Effects of 2-(substituted-sulfanyl)-3,5-dihydro-imidazole-4-one and 2-(Substituted-sulfanyl)-1H-imidazole-4,5-dione derivatives on serum HDL-cholesterol

Article abstract of DOI:10.1016/S0960-894X(00)00338-3

A series of 2-substituted sulfanyl-3,5-dihydro-imidazole-4-ones and 2-substituted sulfanyl-1H-imidazole-4,5-diones was prepared and shown to increase high density lipoprotein cholesterol over other lipid fractions. Compound 1f showed efficacy in additional animal models. The major metabolite of 1f was isolated and its synthesis is reported. The effects of the metabolite on the lipid profile in rats were investigated. (C) 2000 Elsevier Science Ltd. All rights reserved.

Full text of DOI:10.1016/S0960-894X(00)00338-3

Bioorganic & Medicinal Chemistry Letters 10 (2000) 1791±1794
E€ects of 2-(Substituted-sulfanyl)-3,5-dihydro-imidazole-4-one and
2-(Substituted-sulfanyl)-1H-imidazole-4,5-dione Derivatives on
Serum HDL-cholesterol
Hassan Elokdah,a,* Theodore Sulkowski,a David Cochran,b Mar-Lee McKeanc
and Elaine Quinetc
aMedicinal Chemistry, Chemical Sciences, Wyeth-Ayerst Research, CN 8000, Princeton, NJ 08543, USA
bDiscovery Analytical Chemistry, Chemical Sciences, Wyeth-Ayerst Research, CN 8000, Princeton, NJ 08543, USA
cCardiovascular/Women's Health, Wyeth-Ayerst Research, PO Box 42528, Philadelphia, PA 19101, USA
Received 5 May 2000; accepted 2 June 2000
AbstractÐA series of 2-substituted sulfanyl-3,5-dihydro-imidazole-4-ones and 2-substituted sulfanyl-1H-imidazole-4,5-diones was
prepared and shown to increase high density lipoprotein cholesterol over other lipid fractions. Compound 1f showed ecacy in
additional animal models. The major metabolite of 1f was isolated and its synthesis is reported. The e€ects of the metabolite on the
lipid pro®le in rats were investigated. # 2000 Elsevier Science Ltd. All rights reserved.
Numerous studies have demonstrated that both the risk
of coronary heart disease (CHD) in humans and the
severity of experimental atherosclerosis in animals are
inversely correlated with serum High Density Lipoprotein-
Cholesterol (HDL-C) concentrations.1 Atherosclerosis is
the process of accumulation of cholesterol within the
arterial wall that results in the occlusion, or stenosis, of
coronary and cerebral arterial vessels and subsequent
myocardial infarction and stroke. Angiographical studies
have shown that elevated levels of some HDL particles
appear to be correlated to a decreased number of sites
of stenosis in the coronary arteries of humans.2 HDL
may protect against the progression of atherosclerosis
through several mechanisms. In vitro studies have
shown that HDL is capable of removing cholesterol
from cells.3 Data of this nature suggest that one anti-
atherogenic property of HDL may lie in its ability to
deplete tissues of excess free cholesterol and eventually
lead to the delivery of this cholesterol to the liver.4 This
has been supported by experiments showing ecient
transfer of cholesterol from HDL to the liver.5
increase serum HDL cholesterol concentrations would
be of utility as anti-atherosclerotic agents useful in the
treatment of dyslipoproteinemias and coronary heart
disease.
Based on the HDL-C elevating properties of an earlier
series of thio-containing compounds,7 a series of 2-
substituted sulfanyl-3,5-dihydro-imidazole-4-ones (1) was
designed and evaluated for their e€ects on the lipid
pro®le in animal models. Compounds of this series
selectively increased HDL-C over other lipid fractions
such as LDL-C and VLDL-C.
Compounds 1 were prepared8 according to Scheme 1.
Reaction of an isothiocyanate with an amino acid or an
amino acid ester a€ords 2-thioxo-imidazolidin-4-ones
(3). Alkylation of 3 with methyl iodide proceeds in poor
yield to a€ord the corresponding S-methyl product (4).
The product is dicult to purify and the reaction does
not work with higher alkyl halides. Alternatively, in a
preferred general procedure, the reaction of an isothio-
cyanate with an amino acid amide under basic conditions
In addition, HDL may serve as a reservoir in the circula-
tion for apoproteins necessary for the rapid metabolism of
triglyceride-rich lipoproteins.6 Accordingly, agents that
*Corresponding author. Tel.: +1-732-274-4504; fax: +1-732-274-
4505; e-mail: elokdah@war.wyeth.com
0960-894X/00/$ - see front matter # 2000 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(00)00338-3

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H. Elokdah et al. / Bioorg. Med. Chem. Lett. 10 (2000) 1791±1794
in methylene chloride or chloroform a€orded the
thiourea amide (5). Reaction of 5 with 2 equiv of an
alkyl halide or arylalkyl halide in ethanol at re¯ux
e€ected the S-alkylation followed by the cyclization to
the desired target compounds. In the case where R3=O
(2a±b), the compounds were prepared according to
reaction Scheme 2. An isothiocyanate was reacted with
ammonia to form the thiourea (6). Alkylation of 6, as
described above, yielded S-alkyl/S-arylalkyl isothiourea
(7). Reaction of 7 with oxalyl chloride or ethyl oxalyl
chloride in chloroform or methylene chloride a€orded
the desired compounds (2a±b).
increased HDL-C by 140% over controls. The e€ect of
adding a substituent in the 5-position of the dihydro-
imidazole ring was also explored. An oxygen in the 5-
position (compounds 2a and 2b) led to moderate
increases in HDL-C. A mono methyl in the 5-position
yielded a potent compound (compound 1o); however,
compounds with this substitution were not further pursued
due to undesirable side e€ects, namely reduction in body
weight gain and signi®cant elevation of liver enzymes
(SGOT and SGPT). None of the compounds exhibiting
a signi®cant increase in HDL-C produced a signi®cant
increase in LDL-C and only compound 1e induced a
signi®cant increase in VLDL-C (78%).
Target compounds were evaluated in an in vivo assay
for their e€ects on the lipid pro®le.10 HDL cholesterol
concentrations in serum are determined by separating
the lipoprotein classes using a modi®cation of Kieft's11
method.
The changes in HDL-C concentration following treatment
with 2-substituted sulfanyl-3,5-dihydro-imidazole-4-one
and 2-substituted sulfanyl-1H-imidazole-4,5-dione deri-
vatives are presented in Table 1. In general, optimal
increases in HDL-C were observed with 2-methyl-5-
chloro-phenyl analogues (compounds 1c, 1f, 1o, and
2a). Moving the chlorine to the 6, 3, or 4 position of the
phenyl ring (compounds 1g, 1i, and 1j) diminished
activity. While the 2-methyl-5-¯uoro-phenyl analogue
(compound 1h) had no signi®cant e€ect on HDL-C, the
4-¯uoro-phenyl analogue (compound 1l) signi®cantly
Based on the overall ecacy and safety pro®le, compound
1f was further tested in additional animal models (normal
chow-fed rats, cholesterol-fed hamsters and primates).
Compound 1f e€ectively increased HDL-C in these
animal models without increasing other lipid fractions
and had a favorable safety pro®le. The e€ects of com-
pound 1f on altering the lipid pro®le of male cyno-
molgus monkeys following oral treatment at a dose of
10 mg/kg/day for 4 weeks are illustrated in Figure 1.
Signi®cant increases in HDL-C were observed at 2 and
4 weeks with comparable increases in total cholesterol.
There were no signi®cant changes in VLDL-C, LDL-C
or triglycerides.
In vitro metabolism of compound 1f in liver microsomal
preparations (rat, dog, monkey, and human) was inves-
tigated. A major metabolite was prevalent in all four
preparations. The isolated metabolite was assigned the
Table 1. E€ect of 2-substituted sulfanyl-3,5-dihydro-imidazole-4-one
and 2-substituted sulfanyl-1H-imidazole-4,5-dione derivatives on
HDL-C in cholesterol-fed male rats
Compds
R1
R2
R3
R4
HDL-Ca
Scheme 1. Synthesis of 2-substituted sulfanyl-3,5-dihydro-imidazole-
4-one derivatives:9 (a) H2NCH2CO2R, CHCl3; (b) MeI, MeOH, Heat;
(c) H2NCH(R3)CONH2, CHCl3 or CH2Cl2; (d) R4I, R4Br, or R4Cl,
EtOH, Heat.
1a
1b
1c
1d
1e
1f
1g
1h
1i
1j
1k
1l
1m
1n
1o
2a
2b
2-Cl
2-MeO
2-Me
2-Cl
2-Me
2-Me
2-Me
2-Me
2-Me
2-Me
2-Me
4-F
H
3-Cl
2-Me
2-Me
2-Me
6-Cl
5-Cl
5-Cl
H
H
H
H
H
H
H
H
H
H
H
H
H
H
H
Me
Ð
Ð
Et
Et
PhCH2
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
Et
169c
66c
102c
74
139c
153c
71
32
26
39
H
5-Cl
6-Cl
5-F
3-Cl
4-Cl
6-Me
H
75
140b,c
89c
45
H
4-Me
5-Cl
5-Cl
H
211c
85c
48
aAverage % HDL-C change in 6 animals (versus control) after treat-
ment for 8 days at a dose of 100 mg/kg/day.
Scheme 2. Synthesis of 2-substituted sulfanyl-1H-imidazole-4,5-dione
derivatives and 2-substituted sulfanyl-1H-imidazolidine-4,5-dione deri-
vatives: (a) NH4OH; (b) R4I, R4Br, or R4Cl, EtOH, Heat, basic work
up; (c) (COCl)2 or EtO2CCOCl, CHCl3 or CH2Cl2; (d) 5% Pd/C, H2,
EtOH.
bAverage % HDL-C change in 6 animals (versus control) after treat-
ment for 8 days at a dose of 80 mg/kg/day.
cStatistically signi®cant with P<0.05.

H. Elokdah et al. / Bioorg. Med. Chem. Lett. 10 (2000) 1791±1794
1793
structure of 1-(5-chloro-2-methylphenyl)-2-(ethyl sulfanyl)
imidazolidine-4,5-dione (8). 2-Substituted sulfanyl-imid-
azolidine-4,5-dione derivatives are unique and have not
been described in the literature. Initial attempts to prepare
8 via hydride reduction of compound 2a failed to yield
the desired product or yielded an intractable mixture of
products. Compound 8 was successfully prepared from
2a by catalytic hydrogenation (5% Pd/C) in ethanol at
atmospheric pressure (Scheme 2). The reaction pro-
ceeded in good yield and the compound was obtained as
a stable solid.
Saturation of the resonance at 6.23 ppm (Hb) induced
an NOE intensity increase in the aromatic methyl reso-
nance, in the aromatic H6 resonance, and in the S-CH2
resonance. These close interaromatic distances were
con®rmed by saturation of the other half of each dipolar
coupled pair of resonances.
The e€ect of the synthetic metabolite (8) on the lipid
pro®le of test animals was investigated. Compound 8
did not alter the lipid pro®les of either the cholesterol-fed
rats or the cholesterol-fed hamsters at the test dose of
100 mg/kg/day.
Both the synthetic material and the isolated metabolite
were identical as indicated by their HPLC pro®les, UV,
MS, and 1H NMR spectra (Fig.2). The structure
assignment of 8 was based on elemental analysis, mass
and 1H NMR spectroscopy.12 The chemical shift for the
S-CH2 resonance is at 2.5 ppm, up®eld from the corre-
sponding S-CH2 of compound 1f (3.1 ppm) or that of
compound 2a (3.26 ppm). The resonance at 7.65 ppm
shifted to 7.35 ppm when the temperature was raised
from 25 ꢀC to 40 ꢀC, indicating a resonance corre-
sponding to an exchangeable proton. The most impor-
tant structural evidence was derived from a series of
NOE experiments.
In conclusion, novel 2-substituted sulfanyl-3,5-dihydro-
imidazole-4-one derivatives and 2-substituted sulfanyl-
1H-imidazole-4,5-dione derivatives were described.
Their e€ects on increasing serum HDL-C over other
lipid fractions were illustrated in animal models. Con-
cerns about the chemical and metabolic stability of
these classes of compounds directed our e€orts to a
related series of N-alkyl N0-substituted thiohydantoin
derivatives.13 These compounds were also e€ective in
raising HDL-C over other lipid fractions and o€ered
improved stability and metabolic pro®les. This series of
compounds will be the subject of a future publication.
As expected, saturation of the water resonance trans-
ferred saturation to resonance Ha (exchangeable).
Acknowledgements
We would like to thank Mr. Bruce Hofmann and Mr.
James Mattes for performing 1H NMR spectroscopy
experiments, Dr. Mei-Yi Zhang for the mass spectro-
metry, and Ms. Natasha Kagan for isolation of the
metabolite.
References and Notes
1. (a) For a review article see: Barter, P. J.; Rye, K.-A.
Atherosclerosis 1996, 121, 1. (b) Barr, D. P.; Russ, E. M.;
Eder, H. A. Am. J. Med. 1951, 11, 480. (c) Gofman, J. W.;
Young, W.; Tandy, R. Circulation 1966, 34, 679. (d) Miller, G.
J.; Miller, N. E. Lancet 1975, 1, 16. (e) Gordon, D. J.;
Probst®eld, J. L.; Garrison, R. J.; Neaton, J. D.; Castelli, W.
P.; Knoke, J. D.; Jacobs, D. R., Jr.; Bangdiwala, S.; Tyroler,
H. A. Circulation 1989, 79, 8. (f) Stampfer, M. J.; Sacks, F.
M.; Salvini, S.; Willett, W. C.; Hennekens, C. H. N. Engl. J.
Med. 1991, 325, 373. (g) Badimon, J. J.; Badimon, L.; Galuz,
A.; Dische, R.; Fuster, V. Lab. Invest. 1989, 60, 455.
2. Miller, N. E.; Hammett, F.; Saltissi, S.; Rao, S.; Zeller, H.
V.; Coltant, J.; Lewis, B. Br. Med. J. 1981, 282, 1741.
3. Picardo, M.; Massey, J. B.; Kuhn, D. E.; Gotto, A. M., Jr.;
Gianturco, S. H.; Pownall, H. J. Arteriosclerosis 1986, 6, 434.
4. Glomset, J. A. J. Lipid Res. 1968, 9, 155.
Figure 1. Lipoprotein and lipid e€ects in cynomolgus monkeys dosed
with 10 mg/kg/day orally for 4 weeks. Data represent mean for n=4
monkeys at timepoints 0, 2 weeks, and 4 weeks of dosing. VLDL-
C=Very low density lipoprotein cholesterol, LDL-C=low density
lipoprotein cholesterol, HDL-C=high density lipoprotein cholesterol,
TC=total cholesterol, and TG=triglycerides. ÃRepresents sig-
ni®cantly di€erent from baseline at P<0.05.
5. (a) Glass, C. K.; Pittman, R. C.; Keller, G. A.; Steinberg,
D. J. Biol. Chem. 1983, 258, 7161. (b) Mackinnon, M.; Savage,
J.; Wishant, R.; Barter, P. J. Biol. Chem. 1986, 261, 2548.
6. (a) Grow, T. E.; Fried, M. J. Biol. Chem. 1978, 253, 8034. (b)
Lagocki, P. A.; Scanu, A. M. J. Biol. Chem. 1980, 255, 3701. (c)
Schaefer, E. J.; Wetzel, M. G.; Bengtsson, G.; Scow, R. O.;
Brewer, H. B., Jr.; Olivecrons, T. J. Lipid Res. 1982, 23, 1259.
7. Screening of the compound ®le in an in vivo based assay
(see ref 10) led to the identi®cation of a series of aryl thiose-
micarbazones as HDL-C enhancers. For more information
see: (a) Commons, T. J.; Musial, C. L.; Christman, S. US
Figure 2. Selected 1H NMR chemical shifts in (CDCl3, 400 MHz) of
metabolite 8.

1794
H. Elokdah et al. / Bioorg. Med. Chem. Lett. 10 (2000) 1791±1794
Patent 6,008,362, 1999; Chem. Abstr. 1999, 132, 49788. (b)
Commons, T. J.; Christman, S. US Patent 5,968,975, 1999;
Chem. Abstr. 1999, 131, 286270.
8. (a) Elokdah, H. M.; Sulkowski, T. S.; Strike, D. P. US
Patent 5,599,829, 1997; Chem. Abstr. 1997, 126, 195251. (b)
Elokdah, H. M.; Sulkowski, T. S.; Strike D. P. US Patent
5,877,324, 1999; Chem. Abstr. 1999, 130, 196654.
9. All compounds gave satisfactory spectral data. For exam-
ple, 3-(5-chloro-2-methylphenyl)-2-ethylsulfanyl-3,5-dihydro-
imidazol-4-one (1f): mp 137±139 ꢀC, Anal. calcd for C12H13
ClN2OS: C, 53.63; H, 4.88; N, 10.42. Found: C, 53.58; H, 4.74;
N, 10.32. Mass spectrum (EI, M.+) m/z 268/270. 1H NMR
(DMSO-d6, 400 MHz) d 7.48 (dd, 1H, J=8.3, 2.2 Hz), 7.43±
7.40 (m, 2H), 4.35 (dd, 2H, J=42.84, 23.08 Hz), 3.07 (q, 2H,
J=7.27 Hz), 2.1 (s, 3H), and 1.28 (t, 3H, J=7.3 Hz). 1-(5-
Chloro-2-methylphenyl)-2-ethylsulfanyl-1H-imidazol-4,5-dione
(2a): mp 153±155 ꢀC, Anal. calcd for C12H11ClN2O2S: C, 50.98;
H, 3.92; N, 9.91. Found: C, 50.66; H, 3.69; N, 9.70. Mass
spectrum (EI, M.+) m/z 282/284. 1H NMR (DMSO-d6, 400
MHz) d 7.59 (d, 1H, J=2 Hz), 7.54 (dd, 1H, J=8, 2 Hz), 7.45
(d, 1H, J=8 Hz), 3.26 (q, 2H, J=7.2 Hz), 2.18 (s, 3H), and
1.34 (t, 3H, J=7.2 Hz).
to a group of six rats fed the same diet with the test diet mixed
in as 0.005±0.1% of the total diet. Body weight and food con-
sumption are recorded prior to diet administration and at ter-
mination. Typical doses of the test substances are 5±100 mg/
kg/day. At termination, blood is collected from anesthetized
rats and the serum is separated by centrifugation. Total serum
cholesterol is assayed using the Sigma Diagnostics enzymatic
kit for the determination of cholesterol, Procedure No. 352,
modi®ed for use with 96-well microtiter plates.
11. (a) Kieft, K. A.; Bocan, T. M. A.; Krause, B. R. J. Lipid
Res. 1991, 32, 859. (b) The relative concentration of each
lipoprotein class is calculated as the percent of total absor-
bance. HDL cholesterol concentration, in serum, is calculated
as the percent of total cholesterol as determined by FPLC
multiplied by the total serum cholesterol concentration.
12. Analytical data for compound 8: mp 181±183 ꢀC, Anal.
calcd for C12 H13ClN2O2S: C, 50.61; H, 4.60; N, 9.84. Found:
C, 50.77; H, 4.54; N, 9.85. Mass spectrum (EI, M.+) m/z 223/
1
225. H NMR (DMSO-d6, 400 MHz) d 10.78 (broad s, 1H),
7.55 (broad s, 1H), 7.44±7.38 (m, 2H), 6.71 (broad s, 1H), 2.42
(q, 2H, J=7.2 Hz), 2.14 (s, 3H) and 1.07 (t, 3H, J=7.4 Hz).
1H NMR (CDCl3, 400 MHz) d 7.65 (broad s, 1H), 7.35 (dd,
1H), 7.30 (d, 1H), 7.18 (broad s, 1H), 2.5 (q, 2H), 2.24 (s, 3H)
and 1.22 (t, 3H).
10. Male Sprague±Dawley rats weighing 200±225 g are housed
two per cage and fed Purina Rodent Chow Special Mix 5001-S
supplemented with 0.25% cholic acid and 1.0% cholesterol and
water ad libitum for 8 days. Each test substance is administered
13. Elokdah, H. M.; Chai, S.; Sulkowski, T. S.; Strike, D. P.
US Patent 5,554607, 1996; Chem. Abstr. 1996, 125, 275874.