99 Hz), 1.31 (m, 4H)
1.47 (s, 9H), 1.77 (m, 2H), 2.03 (s, 3H), 2.55 (m, 2H,
obscured by DMSO peak), 2.83 (d of ABX, 1H,
J=17.36 Hz), 2.94 (d of ABX, 1H, J=17.36 Hz), 6.67
(d, 2H, J=8.44 Hz), 6.75 (s, 1H), 6.83 (d, 1H, J=
7.96 Hz), 7.0 (d, 2H, J=8.44 Hz), 7.17 (d, 1H, J=
7.96 Hz), 9.19 (s, 1H); MS-APCI (m/z): 469.
(3-(2-tert-Butyl-5-methyl-phenylsulfanyl)-4-hydroxy-6-[2-
(4-hydroxy-phenyl)-ethyl]-6-phenyl-5,6-dihydro-pyran-2-one
(1). The title compound was prepared according to the
general procedure using 4-hydroxy-6-[2-(4-hydroxyphen-
yl)ethyl]-6-phenyl-dihydropyran-2-one (0.2 g, 0.6 mmol),
2-tert-butyl-5-methylphenyl-p-toluenethiosulfonate (0.2 g,
0.7 mmol), K2CO3 (0.4 g, 2.5 mmol) and DMF (2 mL).
The crude product was puri®ed by ¯ash silica gel chro-
matography (i-PrOH:CH2Cl2:hexanes=1:40:10 eluent)
to a€ord the pure material. Isolated yield: 63%. 1H
NMR (400 MHz, CDCl3): d 1.52 (s, 9H), 1.86 (s, 3H),
2.19±2.30 (m, 3H), 2.66 (m, 1H), 3.28 (d, 1H,
J=17.4 Hz), 3.35 (d, 1H, J=17.4 Hz), 4.91 (s, 1H), 6.19
(s, 1H), 6.71 (d, 2H, J=8.4 Hz), 6.82 (d, 1H, J=7.96 Hz),
6.93 (d, 2H, J=8.4Hz), 7.20 (d, 1H, J=7.96 Hz), 7.34±
7.46 (m, 5H), 7.63 (s, 1H); MS-CI (m/z): 489.
(3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phenylsulfa-
nyl)-6-[2-(4-hydroxy-phenyl)-ethyl]-6-pentyl-5,6-dihydro-
pyran-2-one (5). The title compound was prepared
according to the general procedure using 4-hydroxy-6-[2-
(4-hydroxyphenyl)ethyl]-6-pentyl-5,6-dihydropyran-2-
one (0.3 g, 0.8 mmol), 2-tert-butyl-5-methylphenyl-p-
toluenethiosulfonate (0.3 g, 1.0 mmol), K2CO3 (0.3 g)
and DMF (5 mL). Isolated yield: 63%. IR (KBr): 3325,
;
1H NMR
1
2954, 1677, 1597, 1515, 1384, 1046 cm
(400 MHz, DMSO-d6): d 0.89 (t, 3H, J=6.5 Hz), 1.31
(m, 6H) 1.34 (s, 9H), 1.77 (m, 2H), 1.97 (m, 2H), 2.03 (s,
3H), 2.53 (m, 2H, obscured by DMSO peak), 2.86 (d of
ABX, 1H, J=17.84 Hz), 2.97 (d of ABX, 1H, J=
17.84 Hz), 6.66 (d, 2H, J=8.44 Hz), 6.77 (s, 1H), 6.84
(d, 1H, J=7.96 Hz), 6.99 (d, 1H, J=8.44 Hz), 7.17 (d,
1H, J=7.96 Hz), 9.19 (s, 1H); MS-APCI (m/z): 483, 439.
(3-(2-tert-Butyl-5-methyl-phenylsulfanyl)-4-hydroxy-6-[2-
(4-hydroxy-phenyl)-ethyl]-6-methyl-5,6-dihydro-pyran-2-
one (2). The title compound was prepared according to
the general procedure using 4-hydroxy-6-[2-(4-hydroxy-
phenyl)ethyl)-6-methyl-dihydropyran-2-one (1 g, 4.1 mmol),
2-tert-butyl-5-methylphenyl-p-toluenethiosulfonate (1.4 g,
4.1 mmol), K2CO3 (2 g) and DMF (5 mL). Isolated
yield: 83%. IR (KBr): 3293, 2954, 1683, 1589, 1516,
(3-(2-tert-Butyl-5-methyl-phenylsulfanyl)-4-hydroxy-6-[2-
(4-hydroxy-phenyl)-ethyl]-6-isopropyl-5,6-dihydro-pyran-
2-one (6). The title compound was prepared according
to the general procedure using 4-hydroxy-6-(4-hydro-
xyphenyl)ethyl-6-isopropyl-dihydropyran-2-one (0.2 g,
0.4 mmol), 2-tert-butyl-5-methylphenyl-p-toluenethio-
sulfonate (0.2 g, 0.5 mmol), K2CO3 (0.5 g) and DMF
1
1220, 1047, 824 cm 1; H NMR (400 MHz, DMSO-d6):
d 1.4 (s, 3H), 1.47 (s, 9H), 1.97 (dd, 2H, J=6.75 Hz), 2.06
(s, 3H), 2.55 (dd, 2H, obscured by DMSO peak, J=
6.75 Hz), 2.81 (d of ABX, 1H, J=17.36 Hz), 3.0 (d of
ABX, 1H, J=17.36 Hz), 6.66 (d, 2H, J=8.68 Hz), 6.77
(s, 1H), 6.85 (d, 1H, J=7.96 Hz), 7.0 (d, 2H, J=8.68 Hz),
7.17 (d, 1H, J=7.96 Hz), 9.19 (s, 1H); MS-APCI (m/z):
427.
(3 mL). Isolated yield: 50%. IR (KBr): 3426, 2963, 1612,
1
1515, 1387, 1046, 698 cm
;
1H NMR (400 MHz,
DMSO-d6): d 0.93 (d, 3H, J=6.75 Hz), 0.97 (d, 3H,
J=6.75 Hz), 1.47 (s, 9H), 1.94 (s, 3H), 2.0 (m, 2H), 2.19
(m, 1H), 2.55 (m, 2H), 2.83 (d of ABX, 1H, J=17.6 Hz),
2.97 (d of ABX, 1H, J=17.84 Hz), 6.65 (d, 2H, J=
8.44 Hz), 6.72 (s, 1H), 6.81 (d, 1H, J=7.96 Hz), 6.9 (d,
2H, J=8.44 Hz), 7.19 (d, 1H, J=7.96 Hz), 9.19 (s, 1H);
MS-APCI (m/z): 455.
(3-(2-tert-Butyl-5-methyl-phenylsulfanyl)-4-hydroxy-6-[2-
(4-hydroxy-phenyl)-ethyl]-6-propyl-5,6-dihydro-pyran-2-
one (3). The title compound was prepared according to
the general procedure using 4-hydroxy-6-propyl-6-[2-(4-

J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
2793
(3-(2-tert-Butyl-5-methyl-phenylsulfanyl)-6-cyclopropyl-
4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-5,6-dihydro-
pyran-2-one (7). The compound was prepared accord-
ing to the general procedure using 6-cyclopropyl-4-hy-
droxy-6-[2-(4-hydroxyphenyl)ethyl]-5,6-dihydropyran-2-
one (0.2 g, 0.7 mmol), 2-tert-butyl-5-methylphenyl-p-
toluenethiosulfonate (0.4 g, 0.7 mmol), K2CO3 (0.2 g)
(3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phenylsulf-
anyl)-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-6-phenyl-
5,6-dihydro-pyran-2-one (11). The title compound was
prepared according to the general procedure using 4-
hydroxy-6-[2-(4-hydroxyphenyl)ethyl]-6-phenyl-5,6-di-
hydropyran-2-one (0.2 g, 0.6 mmol), 2-tert-butyl-4-
hydroxymethyl-5-methylphenyl-p-toluenethiosulfonate
(0.3 g, 0.71 mmol), K2CO3 (0.4 g, 2.5 mmol) and DMF
(3 mL). Isolated yield: 83%. 1H NMR (400 MHz,
DMSO-d6): d 1.44 (s, 9H), 1.76 (s, 3H), 2.08±2.21 (m,
3H), 2.42 (m, 1H), 3.36 (d, 1H, J=17.4 Hz), 3.46 (d, 1H,
J=17.4 Hz), 4.32 (s, 2H), 4.91 (brs, 1H), 6.16 (s, 1H),
6.61 (d, 2H, J=8.5 Hz), 6.86 (d, 1H, J=8.5 Hz), 7.21 (s,
1H), 7.34±7.46 (m, 5H), 9.14 (s, 1H), 12.15 (brs, 1H);
MS-APCI (m/z): 519.
and DMF (2 mL). Isolated yield: 60%. IR (KBr): 3422,
1
2955, 1681, 1599, 1515, 1263, 1046 cm
;
1H NMR
(400 MHz, DMSO-d6): d 0.37 (m, 1H), 0.55 (m, 3H),
1.25 (m, 1H), 1.47 (s, 9H), 1.99 (s, 3H), 2.03 (m, 2H),
2.64 (m, 2H), 2.77 (d of ABX, 1H, J=17.06 Hz), 2.94 (d
of ABX, 1H, J=17.06 Hz), 6.66 (d, 2H, J=8.44 Hz),
6.77 (s, 1H), 6.83 (d, 1H, J=8.05 Hz), 6.99 (d, 2H,
J=8.44 Hz), 7.17 (d, 1H, J=8.06 Hz), 9.17 (s, 1H); MS-
APCI (m/z): 453, 409.
(3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phenylsulf-
anyl)-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-6-methyl-
5,6-dihydro-pyran-2-one (12). The title compound was
prepared according to the general procedure using 4-
hydroxy-6-[2-(4-hydroxyphenyl)ethyl]-6-methyl-dihydro-
pyran-2-one (0.2 g, 0.6 mmol), 2-tert-butyl-4-hydroxy-
(3-(2-tert-Butyl-5-methyl-phenylsulfanyl)-4-hydroxy-6-[2-
(4-hydroxy-phenyl)-ethyl]-6-cyclopentyl-5,6-dihydro-pyran-
2-one (8). The title compound was prepared according
to the general procedure using 6-cyclopentyl-4-hydrox-
yl-6-[2-(4-hydroxyphenyl)ethyl]-5,6-dihydropyran-2-one
(0.4 g, 1.4 mmol), 2-tert-butyl-5-methylphenyl-p-tolu-
enethiosulfonate (0.5 g, 1.5 mmol), K2CO3 (0.5 g) and
methyl-5-methylphenyl-p-toluenethiosulfonate
0.7 mmol), K2CO3 (0.5 g) and DMF (3 mL). Isolated
(0.3 g,
1
DMF (5 mL). Isolated yield: 56%. IR (KBr): 3347,
1
yield: 60%. IR (KBr): 3429, 2924, 1601, 1452, 759 cm ;
2955, 1677, 1599, 1515, 1264, 1046 cm
;
1H NMR
1H NMR (400 MHz, DMSO-d6): d 1.25 (s, 3H), 1.5 (s,
9H), 1.97 (m, 2H), 2.0 (s, 3H), 2.58 (t, 2H), 2.81 (d of
ABX, 1H, J=17.11 Hz), 2.97 (d of ABX, 1H, J=
17.11 Hz), 4.4 (d, 2H), 6.66 (d, 2H, J=8.44 Hz), 6.72 (s,
1H), 7.2 (d, 2H, J=8.44 Hz), 7.28 (s, 1H), 9.19 (s, 1H);
MS-APCI (m/z): 457, 439.
(400 MHz, DMSO-d6): d 1.33±1.75 (m, 8H), 1.47 (s,
9H), 1.92 (s, 3H), 1.97 (m, 2H), 2.55 (m, 2H), 2.83 (d
of ABX, 1H, J=17.84 Hz), 2.94 (d of ABX, 1H,
J=18.08 Hz), 6.66 (d, 2H, J=8.44 Hz), 6.76 (s, 1H),
6.83 (d, 1H, J=8.2 Hz), 6.98 (d, 2H, J=8.68 Hz), 7.17
(d, 1H, J=8.2 Hz), 9.19 (s, 1H); MS-APCI (m/z): 481,
463, 363.
(3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phenylsulf-
anyl)-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-6-propyl-
5,6-dihydro-pyran-2-one (13). The title compound was
prepared according to the general procedure using 4-
hydroxy-6-[2-(4-hydroxyphenyl)ethyl]-6-propyl-5,6-di-
hydropyran-2-one (0.1 g, 0.2 mmol), 2-tert-butyl-4-
hydroxymethyl-5-methylphenyl-p-toluenethiosulfonate
(0.9 g, 0.2 mmol), K2CO3 (0.2 g) and DMF (2 mL). Iso-
lated yield: 55%. IR (KBr): 3390, 2959, 1682, 1599,
3-(2-tert-Butyl-5-methyl-phenylsulfanyl)-6-cyclohexyl-4-
hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-5,6-dihydro-pyran-
2-one (9). The title compound was prepared according
to the general procedure using 6-cyclohexyl-4-hydroxy-6-
[2-(4-hydroxy-phenyl)-ethyl]-5,6-dihydro-pyran-2-one
(0.6 g, 1.9 mmol), 2-tert-butyl-5-methylphenyl-p-tolu-
enethiosulfonate (0.8 g, 2.3 mmol), K2CO3 (1.1 g,
7.6 mmol) and DMF (5 mL). Isolated yield: 80%. IR
(KBr): 3390, 2930, 2856, 1683, 1600; 1H NMR
(400 MHz, CDCl3): d 1.0±1.4 (m, 6H), 1.56 (s, 9H), 2.05
(s, 3 H), 2.6±2.8 (d, m, 3H, J=17.8 Hz), 3.0 (d, 1H,
J=17.8 Hz), 4.7 (bs, 1H), 6.6±6.7 (d, d, 3 H, J=8.4 Hz,
J=7.96 Hz), 6.9 (d, 2H, J=8.4 Hz), 7.3 (d, 1H, J=
7.96 Hz), 7.26 (s, 1H); MS-APCI: (m/z): 495.
1
1515, 1246, 1050 cm 1; H NMR (400 MHz, DMSO-
d6): d 0.92 (t, 3H, J=7.23 Hz), 1.36 (m, 2H) 1.47 (s, 9H),
1.76 (m, 2H), 1.93 (m, 2H), 1.98 (s, 3H), 2.53 (m, 2H,
obscured by DMSO peak), 2.83 (d of ABX, 1H,
J=17.60 Hz), 2.94 (d of ABX, 1H, J=17.60 Hz), 4.37
(s, 2H), 4.97 (s, 1H), 6.66 (d, 2H, J=8.44 Hz), 6.72 (s,
1H), 6.98 (d, 2H, J=8.44 Hz), 7.25 (s, 1H), 9.17 (s, 1H),
12.0 (brs, 1H); MS-APCI (m/z): 485, 467, 423.
(3-(2-tert-Butyl-5-methyl-phenylsulfanyl)-4-hydroxy-6-[2-
(4-hydroxy-phenyl)-ethyl]-5,6-dihydro-pyran-2-one (10).
The title compound was prepared according to the
general procedure using 4-hydroxy-6-[2-(4-hydroxy-
phenyl)ethyl]-5,6-dihydropyran-2-one (0.2 g, 0.6 mmol),
2-tert-butyl-5-methylphenyl-p-toluenethiosulfonate (0.3 g,
0.8 mmol), K2CO3 (0.5 g) and DMF (2 mL). Isolated
yield: 62%. IR (KBr): 3409, 2923, 1684, 1597, 1515,
6-Butyl-(3-(2-tert-butyl-4-hydroxymethyl-5-methyl-phen-
ylsulfanyl)-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-5,6-
dihydro-pyran-2-one (14). The title compound was pre-
pared according to the general procedure using 6-butyl-
4-hydroxy-6-[2-(4-hydroxyphenyl)ethyl]-5,6-dihydro-
pyran-2-one (0.2 g, 0.7 mmol), 2-tert-butyl-4-hydroxy-
methyl-5-methylphenyl-p-toluenethiosulfonate
(0.3 g,
1
1252, 1046, 698 cm 1; H NMR (400 MHz, DMSO-d6):
0.7 mmol), K2CO3 (0.3 g) and DMF (3 mL). Isolated
yield: 67%. IR (KBr): 3423, 2955, 1680, 1599, 1515,
d 1.47 (s, 9H), 1.94 (m, 2H), 2.14 (s, 3H), 2.92±2.57
(m, 3H), 4.4 (m, 1H), 6.69 (d, 2H, J=8.44 Hz), 6.77 (s,
1H), 6.83 (d, 1H, J=7.96 Hz), 7.03 (d, 2H, J=8.44 Hz),
7.17 (d, 1H, J=8.19 Hz), 9.17 (s, 1H); MS-APCI (m/z):
413.
1
1233 cm 1; H NMR (400 MHz, DMSO-d6): d 0.89 (m,
3H), 1.31 (m, 4H) 1.5 (s, 9H), 1.64 (m, 2H), 1.97 (s, 3H),
1.89±2.03 (m, 2H, 2.44±2.56 (m, 2H, obscured by
DMSO peak), 2.83 (d of ABX, 1H, J=17.60 Hz), 2.94

2794
J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
(d of ABX, 1H, J=17.60 Hz), 4.24 (s, 2H), 4.97 (s, 1H),
6.67 (d, 2H, J=8.44 Hz), 6.72 (s, 1H), 6.98 (d, 1H,
J=8.85 Hz), 7.28 (s, 2H), 9.17 (s, 1H), 12.0 (brs, 1H);
MS-APCI (m/z): 499, 481, 437, 375.
was prepared according to the general procedure using
6-cyclopropyl-4-hydroxy-6-[2-(4-hydroxyphenyl)ethyl]-
5,6-dihydropyran-2-one (0.3 g, 1.1 mmol), 2-tert-butyl-
4-hydroxymethyl-5-methylphenyl-p-toluenethiosulfonate
(0.4 g, 1.1 mmol), K2CO3 (0.4 g) and DMF (3 mL). Iso-
lated yield: 50%. IR (KBr): 3408, 2954, 1681, 1614,
(3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phenylsulf-
anyl)-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-6-pentyl-
5,6-dihydro-pyran-2-one (15). The title compound was
prepared according to the general procedure using 4-
hydroxy-6-[2-(4-hydroxyphenyl)ethyl]-6-pentyl-5,6-di-
hydropyran-2-one (0.2 g, 0.6 mmol), 2-tert-butyl-4-
hydroxymethyl-5-methylphenyl-p-toluenethiosulfonate
(0.2 g, 0.6 mmol), K2CO3 (0.2 g) and DMF (2 mL). Iso-
lated yield: 65%. IR (KBr): 3409, 2929, 1676, 1515,
1
1515, 1263, 1048 cm 1; H NMR (400 MHz, DMSO-
d6): d 0.36 (m, 1H), 0.53 (m, 3H), 1.25 (m, 1H) 1.47 (s,
9H), 1.92 (s, 3H), 2.03 (m, 2H), 2.64 (m, 2H), 2.77 (d
of ABX, 1H, J=17.4 Hz), 2.92 (d of ABX, 1H,
J=17.4 Hz), 4.36 (s, 2H), 4.94 (s, 1H), 6.66 (d, 2H,
J=8.44 Hz), 6.75 (s, 1H), 6.97 (d, 2H, J=8.44 Hz), 7.28
(s, 2H), 9.17 (s, 1H), 12.0 (brs, 1H); MS-APCI (m/z):
483, 465, 421, 365.
1
1253, 1044, 698 cm 1; H NMR (400 MHz, DMSO-d6):
d 0.89 (m, 3H), 1.31 (m, 8H) 1.5 (s, 9H), 1.77 (m, 2H),
1.97 (m, 2H), 2.0 (s, 3H), 2.58 (m, 2H, obscured by
DMSO peak), 2.84 (d of ABX, 1H, J=17.4 Hz), 2.97 (d
of ABX, 1H, J=17.4 Hz), 4.39 (s, 2H), 4.97 (brs, 1H),
6.66 (d, 2H, J=8.44 Hz), 6.72 (s, 1H), 7.0 (d, 2H,
J=8.44 Hz), 7.28 (s, 1H), 9.17 (s, 1H); MS-APCI (m/z):
513, 495, 451, 259.
3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phenylsulf-
anyl)-6-cyclobutyl-4-hydroxy-6-[2-(4-hydroxy-phenyl)-
ethyl]-5,6-dihydro-pyran-2-one (19). The title compound
was prepared according to the general procedure using
6-cyclobutyl-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-
5,6-dihydro-pyran-2-one (0.1 g, 0.5 mmol), 2-tert-butyl-
4-hydroxymethyl-5-methylphenyl-p-toluenethiosulfonate
(0.1 g, 0.4 mmol), K2CO3 (0.2 g, 1.4 mmol) and DMF
(3 mL). Isolated yield: 45%. IR (KBr): 3339, 2946, 2866,
1679, 1599 in cm 1; 1H NMR (400 MHz, CDCl3): d 1.57
(s, 9H), 1.7±2.1 (m, 7H), 2.02 (s, 3H), 2.2±2.4 (m, 1H),
2.5±2.65 (m, 2 H), 2.65 (d, 2H, J=8.1 Hz), 2.65±2.8 (m,
1 H), 2.83 (d, 1 H, J=8.1 Hz), 4.59 (s, 2H), 4.88 (bs,
1H), 6.71 (d, 2H, J=6.5 Hz), 6.76 (s, 1H), 6.96 (d, 2H,
J=6.5 Hz), 7.34 (s, 1H), 7.71 (s, 1H); MS-APCI (m/z):
497.
(3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phenylsulf-
anyl)-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-6-isopro-
pyl-5,6-dihydro-pyran-2-one (16). The title compound
was prepared according to the general procedure using
4-hydroxy-6-[2-(4-hydroxyphenyl)ethyl]-6-isopropyl-5,6-
dihydropyran-2-one (0.2 g, 0.4 mmol), 2-tert-butyl-4-
hydroxymethyl-5-methylphenyl-p-toluenethiosulfonate
(0.2 g, 0.5 mmol), K2CO3 (0.5 g) and DMF (3 mL). Iso-
lated yield: 45%. IR (KBr): 3418, 2964, 1683, 1611,
1
1515, 1233, 1050 cm 1; H NMR (400 MHz, DMSO-
(3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phenylsulf-
anyl)-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-6-cyclo-
pentyl-5,6-dihydro-pyran-2-one (20). The title compound
was prepared according to the general procedure using
6-cyclopentyl-4-hydroxy-6-[2-(4-hydroxyphenyl)ethyl]-
5,6-dihydropyran-2-one (0.2 g, 0.7 mmol), 2-tert-butyl-
4-hydroxymethyl-5-methylphenyl-p-toluenethiosulfonate
(0.2 g, 0.7 mmol), K2CO3 (0.3 g) and DMF (2 mL). Iso-
lated yield: 38%. IR (KBr): 3393, 2955, 1678, 1600,
d6): d 0.92 (d, 3H, J=6.99 Hz), 0.96 (d, 3H, J=6.75 Hz),
1.49 (s, 9H), 1.89 (s, 3H), 1.92±2.0 (m, 2H), 2.2 (m, 1H),
2.35±2.6 (m, 2H), 2.75 (d of ABX, 1H, J=17.60 Hz),
2.97 (d of ABX, 1H, J=17.60 Hz), 4.36 (s, 2H), 4.94
(brs, 1H), 6.65 (d, 2H, J=8.44 Hz), 6.69 (s, 1H), 6.96 (d,
1H, J=8.44 Hz), 7.28 (s, 1H), 9.15 (s, 1H), 11.94 (brs,
1H); MS-APCI (m/z): 485, 423.
1
(3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phenylsulfanyl)-
4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-6-isobutyl-5,6-
dihydro-pyran-2-one (17). The title compound was
prepared according to the general procedure using 4-
hydroxy-6-[2-(4-hydroxyphenyl)ethyl]-6-isobutyl-5,6-
dihydropyran-2-one (0.3 g, 1.0 mmol), 2-tert-butyl-4-
hydroxymethyl-5-methylphenyl-p-toluenethiosulfonate
(0.4 g, 1.0 mmol), K2CO3 (0.4 g) and DMF (3 mL). Iso-
lated yield: 44%. IR (KBr): 3375, 2957, 1682, 1598,
1515, 1259, 1050 cm 1; H NMR (400 MHz, DMSO-
d6): d 1.31±1.55 (m, 8H) 1.83 (s, 9H), 1.92 (m, 2H), 2.34
(m, 1H), 2.55 (m, 2H, obscured by DMSO peak), 2.77
(d of ABX, 1H, J=17.82 Hz), 2.89 (d of ABX, 1H,
J=17.82 Hz), 4.31 (s, 2H), 4.89 (s, 1H), 6.61 (t, 2H),
6.64 (d, 1H, J=7.31 Hz), 6.92 (d, 1H, J=7.31 Hz), 7.2
(s, 1H), 9.17 (s, 1H), 11.9 (brs, 1H); MS-APCI (m/z):
511, 493, 449, 394.
1
1515, 1250, 1042 cm 1; H NMR (400 MHz, DMSO-
3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phenylsulf-
anyl)-6-cyclohexyl-4-hydroxy-6-[2-(4-hydroxy-phenyl)-
ethyl]-5,6-dihydro-pyran-2-one (21). The title compound
was prepared according to the general procedure using
6-cyclohexyl-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-
5,6-dihydro-pyran-2-one (0.2 g, 0.5 mmol), 2-tert-butyl-
4-hydroxymethyl-5-methylphenyl-p-toluenethiosulfonate
(0.3 g, 0.6 mmol), K2CO3 (0.3 mg, 2.2 mmol) and DMF
(4 mL). Isolated yield: 55%. IR (KBr): 3339, 2931, 2857,
d6): d 0.92 (d, 3H, J=6.27 Hz), 0.94 (d, 3H, J=6.51 Hz)
1.47 (s, 9H), 1.66 (m, 1H), 1.72 (m, 2H), 1.97 (m+s,
5H), 2.58 (m, 2H, obscured by DMSO peak), 2.77 (d
of ABX, 1H, J=17.60 Hz), 3.0 (d of ABX, 1H,
J=17.60 Hz), 4.39 (s, 2H), 4.97 (s, 1H), 6.66 (d, 2H,
J=8.44 Hz), 6.75 (s, 1H), 6.99 (s, 1H), 7.28 (d, 2H,
J=8.44 Hz), 9.17 (s, 1H), 12.0 (brs, 1H); MS-APCI (m/
z): 499, 481, 437.
1
1674, 1601 cm 1; H NMR (400 MHz, CDCl3): d 1.0±
(3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phenylsulf-
anyl)-6-cyclopropyl-4-hydroxy-6-[2-(4-hydroxy-phenyl)-
ethyl]-5,6-dihydro-pyran-2-one (18). The title compound
1.30 (m, 6H), 1.48 (s, 9H), 1.60±2.00 (m, 9 H), 1.92 (s,
3H), 2.73 (d, 1H, J=18 Hz), 2.95 (d, 1H, J=18 Hz),
4.36 (s, 2H), 4.95 (brs, 1H), 6.65 (d, 2H, J=8.4 Hz), 6.69

J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
2795
(s, 1H), 6.96 (d, 2H, J=8.5 Hz), 7.27 (s, 1 H), 8.31 (s,
1H), 9.15 (s, 1H); MS-APCI (m/z): 525.
(m, 2H), 2.75 (d of ABX, 1H, J=17.36 Hz), 2.94 (d of
ABX, 1H, J=17.36 Hz), 3.69 (brs, 2H), 3.92 (t, 2H),
4.81 (brs, 1H), 6.67 (d, 2H, J=8.44 Hz), 6.75 (s, 1H), 6.8
(s, 1H), 6.97 (d, 2H, J=8.44 Hz), 9.17 (s, 1H); MS-
APCI (m/z): 487, 443.
(3-(2-tert-Butyl-4-hydroxy-5-methyl-phenylsulfanyl)-4-hy-
droxy-6-[2-(4-hydroxy-phenyl)-ethyl]-6-methyl-5,6-di-
hydro-pyran-2-one (22). The title compound was
prepared according to the general procedure using 4-
hydroxy-6-[2-(4-hydroxyphenyl)ethyl]-6-methyl-dihydro-
pyran-2-one (0.1 g, 0.3 mmol), 2-tert-butyl-4-hydroxy-5-
methylphenyl-p-toluenethiosulfonate (0.1 g, 0.3 mmol),
K2CO3 (0.5 g) and DMF (3 mL). Isolated yield: 67%.
(3-(2-tert-Butyl-4-(2-methoxymethoxy-ethoxy)-5-methyl-
phenylsulfanyl)-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-
6-methyl-5,6-dihydro-pyran-2-one (26). The title com-
pound was prepared according to the general procedure
using 4-hydroxy-6-[2-(4-hydroxyphenyl)ethyl]-6-methyl-
dihydropyran-2-one (0.5 g, 2.03 mmol), 2-tert-butyl-4-
(2-methoxymethoxy-ethoxy)-5-methylphenyl-p-toluene-
thiosulfonate (0.9 g, 2.0 mmol), K2CO3 (1 g) and DMF
1
IR (KBr): 3389, 2954, 1679, 1598, 1385, 1245 cm 1; H
NMR (400 MHz, DMSO-d6): d 1.42 (s, 3H), 1.47 (s,
9H), 1.92 (s, 3H), 1.86 (m, 2H), 2.53 (m, 2H), 2.75 (d of
ABX, 1H, J=17.36 Hz), 2.94 (d of ABX, 1H, J=
17.36 Hz), 6.64 (s, 1H), 6.69 (d, 2H, J=8.44 Hz), 6.77 (s,
1H), 6.97 (d, 2H, J=8.44 Hz), 9.06 (s, 1H), 9.19 (s, 1H),
MS-APCI (m/z): 443.
(5 mL). Isolated yield: 32%. IR (KBr): 3326, 2950, 1682,
1
1598, 1515, 1253, 1040 cm
;
1H NMR (400 MHz,
DMSO-d6): d 1.29 (s, 3H), 1.35 (s, 9H), 1.92 (s, 3H),
1.85±2.0 (m, 2H), 2.63 (s, 3H), 2.61±2.45 (t, 2H), 2.78 (d
of ABX, 1H, J=17.36 Hz), 2.97 (d of ABX, 1H,
J=17.36 Hz), 3.28 (s, 3H), 3.76 (m, 2H), 4.1 (m, 2H),
4.63 (s, 2H) 6.67 (d, 2H, J=8.44 Hz), 6.75 (s, 1H), 6.83
(s, 1H), 6.97 (d, 2H, J=8.44 Hz), 9.14 (s, 1H); MS-
APCI (m/z): 531, 499, 487.
(3-(2-tert-Butyl-4-hydroxy-5-methyl-phenylsulfanyl)-4-hy-
droxy-6-[2-(4-hydroxy-phenyl)-ethyl]-6-isopropyl-5,6-di-
hydro-pyran-2-one (23). The title compound was
prepared according to the general procedure using 4-
hydroxy-6-[2-(4-hydroxyphenyl)ethyl]-6-isopropyl-di-
hydropyran-2-one (0.4 g, 1.6 mmol), 2-tert-butyl-4-hy-
droxy-5-methylphenyl-p-toluenethiosulfonate (0.7 g,
1.9 mmol), K2CO3 (0.4 g) and DMF (5 mL). Isolated
yield: 63%. IR (KBr): 3400, 2963, 1675, 1601, 1515,
(3-(2-tert-Butyl-4-(2-methoxymethoxy-ethoxy)-5-methyl-
phenylsulfanyl)-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-
6-propyl-5,6-dihydro-pyran-2-one (27). The title com-
pound was prepared according to the general procedure
using 4-hydroxy-6-[2-(4-hydroxyphenyl)ethyl]-6-propyl-
5,6-dihydropyran-2-one (0.1 g, 0.5 mmol), 2-tert-butyl-
4-(2-methoxymethoxy-ethoxy)-5-methylphenyl-p-toluene-
thiosulfonate (0.3 g, 0.6 mmol), K2CO3 (0.2 g) and DMF
(2 mL). Isolated yield: 62%. IR (KBr): 3427, 2928, 1604,
1
1387, 1242, 1052 cm 1; H NMR (400 MHz, DMSO-
d6): d 0.92 (d, 3H, J=6.99 Hz), 0.97 (d, 3H, J=
6.75 Hz), 1.44 (s, 9H), 1.77 (s, 3H), 1.94 (m, 2H), 2.19
(m, 1H), 2.53 (m, 2H, obscured by DMSO peak), 2.72
(d of ABX, 1H, J=17.60 Hz), 2.94 (d of ABX, 1H,
J=17.60 Hz), 6.66 (m, 3H), 6.77 (s, 1H), 6.96 (d, 2H,
J=8.44 Hz), 9.01 (s, 1H), 9.14 (s, 1H); MS-APCI (m/z):
471, 379, 307, 277, 107.
1
1515, 1253, 1051 cm 1; H NMR (400 MHz, DMSO-
d6): d 0.92 (t, 3H, J=7.23 Hz), 1.34 (m, 2H), 1.5 (s, 9H),
1.75 (m, 2H), 1.92 (s, 3H), 1.94 (m, 2H), 2.5 (m,
obscured by DMSO peak, 2H), 2.78 (d of ABX, 1H,
J=17.06 Hz), 2.92 (d of ABX, 1H, J=17.06 Hz), 3.69
(q, 2H), 3.97 (t, 2H, J=4.82 Hz), 4.81 (brt, 1H), 6.66 (d,
2H, J=8.44 Hz), 6.75 (s, 1H), 6.83 (s, 1H), 6.99 (d, 2H,
J=8.44 Hz), 9.14 (s, 1H); MS-APCI (m/z): 515, 471.
3-(2-tert-Butyl-4-hydroxy-5-methyl-phenylsulfanyl)-6-cy-
clohexyl-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-5,6-di-
hydro-pyran-2-one (24). The title compound was
prepared according to the general procedure using 6-
cyclohexyl-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-5,6-
dihydro-pyran-2-one (0.2 g, 0.7 mmol), 2-tert-butyl-4-
hydroxy-5-methylphenyl-p-toluenethiosulfonate (0.3 g,
0.7 mmol), K2CO3 (0.4 g, 2.7 mmol) and DMF (4 mL).
Isolated yield: 80%. IR (KBr): 3339, 2931, 2857, 1674,
(3-(2-tert-Butyl-4-(2-hydroxy-ethoxy)-5-methyl-phenyl-
sulfanyl)-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-6-bu-
tyl-5,6-dihydro-pyran-2-one (28). The title compound
was prepared according to the general procedure using
4-hydroxy-6-(4-hydroxyphenyl)ethyl-6-butyl-5,6-dihydro-
pyran-2-one (0.2 g, 0.7 mmol), 2-tert-butyl-4-(2-tert-
butyldimethylsilyloxy-ethoxy)-5-methylphenyl-p-toluene-
thiosulfonate (0.4 g, 0.8 mmol), K2CO3 (0.2 g) and DMF
(3 mL). The crude compound obtained was taken in
2 mL of THF and 2 mL of MeOH. To it 2 mL of con-
centrated HCl was stirred overnight. Solvents were eva-
porated and the residue was puri®ed by ¯ash silica gel
chromatography. Isolated yield: 48%. 1H NMR
(400 MHz, DMSO-d6): d 0.9 (t, 3H, J=6.51 Hz), 1.28
(m, 4H), 1.5 (s, 9H), 1.76 (m, 2H), 1.92 (s, 3H), 1.94 (m,
2H), 2.53 (m, 2H, obscured by DMSO peak), 2.81 (d
of ABX, 1H, J=17.6 Hz), 2.92 (d of ABX, 1H,
J=17.6 Hz), 3.69 (brs, 2H), 3.95 (t, 2H, J=4.82 Hz), 4.8
(brs, 1H), 6.66 (d, 2H, J=8.44 Hz), 6.75 (s, 1H), 6.83 (s,
1H), 6.98 (d, 2H, J=8.44 Hz), 9.17 (s, 1H); APCI (m/z):
529, 485.
1
1601 cm 1; H NMR (400 MHz, DMSO-d6): d 1.0±1.4
(m, 6H), 1.45 (s, 9H), 1.80 (s, 3 H), 1.6±2.0 (m, 9H), 2.71
(d, 1H, J=17.8 Hz), 2.93 (d, 1H, J=17.9 Hz), 6.64 (d,
2H, J=8.4 Hz), 6.66 (s, 1H), 6.77 (s, 1 H), 6.94 (d, 2H,
J=8.4 Hz), 8.31 (s, 1H), 9.02 (s, 1H), 9.13 (s, 1H), 11.75
(brs, 1H); MS-APCI (m/z): 512.
(3-(2-tert-Butyl-5-methyl-phenylsulfanyl)-4-hydroxy-6-[2-
(4-hydroxy-phenyl)-ethyl]-6-methyl-5,6-dihydro-pyran-2-
one (25). The compound 26 (0.1 g) was taken in 2 mL
of THF and 2 mL of methanol. To it 2 mL of con-
centrated HCl was added and kept under stirring over-
night. Solvents were evaporated and the residue was
puri®ed by ¯ash silica gel chromatography. Isolated
yield: 63%. IR (KBr): 3426, 2963, 1612, 1515, 1387,
1046, 698 cm 1; 1H NMR (400 MHz, DMSO-d6): d 1.42
(s, 3H), 1.49 (s, 9H), 1.92 (s, 3H), 1.86±2.0 (m, 2H), 2.5

2796
J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
(3-(2-tert-Butyl-4-(2-hydroxy-ethoxy)-5-methyl-phenyl-
sulfanyl)-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-6-pen-
tyl-5,6-dihydro-pyran-2-one (29). The title compound
was prepared according to the general procedure using
4-hydroxy-6-[2-(4-hydroxyphenyl)ethyl]-6-pentyl-5,6-di-
hydropyran-2-one (0.2 g, 0.6 mmol), 2-tert-butyl-4-(2-tert-
butyldimethylsilyloxy-ethoxy)-5-methylphenyl-p-tolue-
nethiosulfonate (0.4 g, 0.7 mmol), K2CO3 (0.2 g) and
DMF (3 mL). The crude compound obtained was taken
in 2 mL of THF and 2 mL of MeOH. To it 2 mL of
concentrated HCl was stirred overnight. Solvents were
evaporated and the residue was puri®ed by ¯ash silica
4.8 (brs, 1H), 6.66 (d, 2H, J=8.44 Hz), 6.75 (s, 1H), 6.81
(s, 1H), 6.97 (d, 2H, J=8.44 Hz), 9.14 (s, 1H); MS-
APCI (m/z): 513, 416, 305.
(3-(2-tert-Butyl-4-(2-hydroxy-ethoxy)-5-methyl-phenyl-
sulfanyl)-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-6-
cyclopentyl-5,6-dihydro-pyran-2-one (32). The title
compound was prepared according to the general pro-
cedure using 6-cyclopentyl-4-hydroxy-6-[2-(4-hydroxy-
phenyl)ethyl]-5,6-dihydropyran-2-one (0.2 g, 0.7 mmol),
2-tert-butyl-4-(2-tert-butyldimethylsilyloxy-ethoxy)-5-
methylphenyl-p-toluenethiosulfonate (0.7 g, 0.7 mmol),
K2CO3 (0.2 g) and DMF (2 mL). The crude compound
obtained was taken in 3 mL of THF. To it 1 mL of
concentrated HCl was stirred at room temperature for
1 h. Solvents were evaporated and the residue was pur-
i®ed by ¯ash silica gel chromatography. Isolated yield:
56%. IR (KBr): 3406, 2954, 1608, 1515, 1253, 1050
gel chromatography. Isolated yield: 52%. IR (KBr):
1
3429, 2928, 1679, 1603, 1515, 1252, 1048 cm
;
1H
NMR (400 MHz, DMSO-d6): d 0.89 (t, 3H, J=
6.75 Hz), 1.28 (m, 6H), 1.5 (s, 9H), 1.75 (s, 3H), 1.92 (m,
2H), 2.16 (m, 1H), 1.94 (m, 2H), 2.81 (d of ABX, 1H,
J=17.6 Hz), 2.92 (d of ABX, 1H, J=17.6 Hz), 3.7 (brs,
2H), 3.97 (t, 2H), 4.8 (brs, 1H), 6.66 (d, 2H, J=
8.44 Hz), 6.73 (s, 1H), 6.83 (s, 1H), 6.98 (d, 2H, J=
8.44 Hz), 9.17 (s, 1H); MS-APCI (m/z): 543, 499, 335.
1
cm 1; H NMR (400 MHz, DMSO-d6): d 1.33±1.72 (m,
8H), 1.47 (s, 9H), 1.81 (s, 3H), 1.94 (m, 2H), 2.36 (m,
1H), 2.55 (m, 2H, obscured by DMSO peak), 2.81 (d of
ABX, 1H, J=17.60 Hz), 2.92 (d of ABX, 1H, J=
17.60 Hz), 3.69 (brd, 2H), 3.97 (t, 2H, J=5.06 Hz), 4.81
(brs, 1H), 6.66 (d, 2H, J=8.44 Hz), 6.75 (s, 1H), 6.81 (s,
1H), 6.97 (d, 2H, J=8.44 Hz), 9.14 (s, 1H); MS-APCI
(m/z): 541, 497, 423, 259.
(3-(2-tert-Butyl-4-(2-hydroxy-ethoxy)-5-methyl-phenyl-
sulfanyl)-4-hydroxy-6-[2-(4-hydroxy-phenyl)-ethyl]-6-iso-
propyl-5,6-dihydro-pyran-2-one (30). The title compound
was prepared according to the general procedure using
4-hydroxy-6-[2-(4-hydroxyphenyl)ethyl]-6-isopropyl-di-
hydropyran-2-one (0.2 g, 0.4 mmol), 2-tert-butyl-4-(2-
methoxymethoxy-ethoxy)-5-methylphenyl-p-toluenethio-
sulfonate (0.3 g, 0.6 mmol), K2CO3 (0.5 g) and DMF
(2 mL). The crude compound obtained (0.1 g) was taken
in 2 mL of THF and 2 mL of MeOH. To it 2 mL of
concentrated HCl was stirred overnight. Solvents were
evaporated and the residue was puri®ed by ¯ash silica
6-[2-(4-Aminophenyl)-ethyl]-(3-(2-tert-butyl-4-hydroxy-
methyl-5-methyl-phenylsulfanyl)-4-hydroxy-6-phenyl-5,6-
dihydro-pyran-2-one (33). The title compound was pre-
pared according to the general procedure using 6-([2-4-
actylaminophenyl)ethyl]-4-hydroxy-6-phenyl-5,6-dihydro-
pyran-2-one (0.2 g, 0.7 mmol), 2-tert-butyl-4-hydroxy-
methyl-5-methylphenyl-p-toluenethiosulfonate
(0.3 g,
gel chromatography. Isolated yield: 65%. IR (KBr):
1
0.9 mmol), K2CO3 (0.5 g) and DMF (5 mL). The sus-
pension was cooled to 5ꢀC and treated with 20 mL of
water and 1 mL of glacial AcOH. The reaction mixture
was extracted with EtOAc, washed with brine, dried,
and concentrated. The residue on trituration with Et2O
a€orded a solid, which was ®ltered and air-dried. Iso-
lated yield: 64%. 1H NMR (400 MHz, DMSO-d6): d
1.38 (m, 9H), 1.69 (s, 3H), 1.94 (s, 3H), 2.14 (m, 3H),
2.44 (m, 1H, obscured by DMSO peak), 4.26 (s, 2H),
4.90 (brs, 1H), 6.10 (s, 1H), 6.94 (d, 2H, J=8.2 Hz), 7.16
(s, 1H), 7.29±7.47 (m, 7H), 9.78 (s, 1H). The solid
obtained, the N-acetyl derivative (0.2 g, 0.34 mmol), was
taken in 4 mL of 50% NaOH solution, treated with
30 mL of water and 5 mL of MeOH and was re¯uxed
overnight. The reaction was cooled to room tempera-
ture, concentrated, and suspended in phosphate bu€er
(pH 7.5). The reaction mixture was acidi®ed to pH 6.8
with phosphoric acid and extracted with CH2Cl2 (2Â
50 mL); the combined extracts were washed with brine,
3430, 2963, 1684, 1614, 1515, 1253, 1050 cm
;
1H
NMR (400 MHz, DMSO-d6): d 0.92 (d, 3H, J=
6.99 Hz), 0.97 (d, 3H, J=6.55 Hz), 1.47 (s, 9H), 1.81 (s,
3H), 1.93 (m, 2H), 2.16 (m, 1H), 2.43±2.56 (m, 2H), 2.72
(d of ABX, 1H, J=17.36 Hz), 2.81 (d of ABX, 1H,
J=17.36 Hz), 3.67 (brs, 2H), 3.94 (t, 2H), 4.81 (brs, 1H),
6.64 (d, 2H, J=8.44 Hz), 6.72 (s, 1H), 6.81 (s, 1H), 6.94
(d, 2H, J=8.44 Hz), 9.14 (s, 1H); MS-APCI (m/z): 515,
497, 311.
(3-(2-tert-Butyl-4-(2-hydroxy-ethoxy)-5-methyl-phenyl-
sulfanyl)-6-cyclopropyl-4-hydroxy-6-[2-(4-hydroxy-phenyl)-
ethyl]-5,6-dihydro-pyran-2-one (31). The title compound
was prepared according to the general procedure using
6-cyclopropyl-4-hydroxy-6-[2-(4-hydroxyphenyl)ethyl-
5,6-dihydropyran-2-one (0.2 g, 0.6 mmol), 2-tert-butyl-
4-(2-tert-butyldimethylsilyloxy-ethoxy)-5-methylphenyl-
p-toluenethiosulfonate (0.3 g, 0.6 mmol), K2CO3 (0.2 g)
and DMF (2 mL). The crude compound obtained was
taken in 3 mL of THF. To it 1 mL of concentrated HCl
was stirred at room temperature for 1 h. Solvents were
evaporated and the residue was puri®ed by ¯ash chro-
matography. Isolated yield: 53%. IR (KBr): 3400, 2954,
1683, 1611, 1515, 1253, 1051 cm 1; 1H NMR (40 MHz,
DMSO-d6): d 0.36 (m, 3H), 0.53 (m, 3H), 1.25 (m, 1H),
1.5 (s, 9H), 1.86 (s, 3H), 1.98 (t, 2H), 2.61 (m, 2H), 2.72
(d of ABX q, 1H, J=17.60 Hz), 2.86 (d of ABX q, 1H,
J=17.60 Hz), 3.69 (brt, 2H), 3.94 (t, 2H, J=5.06 Hz),
1
dried and concentrated. Isolated yield: 56%. H NMR
(400 MHz, DMSO-d6): d 1.44 (s, 9H), 1.76 (s, 3H), 2.05±
2.22 (m, 3H), 2.4 (m, 1H), 4.32 (s, 2H), 4.90 (brs, 1H),
6.17 (s, 1H), 6.47 (d, 2H, J=8.2 Hz), 6.75 (d, 2H), 7.21
(s, 1H), 7.38±7.43 (m, 5H); MS-APCI (m/z): 518.
6-[2-(4-Aminophenyl)-ethyl]-(3-(2-tert-butyl-4-hydroxy-
methyl-5-methyl-phenylsulfanyl)-4-hydroxy-6-isopropyl-
5,6-dihydro-pyran-2-one (34). The title compound
was prepared according to the general procedure using

J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
2797
6-[2-(4-aminophenyl)ethyl]-4-hydroxy-6-isopropyl-5,6-
dihydropyran-2-one (0.7 mmol prepared from 0.3 g
(0.7 mmol) of the corresponding Boc-derivative and
CH2Cl2 saturated with HCl gas), 2-tert-butyl-4-hydro-
xymethyl-5-methylphenyl-p-toluenethiosulfonate (0.3 g,
0.7 mmol), K2CO3 (1.0 g) and DMF (5 mL). Isolated
(3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phenylsulf-
anyl)-4-hydroxy-6-phenyl-6-phenethyl-5,6-dihydro-pyran-
2-one (38). The title compound was prepared according
to the general procedure using 4-hydroxy-6-phenyl-6-
phenethyl-5,6-dihydropyran-2-one (0.5 g, 1.7 mmol), 2-
tert-butyl-4-hydroxymethyl-5-methylphenyl-p-toluene-
thiosulfonate (0.8 g, 2.1 mmol), K2CO3 (0.7 g) and DMF
(5 mL). Isolated yield: 79%. IR (KBr): 3445, 1699, 1584
1
yield: 80%. H NMR (400 MHz, DMSO-d6): d 0.88 (m,
6H), 1.42 (s, 9H), 1.87 (m, 5H), 2.14 (m, 1H), 2.4 (m,
obscured by DMSO peak, 2H), 2.66 (d, 1H, J=
17.6 Hz), 2.88 (d, 1H, J=17.8 Hz), 4.30 (s, 2H), 4.90
(brs, 1H), 6.43 (d, 2H, J=8.3 Hz), 6.64 (s, 1H), 6.77 (d,
2H, J=8.3 Hz), 7.20 (s, 1H); MS-APCI (m/z): 484.
1
cm 1; H NMR (400 MHz, DMSO-d6): d 1.39 (s, 9H),
1.70 (s, 3H), 2.19 (m, 3H), 2.47±2.53 (m, 1H), 3.35 (q,
obscured by water peak, 2H), 4.26 (s, 2H), 4.85 (brs,
1H), 6.11 (s, 1H), 7.03±7.20 (m, 6H), 7.29±7.33 (m, 1H),
7.38 (m, 4H); MS-APCI (m/z): 501.
6-[2-(4-Aminophenyl)-ethyl]-(3-(2-tert-butyl-4-hydroxy-
methyl-5-methyl-phenylsulfanyl)-4-hydroxy-6-isobutyl-
5,6-dihydro-pyran-2-one (35). The title compound was
prepared according to the general procedure using 6-[2-
(4-aminophenyl)ethyl]-4-hydroxy-6-isobutyl-5,6-dihydro-
pyran-2-one (0.6 mmol prepared from 0.2 g (0.6 mmol)
of the corresponding Boc-derivative and CH2Cl2 satu-
rated with HCl gas), 2-tert-butyl-4-hydroxymethyl-5-
methylphenyl-p-toluenethiosulfonate (0.3 g, 0.7 mmol),
K2CO3 (1.0 g) and DMF (5 mL). Isolated yield: 78%.
1H NMR (400 MHz, DMSO-d6): d 0.93 (m, 6H), 1.48 (s,
9H), 1.62±1.84 (m, 3H), 1.91±1.99 (m, 2H), 2.45 (m,
obscured by DMSO peak, 2H), 2.76 (d, 1H, J=
17.6 Hz), 2.94 (d, 1H, J=17.3 Hz), 4.37 (s, 2H), 4.94
(brs, 1H), 6.49 (d, 2H, J=8.2 Hz), 6.76 (s, 1H), 6.85 (d,
2H, J=8.2 Hz), 7.26 (s, 1H); MS-APCI (m/z): 498.
(3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phenylsulf-
anyl)-4-hydroxy-6-isopropyl-6-phenethyl-5,6-dihydro-
pyran-2-one (39). The title compound was prepared
according to the general procedure using 4-hydroxy-6-
isopropyl-6-phenethyl-5,6-dihydropyran-2-one
(0.2 g,
0.7 mmol), 2-tert-butyl-4-hydroxymethyl-5-methylphe-
nyl-p-toluenethiosulfonate (0.2 g, 0.7 mmol), K2CO3
(0.3 g) and DMF (2 mL). Isolated yield: 72%. IR (KBr):
3424, 2963, 1681, 1603, 1390, 1048, 700 cm 1; 1H NMR
(400 MHz, DMSO-d6): d 0.96 (d, 3H, J=6.99 Hz), 0.98
(d, 3H, J=6.99 Hz), 1.5 (s, 9H), 1.89 (s, 3H), 2.03 (m,
2H), 2.25 (m, 1H), 2.64 (m, 2H), 2.77 (d of ABX, 1H,
J=17.84 Hz), 2.99 (d of ABX, 1H, J=17.84 Hz), 4.36
(s, 2H), 4.97 (s, 1H), 6.69 (s, 1H), 7.19 (m, 3H), 7.28 (m,
3H); MS-APCI (m/z): 469, 451, 407.
6-[2-(4-Aminophenyl)-ethyl]-(3-(2-tert-butyl-4-hydroxy-
methyl-5-methyl-phenylsulfanyl)-6-cyclohexyl-4-hydroxy-
5,6-dihydro-pyran-2-one (36). The title compound was
prepared according to the general procedure using 6-[2-
(4-aminophenyl)ethyl]-4-hydroxy-6-cyclohexyl-5,6-di-
hydropyran-2-one (0.8 mmol) (prepared from 0.3 g
(0.6 mmol) of the corresponding Boc-derivative and
CH2Cl2 saturated with HCl gas), 2-tert-butyl-4-hydro-
xymethyl-5-methylphenyl-p-toluenethiosulfonate (0.3 g,
0.7 mmol), K2CO3 (1.0 g) and DMF (5 mL). Isolated
(3-(2-tert-Butyl-4-hydroxy-5-methyl-phenylsulfanyl)-4-
hydroxy-6-isopropyl-6-phenethyl-5,6-dihydro-pyran-2-one
(40). The title compound was prepared according to the
general procedure using 4-hydroxy-6-(4-hydroxy-
phenyl)ethyl-6-isopropyl-5,6-dihydropyran-2-one (0.4 g,
1.7 mmol), 2-tert-butyl-4-hydroxy-5-methylphenyl-p-tol-
uenethiosulfonate (0.6 g, 1.8 mmol), K2CO3 (0.4 g) and
DMF (5 mL). Isolated yield: 70%. IR (KBr): 3403,
2965, 1680, 1604, 1387, 1161, 1050, 700 cm 1; 1H NMR
(400 MHz, DMSO-d6): d 0.94 (d, 3H, J=6.99 Hz), 0.97
(d, 3H, J=6.75 Hz), 1.45 (s, 9H), 1.75 (s, 3H), 2.0 (t,
2H), 2.2 (m, 1H), 2.61 (m, 2H), 2.75 (d of ABX, 1H,
J=17.84 Hz), 2.95 (d of ABX, 1H, J=17.84 Hz), 6.64
(s, 1H), 6.76 (s, 1H), 7.17 (m, 3H), 7.26 (t, 2H, J=
6.99 Hz), 9.03 (s, 1H); MS-APCI (m/z): 455, 291, 247,
159.
1
yield: 74%. H NMR (400 MHz, DMSO-d6): d 1.0±1.35
(m, 5H), 1.48 (s, 9H), 1.63 (m, 1H), 1.78 (m, 5H), 1.95
(s+m, 7H), 2.45 (m, obscured by DMSO peak, 2H),
2.70 (d, 1H, J=18.0 Hz), 2.85 (d, 1H, J=17.8 Hz), 4.37
(s, 2H), 4.95 (brs, 1H), 6.49 (d, 2H, J=8.2 Hz), 6.70 (s,
1H), 6.83 (d, 2H, J=8.2 Hz), 7.27 (s, 1H); MS-APCI
(m/z): 524.
(3-(2-tert-Butyl-4-(2-hydroxy-ethoxy)-5-methyl-phenyl-
sulfanyl)-4-hydroxy-6-isopropyl-6-phenethyl-5,6-dihydro-
pyran-2-one (41). The title compound was prepared
according to the general procedure using 4-hydroxy-
(3-(2-tert-Butyl-5-methyl-phenylsulfanyl)-4-hydroxy-6-iso-
propyl-6-phenethyl-5,6-dihydro-pyran-2-one (37). The
title compound was prepared according to the general
procedure using 4-hydroxy-6-isopropyl-6-phenethyl-5,6-
dihydropyran-2-one (0.3 g, 1.2 mmol), 2-tert-butyl-4-
hydroxymethyl-5-methylphenyl-p-toluenethiosulfonate
(0.5 g, 1.4 mmol), K2CO3 (0.3 g) and DMF (5 mL). Iso-
lated yield: 70%. IR (KBr): 3482, 2964, 1657, 1602,
6-(4-phenethyl)-6-phenyl-dihydropyran-2-one
(0.3 g,
0.9 mmol), 2-tert-butyl-4-(2-tert-butyldimethylsilyloxy-
ethoxy)-5-methylphenyl-p-toluenethiosulfonate (0.5 g,
0.9 mmol), K2CO3 (0.6 g) and DMF (8 mL). The crude
compound obtained (0.1 g) was dissolved in 2 mL of
methanol and 1 mL of concd HCl was added. The reac-
tion mixture was stirred at room temperature for 0.5 h.
Solvents were evaporated and the residue was puri®ed
by ¯ash silica gel chromatography. Isolated yield: 62%.
IR (KBr): 3335, 2952, 1675, 1604, 1449, 1253, 1170,
1043, 767, 702 cm 1; 1H NMR (400 MHz, DMSO-d6): d
1.53 (s, 9H), 1.75 (s, 3H), 1.92 (m, 1H), 2.19±2.42 (m,
1
1384, 1046, 700 cm 1; H NMR (400 MHz, DMSO-d6):
d 0.94 (d, 3H, J=6.99 Hz), 0.97 (d, 3H, J=6.75 Hz), 1.5
(s, 9H), 1.92 (s, 3H), 2.03 (m, 2H), 2.23 (m, 1H), 2.64
(m, 2H), 2.81 (d of ABX, 1H, J=15.14 Hz), 3.0 (d of
ABX, 1H, J=15.14 Hz), 6.75 (d, 1H, J=1.45 Hz), 6.82
(dd, 1H, J=8.19 Hz, J=1.45 Hz), 7.17 (m, 3H), 7.28 (m,
2H); MS-APCI (m/z): 439, 421, 395, 365.

2798
J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
3H), 2.75 (m, 1H), 3.31 (ABX q, 2H, J=17.36 Hz), 3.94
(m, 2H), 4.03 (t, 2H), 6.19 (s, 1H), 6.83 (s, 1H), 7.08 (d,
2H, J=6.75 Hz), 7.15 (t, 1H, J=7.5 Hz), 7.23 (t, 2H,
J=7.2 Hz), 7.33±7.47 (m, 5H), 7.66 (brs, 1H); MS-APCI
(m/z): 532, 325, 240, 208, 193.
concentrated. The resulting residue on trituration with
Et2O furnished the title compound. 1H NMR (400
MHz, DMSO-d6): d 0.92 (d, 3H, J=7.0 Hz), 0.96 (d,
3H, J=6.75 Hz), 1.49 (s, 9H), 1.89 (s, 3H), 1.92±2.0 (m,
2H), 2.2 (m, 1H), 2.35±2.6 (m, 2H), 2.75 (d of ABX q,
1H, J=18.1 Hz), 2.97 (d of ABX, 1H, J=17.6 Hz), 4.36
(s, 2H), 4.94 (brs, 1H), 6.65 (d, 2H, J=8.2 Hz), 6.69 (s,
1H), 6.96 (d, 2H, J=8.4 Hz), 7.28 (s, 1H), 9.15 (s, 1H),
11.97 (brs, 1H); MS-CI (m/z): 485.
(3-(2-tert-Butyl-4-(2-hydroxy-ethoxy)-5-methyl-phenyl-
sulfanyl)-4-hydroxy-6-isopropyl-6-phenethyl-5,6-dihydro-
pyran-2-one (42). The title compound was prepared
according to the general procedure using 4-hydroxy-6-
(4-hydroxyphenyl)ethyl-6-isopropyl-dihydropyran-2-one
(0.2 g, 0.8 mmol), 2-tert-butyl-4-(2-tert-butyldimethyl-
silyloxy-ethoxy)-5-methylphenyl-p-toluenethiosulfonate
(0.4 g, 0.8 mmol), K2CO3 (0.2 g) and DMF (3 mL). The
crude compound obtained (0.1 g) was taken in 2 mL of
THF and 2 mL of methanol. To it 2 mL of concd HCl
was stirred overnight. Solvents were evaporated and the
residue was puri®ed by ¯ash silica gel chromatography.
Isolated yield: 48%. IR (KBr): 3419, 2962, 1604, 1486,
(S)-6-[2-(4-Aminophenyl)-ethyl]-(3-(2-tert-butyl-5-methyl-
phenylsulfanyl)-4-hydroxy-6-isopropyl-5,6-dihydro-py-
ran-2-one (34S). The title compound was prepared
according to the general procedure using (S)-4-hydroxy-
6-[2-(4-tert-butoxycarbonylamino-phenyl)-ethyl]-6-iso-
propyl-5,6-dihydro-pyran-2-one (S-X, X=NH-Boc,
15.0 g, 40 mmol), p-toluene-4-thiosulfonic acid S-(2-tert-
butyl-4-hydroxymethyl-5-methyl-phenyl) ester (16.0 g,
43.9 mmol), K2CO3 (24.3 g, 175.8 mmol) and DMF
(50 mL). To the reaction mixture water was added and
brought to pH 7.0 using ammonium phosphate solu-
tion. The product was extracted with EtOAc; the
extracts were dried and concentrated to yield pure (S)-6-
[2-(4-tert-butoxycarbonylaminophenyl)-ethyl]-(3-(2-tert-
butyl-5-methyl-phenylsulfanyl)-4-hydroxy-6-isopropyl-
5,6-dihydro-pyran-2-one. Isolated yield: 86%. 1H NMR
(300 MHz, MeOH-d4): d 0.83±0.94 (m, 6H), 1.44 (s, 9H),
1.45 (s, 9H), 1.86 (s, 3H), 1.93±1.98 (m, 2H), 2.16±2.2
(m, 1H), 2.52±2.57 (m, 2H), 2.75 (d, 1H), 2.96 (d, 1H),
4,35 (s, 2H), 6.68 (s, 1H), 7.03 (d, 2H), 7.21 (s, 1H), 7.26
(d, 2H), 9.22 (s, 1H). The above compound (17.3 g,
29.6 mmol) taken in DMSO (50 mL) was added to
sodium hydroxide (11.9 g, 296.3 mmol) in water
(50 mL). The reaction mixture was degassed with nitro-
gen and heated to 120ꢀC. After 2 h, the reaction mixture
was cooled to room temperature and to it water
(ꢁ400 mL) was added. The reaction mixture was neu-
tralized with ammonium phosphate solution to pH 7.0.
The product was extracted with EtOAc and the organic
layer was ®ltered through a plug of Celite. Concentra-
tion of the organic layer a€orded a solid, which was
taken in Et2O and ®ltered to obtain a solid. Isolated
1
1384, 1253, 1047 cm 1; H NMR (400 MHz, DMSO-
d6): d 0.94 (d, 3H, J=7.23 Hz), 0.97 (d, 3H, J=6.99 Hz),
1.5 (s, 9H), 1.81 (s, 3H), 2.0 (m, 2H), 2.2 (m, 1H), 2.64
(m, 2H), 2.75 (d of ABX, 1H, J=17.84 Hz), 2.97 (d of
ABX, 1H, J=17.84 Hz), 3.66 (brs, 2H), 3.94 (t, 2H,
J=5.06 Hz), 4.8 (brs, 1H), 6.72 (s, 1H), 6.81 (s, 1H),
7.17 (t, 3H), 7.27 (t, 2H); MS-APCI (m/z): 499, 481, 291.
(3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phenylsulf-
anyl)-4-hydroxy-6-[2-(4-hydroxypheny)-ethyl]-6-isopropyl-
5,6-dihydro-pyran-2-one (16S). (S)-4-Hydroxy-6-[2-(4-
hydroxy-phenyl)-ethyl]-6-isopropyl-5,6-dihydro-pyran-2-
one (S-X, X=OH 0.3 g, 1.1 mmol) in DMF (12 mL),
K2CO3 (0.6 g, 4.34 mmol) was added followed by tol-
uene-4-thiosulfonic acid S-(2-tert-butyl-4-hydroxy-
methyl-5-methyl-phenyl) ester (0.4 g, 1.2 mmol). After
stirring the reaction mixture overnight at room tem-
perature, the product was partitioned between 1 N
NaOH and Et2O. The aqueous layer was acidi®ed to
pH 4±5 with 1 N HCl and extracted with EtOAc. The
combined organic phases were washed dried and con-
centrated. The resulting residue on trituration with
Et2O furnished the title compound. 1H NMR
(400 MHz, DMSO-d6): d 0.92 (d, 3H, J=7.0 Hz), 0.96
(d, 3H, J=6.75 Hz), 1.49 (s, 9H), 1.89 (s, 3H), 1.92±2.0
(m, 2H), 2.2 (m, 1H), 2.35±2.6 (m, 2H), 2.75 (d of ABX
q, 1H, J=18.3 Hz), 2.97 (d of ABX, 1H, J=17.8 Hz),
4.36 (s, 2H), 4.94 (brs, 1H), 6.65 (d, 2H, J=8.4 Hz), 6.69
(s, 1H), 6.96 (d, 2H, J=8.4 Hz), 7.28 (s, 1H), 9.15 (s,
1H), 11.97 (brs, 1H); MS-CI (m/z): 485.
yield: 87%. IR (KBr): 8429, 2960, 2874, 1616, 1601,
1
1514, 1481, 1047, 1037 cm
;
1H NMR (300 MHz,
MeOH-d4): d 1.02 (d, 3H, J=6.84 Hz), 1.04 (d, 3H,
J=6.6 Hz), 1.55 (s, 9H), 1.96 (s, 3H), 2.00±2.17 (m, 2H),
2.30 (m, 1H), 2.59±2.67 (m, 3H), 2.95 (d, 1H, J=16.60),
4.49 (s, 2H), 6.81±6.85 (m, 3H), 7.01 (d, 2H,
J=8.30 Hz), 7.29 (s, 1H); MS-APCI (m/z): 484.
(3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phenylsulf-
anyl)-4-hydroxy-6-[2-(4-hydroxypheny)-ethyl]-6-isopropyl-
5,6-dihydro-pyran-2-one (16R). To (R)-4-hydroxy-6-[2-
(4-hydroxy-phenyl)-ethyl]-6-isopropyl-5,6-dihydro-pyran-
2-one (R-X, X=OH, 0.12g, 0.43mmol) in DMF (5 mL),
K2CO3 (0.2 g, 1.74 mmol) was added followed by tol-
uene-4-thiosulfonic acid S-(2-tert-butyl-4-hydroxy-
methyl-5-methyl-phenyl) ester (0.2 g, 0.5 mmol). After
stirring the reaction mixture overnight at room tem-
perature, the product was partitioned between 1 N
NaOH and Et2O. The aqueous layer was acidi®ed to
pH 4±5 with 1 N HCl and extracted with EtOAc. The
combined organic phases were washed, dried and
(R)-6-[2-(4-Aminophenyl)-ethyl]-(3-(2-tert-butyl-5-methyl-
phenylsulfanyl)-4-hydroxy-6-isopropyl-5,6-dihydro-pyran-
2-one (34R). The title compound was prepared accord-
ing to the general procedure using (R)-4-hydroxy-6-[2-
(4-tert-butoxycarbonylamino-phenyl)-ethyl]-6-isopropyl-
5,6-dihydro-pyran-2-one (R-X, X=NH-Boc, 1.9 g,
5.1 mmol), p-toluene-4-thiosulfonic acid S-(2-tert-
butyl-4-hydroxymethyl-5-methyl-phenyl) ester (2.0 g,
5.6 mmol), K2CO3 (2.1 g, 15.2 mmol) and DMF (5 mL).
To the reaction mixture water was added and brought
to pH 7.0 using ammonium phosphate solution. The
product was extracted with EtOAc; the extracts were
dried and concentrated to yield pure (R)-6-[2-(4-tert-

J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
2799
butoxycarbonylaminophenyl)-ethyl]-(3-(2-tert-butyl-5-
Acknowledgements
methyl-phenylsulfanyl)-4-hydroxy-6-isopropyl-5,6-dihy-
dro-pyran-2-one. Isolated yield: 68%. Spectral data
were the same as its S enantiomer. The Boc group from
above product was deprotected using TFA (5 mL) and
CH2Cl2 (5 mL). The crude product was puri®ed by ¯ash
silica gel chromatography (5% EtOH in CH2Cl2). The
spectral data of the ®nal product is the same as its S
enantiomer. Isolated yield: 45%.
We thank the Analytical Chemistry Department of
Parke-Davis for spectral and analytical data. We also
thank the group at Southern Research Institute for the
EC50 and TC50 determinations. We also thank Dr.
James Kaltenbron for proof reading as well as his
suggestions.
References
(S)-3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phenylsulf-
anyl)-4-hydroxy-6-isopropyl-6-phenethyl-5,6-dihydro-pyran-
2-one (39S). To (S)-4-hydroxy-6-isopropyl-6-(2-phenthyl)-
5,6-dihydropyran-2-one (S-X, X=H, 0.5 g, 1.9 mmol) in
DMF (12 mL), K2CO3 (0.8 g, 5.8 mmol) was added fol-
lowed by toluene-4-thiosulfonic acid S-(2-tert-butyl-4-
hydroxymethyl-5-methyl-phenyl) ester (0.8 g, 2.1 mmol).
The reaction mixture was stirred overnight at room
temperature, poured into saturated NH4Cl and extrac-
ted twice with EtOAc. The combined organic phases
were washed twice with 1:1 H2O:brine followed by
brine, dried, ®ltered and concentrated. The resulting
residue was puri®ed by ¯ash silica gel chromatography
(4:1 Et2O:hexanes) to give pure material, which on tri-
turation with diethyl ether/hexanes furnished the
desired product as a white solid. Isolated yield: 60%. IR
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(KBr): 3425, 2963, 2877, 1683, 1603, 1454, 1387, 1269,
;
1H NMR (300 MHz,
1
1236, 1048, 761, 700 cm
11. Romines, K. R.; Chrusciel, R. A. Current Medicinal
Chemistry 1995, 2, 825 and references therein.
DMSO-d6): d 0.92±0.98 (dd, 6H, J=6.95 Hz), 1.47 (s,
9H), 1.85 (s, 3H), 1.98±2.06 (m, 2H), 2.16±2.27 (m, 1H),
2.61±2.68 (m, 2H), 2.77 (d of ABX q, 1H, J=17.76 Hz),
2.98 (d of ABX q, 1H, J=17.94 Hz), 4.34 (s, 2H), 6.68
(s, 1H), 7.16±7.27 (m, 6H); MS-APCI (m/z): 469.
12. Vara Prasad, J. V. N.; Lunney, E.; Para, K. S.; Tummino,
P. J.; Ferguson, D.; Hupe, D.; Domagala, J. M.; Erickson, J. W.
Drug Design and Discovery 1996, 13, 15 and references therein.
13. Eyermann, C. J.; Jadhav, P. K.; Hodge, C. N.; Chang, C.-H.;
Rodgers, J. D.; Lam, P. Y. S. In Advances in Amino Acid
Mimetics and Peptidomimetics; Bell, A., Ed.; Jai Press, 1997;
Vol. 1, pp 1±40.
14. Turner, S. R.; Strobach, J. W.; Tommasi, R. A.; Aristo€,
P. A.; Johnshon, P. A.; Skulnick, H. I.; Dolak, L. A.; Seest, E.
P.; Tomich, P. K.; Bohanon, M. J.; Horng, M.-M.; Lynn, J. C.;
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(R)-(3-(2-tert-Butyl-4-hydroxymethyl-5-methyl-phen-
ylsulfanyl)-4-hydroxy-6-isopropyl-6-phenethyl-5,6-dihydro-
pyran-2-one (39R). To the (R)-4-hydroxy-6-isopropyl-
6-(2-phenthyl)-5,6-dihydropyran-2-one (R-X, X=H,
0.12g, 0.46mmol) taken in DMF (12 mL), K2CO3 (0.2g,
1.4 mmol) was added followed by toluene-4-thiosulfonic
acid S-(2-tert-butyl-4-hydroxymethyl-5-methyl-phenyl)
ester (0.2 g, 0.5 mmol). The reaction mixture was stirred
overnight at room temperature, poured into saturated
NH4Cl and extracted twice with EtOAc. The combined
organic phases were washed twice with 1:1 H2O:brine
followed by brine, dried, ®ltered and concentrated. The
residue, after ¯ash silica gel chromatography (1:1
EtOAc:hexanes eluents) followed by trituration with
Et2O/hexanes, a€orded the desired product as a white
solid. Isolated yield: 74%. IR (KBr): 3426, 3412, 2963,
2877, 1680, 1603, 1478, 1453, 1390, 1321, 1266, 1235,
1
1198, 1048, 760, 700 cm
;
1H NMR (300 MHz,
DMSO-d6): d 0.92±0.97 (dd, 6H, J=6.95 Hz), 1.47 (s,
9H), 1.85 (s, 3H), 1.98±2.07 (m, 2H), 2.17±2.26 (m, 1H),
2.61±2.68 (m, 2H), 2.77 (d of ABX q, 1H, J=18.1 Hz),
2.98 (d of ABX q, 1H, J=17.8 Hz), 4.34 (s, 2H), 6.68 (s,
1H), 7.16±7.27 (m, 6H); MS-APCI (m/z): 469.
18. Fritzerald, P. M. D. Current Opin. Struct. Biol. 1993, 1,
868.
19. Hagen, S.; Vara Prasad, J. V. N.; Boyer, F. E.; Domagala,
J. M.; Ellsworth, E. L.; Gajda, C.; Hamilton, H. W.; Markoski,
L. J.; Steinbaugh, B.; Tait, B. D.; Lunney, E. A.; Tummino, P.
J.; Ferguson, D.; Hupe, D.; Nouhan, C.; Gracheck, S. J.;
Supporting information. All the CHN data of the ®nal
compounds 1±42 (2 pages).

2800
J. V. N. Vara Prasad et al. / Bioorg. Med. Chem. 7 (1999) 2775±2800
Saunder, J. M.; VanderRoest, S. J. Med. Chem. 1997, 40,
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20. Sharmeen, L. (unpublished results).
21. Vara Prasad, J. V. N.; Lunney, E. A.; Steibaugh, B. A.;
Hamilton, H. W.; Tummino, P. J.; Nouhan, C.; Graham, N.;
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