Synthesis and modeling studies with monocyclic analogues of mycophenolic acid

Article abstract of DOI:10.1021/jm9501339

Two stepwise procedures, developed for the introduction of the (E)-4- methyl-4-hexenoic acid side chain of mycophenolic acid, were used in the synthesis of monocyclic mycophenolic acid analogues 2a-i. The derivatives with a methyl group or hydrogen at C-4 and lacking the lactone moiety were much less cytotoxic than mycophenolic acid. The menocyclic analogues with a C-4 chloro group did show some activity, albeit much less than mycophenolic acid. The observed differences in potency are rationalized by semiempirical calculations of intramolecular H-bonds.

Full text of DOI:10.1021/jm9501339

46
J . Med. Chem. 1996, 39, 46-55
Syn th esis a n d Mod elin g Stu d ies w ith Mon ocyclic An a logu es of
Mycop h en olic Acid
Wayne K. Anderson,* Terri L. Boehm, Gergely M. Makara, and R. Thomas Swann
Department of Medicinal Chemistry, School of Pharmacy, State University of New York at Buffalo, Buffalo, New York 14260
Received February 21, 1995X
Two stepwise procedures, developed for the introduction of the (E)-4-methyl-4-hexenoic acid
side chain of mycophenolic acid, were used in the synthesis of monocyclic mycophenolic acid
analogues 2a -i. The derivatives with a methyl group or hydrogen at C-4 and lacking the
lactone moiety were much less cytotoxic than mycophenolic acid. The monocyclic analogues
with a C-4 chloro group did show some activity, albeit much less than mycophenolic acid. The
observed differences in potency are rationalized by semiempirical calculations of intramolecular
H-bonds.
In tr od u ction
I isoform. The higher activity of mycophenolic acid
against the type II isoform is significant because the
type II isoform of IMPD has been shown to be selectively
upregulated in human tumor cells.9
Inosine monophosphate dehydrogenase (IMP:NAD+
oxireductase, EC 1.1.1.205), the rate-limiting enzyme
in de novo guanine nucleotide biosynthesis, catalyzes
the conversion of inosine 5′-monophosphate (IMP) to
xanthosine 5′-monophosphate (XMP), presumably
through a tetrahedral1,2 intermediate. Inhibition of this
enzyme (IMPD) leads to elevated IMP levels which
inhibit one of the principal salvage pathways through
feedback regulation of hypoxanthine-guanine phospho-
ribosyl transferase (HGPRT). The biosynthesis of pu-
rine nucleosides is subject to complex control mecha-
nisms, and the consequences of IMPD inhibition extend
to the adenine nucleotide pool. For example, as IMPD
inhibition reduces GTP levels, GTP feedback inhibition
of AMP deaminase is reduced, and the extent of AMP
deamination (to IMP) increases. The conversion of IMP
to AMP via adenylosuccinic acid is also inhibited by
reduced levels of the required cofactor, GTP. Thus,
inhibitors of IMPD inhibit both the de novo and salvage
pathways to GMP and have an indirect, down-regula-
tory effect on AMP.
Inhibitors of IMPD reduce GTP and deoxyGTP pool
levels and have been shown to possess antineoplastic,
antiparasitic, antiviral3 (including anti-HIV4), and im-
munosuppressive activity. Inhibitors of IMPD have also
been shown to induce differentiation5 in certain cell
lines. The utility of the IMPD inhibitor tiazofurin in
the treatment of human leukemia is a result of cyto-
toxicity and differentiation-induction (maturation-
induction). IMPD inhibitors also act in synergy with
antiviral nucleosides, including 2′,3′-dideoxy nucleosides
active against HIV, by stimulating nucleoside phospho-
rylation.6 For convenience, we have broadly classified
the inhibitors into three groups based on the mode of
enzyme binding:7 (group I) IMP/XMP analogues, (group
II) NAD+/NADH analogues, and (group III) multisub-
strate inhibitors.
Mycophenolic acid (1, MPA) is a group II IMPD
inhibitor that requires no metabolic activation (i.e., it
is a “direct acting” inhibitor). It has been shown to
possess significant antineoplastic,10 antiparasitic,11 an-
tiviral,12 and immunosuppressive13 activity [the mor-
pholinoethyl ester prodrug of MPA (mycophenolate
mofetil, RS-61443) is undergoing extensive clinical
studies for the prevention and reversal of tranplant
rejection]. MPA is also very active against psoriasis.14
Low toxicity and the fact that the toxic effects (GIT
irritation caused by the glucuronide conjugate of MPA)
are reversible upon withdrawal of the drug are attrac-
tive features. The major problem with MPA as an
antitumor drug in humans is that rapid conjugation of
the C-7 phenolic hydroxyl group with glucuronic acid15
makes it very difficult to achieve the drug levels needed
for antitumor activity.16 The dilemma is that a free C-7
hydroxyl group is an absolute requirement for MPA
activity.17
The MPA structure has been extensively modified,
and except for derivatives that can be converted to MPA
in vivo, all the reported analogues are either inactive
or have markedly diminished activity. A summary of
the major structure-activity relationships (activity
against murine lymphosarcoma or suppression of mi-
tosis in mouse fibroblasts) for MPA follows. In the side
chain the terminal carboxylic acid is essential, 2′,3′-
dihydroMPA is 15-fold less active than MPA, and
analogues with shorter or longer side chains have poor
to no activity. Replacement of the carboxylic acid with
a 5-tetrazolyl moiety, a carboxamido group, or a nitrile
function produced inactive compounds. Replacement of
the C-5 methoxy with ethoxy, propoxy, and hydroxy
gives analogues that are 4, 8, and 15 times less active
Human IMPD exists as two tetrameric isoforms, types
I and II, with 84% amino acid identity.8 Both isoforms
follow Ordered Bi-Bi kinetics and have similar kcat
values and comparable Km values for IMP and NAD+.
Inhibitors of the two isoforms do, however, show differ-
ent Ki values; for example, the Ki for mycophenolic acid
is 4.8-fold lower for the type II isoform than for the type
X Abstract published in Advance ACS Abstracts, December 1, 1995.
0022-2623/96/1839-0046$12.00/0 © 1996 American Chemical Society

Monocyclic Analogues of Mycophenolic Acid
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 1 47
Sch em e 1
than MPA, respectively. Methylation of the C-7 phenol
eliminates activity; esters (prodrugs) are active only if
the ester can be hydrolyzed in vivo. Replacement of the
C-7 phenolic hydroxyl with a thiol produced an inactive
compound. The lactone is also important: MPA ana-
logues with a free C-7 carboxylic acid are inactive, and
reduction of the carboxylic acid (in the ring-opened
hydroxy acid form of MPA) to a methyl group completely
abolishes activity. Removal of the C-4 methyl group
results in a 30-fold decrease in activity [the C-4 methyl
group destabilizes the ring-opened hydroxy acid form
of the phthalide lactone18 (a steric effect between C-3
and the methyl at C-4)]. The MPA side chain was
incorporated into a small series of N-substituted pyri-
dones and glutarimides, but none of the compounds
possessed appropriate replacements for the substituted
phthalide moiety in MPA and all were inactive.19 Two
new cytotoxic phenols related to MPA have recently
been reported: the lactam, hericenone B, was 16-fold
more cytotoxic to HeLa cells in vitro than the lactone,
hericenone A, but no biochemical data (IMPD inhibition)
were reported for either compound.20 The IMPD inhibi-
tory and immunosuppressive activities of a series of side
chain modified MPA analogues has been reported.21 The
compounds were side chain analogues in which the (E)-
alkene was replaced by other π-electron groups or
mimics (a (Z)-alkene, an alkyne, an allene, a thioether,
or cyclopropyl moieties), but the analogues were either
inactive or showed markedly reduced activities.
The monocyclic analogues reported in the present
study were designed to retain the MPA carbonyl but
replace the lactone with other uncharged carbonyl
moieties such as esters, carboxamides, or ketones. The
important MPA hexenoic acid side chain was unmodi-
fied in this series. Furthermore, the MPA C-5 methoxy
group was retained because of its potential influence
on the conformation of the critical hexenoic acid side
chain. The change from a bicyclic phthalide, in the MPA
lactone, to a series of monocyclic compounds would be
expected to influence intramolecular hydrogen bonding
between the phenol and the carbonyl moiety which could
interfere with in vivo conjugation of the phenol. The
monocyclic analogues were also designed as part of our
larger study to develop an IMPD inhibitor binding site
model (to be published elsewhere); as such, these MPA
analogues more closely mimicked the nicotinamide
riboside segment of the NAD+.
chloride to give 5a . This aldehyde was reduced to 5b
in 62% yield. The o-methoxy group was selectively
removed with boron trichloride to give the desired
phenol 3b (86%). The resulting phenols 3a -c were
converted to the O-allyl derivatives 3d -f. The crude
allyl phenyl ethers were then heated at 210 ( 5 °C for
3-4 h to give 6a (99% for the two steps), 6b (81% from
5a ), and 6c (46% for the two steps; the rearrangement
of 3f was slow, presumably because of the electron-
withdrawing property of the chloro group) (Scheme 2).
Ozonolysis of 6a -c in dichloromethane-methanol (3:
1) allowed the initially formed ozonide to be converted
to the more stable methyl hemiacetal hydroperoxide
which, upon reduction with triphenylphosphine, gave
the aldehydes 7a , 7b, and 7c (85, 77 and 91%, respec-
tively). Homologation of the aldehydes 7a -c using the
stabilized ylide (1-formylethylidene)triphenylphosphorane
gave the E-alkenes 8a -c (based on NOE studies) in
average yields of 92%. Protection of the free phenols
was accomplished using MEM chloride and a slight
excess of sodium hydride. For 8a , when large quantities
of base was used, markedly lower yields resulted. The
yields are 87, 77, and 92% for 8d , 8e, and 8f, respec-
tively (based on unrecovered starting material). The
enals were then reduced, in good yields, to the enols
9a -c with sodium borohydride (Scheme 3). The alco-
hols were then converted to the allylic bromides 10a -c
(85, 79, and 83% yield, respectively) with triphenylphos-
phine-tetrabromomethane in the presence of N,N-
diisopropylethylamine (to prevent cleavage of the MEM
protecting groups).
This report describes the synthesis of the monocyclic
MPA analogues 2a -i as part of an ongoing project in
our laboratory on MPA structure-activity requirements
and the study of inosine monophosphate dehydrogenase
inhibitors.22
Ch em istr y
The monocyclic aromatic moieties were synthesized
in the stepwise approach summarized in Scheme 1. The
approach is a variant of that used in the original
synthesis of MPA by Birch23 (several other total24 and
formal25 syntheses of MPA have also been published).
The syntheses of the monocyclic MPA analogues 2a -i
are summarized in Schemes 1-4. The starting phenols
were synthesized from the commercially available 2-hy-
droxy-4-methoxybenzoate 3a . The chlorophenol 3c was
synthesized from 3a in 93% using sulfuryl chloride.
Methylation of 3a afforded 4 which was formylated with
R,R-dichloromethyl methyl ether and titanium tetra-
The displacement of the allylic bromide 10a with
anions such as those derived from tert-butyl acetate or
acetic acid proved problematic; however, the reaction
with the softer anion derived from methyl (phenylsul-
fonyl)acetate gave the sulfone 11a (11b and 11c were
prepared similarly); reductive cleavage of the activating
sulfonyl group in 11a ,b gave 12a ,b (81% from 10a and
68% from 10b). Reductive cleavage of 11c resulted in
concomitant reduction of the aromatic chloro group;
therefore an alternate route was investigated. Selective
base hydrolysis of the side chain ester of 12a followed
by TFA cleavage of the MEM ether gave 2a (61%). The

48 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 1
Anderson et al.
Sch em e 2
Sch em e 3
Sch em e 4
MEM group of 12b was removed by TFA followed by
base hydrolysis of the ester to afford 2d in 78% yield.
The displacement of the allylic bromide 10c was carried
out using the anion derived from di-tert-butyl malonate
to give the diester 13 (84%) (Scheme 4). Hydrolysis of
the di-tert-butyl ester (by formic acid) occurred concomi-
tantly with cleavage of the MEM group. The resulting
crude diacid phenol was subjected to thermal decar-
boxylation to give 2g in 60% yield. Aminolysis of 2a ,
2d , and 2g gave 2b, 2e, and 2h (68, 63, and 98%,
respectively). The esters 2a , 2d , and 2g were converted
to the corresponding â-keto sulfoxides using excess
sodium hydride in DMSO. Subsequent reductive cleav-
age afforded the methyl ketones 2c, 2f, and 2i (23, 64,
and 61%, respectively, over the two steps).
Biologica l Eva lu a tion
Two of the nine monocyclic MPA analogues showed
activity against L1210 leukemia cells in tissue culture.26
The chloro compounds 2g and 2i showed modest activ-
ity: the ester 2g had an IC50 ) 61 µM whereas the
ketone exhibited 21% inhibition at 100 µM, the highest
concentration tested (IC50 > 100 µM for 2a -f and 2h ).
Mycophenolic acid (1) had an IC50 ) <0.2 µM in this

Monocyclic Analogues of Mycophenolic Acid
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 1 49
Ta ble 1. Calculation of the Intramolecular H-Bonds and
Rotational Barriers of Phenolic Hydroxy
benzoate analogues 2g and 2i suggests a possible role
for groups at that position in MPA which may enhance
the acidity of the phenol.
HO---OdC(1)
distance (Å)
barrier around C(7)-OH
compd
bond (kcal/mol)
Exp er im en ta l Section
1
3.269
2.649
2.649
2.640
2.634
2.648
2.632
5.92
10.00
9.82
11.32
10.29
10.12
9.74
2a
2d
2e
2f
2g
2i
Melting points (uncorrected) were determined in an open
capillary with
a Thomas-Hoover Unimelt apparatus. IR
spectra were determined with a Matteson FT-IR interferom-
eter. 1H NMR spectra were determined at 90 MHz with a
Varian EM 390 or at 300 MHz with
a Varian Gemini
spectrometer in CDCl3 solution (unless noted otherwise) with
TMS as internal standard. Microanalyses were performed by
Atlantic Microlab, Atlanta, GA. Silica gel for flash column
chromatography (230-400 mesh ASTM) was obtained from
EM Science. Organic solutions were dried with anhydrous
sodium sulfate unless otherwise noted.
assay. Compounds 2a , 2b, and 2c were also inactive
against a HT-29 human colon adenocarcinoma cell line
(MPA had an IC50 ) 0.4 µM). The ketone 2c was
inactive (>32.5 µM) against human A121 ovarian, A549
lung carcinoma, and MCF7 breast adenocarcinoma cell
lines (MPA had IC50 ) 0.2-0.3 µM). The chloro
compound is 2 orders of magnitude less active than
MPA, but it is significant that the compound represents
the first monocyclic MPA analogue with any antitumor
activity.
(E)-4-Met h yl-6-[3-(2-h yd r oxy-1-(m et h oxyca r b on yl)-4-
m eth oxyp h en yl)]-4-h exen oic Acid (2a ). A solution of 12a
(2.53 g, 6.16 mmol) in methanol (65 mL) was treated with
aqueous sodium hydroxide (0.98 M, 6.6 mL, 6.47 mmol) and
stirred for 60 h at 43 °C (the disappearance of starting material
was monitored by TLC, silica gel-ether). Water (150 mL) was
added, and the mixture was extracted with ether (2 × 150 mL).
The aqueous phase was acidified (3 M HCl, 2.4 mL) and then
extracted with ethyl acetate (3 × 100 mL). The combined ethyl
acetate extract was dried and concentrated to give the crude
monoacid as a colorless oil. The crude acid was dissolved in
dichloromethane (15 mL), and TFA (0.52 mL, 6.7 mmol) was
added. Removal of the MEM group was monitored by TLC
[silica gel, hexane-formic acid-ethyl acetate (70:1:29)]. The
reaction was complete after 10 min. The solution was ex-
tracted with water (3 × 10 mL). The combined aqueous extract
was washed with ethyl acetate (4 × 10 mL); addition of sodium
chloride to the aqueous solution was necessary to break the
emulsion which formed. The combined organic solution was
dried and evaporated to afford a yellow oil. Flash column
chromatography (silica gel, hexane-formic acid-ethyl acetate,
80:1:19) of the crude oil provided 2a (1.16 g, 61% from 12a ) as
a white solid. A sample was crystallized from ethyl acetate-
hexane (1:6) to give fine white needles: mp 106.5-107.5 °C;
1H NMR δ 1.79 (s, 3 H), 2.30 (m, 4 H), 3.33 (d, 2 H), 3.83 (s, 3
H), 3.87 (s, 3 H), 5.24 (t, 1 H), 6.42 (d, 1 H), 7.69 (d, 1 H), 10.0
(br s, 1 H), 11.03 (s, 1 H); IR (KBr) 3571-3352, 1718, 1670,
1618 cm-1; UV (CH3OH) 300 (4800), 264.5 (14 000) nm. Anal.
(C16H20O6) C, H.
Discu ssion
Superposition of the minimized conformations of 2a -i
on that of MPA (PM3, precise criteria) showed the
expected fit in the alignment of the hexenoic acid side
chains. Furthermore, the carbonyl groups (which re-
placed the MPA lactone in these monocyclic analogues)
were projected along a similar vector in comparison with
the MPA lactone. This was due to stabilization by
intramolecular hydrogen bonding with the phenolic
hydroxyls. Thus, compounds 2a -i retained the hydro-
gen-bonding character of the MPA lactone oxygen. The
absence of the C-3 methylene group in the monocyclic
analogues is unlikely to result in major loss in binding
energy.
The molecular electrostatic potential surfaces were
calculated27 (from Mulliken population derived from
semiempirical PM3) and compared with MPA. Two
significant differences between MPA and the monocyclic
analogues were the electrostatic potential around the
phenolic hydrogen and the intramolecular distance
between the phenol and the o-carbonyl oxygen (HO---
OdC). The appropriate angles and distances for in-
tramolecular hydrogen bonding between the phenol and
the adjacent carbonyl were found to be less favorable
for MPA (1) compared to the monocyclic analogues. The
(HO---OdC) distance in the X-ray structure of MPA (1)
was 3.022 Å (ca. 0.2 Å shorter than the calculated
value), but the trends in Table 1 are still significant.
The conclusion that the monocyclic MPA analogues form
stronger intramolecular H-bonds was confirmed in
calculations of the rotational barrier around the C-OH
bond. These data show the monocyclic analogues have
a 4-5 kcal/mol higher barrier than MPA (1).
(E)-4-Meth yl-6-[3-(1-(am in ocar bon yl)-2-h ydr oxy-4-m eth -
oxyp h en yl)]-4-h exen oic Acid (2b). A solution of the ester
2a (1.069 g, 34.7 mmol) in methanol (50 mL) in a 3 oz Fisher-
Porter aerosol pressure vessel was cooled to 0 °C, and
anhydrous ammonia was bubbled through the solution for 15
min. The vessel was closed and then heated at 55 °C with
stirring for 45 h [TLC analysis (silica gel, hexane-formic acid-
ethyl acetate, 70:1:29) showed only a trace of starting mate-
rial]. The solution was concentrated to dryness, and the brown
residue was purified by successive column chromatography
(silica gel, column 1 eluant, ethyl acetate-hexane, 40:60;
column 2 eluant, hexane-formic acid-ethyl acetate, 20:1:79;
the sample was preadsorbed silica gel using methanol for the
second column) to give 2b (0.69 g, 68%) as an off-white solid:
1
mp 193-195 °C; H NMR (DMSO-d6) δ 1.72 (s, 3 H), 2.20 (br
s, 4 H), 3.22 (d, 2 H), 3.81 (s, 3 H), 5.16 (t, 1 H), 6.52 (d, 1 H),
7.71 (d, 1 H), 7.80 (obscured br s, 1 H), 8.11 (br s, 2 H), 12.00
(br s, 1 H); IR (KBr): 3569-3200, 1701, 1618 cm-1
(C15H19NO5) C, H, N.
. Anal.
The low levels of antitumor activity exibited by the
monocyclic analogues emphasize the importance of the
bicyclic lactone in MPA. It is possible, considering the
absolute requirement for the MPA phenol moiety, that
the hydroxyl group serves as a H-bond donor, binding
to a specific site on the enzyme IMPD. Thus, the
strength of the intramolecular hydrogen bond in the
unbound compounds may be an important factor. The
intramolecular hydrogen bonds are significantly stron-
ger in the monocyclic analogues compared to MPA
(Table 1). The activity for the 5-chloro-substituted
(E )-4-Me t h y l-6-[3-(2-h y d r o x y -4-m e t h o x y -1-a c e t y l-
p h en yl)]-4-h exen oic Acid (2c). Sodium hydride (60% dis-
persion in mineral oil, 0.40 g, 10.0 mmol) was washed with
dry hexanes (2 mL). The flask was evacuated and purged
several times with nitrogen, and while under
a flow of
nitrogen, DMSO (7 mL, distilled from calcium hydride) was
added. The resulting gray solution was warmed to 75-80 °C.
After the evolution of hydrogen had subsided, the flask was
cooled to ca. 8 °C and a solution of 2a (0.497 g, 1.62 mmol) in
dry DMSO (4 mL) was added dropwise. The cooling bath was
removed, and the resulting brown solution was allowed to
warm to room temperature over 0.5 h. The reaction mixture

50 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 1
Anderson et al.
was then poured into 20 mL of water, and the yellow solution
was acidified (pH 1-2, pH test paper) with concentrated HCl.
The white cloudy solution was extracted with chloroform (4 ×
50 mL). The combined organic layer was washed with water
(50 mL) and brine (50 mL), then dried, filtered, and concen-
trated to give 0.61 g of a yellow-white solid. The product was
crystallized from chloroform to give the â-keto sulfoxide as a
white powdery solid (0.438 g, 74%): mp 122-124.5 °C dec; 1H
NMR (CDCl3-DMSO-d6) δ 1.76 (s, 3 H), 2.26 (m, 2 H), 2.75
(s, 3 H), 3.31 (m, 2 H), 3.91 (s, 3 H), 4.40 (s, 2 H), 5.19 (t, 1 H),
6.56 (d, 1 H), 7.76 (d, 1 H), 12.38 (s, 1 H); IR 3300-2500, 1733,
1629, 1283, 1117, 1083, 1067 cm-1. Anal. (C17H22O6S) C, H,
S.
dispersion in mineral oil, 0.385 g, 9.63 mmol) was washed with
dry hexanes (2 × 2 mL). The flask was evacuated and purged
several times, and while under a flow of nitrogen, DMSO (10
mL) was added. The resulting gray solution was warmed to
75-80 °C until the evolution of hydrogen had subsided. The
flask was then cooled to 0 °C, and a solution of 2d (0.500 g,
1.55 mmol) in DMSO (7 mL) was quickly added. The ice bath
was removed immediately, and the reaction mixture was
allowed to warm to room temperature over 0.5 h. The reaction
mixture was then poured into chloroform (50 mL) and water
(50 mL). The aqueous layer was acidified with concentrated
HCl (pH 2) and then extracted with chloroform (2 × 25 mL).
The combined organic layer was washed with water (25 mL)
and brine (25 mL), dried, filtered, and concentrated in vacuo.
The resulting oil was subjected to flash chromatography (ethyl
acetate-hexanes, 8:2 with 1% formic acid) to give a yellow oily
solid that was crystallized from dichloromethane and hexanes
to give the â-keto sulfoxide (0.385 g, 67%) as a cream-colored
The â-keto sulfoxide (0.180 g, 0.51 mmol) was dissolved in
10% aqueous THF (11 mL), cooled to 0 °C, and treated with
aluminum foil [(0.141 g, 5.10 mmol) in 1 cm squares, which
had been immersed in a 2% aqueous solution of mercuric
chloride for 15 s, and then rinsed in absolute methanol and
anhydrous ether]. The resulting yellow-green solution was
stirred at 0 °C for 50 min and then filtered through a pad of
Celite. The solids were washed with THF (100 mL), and then
most of the THF was evaporated. Ethyl acetate (30 mL) was
added, and the mixture was washed several times with water
(30 mL), dried, and concentrated to a yellow oily residue. The
residue was subjected to flash chromatography (hexanes-ethyl
acetate, 3:2, 10% formic acid) to give 2c as an off-white solid
1
solid: mp 120-122 °C dec; H NMR δ 1.81 (s, 3 H), 2.25 (s, 3
H), 2.37 (m, 4 H), 2.79 (s, 3 H), 3.37 (d, 2 H), 3.76 (s, 3 H),
4.36 (dd, 2 H), 5.24 (t, 1 H), 7.43 (s, 1 H); IR (CHCl3) 754, 1127,
1286, 1352, 1433, 1626, 1713, 2944 cm-1. Anal. (C18H24O6S)
C, H, S.
A solution of the â-keto sulfoxide (0.200 g, 0.543 mmol) in
acetic acid (6 mL) and ethanol (2 mL) was slowly treated with
zinc dust (0.359 g, 5.49 mmol). The reaction mixture was
sonicated at 28 ( 2 °C for 55 min and then vacuum filtered.
The solid was washed with ethanol (10 mL) and ethyl acetate
(25 mL). Ethyl acetate (30 mL) was added to the filtrate. The
aqueous layer was removed, and the organic phase was washed
with water (2 × 25 mL) and brine (25 mL), dried, filtered, and
concentrated in vacuo. The resulting oily solid was subjected
to flash chromatography (ethyl acetate-hexanes, 1:1 with 1%
formic acid) to give 2f (0.160 g, 96%) as a slightly yellow
1
(0.044 g, 31%): mp 120-121 °C dec; H NMR δ 1.76 (s, 3 H),
2.33 (m, 4 H), 2.53 (s, 3 H), 3.34 (m, 2 H), 3.86 (s, 3 H), 5.26 (t,
1 H), 6.38 (d, 1 H), 7.58 (d, 1 H), 12.73 (s, 1 H); IR 3160, 3000-
2500, 1719, 1629, 1275, 1096 cm-1
. Anal. (C16H20O5) C, H.
(E)-4-Met h yl-6-[3-(2-h yd r oxy-1-(m et h oxyca r b on yl)-4-
m eth oxy-5-m eth ylp h en yl)]-4-h exen oic Acid (2d ). TFA
(0.06 mL, 0.794 mmol) was added to a solution of 12b (0.281
g, 0.662 mmol) in dichloromethane (2 mL) at 0 °C. The
mixture was stirred at 0 °C for 20 min and then allowed to
warm to room temperature over 45 min. The reaction was
then partitioned between dichloromethane (5 mL) and water
(5 mL). The aqueous layer was extracted with dichlo-
romethane (3 × 5 mL), and the combined organic layer was
dried, filtered, and concentrated in vacuo. The resulting oil
was subjected to flash chromatography (hexanes-ether, 7:3)
to give the phenol (0.199 g, 89%) as a cloudy oil: 1H NMR δ
1.77 (s, 3 H), 2.19 (s, 3 H), 2.30 (m, 2 H), 2.38 (m, 2 H), 3.36
(d, 2 H), 3.58 (s, 3 H), 3.70 (s, 3 H), 3.89 (s, 3 H), 5.24 (t, 1 H),
7.52 (s, 1 H), 10.87 (s, 1 H); IR (neat) 908, 984, 1095, 1168,
1
solid: mp 91-93.5 °C; H NMR δ 1.81 (s, 3 H), 2.25 (s, 3 H),
2.30 (t, 2 H), 2.43 (t, 2 H), 2.58 (s, 3 H), 3.38 (d, 2 H), 3.74 (s,
3 H), 5.27 (t, 1 H), 7.43 (s, 1 H), 12.57 (s, 1 H); IR (KBr) 1096,
1206, 1289, 1372, 1435, 1636, 1719, 2925 cm-1
(C17H22O5) C, H.
.
Anal.
(E)-4-Meth yl-6-[3-(5-ch lor o-2-h yd r oxy-1-(m eth oxyca r -
bon yl)-4-m eth oxyp h en yl)]-4-h exen oic Acid (2g). Meth od
A. A mixture of 13 (0.204 g, 0.347 mmol) and formic acid (2
mL) was stirred at room temperature for 4 h. The reaction
mixture was partitioned between water (10 mL) and ethyl
acetate (10 mL). The organic layer was washed with water
(10 mL) and brine (10 mL), dried, filtered, and concentrated
in vacuo. The resulting slightly pink oily solid was heated
for 1 h at 160 ( 5 °C, while under a flow of argon. The
resulting yellowish solid was subjected to column chromatog-
raphy (hexanes-ethyl acetate, 7:3 with 1% formic acid) to give
2g (0.071 g, 60%) as a white solid: mp 122-123.5 °C; 1H NMR
δ 1.81 (s, 3 H), 2.31 (t, 2 H), 2.44 (t, 2 H), 3.41 (d, 2 H), 3.86 (s,
3 H), 3.94 (s, 3 H), 5.25 (t, 1 H), 7.76 (s, 1 H), 11.01 (s, 1 H); IR
(KBr) 1206, 1269, 1345, 1428, 1615, 1670, 1719, 2917, 3084
cm-1. Anal. (C16H19O6Cl) C, H, Cl.
Meth od B. TFA (0.09 mL, 1.11 mmol) was added to an
ice-cold solution of 13 (0.200 g, 0.341 mmol) in dichloromethane
(2 mL). The resulting mixture was stirred at 0 °C for 15 min
and then allowed to warm to room temperature over a 1 h
period. The solvent was concentrated in vacuo, and the
resulting oil was dissolved in ethyl acetate (10 mL). The
organic layer was washed with water (2 × 10 mL) and brine
(10 mL), dried , filtered and concentrated in vacuo. The
resulting oil was stirred with formic acid (1 mL), at room
temperature, for 7 h. The white solid that formed was
partitioned between water (10 mL) and ethyl acetate (10 mL).
The organic layer was washed with water (10 mL) and brine
(10 mL), dried, filtered, and concentrated in vacuo. The
resulting white solid was heated to 150 ( 5 °C, while under a
flow of argon, for 1 h. The resulting solid was subjected to
flash chromatography (hexanes-ethyl acetate, 7:3 with 1%
formic acid) to give 2g (0.072 g, 63%) as a white solid, identical
with the sample prepared by method A (TLC, NMR, melting
point).
1348, 1382, 1442, 1464, 1668, 1731 cm-1
C, H.
. Anal. (C18H24O6)
A solution of the phenol (0.666 g, 1.98 mmol) in THF (7 mL)
was treated with 1 N LiOH (4.4 mL, 4.40 mmol) at 0 °C. The
mixture was stirred at 0 °C for 7 h and then acidified (pH 2)
with 1 N HCl. The THF was then removed in vacuo, and the
aqueous layer was extracted with ethyl acetate (3 × 15 mL).
The organic layer was washed with brine (5 mL), dried, and
concentrated in vacuo. The resulting oil was subjected to flash
chromatography (ethyl acetate-hexanes, 3:7 with 1% formic
acid) to give 2d (0.564 g, 88%) as an off-white solid: mp 74-
1
76 °C; H NMR δ 1.81 (s, 3 H), 2.22 (s, 3 H), 2.28 (m, 2 H),
2.43 (m, 2 H), 3.39 (d, 2 H), 3.73 (s, 3 H), 3.92 (s, 3 H), 5.28 (t,
1 H), 7.54 (s, 1 H), 10.90 (s, 1 H); IR (neat) 1228, 1283, 1352,
1442, 1678, 1708, 2952, 3160 cm-1
. Anal. (C17H22O6) C, H.
(E)-4-Meth yl-6-[3-(1-(am in ocar bon yl)-2-h ydr oxy-4-m eth -
oxy-5-m eth ylp h en yl)]-4-h exen oic Acid (2e). A solution of
2d (1.07 g, 3.32 mmol) in methanol (35 mL) was saturated
with ammonia and heated at 55 ( 5 °C for 133 h in a Fisher-
Porter bottle. The resulting dark brown solution was filtered
and concentrated in vacuo. The brown residue was dissolved
in ethyl acetate, filtered through a pad of Celite, and concen-
trated in vacuo. The resulting brown solid was subjected to
flash chromatography (ethyl acetate-hexanes, 1:1 with 1%
formic acid) and then crystallized from ethyl acetate to give
2e (0.642 g, 63%) as a gray crystalline solid: mp 185-188 °C;
1H NMR (CD3OD) δ 1.72 (s, 3 H), 2.12 (s, 3 H), 2.20 (t, 2 H),
2.28 (t, 2 H), 3.27 (d, 2 H), 3.63 (s, 3 H), 5.18 (t, 1 H), 7.35 (s,
1 H); IR (KBr) 1109, 1276, 1448, 1622, 1650, 1698, 3236, 3451
cm-1. Anal. (C16H21NO5) C, H, N.
(E)-4-Met h yl-6-[3-(1-(a m in oca r b on yl)-5-ch lor o-2-h y-
d r oxy-4-m eth oxyp h en yl)]-4-h exen oic Acid (2h ). A solu-
tion of 2g (1.03 g, 3.01 mmol) in methanol (35 mL) was
(E)-4-Met h yl-6-[3-(2-h yd r oxy-4-m et h oxy-5-m et h yl-1-
a cetylp h en yl)]-4-h exen oic Acid (2f). Sodium hydride (60%

Monocyclic Analogues of Mycophenolic Acid
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 1 51
saturated with ammonia and heated to 60 ( 5 °C for 4 days
in a Fisher-Porter bottle. The resulting dark reaction mixture
was filtered, preadsorbed onto silica gel (10 g), and subjected
to flash chromatography (1% formic acid in ethyl acetate-
hexanes, 3:7) to give 2h (0.97 g, 98%) as a cream-colored
mmol), allyl bromide (5.30 g, 43.8 mmol), and anhydrous
potassium carbonate (2.68 g, 19.4 mmol) was heated at reflux
in dry acetone (25 mL) for 34 h under an atmosphere of argon.
The mixture was filtered, and the filter cake was washed with
ether. Evaporation of the filtrate gave 3d as a pale yellow oil
1
1
solid: mp 172-175 °C dec; H NMR (CD3OD) δ 1.60 (s, 3 H),
(3.9 g, 100%). This material was pure by H NMR and TLC
2.12 (m, 4 H), 3.18 (d, 2 H), 3.62 (s, 3 H), 5.04 (t, 1 H), 7.52 (s,
1 H); IR (KBr) 1269, 1435, 1615, 1657, 1684, 2945, 3195, 3423
cm-1. Anal. (C15H18O5ClN) C, H, Cl, N.
(silica gel, ether-petroleum ether, 2:8) and was used directly
in the Claisen rearrangement. A sample, purified by TLC
(silica gel, ether-petroleum ether, 2:8) had the following prop-
erties: 1H NMR δ 3.81 (s, 3 H), 3.83 (s, 3 H), 4.62 (m, 2 H),
5.32 (m, 2 H), 6.09 (m, 2 H), 6.49 (t, 2 H), 7.87 (d, 1 H); IR
(E )-4-Me t h yl-6-[3-(5-ch lor o-2-h yd r oxy-4-m e t h oxy-1-
a cetylp h en yl)]-4-h exen oic Acid (2i). Sodium hydride (60%
dispersion in mineral oil, 0.90 g, 22.50 mmol) was washed with
dry hexanes (2 × 4 mL). The flask was evacuated and purged
several times, and while under a flow of nitrogen, DMSO (25
mL) was added. The resulting gray solution was warmed to
75-80 °C until the evolution of hydrogen had subsided. The
flask was then cooled to 0 °C, and 2g (1.25 g, 3.65 mmol) in
DMSO (15 mL) was quickly added. The ice bath was removed
immediately, and the reaction mixture was then allowed to
warm to room temperature over a 0.5 h period. The green
mixture was then poured into chloroform (150 mL) and water
(150 mL). The yellow aqueous layer was acidified with
concentrated HCl (pH 2) and extracted with chloroform (2 ×
80 mL). The combined organic layer was washed with water
(90 mL) and brine (90 mL), dried, filtered, and concentrated
in vacuo. The resulting yellow solid was crystallized from
chloroform and hexanes to give the â-keto sulfoxide as a yellow
(neat) 3011, 2949, 2905, 2837, 1718, 1693, 1608, 1575 cm-1
Anal. (C12H14O4) C, H.
.
Meth yl 2-(Allyloxy)-4-m eth oxy-5-m eth ylben zoa te (3e).
A solution of 3b (3.23 g, 16.46 mmol) in acetone (35 mL) was
heated at reflux with potassium carbonate (3.41 g, 24.69 mmol)
and allyl bromide (3.56 mL, 41.15 mmol) for 84 h. The reaction
mixture was filtered and concentrated in vacuo to give 3e (3.55
g, 92% crude yield) as an off-white crystalline solid. An
analytical sample was obtained by crystallization from hex-
anes: mp 55.5-56.5 °C; 1H NMR δ 2.15 (s, 3 H), 3.86 (s, 3 H),
3.87 (s, 3 H), 4.64 (d, 2 H), 5.32 (d, 1 H), 5.57 (d, 1 H), 6.11 (m,
1 H), 6.45 (s, 1 H), 7.69 (s, 1 H); IR (CHCl3) 908, 1155, 1258,
1614, 1709 cm-1. Anal. (C13H16O4) C, H.
Meth yl 2-(Allyloxy)-5-ch lor o-4-m eth oxyben zoa te (3f).
A mixture of 3c (7.50 g, 34.62 mmol), potassium carbonate
(7.18 g, 51.93 mmol), and allyl bromide (7.5 mL, 86.55 mmol)
in acetone (350 mL) was heated at reflux for 7.25 h. The
reaction mixture was filtered and concentrated in vacuo, and
the resulting white solid was subjected to flash chromatogra-
phy (dichloromethane-hexanes, 4:1) to give 3f (8.03 g, 90%)
1
solid (1.06 g, 75%): mp 139-140 °C; H NMR δ 1.80 (s, 3 H),
2.37 (m, 4 H), 2.80 (s, 3 H), 3.40 (d, 2 H), 3.89 (s, 3 H), 4.32 (s,
2 H), 5.22 (t, 1 H), 7.65 (s, 1 H), 12.17 (s, 1 H); IR (CHCl3)
1036, 1111, 1273, 1342, 1423, 1630, 1711 cm-1
(C17H21O6ClS) C, H, Cl, S.
.
Anal.
1
as a white solid: mp 68-70 °C; H NMR δ 3.84 (s, 3 H), 3.90
(s, 3 H), 4.66 (d, 2 H), 5.26 (d, 1 H), 5.48 (d, 1 H), 6.00 (dt, 1
H), 6.44 (s, 1 H), 7.85 (s, 1 H); IR (CHCl3) 907, 1105, 1443,
1603, 1718 cm-1. Anal. (C12H13O4Cl) C, H, Cl.
The â-keto sulfoxide (0.250 g, 0.643 mmol) was dissolved in
acetic acid (5 mL) and ethanol (2 mL), and then zinc dust
(0.420 g, 6.43 mmol) was slowly added. The reaction mixture
was sonicated at 28 ( 5 °C for 1 h, and then the reaction
mixture was vacuum filtered. The solids were washed with
ethanol and ethyl acetate. The resulting filtrate was washed
with water (1 × 20 mL, 3 × 10 mL) and brine (10 mL), dried,
filtered, and concentrated in vacuo. The remaining acetic acid
was removed by azeotrope with benzene. The resulting oily
solid was subjected to flash chromatography (1% formic acid
in hexanes-ethyl acetate, 7:3) to give 2i (0.170 g, 81%) as a
cream-colored solid: mp 102.5-105.5 °C; 1H NMR δ 1.81 (s, 3
H), 2.37 (m, 2 H), 2.59 (s, 3 H), 3.41 (d, 2 H), 3.87 (s, 3 H),
5.24 (t, 1 H), 7.63 (s, 1 H), 12.63 (s, 1 H); IR (CHCl3) 724, 1273,
1323, 1368, 1431, 1640, 1708, 2935 cm-1. Anal. (C16H19O5Cl)
C, H, Cl.
Meth yl 2-Hyd r oxy-4-m eth oxy-5-m eth ylben zoa te (3b).
A stirred solution of 5b (4.11 g, 19.55 mmol) in dichlo-
romethane (50 mL) was cooled in an ice-salt bath, and 1 M
boron trichloride (80 mL) was slowly added. After the addition
was completed, the ice-salt bath was removed and the
resulting lime-colored solution was stirred at room tempera-
ture for 2 h. The solution was then cooled in an ice bath, and
10 mL of 3 N HCl was added. The ice bath was removed, and
the solution was stirred at room temperature for 3 h. The
dichloromethane was then removed in vacuo, and the resulting
aqueous layer was extracted with ethyl acetate (2 × 50 mL).
The combined organic layer was concentrated, and the yellow
solid residue was subjected to flash chromatography (chloro-
form) to give 3b as an off-white crystalline solid (3.31 g, 86%),
mp 93.5-95 °C (lit.28 mp 95-96 °C).
Meth yl 3-Allyl-2-h ydr oxy-4-m eth oxyben zoate (6a). The
crude allyl ether 3d (85.6 mmol) was degassed at 10-1 Torr
for 15 min. The material was then heated under an atmo-
sphere of argon at 210 °C for 3 h and cooled to room
temperature to give crude 6a as yellow crystals (18.95 g, 99%).
1H NMR and TLC analysis (silica gel, ether-petroleum ether,
2:8) showed the material to be pure so it was used directly in
the ozonolysis step. A sample was chromatographed (TLC,
silica gel, ether-petroleum ether, 2:8) for analysis: 1H NMR
δ 3.43 (dd, 2 H), 3.86 (s, 3 H), 3.90 (s, 3 H), 5.01 (m, 2 H), 5.98
(m, 1 H), 6.45 (s, 1 H), 7.72 (d, 1 H), 11.03 (s, 1 H); IR (CHCl3)
3178, 1669, 1619 cm-1. Anal. (C12H14O4) C, H.
Meth yl 3-Allyl-2-h ydr oxy-4-m eth oxy-5-m eth ylben zoate
(6b). The crude allyl ether 3e (34.85 g, 148.78 mmol) was
heated to 210 ( 5 °C for 4 h while under nitrogen. The
resulting light brown oil was subjected to flash chromatogra-
phy (dichloromethane-hexanes, 1:1) to give 6b (30.47 g) as a
clear slightly yellow oil (81% from methyl 2,4-dimethoxy-5-
1
methylbenzoate): H NMR δ 2.24 (s, 3 H), 3.46 (d, 2 H), 3.78
(s, 3 H), 3.90 (s, 3 H), 4.95 (m, 2 H), 6.09 (m, 1 H), 7.65 (s, 1
H), 10.99 (s, 1 H); IR (CHCl3) 908, 1359, 1442, 1670 cm-1. Anal.
(C13H16O4) C, H.
Meth yl 3-Allyl-5-ch lor o-2-h yd r oxy-4-m eth oxyben zoa te
(6c). Neat 3f (0.70 g, 2.73 mmol) was heated to 210 ( 5 °C
for 4 h while under a flow of nitrogen. The reaction mixture
was allowed to cool to room temperature, and the resulting
brown oil was subjected to flash chromatography (dichlo-
romethane-hexanes, 1:1) to give 6c (0.358 g, 51%) as a white
Meth yl 5-Ch lor o-2-h yd r oxy-4-m eth oxyben zoa te (3c).
A solution of 3a (0.88 g, 4.83 mmol) in dichloromethane (10
mL) was treated with sulfuryl chloride (0.43 mL, 5.35 mmol),
and the mixture was heated at reflux for 25 h. Then,
additional sulfuryl chloride (0.200 mL, 2.49 mmol) was added,
and the mixture was heated at reflux for another 15.5 h. The
yellow solution was concentrated in vacuo, and the resulting
white solid was subjected to flash chromatography (ethyl
acetate-hexanes, 1:1) to give 3c as a white solid (0.971 g,
93%): mp 127-129 °C; 1H NMR δ 3.93 (s, 6 H), 6.50 (s, 1 H),
7.83 (s, 1 H), 10.93 (s, 1 H); IR (CHCl3) 1671, 1443, 1348, 1250,
908 cm-1. Anal. (C9H9O4Cl) C, H, Cl.
1H NMR δ 3.44 (d, 2 H), 3.84 (s, 3
oily solid: mp 38-39.5 °C;
H), 3.90 (s, 3 H), 5.00 (m, 2 H), 6.00 (m, 1 H), 7.78 (s, 1 H),
11.0 (s, 1 H); IR (CHCl3) 908, 1213, 1269, 1338, 1476, 1670
cm-1. Anal. (C12H13O4Cl) C, H, Cl.
2-(2-H y d r o x y -4-m e t h o x y -1-(m e t h o x y c a r b o n y l)-3-
p h en yl)eth a n a l (7a ). A solution of 6a (5.046 g, 22.7 mmol)
in dichloromethane-methanol (720 mL, 3:1) was cooled to -76
°C. A stream of ozone in oxygen was bubbled through the
solution. When the colorless solution acquired a bluish tint,
indicating the presence of excess ozone (ca. 30 min), nitrogen
was bubbled through the solution. TLC analysis (silica gel,
dichloromethane) showed complete reaction. Triphenylphos-
phine (7.761 g, 29.6 mmol) was added, and the solution was
stirred for 30 min; aqueous sodium bicarbonate (5%, 100 mL)
Meth yl 2-(Allyloxy)-4-m eth oxyben zoa te (3d ). A mix-
ture of methyl 2-hydroxy-4-methoxybenzoate (3a , 3.20 g, 17.6

52 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 1
Anderson et al.
was then added to the vigorously stirring solution, and the
mixture was allowed to warm to room temperature. The
aqueous phase was extracted with dichloromethane (2 × 100
mL). The combined organic solution was dried and concen-
trated. The crude yellow oil was purified by flash column
chromatography (silica gel, ether-hexane, 4:6) to give 7a as
(ether-hexanes, 3:7) to give 8c (11.1 g, 96%) as a yellow oily
1
solid: mp 49-53 °C; H NMR δ 1.94 (s, 3 H), 3.80 (d, 2 H),
3.92 (s, 3 H), 3.97 (s, 3 H), 6.57 (tq, 1 H), 7.90 (s, 1 H), 9.48 (s,
1 H), 11.24 (s, 1 H); IR (CHCl3) 1267, 1346, 1438, 1616, 1681
cm-1. Anal. (C14H15O5Cl) C, H, Cl.
(E)-2-Meth yl-4-[2-((2-m eth oxyeth oxy)m eth oxy)-1-(m eth -
oxyca r bon yl)-4-m eth oxy-3-p h en yl]-2-bu ten a l (8d ). A so-
lution of the phenol 8a (10.93 g, 41.4 mmol) in dry THF (200
mL) was cooled to 0 °C under an atmosphere of argon. Sodium
hydride (1.91 g of a 60% dispersion, 47.6 mmol) was added,
followed after 40 min by chloroethoxymethoxymethane (7.0
mL, 61.3 mmol). The mixture was stirred for an additional
15 min at 0 °C and then at 25 °C for 25 h. The mixture was
concentrated to ca. 50 mL. The yellow residue was dissolved
in ether-THF (500-600 mL), and the solution was extracted
sequentially with water (3 × 200 mL) and saturated aqueous
sodium chloride (100 mL). The organic phase was dried and
concentrated in vacuo to give a yellow solid. Purification by
flash column chromatography (silica gel, ether-hexane, 1:1)
provided the starting phenol (1.32 g, 12%) and 8d as a white
solid (10.91 g, 87% based on unrecovered starting material):
1
a white solid (4.33 g, 85%): mp 85-86.5 °C; H NMR δ 3.71
(d, 2 H), 3.84 (s, 3 H), 3.91 (s, 3 H), 6.47 (d, 2 H), 7.78 (d, 1 H),
9.61 (t, 1 H), 11.18 (s, 1 H); IR (CHCl3) 3148, 3028, 1724, 1668,
1619 cm-1. Anal. (C11H12O5) C, H.
2-(2-Hydr oxy-4-m eth oxy-5-m eth yl-1-(m eth oxycar bon yl)-
3-p h en yl)eth a n a l (7b). A solution of 6b (0.656 g, 2.80 mmol)
in dichloromethane (9 mL) and methanol (3 mL) was cooled
to -76 °C. Ozone (2 psi, 2.0 mL/min) was bubbled through
the solution for 5 min, at which time a TLC of the reaction
mixture showed no starting material. Nitrogen was then
bubbled through the solution for 5 min, and then triphen-
ylphosphine (0.881 g, 3.36) was added to the reaction mixture.
The resulting solution was stirred for 15 min, then 5% sodium
bicarbonate (10 mL) was added, and the mixture was allowed
to warm to room temperature. The organic layer was sepa-
rated from the aqueous layer, and the aqueous layer was
extracted with dichloromethane (4 × 10 mL). The combined
organic layer was dried, filtered, and concentrated in vacuo
to yield 1.45 g of an orange oil. The oil was subjected to flash
chromatography to give 7b (0.516 g, 77%) as an off-white
solid: mp 89.5-92.5 °C; 1H NMR δ 2.24 (s, 3 H), 3.86 (s, 3 H),
3.88 (d, 1 H), 3.92 (s, 2 H), 7.67 (s, 1 H), 9.75 (s, 1 H), 10.99 (s,
1
mp 83.5-84.5 °C; H NMR δ 1.92 (s, 3 H), 3.36 (s, 3 H), 3.74
(m, 6 H), 3.87 (s, 6 H), 5.20 (s, 2 H), 6.57 (t, 1 H), 6.74 (d, 1 H),
7.89 (d, 1 H), 9.39 (s, 1 H); IR (CHCl3) 3016, 1715, 1681, 1596
cm-1. Anal. (C18H24O7) C, H.
(E)-2-Meth yl-4-[2-((2-m eth oxyeth oxy)m eth oxy)-1-(m eth -
oxyca r b on yl)-4-m et h oxy-5-m et h yl-3-p h en yl]-2-b u t en a l
(8e). A stirred solution of 8b (1.0 g, 3.59 mmol) in dry THF
(20 mL) was maintained under a flow of nitrogen, treated with
60% sodium hydride (0.161 g, 4.03 mmol) at 0 °C for 20 min,
and then chloroethoxymethoxymethane (0.45 mL, 3.95 mmol)
1 H); IR (CHCl3) 902, 1352, 1442, 1678, 1719 cm-1
(C12H14O5) C, H.
. Anal.
2-(5-Ch lor o-2-h ydr oxy-4-m eth oxy-1-(m eth oxycar bon yl)-
3-p h en yl)eth a n a l (7c). A solution of 6c (11.19 g, 43.60 mmol)
in dichloromethane (420 mL) and methanol (140 mL) was
cooled to -76 °C, and ozone (2 in/min, and 2 psi) was bubbled
through the solution for 50 min. When the solution turned
blue, nitrogen was bubbled through for 15 min, triphenylphos-
phine (13.72 g, 52.31 mmol) was added, and the mixture was
stirred for 20 min at -76 °C. A solution of 5% sodium
bicarbonate (100 mL) was added to the solution, and the
mixture was allowed to warm to room temperature. The
resulting yellow organic layer was separated from the aqueous
layer. The aqueous layer was extracted with dichloromethane
(3 × 100 mL). The combined organic layer was dried, filtered,
and concentrated in vacuo to yield 27.44 g of an orange oil
that was subjected to flash chromatography to give 7c (10.30
was added. The resulting mixture, with
a yellow solid
precipitate, was allowed to warm to room temperature over a
1 h period. The mixture was then cooled to 0 °C, methanol (2
mL) was added, and the mixture was stirred at 0 °C for 15
min and then allowed to warm to room temperature over a 30
min period. The solvent was then removed in vacuo, and the
oily residue was subjected to flash chromatography (ethyl
acetate-hexane, 4:6) to give 8e (0.761 g, 77% based on
unrecovered 8b) as a yellow oil: 1H NMR δ 1.90 (s, 3 H), 2.28
(s, 3 H), 3.36 (s, 3 H), 3.54 (m, 2 H), 3.72 (s, 3 H), 3.84 (m, 4
H), 3.88 (s, 3 H), 5.16 (s, 2 H), 6.59 (t, 1 H), 7.66 (s, 1 H), 9.37
(s, 1 H); IR (CHCl3) 908, 1345, 1448, 1615, 1678, 2932 cm-1
Anal. (C19H26O7) C, H.
.
(E)-2-Meth yl-4-[5-ch lor o-2-((2-m eth oxyeth oxy)m eth oxy)-
1-(m eth oxycar bon yl)-4-m eth oxy-3-ph en yl]-2-bu ten al (8f).
A solution of 8c (2.00 g, 6.70 mmol) in dichloromethane (30
mL) was treated with N,N-diisopropylethylamine (2.00 mL,
11.48 mmol) and methoxyethoxymethyl chloride (1.30 mL,
11.48 mmol), and the mixture was stirred at room temperature
for 1 h. The solvent was then concentrated in vacuo, and the
residue was subjected to flash chromatography (ethyl acetate-
hexanes, 2:3) to give 8f (2.26 g, 92% based on unrecovered 8c)
as a slightly yellow solid: mp 52-53.5 °C; 1H NMR δ 1.91 (s,
3 H), 3.36 (s, 3 H), 3.54 (m, 2 H), 3.74 (m, 4 H), 3.88 (s, 3 H),
3.89 (s, 3 H), 5.18 (s, 2 H), 6.55 (t, 1 H), 7.88 (s, 1 H), 9.38 (s,
1 H); IR (CHCl3) 911, 1053, 1161, 1276, 1431, 1472, 1681, 1723,
2929, 3025 cm-1. Anal. (C18H24O7Cl) C, H, Cl.
1
g, 91%) as a yellow solid: mp 114-115.5 °C; H NMR δ 3.70
(d, 2 H), 3.79 (s, 3 H), 3.89 (s, 3 H), 7.79 (s, 1 H) 9.69 (t, 1 H),
11.01 (s, 1 H); IR (CHCl3) 908, 1380, 1470, 1678, 1726 cm-1
Anal. (C11H11O5Cl) C, H, Cl.
.
(E)-2-Meth yl-4-(2-h ydr oxy-1-(m eth oxycar bon yl)-4-m eth -
oxy-3-p h en yl)-2-bu ten a l (8a ). A mixture of aldehyde 7a
(7.651 g, 34.12 mmol) and (1-formylethylidene)triphenylphos-
phorane (11.953 g, 37.55 mmol) in benzene (200 mL) was
heated at reflux for 28.5 h. The solvent was evaporated, and
the crude solid was purified by flash column chromatography
(silica gel, ether-hexanes, 3:7) to afford 8a as white crystals
(8.05 g, 89%): mp 86.0-87.5 °C; 1H NMR δ 1.91 (s, 3 H), 3.72
(d, 2 H), 3.89 (s, 3 H), 3.91 (s, 3 H), 6.49 (d, 1 H), 6.57 (t, 1 H),
7.79 (d, 1 H), 9.37 (s, 1 H), 11.17 (s, 1 H); IR (CHCl3) 3025,
1675, 1620, 1501 cm-1. Anal. (C14H16O5) C, H.
(E)-2-Meth yl-4-(2-h ydr oxy-1-(m eth oxycar bon yl)-4-m eth -
oxy-5-m eth yl-3-p h en yl)-2-bu ten a l (8b). A mixture of 7b
(1.50 g, 6.30 mmol) and (R-formylethylidene)triphenylphos-
phorane (2.20 g, 6.91 mmol) in benzene (70 mL) was heated
at reflux for 28 h. The solvent was removed in vacuo, and the
residue was subjected to flash chromatography (ether-hex-
anes, 3:7) to give 8b (1.57 g, 90%) as a yellow oil: 1H NMR δ
1.92 (s, 3 H), 2.25 (s, 3 H), 3.72 (d, 2 H), 3.73 (s, 3 H), 3.95 (s,
3 H), 6.57 (complex t, 1 H), 7.62 (s, 1 H), 9.39 (s, 1 H), 10.99
(s, 1 H); IR (neat) 1005, 1172, 1206, 1283, 1345, 1442, 1622,
1685 cm-1. Anal. (C15H18O5) C, H.
(E)-Meth yl 3-(3-Meth yl-4-h yd r oxy-2-bu ten yl)-4-m eth -
oxy-2-((2-m eth oxyeth oxy)m eth oxy)ben zoate (9a). A cooled
(ice bath) stirred suspension of the aldehyde 8d (7.07 g, 20.1
mmol) in methanol (50 mL) at 0 °C was treated with sodium
borohydride (0.84 g, 22.3 mmol). The ice bath was removed,
and the mixture was stirred for 4.5 h. The resulting clear
solution was evaporated, and the residue was dissolved in
chloroform (40 mL) and extracted with 0.5 M HCl (40 mL).
The aqueous phase was washed with chloroform (2 × 15 mL),
and the combined chloroform solution was extracted with
saturated sodium chloride (20 mL) and dried. The solution
was concentrated in vacuo, and the yellow oily residue was
purified by flash column chromatography (silica gel, ether-
hexane, 8:2) to afford 9a (6.44 g, 91%) as a colorless oil which
(E)-2-Meth yl-4-(5-ch lor o-2-h yd r oxy-1-(m eth oxyca r bo-
n yl)-4-m eth oxy-3-p h en yl)-2-bu ten a l (8c). A mixture of 7c
(10.0 g, 38.66 mmol) and (R-formylethylidene)triphenylphos-
phorane (14.77 g, 46.39 mmol) in benzene (500 mL) was heated
at reflux for 8 h. The solvent was removed in vacuo, and the
resulting residue was subjected to flash chromatography
1
slowly solidified: mp 44.5-46.0 °C; H NMR δ 1.82 (s, 3 H),
2.13 (bs, 1 H), 3.36 (s, 3 H), 3.50 (m, 4 H), 3.83 (s, 6 H), 3.87
(m, 4 H), 5.13 (s, 2 H), 5.47 (bt, 1 H), 6.67 (d, 1 H), 7.78 (d, 1
H); IR (CHCl3) 3012, 2941, 1714, 1595 cm-1. Anal. (C18H26O7)
C, H.

Monocyclic Analogues of Mycophenolic Acid
J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 1 53
(E)-Meth yl 3-(3-Meth yl-4-h yd r oxy-2-bu ten yl)-4-m eth -
oxy-((2-m eth oxyeth oxy)m eth oxy)-5-m eth ylben zoate (9b).
A solution of 8e (1.82 g, 4.97 mmol) in methanol (20 mL) was
stirred at 0 °C for 15 min with sodium borohydride (0.207 g,
5.46 mmol). The yellow reaction mixture was then allowed to
warm to room temperature over 45 min. The solvent was then
removed in vacuo, and the residue was partitioned between
chloroform (10 mL) and 0.5 N HCl (10 mL). The aqueous layer
was extracted with chloroform (3 × 10 mL). The combined
chloroform layer was washed with saturated sodium bicarbon-
ate (10 mL) and brine (10 mL), dried, filtered, and concentrated
in vacuo. The resulting oil was subjected to flash chromatog-
raphy (dichloromethane-ether, 1:1) to give 9b (1.56 g, 85%)
as a clear oil: 1H NMR δ 1.82 (s, 3 H), 2.26 (s, 3 H), 3.37 (s, 3
H), 3.53 (m, 4 H), 3.72 (s, 3 H), 3.87 (s, 3 H), 3.88 (m, 2 H),
3.97 (s, 2 H), 5.11 (s, 2 H), 5.50 (t, 1 H), 7.57 (s, 1 H); IR (neat)
1087, 1256, 1287, 1420, 1571, 1577, 2881, 2405, 3422, 3432,
3455, 3462, 3471, 3481 cm-1. Anal. (C19H28O7) C, H.
(E)-Meth yl 3-(3-Meth yl-4-h yd r oxy-2-bu ten yl)-5-ch lor o-
4-m eth oxy-2-((2-m eth oxyeth oxy)m eth oxy)ben zoa te (9c).
A suspension of 8f (4.23 g, 10.94 mmol) in methanol (45 mL)
was cooled to 0 °C and treated with sodium borohydride (0.455
g, 12.03 mmol). The resulting yellow mixture was stirred at
0 °C until the bubbling subsided. The ice bath was then
removed, and the slightly yellow reaction mixture was allowed
to warm to room temperature over a 1 h period. The solvent
was then evaporated, and the oily residue was partitioned
between 0.5 N HCl (22 mL) and chloroform (22 mL). The
aqueous layer was extracted with chloroform (3 × 20 mL). The
combined organic layer was washed with brine (20 mL), dried,
filtered, and concentrated in vacuo. The resulting cloudy oil
was purified by flash chromatography (dichloromethane-
ether, 7:3) to give 9c (4.11 g, 97%) as a clear oil: 1H NMR δ
1.82 (s, 3 H), 3.37 (s, 3 H), 3.54 (m, 4 H), 3.86 (s, 3 H), 3.87 (s,
3 H), 3.90 (m, 2 H), 3.98 (s, 2 H), 5.14 (s, 2 H), 5.48 (t, 1 H),
7.79 (s, 1 H); IR (neat) 1054, 1165, 1276, 1435, 1463, 1581,
1727, 2947, 3436 cm-1. Anal. (C18H25O7Cl) C, H, Cl.
mmol) in dichloromethane (110 mL) was cooled to -76 °C in
a dry ice-ethanol bath and treated dropwise with a solution
of triphenylphosphine (6.01 g, 22.90 mmol) in dichloromethane
(40 mL). The yellow mixture was stirred at -76 °C for 20 min
and then allowed to warm to room temperature over 12 h. The
solvent was concentrated in vacuo, and the resulting residue
was subjected to flash chromatography (ethyl acetate-hex-
anes, 3:7) to give 10c (7.13 g, 83%) as a clear oil: 1H NMR δ
1.93 (s, 3 H), 3.38 (s, 3 H), 3.55 (m, 4 H), 3.89 (s, 2 H), 3.95 (s,
2 H), 5.14 (s, 2 H), 5.68 (t, 1 H), 7.81 (s, 1 H); IR (neat) 910,
1052, 1161, 1197, 1257, 1274, 1433, 1728 cm-1
(C18H24O6ClBr) C, H, Cl, Br.
.
Anal.
(E)-Meth yl 2-(P h en ylsu lfon yl)-4-m eth yl-6-{3-[1-(m eth -
oxyca r bon yl)-2-((2-m eth oxyeth oxy)m eth oxy)-4-m eth ox-
yp h en yl]}-4-h exen oa te (11a ). A stirred suspension of so-
dium hydride (0.079 g, 1.97 mmol) in dry DMF under an
atmosphere of nitrogen was cooled to 0 °C and treated with
methyl (phenylsulfonyl)acetate (0.33 mL, 1.97 mmol). After
the evolution of hydrogen had subsided (5 min), the ice bath
was removed and stirring was continued for 10 min. The
bromide 10a (0.615 g, 1.47 mmol, in 2 mL dry DMF) was then
introduced, and the resulting yellow solution was stirred for
18 h. The DMF was distilled at ca. 10-1 Torr, and the
remaining residue was partitioned between water and ether
(30 mL of each). The organic phase was washed with water
(25 mL) and saturated sodium chloride (25 mL), dried, and
concentrated to dryness in vacuo to give a yellow oil which
could be used directly in the desulfonylation step or further
purified by flash column chromatography (silica gel, ether-
hexane, 9:1) to give 11a (0.652 g, 81%) as a colorless oil: 1H
NMR δ 1.74 (s, 3 H), 2.58 (m, 2 H), 3.37 (s, 3 H), 3.43 (m, 4 H),
3.46 (s, 3 H), 3.84 (br s, 8 H), 4.10 (m, 1 H), 5.10 (s, 2 H), 5.21
(t, 1 H), 6.67 (d, 1 H), 7.74 (m, 6 H); IR (neat) 2950, 1743,
1718, 1594 cm-1. Anal. (C27H34O10S) C, H, S.
(E)-Meth yl 2-(P h en ylsu lfon yl)-4-m eth yl-6-{3-[1-(m eth -
oxyca r bon yl)-2-(2-m eth oxyeth oxym eth oxy)-4-m eth oxy-
5-m eth ylp h en yl]}-4-h exa n oa te (11b). Methyl (phenylsul-
fonyl)acetate (1.1 mL, 6.75 mmol) was added to an ice-cold
suspension of 60% sodium hydride (0.27 g, 6.75 mmol) and
DMF (10 mL). After the evolution of hydrogen subsided, the
reaction mixture was stirred at room temperature for an
additional 15 min, and then a solution of 10b (2.24 g, 5.19
mmol) in DMF (15 mL) was added. The reaction mixture was
stirred at room temperature for 12 h, at which time the
mixture was partitioned between ether (75 mL) and water (75
mL). The aqueous layer was extracted with ether (2 × 75 mL).
The combined ether layer was washed with water (75 mL) and
brine (75 mL), then dried, filtered, and concentrated in vacuo.
The resulting amber oil was subjected to flash chromatography
(ether-hexanes, 4:1) to give 11b (2.54 g, 87%) as a clear oil:
1H NMR δ 1.75 (s, 3 H), 2.23 (s, 3 H), 2.60 (m, 2 H), 3.36 (s, 3
H), 3.38 (m, 2 H), 3.51 (s, 3 H), 3.53 (m, 2 H), 3.66 (s, 3 H),
3.83 (m, 2 H), 3.85 (s, 3 H), 4.11 (m, 1 H), 5.06 (s, 2 H), 5.24 (t,
1 H), 7.69 (m, 6 H); IR (neat) 943, 1003, 1257, 1474, 2934,
2950 cm-1. Anal. (C28H30O10S) C, H, S.
(E)-Meth yl 3-(4-Br om o-3-m eth yl-2-bu ten yl)-4-m eth oxy-
2-((2-m eth oxyeth oxy)m eth oxy)ben zoa te (10a ). N,N-Di-
isopropylethylamine (0.81 mL, 4.7 mmol) was added to a
mixture of 9a (6.44 g, 18.2 mmol) and tetrabromomethane
(7.31 g, 22.0 mmol) in dichloromethane (60 mL), under a
nitrogen atmosphere. The solution was cooled to -78 °C, and
a
solution of triphenylphosphine (5.25 g, 20.0 mmol) in
dichloromethane (20 mL) was introduced dropwise over a 30
min period. After 3 h, the cooling bath was removed and the
white slurry was stirred for 16 h. The solvent was evaporated,
and the resulting residue was purified by flash column
chromatography (silica gel, ether-dichloromethane, 0.5:9.5)
to provide 10a (6.47 g, 85%) as a clear oil, which slowly
crystallized to a white solid: mp 66-68 °C; 1H NMR δ 1.92 (s,
3 H), 3.03 (s, 3 H), 3.55 (m, 6 H), 3.83 (s, 6 H), 3.93 (s, 2 H),
5.13 (s, 2 H), 5.67 (t, 1 H), 6.67 (d, 1 H), 7.79 (d, 1 H); IR
(CHCl3) 3010, 2952, 1714, 1668, 1595 cm-1. Anal. (C18H25O6-
Br) C, H, Br.
(E)-Meth yl 3-(4-Br om o-3-m eth yl-2-bu ten yl)-4-m eth oxy-
2-((2-m eth oxyeth oxy)m eth oxy]-5-m eth ylben zoa te (10b).
A solution of 9b (2.62 g, 7.11 mmol), tetrabromomethane (2.83
g, 8.53 mmol), and N,N-diisopropylethylamine (0.62 mL, 3.56
mmol) in dry dichloromethane (35 mL) was cooled to -76 °C
in a dry ice-ethanol bath and maintained under a flow of
nitrogen. A solution of triphenylphosphine (2.24 g, 8.53 mmol)
in dry dichloromethane (15 mL) was added slowly dropwise.
The resulting solution was stirred at -76 °C for 15 min and
then allowed to warm to room temperature, with stirring, over
a 10.5 h period. The resulting solution was concentrated in
vacuo, and the green residue was subjected to flash chroma-
tography (ethyl acetate-hexanes, 3:7) to give 10b (2.41 g, 79%)
as a clear oil: 1H NMR δ 1.93 (s, 3 H), 2.27 (s, 3 H), 3.39 (s, 3
H), 3.50 (d, 2 H), 3.57 (t, 2 H), 3.73 (s, 3 H), 3.87 (s, 3 H), 3.89
(t, 2 H), 3.96 (s, 2 H), 5.13 (s, 2 H), 5.72 (t, 1 H), 7.60 (s, 1 H);
IR (neat) 908, 1096, 1387, 1470, 1719 cm-1. Anal. (C19H27O6-
Br) C, H, Br.
(E)-Meth yl 2-(P h en ylsu lfon yl)-4-m eth yl-6-{3-[5-ch lor o-
1-(m eth oxyca r bon yl)-2-((2-m eth oxyeth oxy)m eth oxy)-4-
m eth oxyp h en yl]}-4-h exen oa te (11c). Sodium hydride, 60%
(0.81 g, 20.18 mmol) was suspended in DMF (30 mL) and
cooled to 0 °C in an ice bath. Methyl (phenylsulfonyl)acetate
(3.4 mL, 20.18 mmol) was quickly added to the stirring ice-
cold solution. After the evolution of hydrogen subsided, the
ice bath was removed, the reaction mixture was stirred for an
additional 15 min, and then a solution of 10c (7.01 g, 15.52
mmol) in DMF (30 mL) was added in one portion. The reaction
mixture was stirred at room temperature for 5 h, and then
the DMF was removed by distillation. The resulting yellow
residue was partitioned between ether (200 mL) and water
(200 mL). The ether layer was washed with water (100 mL)
and brine (100 mL), then dried, filtered, and concentrated in
vacuo. The resulting yellow oil was purified by flash chroma-
tography (ether-hexanes, 4:1) to give 11c (8.03 g, 88%) as a
sticky oil: 1H NMR δ 1.74 (s, 3 H), 2.60 (m, 2 H), 3.36 (s, 3 H),
3.41 (d, 2 H), 3.51 (s, 3 H), 3.53 (m, 2 H), 3.80 (s, 3 H), 3.83
(m, 2 H), 3.85 (s, 3 H), 4.10 (m, 1 H), 5.07 (s, 2 H), 5.25 (t, 1
H), 7.59 (m, 6 H); IR (neat) 1158, 1200, 1258, 1272, 1310, 1326,
1424, 1587, 1733 cm-1. Anal. (C27H33O10SCl) C, H, S, Cl.
(E)-Meth yl 3-(4-Br om o-3-m eth yl-2-bu ten yl)-5-ch lor o-4-
m eth oxy-2-((2-m eth oxyeth oxy)m eth oxy)ben zoa te (10c).
A solution of 9c (7.42 g, 19.08 mmol), tetrabromomethane (7.59
g, 22.90 mmol), and N,N-diisopropylethylamine (1.0 mL, 5.74

54 J ournal of Medicinal Chemistry, 1996, Vol. 39, No. 1
Anderson et al.
(E)-Meth yl 4-Meth yl-6-{3-[1-(m eth oxyca r bon yl)-2-((2-
m e t h oxye t h oxy)m e t h oxy)-4-m e t h oxyp h e n yl]}-4-h e x-
en oa te (12a ). Crude sulfone 11a (from 23.6 mmol of bromide
10a ) was dissolved in methanol (120 mL). Anhydrous dibasic
sodium phosphate (6.73 g, 47.4 mmol) was introduced, and the
suspension was placed under a nitrogen atmosphere and cooled
to 0 °C. Sodium amalgam (6%, 18.17 g, 47.4 mmol Na) was
added, and the mixture was stirred vigorously for 3.25 h. A
significant amount of starting sulfone was still present (TLC,
silica gel, ether-hexane, 7:3), so additional aliquots of anhy-
drous dibasic sodium phosphate (1.69 g, 11.9 mmol) and
sodium amalgam (4.59 g, 12.0 mmol Na) were added. The
mixture was stirred for 75 min at 0 °C, whereupon more
sodium phosphate and sodium amalgam (1.69 g, 11.9 mmol
and 4.54 g, 11.8 mmol Na respectively) was introduced. The
mixture was stirred for 45 min and filtered through Celite,
and the filter cake was rinsed with ether (2 × 40 mL). Ether
was added to the filtrate to bring the volume to ca. 300 mL
after which the solution was extracted with water (300 mL).
The aqueous layer was extracted with ether (4 × 100 mL).
The combined organic solution was dried (over Na2SO4 and
then MgSO4) and evaporated to give a yellow oil which was
further dried by azeotropic distillation (at ca. 20 Torr) with
toluene. Purification of the residue by flash column chroma-
tography (silica gel, ether-hexane, 7:3) afforded 12a (7.80 g,
81% from 10a ) as a colorless oil: 1H NMR δ 1.78 (s, 3 H), 2.33
(br s, 4 H), 3.38 (s, 3 H), 3.48 (m, 4 H), 3.60 (s, 3 H), 3.86 (s, 6
H), 3.88 (m, 2 H), 5.13 (s, 2 H), 5.22 (t, 1 H), 6.68 (d, 1 H), 7.79
(d, 1 H); IR (neat): 2949, 1717, 1594 cm-1. Anal. (C21H30O8)
C, H.
Meth yl 5-F or m yl-2,4-d im eth oxyben zoa te (5a ) was pre-
pared by a previously reported procedure,28 in 69% yield,
except 3 molar equiv of R,R-dichloromethyl methyl ether was
used and the reaction mixture was stirred at room temperature
for 2 h. Also during the workup, the quenched reaction
mixture was extracted with dichloromethane instead of ether.
Meth yl 2,4-Dim eth oxy-5-m eth ylben zoa te (5b). A sus-
pension of 5a (5.37 g, 23.95 mmol) in ethyl acetate (200 mL)
and glacial acetic acid (15 mL) containing 10% palladium on
carbon (1.0 g) was stirred in an atmosphere of hydrogen for
48 h. The reaction mixture was filtered through a pad of
Celite, and the solvent was then removed in vacuo to give 5b
(4.72 g, 94%) as a grayish crystalline solid: mp 90-91 °C; 1H
NMR δ 2.13 (s, 3 H), 3.80 (s, 3 H), 3.83 (s, 3 H), 3.86 (s, 3 H),
6.40 (s, 1 H), 7.63 (s, 1 H); IR 1709, 1260, 1152 cm-1
.
Ack n ow led gm en t. This work was supported by
Grant No. CA54507 from the National Cancer Institute.
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(E)-Meth yl 4-Meth yl-6-{3-[1-(m eth oxyca r bon yl)-2-((2-
m eth oxyeth oxy)m eth oxy)-4-m eth oxy-5-m eth ylp h en yl]}-
4-h exen oa te (12b). Sodium phosphate (0.378, 2.66 mmol)
and 6% sodium amalgam (1.02 g, 2.66 mmol) was added to a
solution of 11b (0.500 g, 0.886 mmol) in anhydrous methanol
(5 mL) at 0 °C, while under a flow of argon. The mixture was
stirred at 0 °C for 4 h. The reaction mixture was then filtered
and partitioned between ether (25 mL) and water (25 mL).
The aqueous layer was extracted with ether (3 × 10 mL). The
combined organic layer was dried, filtered, and concentrated
in vacuo. The resulting clear oil was subjected to flash
chromatography (ether-hexanes, 3:2) to give 12b (0.293 g, 78%)
as a clear oil: 1H NMR δ 1.78 (s, 3 H), 2.27 (s, 3 H), 2.33 (m, 4
H), 3.39 (s, 3 H), 3.45 (d, 2 H), 3.57 (t, 2 H), 3.62 (s, 3 H), 3.72
(s, 3 H), 3.87 (s, 3 H), 3.89 (t, 3 H), 5.11 (s, 2 H), 5.26 (t, 1 H),
7.57 (s, 1 H); IR (neat) 943, 982, 1024, 1112, 1287, 1467, 1473,
1574, 1601, 1726, 2950 cm-1. Anal. (C22H32O8) C, H.
Di-ter t-bu tyl {(E)-4-[5-Ch lor o-1-(m eth oxyca r bon yl)-2-
((2-m eth oxyeth oxy)m eth oxy)-4-m eth oxyp h en yl]-2-m eth -
yl-2-bu ten yl}m a lon a te (13). Di-tert-butyl malonate (1.8 mL,
8.37 mmol) was added to a suspension of sodium hydride (60%
in mineral oil, 0.33 g, 8.37 mmol) in DMF (30 mL). The
mixture was stirred at room temperature for 20 min, and then
a solution of 10c (2.91 g, 6.44 mmol) in DMF (30 mL) was
quickly added. The resulting mixture was stirred at room
temperature for 14 h, and then the solvent was removed by
distillation. The residue was then subjected to flash chroma-
tography (ether-hexanes, 3:2) to give 13 (3.13 g, 84%) as a
clear, sticky oil: 1H NMR δ 1.38 (s, 18 H), 1.80 (s, 3 H), 2.47
(d, 2 H), 3.31 (t, 1 H), 3.38 (s, 3 H), 3.46 (d, 2 H), 3.56 (t, 2 H),
3.87 (m, 8 H), 5.11 (s, 2 H), 5.28 (t, 1 H), 7.76 (s, 1 H); IR (neat)
1151, 1276, 1372, 1470, 1581, 1733, 2932, 2980 cm-1. Anal.
(C29H43O10Cl) C, H, Cl.
Meth yl 2,4-Dim eth oxyben zoa te (4). A solution of 3a
(50.00 g, 0.274 mol) in acetone (1750 mL) was treated with
dimethyl sulfate (100.00 g, 0.791 mol) and potassium carbonate
(312.93 g, 2.264 mol), and then the heterogeneous mixture was
heated at reflux, with stirring, for 24 h. The reaction mixture
was then filtered through a pad of Celite and then concen-
trated to give an amber oil. Water (250 mL) was added to the
oil, and the solution was stirred at room temperature for 0.5
h. The organic and aqueous layers were separated, and the
aqueous phase was extracted with diethyl ether (3 × 500 mL),
dried, and concentrated in vacuo to yield (51.61 g, 96%) of 4
as an amber oil: 1H NMR δ 3.81 (s, 6 H), 3.84 (s, 3 H), 6.48
(m, 2 H), 7.84 (d, 1 H); IR 1723, 1609, 1435, 1257 cm-1
.

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(26) We thank Dr. R. J . Bernacki and P. Pera, Department of
Experimental Therapeutics, Roswell Park Memorial Institute,
Buffalo, NY, for the L1210 assay data. The test compounds were
dissolved in DMSO; the cells were exposed to the test compounds
for 48 h. Compounds 3a -c were also inactive against a HT-29
) 0.4
human colon adenocarcinoma cell line (MPA had an IC50
µM). The amide 3c was inactive (>32.5 µM) against human A121
ovarian, A549 lung carcinoma, and MCF7 breast adenocarci-
noma cell lines (MPA had IC50 ) 0.2-0.3 µM).
(27) All calculations were performed by SYBYL 6.03 (Tripos Associ-
ates Inc.) with an interface to MOPAC 5.0 (QCPE no. 455).
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Formylation and Bromination ortho to the Hydroxy-group of
2-Carbonyl-substituted Phenols in the Presence of Titanium (IV)
Chloride. J . Chem. Soc. Perkin Trans. 1 1973, 340.
J M9501339