1-Hydroxyalkyl-3-phenylthioureas as novel HDL-elevating agents

Article abstract of DOI:10.1016/j.bmcl.2004.10.094

A series of 1-hydroxyalkyl-3-phenylthiourea analogs were prepared and evaluated as HDL-and Apo A-I-elevating agents. Derivatives 5h, 7j, 7n, and 7o were found to be as effective or superior to gemfibrozil (1).

Full text of DOI:10.1016/j.bmcl.2004.10.094

Bioorganic & Medicinal Chemistry Letters 15 (2005) 809–812
1-Hydroxyalkyl-3-phenylthioureas as novel HDL-elevating agents
Gary M. Coppola,a,* Robert E. Damon,a J. Bruce Eskesen,a
Dennis S. Francea and James R. Paterniti, Jr.b
aDepartment of Diabetes and Metabolism, Novartis Institutes for Biomedical Research, 100 Technology Square,
Cambridge, MA 02139, USA
bAmylin Pharmaceuticals, 9373 Towne Centre Drive, San Diego, CA 92121, USA
Received 4 May 2004; accepted 29 October 2004
Available online 10 December 2004
Abstract—A series of 1-hydroxyalkyl-3-phenylthiourea analogs were prepared and evaluated as HDL-and Apo A–I-elevating
agents. Derivatives 5h, 7j, 7n, and 7o were found to be as effective or superior to gemfibrozil (1).
Ó 2004 Elsevier Ltd. All rights reserved.
Cardiovascular disease is the leading cause of mortality
in the United States and many other industrialized
countries and atherosclerosis accounts for the majority
of these deaths.1 Approximately 1% of the population
have an inherited lipid disorder and are predisposed to
premature onset of this disease. It is well known that
major risk factors for atherosclerotic cardiovascular
disease include such dyslipidemias as elevated low-
density lipoprotein (LDL) cholesterol, low levels of
high-density lipoprotein (HDL) cholesterol, and high
levels of triglycerides.
els.7 Additionally, the Veterans Administration HDL
Intervention Trial demonstrated that gemfibrozil ther-
apy in men with coronary heart disease and low HDL
cholesterol levels raised HDL cholesterol modestly and
reduced coronary events by 22%, despite not lowering
LDL cholesterol levels.8
One of the possible mechanisms for the protective nat-
ure of HDL against the development of atherosclerosis
is its ability to extract cholesterol from cells,9 thus coun-
teracting the effects of LDL cholesterol and subse-
quently preventing the formation of foam cells, the
genesis of atherosclerotic lesions. In vitro studies have
supported this postulate.10,11 The cholesterol-laden
HDL particle is then transported to the liver where the
cholesterol is recycled or removed by excretion in
bile.4,11
Atherosclerosis is a complex disease where the progres-
sive accumulation of cholesterol within the arterial wall
eventually results in occlusion of the coronary or cere-
bral arteries ultimately leading to myocardial infarction
or stroke. Extensive epidemiological studies have shown
a strong inverse correlation between serum HDL choles-
terol levels and coronary heart disease.2–4 The Framing-
ham heart study showed that a 10mg/dL increase in
HDL cholesterol was associated with a 19% decrease
in coronary artery disease (CAD) death and a 12% de-
crease in all-cause mortality.5 The Helsinki heart study,6
a primary prevention trial in dyslipidemic men, demon-
strated a reduced incidence of cardiovascular events in
response to treatment with the PPARa agonist gemfi-
brozil (1). This study showed a 1% increase in HDL cho-
lesterol was associated with a 2–3% decrease in CHD
events independent of changes in LDL cholesterol lev-
Further support that HDL has antiatherogenic proper-
ties was demonstrated in transgenic mice where over
expression of the human apolipoprotein (Apo) A–I
gene, the carrier protein for HDL cholesterol, resulted
in elevated levels of HDL cholesterol and significant
protection from the development of aortic fatty streak
lesions.12 This protection was also seen in spontaneously
Atherosclerotic Apo E-deficient mice.13,14
Molecular mechanisms involved in overall HDL meta-
bolism have not been completely elucidated. We there-
fore embarked on a program to identify agents that
would elevate HDL cholesterol as well as Apo A–I plasma
levels. Between 1967 and 1978 we (formerly Sandoz,
Inc.) had a cholesterol-lowering program which used
*
Corresponding author. Fax: +617 871 7043; e-mail: gary.oppola@
pharma.novartis.com
0960-894X/$ - see front matter Ó 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2004.10.094

810
G. M. Coppola et al. / Bioorg. Med. Chem. Lett. 15 (2005) 809–812
rat as the in vivo model. At that time serum cholesterol
was not fractionated and total cholesterol was mea-
sured. Since rats carry the majority of their cholesterol
in the HDL fraction, we searched those compounds
for the ones that raised cholesterol. We screened a subset
of those compounds in rats fed with cholic acid and cho-
lesterol-supplemented diet (a model of reduced HDL
cholesterol and Apo A–I),15 and identified thiourea 2
as a compound that raised serum levels of both HDL
cholesterol and Apo A–I as well as reducing triglyceride
levels.
(R)-amino alcohol 10. The opposite enantiomer (not
shown) was prepared analogously by resolution with
D-tyrosinehydrazide.
Cbz
N
Cbz
N
H
N
COOH
CH2OH
CH2OH
B2H6
97%
H2 Pd/C
100%
8
9
10
Compounds were administered in diet (ad libitum) to
groups of six male Sprague–Dawley rats for eight days
as described in our previous publication.16 The lipopro-
teins were separated by classical ultracentrifugation
techniques and cholesterol was quantitated by enzy-
matic colorimetric methods. Serum Apo A–I was mea-
sured by SDS polyacrylamide gel electrophoresis20 or a
rat competition ELISA.16 Within each study, gemfibro-
zil (1) was used as an internal positive control.
CH3
Cl
S
COOH
OH
O
N
H
N
H
CH3
CH3
1
2
Cl
S
COOH
N
H
N
H
Initial modifications of structure 2 focused on the aro-
matic substituents (Table 1). Removal of the chlorine
atom (5a) resulted in complete loss of activity whereas
removal of the methyl group (5b) had no significant
effect on HDL cholesterol or Apo A–I. Replacing the
chlorine atom of 5b with CF3 (5k) also retained HDL
activity, however, total cholesterol (TC) was raised
slightly. Moving the chlorine around the ring produced
varying results. The 6-chloro derivative 5d did not raise
HDL cholesterol and lowered Apo A–I whereas the cor-
responding 3- and 4-chloro analogues 5f and 5e showed
moderately elevated HDL cholesterol levels. Replacing
the 2-methyl group with either chlorine or methoxy
(5g or 5h) retained activity, however, TC levels in 5h
were raised 66%. Replacing the 5-chloro with methyl
(5j) raised HDL cholesterol but not Apo A–I. All com-
pounds in Table 1 exhibited reductions in body weight
gain which were highly correlated to effects on food con-
sumption (R2 = 0.89, p < 0.0001; data not shown). It
cannot be ruled out that a portion of the HDL effects
in this series of compounds may be attributable to the
diminished food consumption.
CH3
3
Reported in a previous publication, we combined the
features of 1 and 2 to produce a gemfibrozil ÔhybridÕ 3
which raised HDL cholesterol and Apo A–I as effec-
tively as 1.16 Since the thiourea group appears to be
needed for biological activity17,18 we undertook an
investigation of the effects of aromatic substitution and
the nature of the hydroxyalkyl chain of 2 on HDL eleva-
tion. The structure–activity relationship will be pre-
sented in this letter.
The aromatic substituted thioureas (5) were readily pre-
pared by reaction of a phenyl isothiocyanate with etha-
nolamine in methylene chloride (Scheme 1). Conversely,
chain variants 7 were synthesized by reaction of
5-chloro-2-methylphenyl isothiocyanate (6) with an
appropriate amino alcohol. In many instances the prod-
ucts precipitated from the reaction mixture were isolated
by simple filtration. All amino alcohols were commer-
cially available with the exception of the chiral piper-
idine derivatives. Cbz-Pipecolic acid was resolved with
L-Tyrosinehydrazide to give the (R)-enantiomer 8.19
Reduction of the acid with diborane followed by cata-
lytic hydrogenolysis of the protecting group gave the
Another series of analogs with the same aromatic substi-
tution pattern as 2 is shown in Table 2. Replacing the
hydroxyl group with thiol (7a) results in loss of all activ-
ity. When the hydroxyl moiety is part of an acid func-
tionality (7c) activity is also lost. Extension of the
chain by one methylene (7d) retains HDL cholesterol
elevating activity but not Apo A–I. A small series of
C-methylated derivatives 7e–i exhibited only modest in-
creases in HDL cholesterol but none raise Apo A–I
appreciably. The N-methyl analogue 7j, however, re-
tained HDL activity with no increase in TC. Conforma-
tionally restrained analogue 7k loses all activity. The
corresponding 6-membered ring analogue (not shown)
had a profile identical to 7k. Restraining the ring at
the carbon adjacent to nitrogen (prolinol derivatives 7l
and 7m) also resulted in complete loss of activity. Inter-
estingly, the analogous piperidine derivatives 7n and 7o
significantly increased HDL cholesterol by 134% and
156% over controls, respectively, however 7n had no
R2
R2
R5
R1
R1
R3
R4
R3
R4
OH
H2N
S
OH
NCS
N
H
N
H
R5
4
5
Cl
Cl
aminoalcohol
S
N
R
NCS
H
Me
Me
7
6
Scheme 1. General preparation of arylthiourea derivatives.

G. M. Coppola et al. / Bioorg. Med. Chem. Lett. 15 (2005) 809–812
Table 1. Lipid profiles of aromatic variants 5 in cholesterol-fed male rats
811
5a
R1
R2
R3
R4
R5
Dose (mg/kg/day)
HDL (%)b Apo A–I (%)b Total chol. (%)b
TG (%)b
WG (%)c
a
b
c
H
H
H
Cl
H
H
H
H
H
H
H
H
H
H
H
Me
H
Cl
H
H
H
H
H
H
H
H
H
H
H
H
Cl
H
H
Cl
H
H
H
Me
H
51
66
74
40
42
67
68
80
60
63
68
55
50
3 (NS)
79
72
À18
66
À51
À138
À70
À77
À155
À229
À56
À66
À38
À90
À117
À76e
À104
2
Cl
Cl
H
43
30 (NS)
15 (NS)
8 (NS)
17 (NS)
10 (NS)
21
À31
H
À5 (NS)
À15 (NS)
À48
d
e
Me
Me
Me
Cl
23 (NS)
53
63
À34
18
H
À8 (NS)
À16 (NS)
À13 (NS)
À27e
f
H
27
36
30e
g
h
i
Cl
Cl
Cl
Me
CF3
Cl
71
106e
OMe
H
66e
50
62
66e
75
48
9 (NS)
32
44e
39
À35
j
Me
H
0 (NS)
À32
k
2f
1d
36e
48
À15e
Me
À53
104
54
À23
À29
a Satisfactory elemental analysis obtained for all compounds.
b Relative to untreated controls. Values are significantly different (p < 0.05) relative to untreated controls unless otherwise indicated (NS).
c % Change in body weight gain relative to untreated controls.
d Mean value of 160 studies.
e Mean value of 3 studies.
f Mean value of 26 studies. TG = triglycerides. WG = weight gain.
Table 2. Lipid profile of chain variants 7 in cholesterol-fed male rats
7a
R
Dose (mg/kg/day)
36
HDL (%)b
Apo A–I (%)b
10 (NS)
Total Chol. (%)b
8 (NS)
TG (%)b
WG (%)c
SH
N
H
a
25 (NS)
À3 (NS)
À20
OMe
OH
N
H
b
c
d
e
f
36
38
74
75
76
30
33
20 (NS)
24 (NS)
3 (NS)
85
À47
À3 (NS)
10
N
H
8 (NS)
82
14 (NS)
24 (NS)
6 (NS)
20
4 (NS)
À80
O
N
H
OH
À63
Me
OH
OH
13 (NS)
32
À23
À4 (NS)
10
N
H
Me
48
1 (NS)
N
H
OH
OH
g
h
i
80
68
62
75
78
58
33
23 (NS)
8 (NS)
25 (NS)
40
À13 (NS)
30 (NS)
À1 (NS)
29 (NS)
À5 (NS)
À15
À75
À68
À47
À24
À23
N
H
N
H
À68
Me
OH
Me
N
H
60
À69
OH
N
Me
j
100
9 (NS)
À31
OH
N
k
4 (NS)
2 (NS)
OH
l
81
83
74
7 (NS)
19 (NS)
134
25 (NS)
6 (NS)
28
43
87
19
30
5 (NS)
29
N
OH
OH
m
n
N
N
15 (NS)
À36
À35
OH
o
79
50
156
104
94
54
93
À67
À29
À41
2
N
1d
À23
a Satisfactory elemental analysis obtained for all compounds.
b Relative to untreated controls. Values are significantly different (p < 0.05) relative to untreated controls unless otherwise indicated (NS).
c % Change in body weight gain relative to untreated controls.
d Mean value of 160 studies. TG = triglycerides. WG = weight gain.

812
G. M. Coppola et al. / Bioorg. Med. Chem. Lett. 15 (2005) 809–812
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effect on Apo A–I whereas 7o raised Apo A–I 94%,
although both significantly raised TC, reduced triglyce-
rides, and had modest effects on reduction of body
weight gain. The sulfur atom of the thiourea in 2 is
required for activity. The corresponding urea analogue
of 2 (compound 11) is totally inactive.
Cl
O
OH
N
H
N
H
CH3
11
The liver enzymes ALT, AST, and ALP were measured
for compounds 2, 5h, 7n, and 7o. The liver enzymes for 2
and 5h remained at normal levels relative to untreated
controls. Elevation of ALP (87%) was observed for 7n
whereas all three enzyme levels were elevated for 7o
(ALT, 142%; AST, 95%; ALP, 72%).
In conclusion, 1-hydroxyalkyl-3-phenylthioureas have
been shown to be effective HDL and Apo A–I elevating
agents as well as exhibiting TG-lowering properties. Sev-
eral examples were superior to gemfibrozil. Aryl analogs
5 consistently showed reductions in body weight gain.
Compound 7j had a profile similar to 1 although it
was superior at lowering TG. The most active com-
pounds relative to controls were 7n and 7o. These com-
pounds also raised TC levels, although much of that was
in the HDL fraction.
´
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