Novel 1,4-diarylpiperidine-4-methylureas as anti-hyperlipidemic agents: Dual effectors on acyl-CoA:cholesterol O-acyltransferase and low-density lipoprotein receptor expression

Article abstract of DOI:10.1016/j.bmcl.2009.01.020

A family of 1,4-diarylpiperidine-4-methylureas were designed and synthesized as novel dual effectors on ACAT and LDL receptor expression. We examined SAR of the synthesized compounds focusing on substitution at the three aromatic parts of the starting compound 1 and succeeded in identifying essential substituents for inhibition of ACAT and up-regulation of hepatic LDL receptor expression. Especially, we found that compound 12f, which can easily be prepared, has biological properties comparable to those of SMP-797, a promising ACAT inhibitor. In addition, the in vitro effects of 12f on lipid metabolism were substantially superior to those of a known ACAT inhibitor, Avasimibe.

Full text of DOI:10.1016/j.bmcl.2009.01.020

Bioorganic & Medicinal Chemistry Letters 19 (2009) 1062–1065
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Novel 1,4-diarylpiperidine-4-methylureas as anti-hyperlipidemic agents:
Dual effectors on acyl-CoA:cholesterol O-acyltransferase and low-density
lipoprotein receptor expression
*
Shigehiro Asano , Hitoshi Ban, Kouichi Kino, Katsuhisa Ioriya, Masami Muraoka
Research Division, Dainippon Sumitomo Pharma Co., Ltd, 3-1-98 Kasugade-naka, Konohana-ku, Osaka 554-0022, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
A family of 1,4-diarylpiperidine-4-methylureas were designed and synthesized as novel dual effectors on
ACAT and LDL receptor expression. We examined SAR of the synthesized compounds focusing on substi-
tution at the three aromatic parts of the starting compound 1 and succeeded in identifying essential sub-
stituents for inhibition of ACAT and up-regulation of hepatic LDL receptor expression. Especially, we
found that compound 12f, which can easily be prepared, has biological properties comparable to those
of SMP-797, a promising ACAT inhibitor. In addition, the in vitro effects of 12f on lipid metabolism were
substantially superior to those of a known ACAT inhibitor, Avasimibe.
Received 1 November 2008
Revised 7 January 2009
Accepted 8 January 2009
Available online 11 January 2009
Keywords:
ACAT inhibitor
LDL receptor up-regulator
1,4-Diarylpiperidine-4-methylureas
Anti-hyperlipidemic agent
Ó 2009 Elsevier Ltd. All rights reserved.
Hyperlipidemia and related cardiovascular diseases, such as
atherosclerosis, are risk factors for stroke and coronary heart dis-
eases, which are among the leading causes of death in many indus-
trialized countries. Acyl-coenzyme A:cholesterol acyltransferase
(ACAT), which catalyzes intracellular cholesterol esterification,1
plays important roles in several physiological processes, such as
absorption of dietary and biliary cholesterol in the small intestine,2
secretion of very low-density lipoprotein (VLDL) in the liver,3 and
accumulation of cholesteryl esters in macrophages in the arterial
wall.4 It is therefore believed that inhibition of ACAT may lower
plasma cholesterol level and help prevent atherosclerosis.
It is known that expression of hepatic low-density lipoprotein
(LDL) receptor is extremely important for lipid homeostasis. Stat-
ins, which are HMG-CoA reductase inhibitors that increase hepatic
LDL receptor expression, are known to be effective in lowering to-
tal cholesterol and LDL cholesterol levels in hyperlipidemic pa-
tients.5 From these findings, it is believed that dual effectors on
ACAT and LDL receptor expression may be promising agents in
the treatment of hyperlipidemia and related cardiovascular
diseases.
SMP-797 at a concentration much higher than that needed for
LDL receptor up-regulation, that is, 1 M, had no effect on choles-
l
terol synthesis in HepG2 cells. From these findings, we expect
SMP-797 to be a next generation anti-hyperlipidemic agent.
Although SMP-797 is a promising compound, its preparation re-
quires eight reaction steps.7 Our aim is therefore to find back-up
compounds with different mother templates and easy synthetic
routes. Based on previous studies of SMP-797 (Fig. 1), the 2,6-diiso-
propylphenylurea part is essential for ACAT inhibitory activity.
Therefore we examined replacement of the 1,8-naphthyridine moi-
ety with other hydrophilic groups and succeeded in finding com-
OH
O
H
N
H
N
NH2
B
O
OMe
N
N
O
We have previously reported a novel ACAT inhibitor, SMP-797
(Fig. 1), with potent cholesterol-lowering activity and direct
regressive effect on atherosclerotic lesions.6 We have also shown
that SMP-797 up-regulate hepatic LDL receptor expression, an ef-
fect not reported with known ACAT inhibitors. Furthermore,
HCl, H2O
SMP-797
H
N
H
N
A
N
O
C
1
* Corresponding author. Tel.: +81 6 6466 5185; fax: +81 6 6466 5287.
E-mail address: shigehiro-asano@ds-pharma.co.jp (S. Asano).
Figure 1. Structures of SMP-797 and compound 1.
0960-894X/$ - see front matter Ó 2009 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2009.01.020

S. Asano et al. / Bioorg. Med. Chem. Lett. 19 (2009) 1062–1065
1063
5a R2=CHPh2
5f R2=3-OMe-C6H4
MeO
MeO
2
5b R2=Me
5g R =4-OMe-C6
H
4
H
5c R2=nPr
5h R =2-O Bu-C6
2
n
b
5i R2=2-OCF -C6H44
HO
HO
5d R2=Ph
3
CN
CN
4
5e R2=2-OMe-C6H4
5j R2=2-OCH2CF3-C6H4
N
R2
a
c
3
R1
Cl
CN
3
2
R1
6a R1=H
2
OMe
6b R1=3-F
N
OMe
Cl
CN
6c R1=3-CF3
6d R1=2-OMe
6e R1=4-OMe
N
7
Scheme 1. Synthesis of Nitriles 5a–j and 6a–e. Reagents and conditions: (a) 1—NaH, BrCH2CH2OTHP, DMF, 0 °C ? rt; 2—p-TsOHꢀH2O, MeOH, rt, 74%; (b) 1—triflic anhydride,
DIPEA, EtOAc, ꢁ30 °C; 2—R2NH2 4, DIPEA, ꢁ30 °C ? rt, 26–89%; (c) 7, CH3(CH2)15P+Bu3ꢀBrꢁ, 50% NaOHaq, 100 °C, 52–68%.
pound 1 as a potent ACAT inhibitor. The IC50 of 1 toward ACAT
(IC50 = 35 nM) was comparable to that of SMP-797 (IC50 = 31 nM).
Herein, we reported the design, synthesis, and biological activity
of a novel series of 1,4-diarylpiperidine-4-methylureas as anti-
hyperlipidemic agents.
which were either commercially available or synthesized by
known literature procedures. The stable key intermediates 9a
and 9b were prepared by catalytic hydrogenation of the corre-
sponding 8b and 8c followed by selective protection of the less
hindered amino group by tert-butylcarbonyl group (Boc). Thus,
the desired p-nitrophenylcarbamates 10a–c could be obtained in
excellent yields.
The ureas 1, 11, and 12 were achieved as illustrated in Scheme
3. These ureas were prepared in excellent yields by coupling reac-
tion of the primary amines with the corresponding phenylcarba-
mates 10a–c. The primary amines provided by reduction of the
nitrile moiety were used following the coupling reaction without
purification because of their polarity. In the case of compound
11b, the benzohydryl group of compound 11a was removed by pal-
ladium-catalyzed hydrogen transfer reaction with ammonium for-
mate. In the case of urea 12, Boc group was removed by 10%
methanolic HCl in the final step to give the desired compounds
as HCl salts.
Compounds 1, 11b–e, and 12a–e inhibitory activity for ACAT
and up-regulation of LDL receptor expression are shown in Table
1. As compared to 1 or 11e, the inhibitory activity of 11b, 11c, or
11d for ACAT decreased more than 10-fold. These findings suggest
that the aryl substituent on the nitrogen of the piperidine (A-part)
is important for ACAT inhibition. Compounds 1, 11e, and 12a–e
inhibited ACAT with similar IC50 values, however, only 12c up-reg-
ulated LDL receptor expression. From these results it is assumed
that the 2-methoxyphenyl group in A-part (Fig. 1) and the 4-ami-
no-2,6-diisopropylphenyl group in C-part are essential for the dual
inhibition of ACAT and up-regulation of LDL receptor expression.
Next, we turned our attention to the effects of a substitution on
the phenyl ring of B-part (Fig. 1). The inhibitory activity for ACAT of
compounds 12c and 12i–m and their up-regulation of LDL receptor
expression are summarized in Table 2. Substitution on the phenyl
ring of B-part was well tolerated for ACAT inhibitory activity. How-
ever, for up-regulation of LDL receptor expression, electron donat-
ing groups, such as a methoxy group, were preferred to electron-
withdrawing groups.
Finally, in order to improve both the inhibitory activity for ACAT
and the up-regulatory effect on LDL receptor expression, we car-
ried out SAR studies on the 2-alkoxy groups of A-part. As shown
in Table 3, 2-alkoxyl substituents on the phenyl ring were well tol-
erated with IC50 values for inhibition of ACAT ranging from 32 to
68 nM. Interestingly, the up-regulatory effect on LDL receptor
expression was improved in the case of n-butoxy (12f)12 and fluor-
oalkoxy (12g and 12h) as compared to that of compound 12c.
These findings indicate that an increase in compounds hydropho-
bicity is effective in improving both the inhibitory activity for ACAT
We initially synthesized the precursor nitriles 5 and 6 to afford
the ureas 11 and 12. These nitriles were prepared by two synthetic
methods using different functional groups (Scheme 1). The first
synthetic method was conversion of the N-substituted piperidines
in part A,Figure 1. The diol 3 was prepared by common dialkylation
of the 3-methoxyphenylacetonitrile with the commercially avail-
able 2-(2-bromoethoxyl)tetrahydro-2H-pyran followed by meth-
anolysis. The diol 3 thus obtained was converted to the nitriles
5a–j by one-pot preparation via bis-triflate with the appropriate
amines 4 (R2NH2).8 The second synthetic method was conversion
of the substituent on the phenyl ring in part B, Figure 1. The nitriles
6a–e were prepared in moderate yields by dialkylation of the com-
mercially available phenylaceto-nitriles 2 with N,N-bis(2-chloro-
ethyl)anisidine9
7
in the presence of
a
catalytic amount of
phosphonium bromide.10
The p-nitrophenylcarbamates 10a–c were obtained as illus-
trated in Scheme 2. The carbamates were synthesized in a few
reaction steps from the 2,6-diisopropylanilines 8a, 9a,11 and 9b,7b
R3
4'
R3
4'
a
H2N
H2N
3'
3'
8a R3=H
8b R3=3'-NO2
8c
9a R3=3'-NHBoc
9b R3=4'-NHBoc
b
R3=4'-NO2
b
R3
4'
H
O
N
3'
O
O2N
10a R3=H
10b R3=3'-NHBoc
10c
R3=4'-NHBoc
Scheme 2. Synthesis of phenylcarbamates 10a–c. Reagents and conditions: (a)
1—H2, 10% Pd/C, MeOH, rt; 2—Boc2O, 2 N NaOHaq, THF, rt, 75–87%; (b)
p-NO2C6H4OCOCl, THF, rt, 78–95%.

1064
S. Asano et al. / Bioorg. Med. Chem. Lett. 19 (2009) 1062–1065
R2=CHPh2
MeO
11a
c
11b R2=H
11c R2=Me
11d R2=nPr
H
N
H
4
N
4
R2=Ph
3
2
N
1
R1
N
R2
O
O
3
2
b
11e R2=2-OMe-C6H4
R1
N
a
CN
NH2
d, e
4
R2
R2
2HCl
3
2
R1
N
5a-j, 6a-e
R3
4'
H
N
H
N
R2
3'
12a R1=3-OMe R2=Ph
R3=4'-NH2
R3=3'-NH2
R3=4'-NH2
R3=4'-NH2
R3=4'-NH2
R3=4'-NH2
R3=4'-NH2
R3=4'-NH2
R3=4'-NH2
R3=4'-NH2
R3=4'-NH2
R3=4'-NH2
R3=4'-NH2
12b R1=3-OMe R2=2-OMe-C6H4
12c R1=3-OMe R2=2-OMe-C6H4
12d R1=3-OMe R2=3-OMe-C6H4
12e R1=3-OMe R2=4-OMe-C6H4
12f
R1=3-OMe R2=2-OnBu-C6H4
12g R1=3-OMe R2=2-OCF-C6H4
3
R1=3-OMe R2=2-OCH CF3-C6H4
12h
12i
12j
12k
12l
2
2
R1=H
R =2-OMe-C6
H
R1=3-F
R1=3-CF
R2=2-OMe-C6H44
R2=2-OMe-C6H4
3
R1=2-OMe R2=2-OMe-C6H4
R1=4-OMe R2=2-OMe-C6H4
12m
Scheme 3. Synthesis of ureas 1, 11a–e and 12a–m. Reagents and conditions: (a) LiAlH4, THF, reflux; (b) 10a, THF, rt, 85–92%; (c) 10% Pd/C, HCO2NH4, EtOH, reflux, 36%; (d)
10b or 10c, THF, rt; (e) 10% HCl/MeOH, rt, 70–91%.
and the up-regulatory effect on LDL receptor expression. Particu-
larly, compound 12f demonstrated biological properties compara-
ble to those of SMP-797.
In summary, we disclose here a new class of piperidine-based
ACAT inhibitors. These compounds, which like SMP-797 show po-
tent ACAT inhibitory activity and remarkable up-regulation of he-
patic LDL receptor expression, can easily be synthesized in three to
five reaction steps. Furthermore, these compounds in vitro activity
on lipid metabolism was substantially superior to that of a known
ACAT inhibitor, Avasimibe (IC50 = 479 nM, in house data).6,13 How-
ever, the solubility of these compounds, including the selected 12f
was not high enough (e.g., 12f; 0.0003 mg/mL, at pH 7.4). In order
to improve the solubility further optimization studies are neces-
sary. In addition, studies to unveil the mechanism by which the
synthesized compounds up-regulate hepatic LDL receptor expres-
sion are underway.
Table 1
Effects of a substitution on the nitrogen of piperidine (A-part) and 2,6-diisopropyl-
phenyl (C-part) on biological activity
MeO
Table 2
R3
4'
3'
H
N
H
N
Effects of a substitution on the phenyl ring (B-part) on biological activity
A
N
R2
O
C
4
B
3
2
Compound R2
R3
ACAT inhibition LDL receptor expressionb
R1
N
a
IC50 (nM)
(100 nM)
H
H
11b
H
H
H
H
H
H
>1000
664
547
35
ntc
ntc
ntc
MeO
N
N
NH2
11c
11d
1
Me
nPr
Ph
O
d
ꢁ
2HCl
11e
2-OMe-C6H4
Ph
47
ꢁ
Compound
R1
ACAT inhibition
IC50 (nM)
LDL receptor
12ae
12be
12ce
12de
12ee
SMP-797
40-NH2 40
ꢁ
d
expressionb (100 nM)
a
2-OMe-C6H4 30-NH2 81
2-OMe-C6H4 40-NH2 37
3-OMe-C6H4 40-NH2 48
4-OMe-C6H4 40-NH2 142
31
ꢁ
+
12i
12j
12k
12l
12c
12m
SMP-797
H
3-F
3-CF3
2-OMe
3-OMe
4-OMe
82
77
32
43
37
49
31
ꢁ
ꢁ
ꢁ
+
+
+
ꢁ
ꢁ
++
a
Compounds inhibitory activity for ACAT in HepG2.
b
c
Effect of compounds on expression of LDL receptor in HepG2.
Not tested.
++
d
e
a
10
l
M.
Compounds inhibitory activity for ACAT in HepG2.
Effect of compounds on expression of LDL receptor in HepG2.
b
2HCl salts.

S. Asano et al. / Bioorg. Med. Chem. Lett. 19 (2009) 1062–1065
1065
Table 3
2. (a) Field, F. J.; Salome, R. G. Biochim. Biophys. Acta 1982, 712, 557; (b) Heider, J.
G.; Pickens, C. E.; Kelly, L. A. J. Lipid Res. 1983, 24, 1127.
Effects of the 2-alkoxy substituent on the phenyl ring (A-part) on biological activity
3. (a) Drevon, C. A.; Engelhorn, S. C.; Steinberg, D. J. Lipid Res. 1980, 21, 1065; (b)
Khan, B.; Wilcox, H. G.; Heimberg, M. Biochem. J. 1989, 258, 807; (c) Cianflone,
K. M.; Yasruel, Z.; Rodriguez, M. A.; Vas, D.; Sniderman, A. D. J. Lipid Res. 1990,
31, 2045.
MeO
4. (a) Brecher, P. I.; Chobanian, A. V. Circ. Res. 1974, 35, 692; (b) Day, A. J.;
Proudlock, J. W. Atherosclerosis 1974, 19, 253; (c) Hashimoto, S.; Dayton, S.
Atherosclerosis 1977, 28, 447.
5. Endo, A. J. Lipid Res. 1992, 33, 1569.
6. Ioriya, K.; Kino, K.; Horisawa, S.; Nishimura, T.; Muraoka, M.; Noguchi, T.;
Ohashi, N. J. Cardiovasc. Pharmacol. 2006, 47, 322.
7. (a) Ban, H.; Muraoka, M.; Ioriya, K.; Ohashi, N. Bioorg. Med. Chem. Lett. 2006, 16,
44; (b) Ban, H.; Muraoka, M.; Ohashi, N. Tetrahedron 2005, 10081.
8. Asano, S.; Ban, H. Heterocycles 2008, 75, 183.
H
N
H
N
NH2
N
R2
O
A
2HCl
Compound
R2
ACAT inhibition
IC50 (nM)
LDL receptor
expressionb (100 nM)
a
9. Sera, A.; Takemura, T.; Inoue, Y.; Magara, Y.; Seguchi, K.; Goto, R. Nippon Kagaku
Zasshi 1970, 91, 494.
12c
12f
12g
12h
SMP-797
Avasimibe
2-OMe-C6H4
37
32
68
48
+
2-OnBu-C6H4
2-OCF3-C6H4
++
++
++
++
ꢁ
10. Thompson, D.; Reeves, P. J. Heterocycl. Chem. 1983, 20, 771.
11. Giumanini, A. G.; Verardo, G.; Polana, M. J. Prakt. Chem. 1988, 330, 161.
12. Compound 12f; mp 168–170 °C (dec.); 1H NMR (DMSO-d6, 300 MHz) d 0.88
(3H, t, J = 7.3 Hz), 1.08 (12H, d, J = 6.8 Hz), 1.30 (2H, m), 1.51 (2H, m), 2.39 (2H,
m), 2.51 (2H, m), 3.08 (2H, qq, J = 6.8, 6.8 Hz), 3.45 (2H, m), 3.56 (2H, m), 3.60
(2H, m), 3.81 (3H, s), 3.98 (2H, m), 6.07 (1H, s), 6.89 (1H, m), 7.01 (3H, m), 7.10
(2H, s), 7.21 (1H, d, J = 8.1 Hz), 7.36 (2H, m), 7.67 (1H, s), 8.07 (1H, m); 13C NMR
(DMSO-d6, 75 MHz) d 13.2, 18.4, 23.0, 27.7, 29.8, 29.9, 33.8, 49.0, 54.8, 68.4,
111.6, 112.6, 114.4, 117.3, 118.4, 120.7, 123.1, 129.3, 130.0, 130.3, 132.7, 148.2,
2-OCH2CF3-C6H4
31
479c
a
Compounds inhibitory activity for ACAT in HepG2.
Effect of compounds on expression of LDL receptor in HepG2.
In-house data.
b
c
151.2, 156.6, 159.4; IR (ATR)
m/z calcd for C36H51O3N4 587.3956; found 587.3936 (
Calcd for C36H50N4O3?2HCl?2.25H2O: C, 61.75; H, 8.13; N, 8.00. Found: C,
61.62; H, 8.01; N, 7.99.
m
2960, 2568, 1653, 1606, 1558 cmꢁ1; HRMS (ESI)
D
= ꢁ3.39 ppm); Anal.
References and notes
13. Lee, H. T.; Sliskovic, D. R.; Picard, J. A.; Roth, B. D.; Wierenga, W.; Hcks, J. L.;
Bousley, R. F.; Hamelehle, K. L.; Homan, R.; Speyer, C.; Stanfield, R. L.; Krause, B.
R. J. Med. Chem. 1996, 39, 5031.
1. (a) Spector, A. A.; Mathur, S. N.; Kaduce, T. L. Prog. Lipid Res. 1979, 18, 31; (b)
Suckling, K. E.; Stange, E. F. J. Lipid Res. 1985, 26, 647.