Design and synthesis of disubstituted (4-piperidinyl)-piperazine derivatives as potent acetyl-CoA carboxylase inhibitors

Article abstract of DOI:10.1016/j.bmcl.2010.04.134

Acetyl-CoA carboxylases (ACCs), the rate limiting enzymes in de novo lipid synthesis, play important roles in modulating energy metabolism. The inhibition of ACC has demonstrated promising therapeutic potential for treating obesity and type 2 diabetes mellitus in transgenic mice and preclinical animal models. We describe herein the structure-based design and synthesis of a novel series of disubstituted (4-piperidinyl)-piperazine derivatives as ACC inhibitors. Our structure-based approach led to the discovery of the indole derivatives 13i and 13j, which exhibited potent in vitro ACC inhibitory activity.

Full text of DOI:10.1016/j.bmcl.2010.04.134

Bioorganic & Medicinal Chemistry Letters 20 (2010) 3965–3968
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Design and synthesis of disubstituted (4-piperidinyl)-piperazine derivatives
as potent acetyl-CoA carboxylase inhibitors
a
b
c
a
Tomomichi Chonan a, , Hiroaki Tanaka , Daisuke Yamamoto , Miyoko Yashiro , Takahiro Oi ,
*
Daisuke Wakasugi a, Ayumi Ohoka-Sugita b, Fusayo Io b, Hiroko Koretsune b, Akira Hiratate a
a Medicinal Chemistry Laboratories, Taisho Pharmaceutical Co., Ltd, 1-403 Yoshino-cho, Kita-ku, Saitama-shi, Saitama 331-9530, Japan
b Molecular Function and Pharmacology Laboratories, Taisho Pharmaceutical Co., Ltd, 1-403 Yoshino-cho, Kita-ku, Saitama-shi, Saitama 331-9530, Japan
c Research Computer System, Taisho Pharmaceutical Co., Ltd, 1-403 Yoshino-cho, Kita-ku, Saitama-shi, Saitama 331-9530, Japan
a r t i c l e i n f o
a b s t r a c t
Article history:
Acetyl-CoA carboxylases (ACCs), the rate limiting enzymes in de novo lipid synthesis, play important
roles in modulating energy metabolism. The inhibition of ACC has demonstrated promising therapeutic
potential for treating obesity and type 2 diabetes mellitus in transgenic mice and preclinical animal
models. We describe herein the structure-based design and synthesis of a novel series of disubstituted
(4-piperidinyl)-piperazine derivatives as ACC inhibitors. Our structure-based approach led to the dis-
covery of the indole derivatives 13i and 13j, which exhibited potent in vitro ACC inhibitory activity.
Ó 2010 Elsevier Ltd. All rights reserved.
Received 26 January 2010
Revised 14 April 2010
Accepted 28 April 2010
Available online 4 May 2010
Keywords:
Acetyl-CoA carboxylase
Inhibitor
(4-Piperidinyl)-piperazine
Acetyl-CoA carboxylase (ACC) is a biotin-dependent homo olig-
omeric protein composed of a carboxyltransferase (CT), a biotin
carboxyl carrier protein and biotin carboxylase (BC) domains.
ACC is involved in the synthesis of malonyl-CoA from acetyl-CoA
in an ATP-dependent manner. Malonyl-CoA works not only as a
substrate for de novo fatty acid synthesis, but also as an allosteric
inhibitor of carnitine palmitoyl transferase (CPT-1), a key enzyme
that positively regulates mitochondrial b-oxidation. Therefore,
inhibition of ACC is expected to reduce de novo fatty acid synthesis
(FAS) and to enhance fatty acid b-oxidation (FAO) through disinhi-
bition of CPT-1, which might benefit treatment of metabolic disor-
ders such as obesity and diabetes.1
Two ACC isoforms, ACC1 and ACC2, have been cloned in rodents
and humans. ACC1 is predominantly expressed in lipogenic tissues
such as liver and adipose tissue, while ACC2 is predominantly
expressed in oxidative tissues such as liver, skeletal muscle and
heart.2 Recent studies reported by Harada et al. indicate that hepa-
tic ACC2 could partially cover ACC1 function as a backup system.3
Consequently, reduction of malonyl-CoA levels in these tissues by
ACC1/2 non-selective inhibitors is expected to reduce de novo fatty
acid synthesis and triglyceride (TG)-rich lipoprotein secretion in li-
ver, while increasing fatty acid b-oxidation in liver and skeletal
muscle. Therefore, an ACC1/2 non-selective inhibitor might pro-
vide a novel therapeutic approach for treating various metabolic
disorders.
We previously reported preliminary structure–activity relation-
ships (SAR) of disubstituted (4-piperidinyl)-piperazine derivatives
and the discovery of compounds 1 and 2 as potent ACC1/2 non-
selective inhibitors (Fig. 1).4 In this Letter, further optimization of
compound 1 by modification of the 2,6-diarylpyridine portion is
reported.
To obtain clues for further optimization, the previously con-
structed ACC-compound 1 docking model was reexamined.5 The
sites in which the 2,6-diaryl groups on the left-hand pyridine
group fit were found to be quite different. One site provided a tight
lipophilic space, while the other site provided a large space, which
was connected to the acetyl-CoA binding site. Thus, we hypothe-
sized that appropriate modification of one of the 2,6-diphenyl
* Corresponding author.
E-mail address: tomomichi.chonan@po.rd.taisho.co.jp (T. Chonan).
Figure 1. Structure and ACC activity of compounds 1 and 2.
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.04.134

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T. Chonan et al. / Bioorg. Med. Chem. Lett. 20 (2010) 3965–3968
Scheme 1. Reagents and conditions: (a) (COOEt)2, Na, EtOH, rt, 97%; (b) 2-cyanoacetamide, K2CO3, acetone, 60 °C, 57%; (c) concd H2SO4, H2O, 160 °C, 63%; (d) POCl3, PCl5,
110 °C, obtained as a mixture with 2-oxo-6-phenyl-1,2-dihydropyridine-4-carbonyl chloride (40) (4:40 = 3.5:1); (e) 1-{1-[(1-acetylpiperidin-4-yl)carbonyl]piperidin-4-
yl}piperazine (5), Et3N, CHCl3, 0 °C, 48%; (f) arylboronic acid or arylboronic acid pinacol ester, Pd(PPh3)2Cl2, Na2CO3, CH3CN/H2O, 90 °C.
groups of compound 1 would influence the acetyl-CoA binding site,
resulting in interference of acetyl-CoA binding and thereby
improvement of ACC inhibitory activity.
Table 1
In vitro activities of ACC inhibitors 1, 7a–7m
The synthetic approaches employed to prepare various substi-
tuted aryl derivatives are outlined in Schemes 1 and 2. Scheme 1
illustrates the synthesis of compounds 7a–m and 13a–j. The
synthesis of the starting 2-chloro-6-phenyl isonicotinoyl chloride
(4) was reported by Isler et al.6 Acid chloride 4 was treated with
1-{1-[(1-acetylpiperidin-4-yl)carbonyl]piperidin-4-yl}piperazine (5)4
to give amide 6, which was coupled with the desired aryl boro-
nic acid or aryl boronic acid pinacol ester7 to afford target com-
pounds 7a–m and 13a–j. Preparation of the indole derivatives
12a–k is illustrated in Scheme 2. Commercially available 2,6-
dichloroisonicotinoic acid (8) was coupled with 5-indole boronic
acid pinacol ester (9) followed by condensation with 5 to give
11. Compound 11 was coupled with the desired arylboronic acid
or arylboronic acid pinacol ester to furnish the target compounds
12a–k.
The derivatives were screened against partially purified human
liver ACC enzymes. Among the tested compounds, the selected po-
tent compounds were further evaluated for their ability to de-
crease FAS and increase FAO in HepG2 cells. FAS inhibition was
assessed by measuring the decrease in [14C] acetate incorporation
into cellular lipids,1a and the effects on FAO were evaluated by
measuring the generation of T2O in the culture media.8
a
Compd
R2
ACC IC50 (nM)
1
Phenyl
4-HO-phenyl
126
47
47
42
80
27
75
47
70
55
47
42
57
54
7a
7b
7c
7d
7e
7f
7g
7h
7i
3-HOCH2-phenyl
4-HOCH2-phenyl
4-H2NCO-phenyl
4-HOCH2CH2-phenyl
4-HOOCCH2-phenyl
4-HOCH2CH2O-phenyl
4-HOCH2CH2CH2-phenyl
1H-Indole-5-yl
7j
7k
7l
1H-Indole-6-yl
1H-Indazole-5-yl
1H-Indazole-6-yl
Indolin-2-one-5-yl
7m
The unsymmetric substituted derivatives 7a–m were initially
evaluated (Table 1). Substitution of the 3- or 4-position of the phe-
nyl ring with polar functional groups such as hydroxyl, carbamoyl,
or carboxylic acid groups as in 7a–h led to a three to fourfold
improvement in potency. Of these, the 4-hydroxyethylphenyl
derivative 7e displayed the most potent activity (IC50 = 27 nM).
However, compound 7e exhibited considerably reduced activity
in the cell based FAS assay (IC50 = 1622 nM). The discrepancy be-
tween the enzyme and cell activities was considered to be due to
a
Inhibitory activity of compounds on the malonyl-CoA synthesis of human
ACC1/2. The IC50 value represents the mean from at least two independent
experiments.
the limited cell permeability of 7e. Indeed, 7e was found to have
poor membrane permeability: PAMPA permeability of 7e was
6.7 ꢀ 10ꢁ6 cm/s at pH 6.2. In contrast, compound 1 exhibited high
permeability in the PAMPA assay (61.5 ꢀ 10ꢁ6 cm/s at pH 6.2) and
Scheme 2. Reagents and conditions: (a) 8, Pd(PPh3)4, Na2CO3, DME/H2O/EtOH = 7/3/2, 150 °C/20 min (microwave); (b) 1-{1-[(1-acetylpiperidin-4-yl)carbonyl]piperidin-4-
yl}piperazine (5), WSC, HOBt, CHCl3, rt, 62% (from 8); (c) arylboronic acid or arylboronic acid pinacol ester, Pd(PPh3)2Cl2, Na2CO3, CH3CN/H2O, 150 °C/20 min (microwave),
73–86%.

T. Chonan et al. / Bioorg. Med. Chem. Lett. 20 (2010) 3965–3968
3967
exhibited a relatively small discrepancy between the enzyme and
cell assays (IC50 = 540 nM). Subsequently, fused heterocycle deriv-
atives were investigated. The 1H-indole, 1H-indazole and indoline-
2-one derivatives 7i–m were found to be two to three fold more
potent than compound 1. Herein, we focus on the 1H-indole-5-yl
derivative 7i and describe further SAR studies for the substituent
effects on the 6-phenyl and 2-indolyl groups. Membrane perme-
ability of 7i was good (PAMPA, Pe 46.5 ꢀ 10ꢁ6 cm/s at pH 6.2)
and the cell activity of 7i exhibited an IC50 value of 467 nM.
Substituent effects on the 6-phenyl group of 7i were evaluated
(Table 2). The introduction of fluorine or methyl groups to the phe-
nyl ring at the 3- or 4-position are essentially equipotent to 7i. The
3- or 4-methoxy derivatives 12e and 12f provides slight increased
in potency. The trifluoromethyl derivatives 12g and 12h were less
potent than the parent 7i. The 3,4-disubstituted derivatives 12i,
12j and 12k were as well or less potent than the mono-substituted
derivatives 12a, 12d, 12e and 12f. No significant substitution ef-
fects were observed with this modification. Most likely, the 6-phe-
nyl group is placed in the tight lipophilic pocket while the 2-
indolyl group is in the large space connected to the acetyl-CoA
binding site.
formed with the acetyl-Tyr1974 and amide-Glu22300.4 The 2-
methyl and 3-cyano substituents on the indole group of 13i are
in close proximity to acetyl-CoA in the acetyl-CoA binding site
where the nitrogen atom of the cyano group of compound 13i
and the oxygen atom of the phosphate group of acetyl-CoA are
close enough to cause steric repulsion (3.19 Å). Consequently,
Table 3
In vitro activities and metabolic stability in human liver microsomes of ACC inhibitors
7i, 13a–13j
Finally, substituent effects on the 2-indolyl group of 7i were
examined (Table 3). The mono-methyl derivatives 13a–c were
equipotent to the parent 7i. Among the dimethyl derivatives
13d–f, the 2,3-dimethyl derivative 13f showed the most potent
activity. The trimethyl derivative 13g was less potent than 13f.
Hence, we focused on 2,3-disubstituted derivatives. The 3-ethyl
derivative 13h was substantially less potent than the correspond-
ing dimethyl derivative 13f. However, the 2-methyl-3-cyano deriv-
ative 13i and 2-N,N-dimethylaminomethyl-3-methyl derivative
13j had significantly potent activity.
a
Compd
R5
R6
R7
ACC IC50 (nM)
hMSb (%)
7i
H
Me
H
H
H
Me
H
Me
H
Me
Me
H
H
H
Me
H
Me
Me
Me
Et
CN
Me
55
69
59
36
117
127
33
105
169
9.7
8.4
64
13a
13b
13c
13d
13e
13f
13g
13h
13i
13j
85
NDc
72
H
Me
Me
H
Me
H
NDc
NDc
99
NDc
NDc
NDc
NDc
Me
Me
CH2NMe2
H
H
Molecular modeling studies of compound 13i (in yellow) are
shown in Figure 2 along with overlays of CP-640186 (in purple)
and acetyl-CoA (in brown).5,9 The proposed binding mode of com-
pound 13i and hACC2 indicates that two hydrogen bonds are
a
Inhibitory activity of compounds on the malonyl-CoA synthesis of human
ACC1/2. The IC50 value represents the mean from at least two independent
experiments.
b
% Remaining after 15-min incubation with human liver microsomes (1 mg
protein/mL).
c
No data.
Table 2
In vitro activities and PAMPA permeability of ACC inhibitors 7i, 12a–12k
R3
R4
ACC IC50 (nM)
PAMPA Peb (ꢀ10ꢁ6 cm/s)
a
Compd
7i
H
F
H
Me
H
MeO
H
CF3
H
F
F
H
H
F
H
Me
H
MeO
H
CF3
Me
MeO
MeO
55
33
48
37
30
32
21
100
72
49
61
30
46.5
19.9
44.3
28.1
39.8
NDc
21.5
NDc
NDc
NDc
NDc
NDc
12a
12b
12c
12d
12e
12f
12g
12h
12i
12j
12k
MeO
a
Inhibitory activity of compounds on the malonyl-CoA synthesis of human
ACC1/2. The IC50 value represents the mean from at least two independent
experiments.
b
Effective permeability at pH 6.2.
No data.
c
Figure 2. Optimized binding mode of 13i and acetyl-CoA.

3968
T. Chonan et al. / Bioorg. Med. Chem. Lett. 20 (2010) 3965–3968
2. Abu-Elheiga, L.; Matzuk, M. M.; Abo-Hashema, K. A.; Wakil, S. J. Science 2001,
291, 2613.
3. Harada, N.; Oda, Z.; Hara, Y.; Fujinami, K.; Okawa, M.; Ohbuchi, K.; Yonemoto,
M.; Ikeda, Y.; Ohwaki, K.; Aragane, K.; Tamai, Y.; Kusunoki, J. Mol. Cell. Biol.
2007, 27, 1881.
compound 13i would be predicted to interfere in the binding of
acetyl-CoA, leading to the observed improvement in the ACC inhib-
itory activity of 13i.
Compound 13f was metabolically stable in human liver micro-
somes.10 In HepG2 cell assays, compound 13f showed dose-depen-
dent inhibition of FAS with an IC50 of 290 nM. In addition, 13f
4. Chonan, T.; Oi, T.; Yamamoto, D.; Yashiro, M.; Wakasugi, D.; Tanaka, H.; Ohoka-
Sugita, A.; Io, F.; Koretsune, H.; Hiratate, A. Bioorg. Med. Chem. Lett. 2009, 19,
6645.
5. Modeling studies were carried out using MOE (see Ref.4). The homology model
of the CT domain of human ACC2 from the crystal structure of yeast ACC in
complex with CP-640186 (PDB ID: 1W2X) was used. MOE (Molecular
Operating Environment); Chemical Computing Group: Montreal, Quebec,
Canada, 2006.
showed good solubility in water (1116 lg/mL) and good perme-
ability (PAMPA, Pe 32.8 ꢀ 10ꢁ6 cm/s at pH 6.2).
In summary, the synthesis and evaluation of novel unsymmetric
disubstituted pyridines as ACC1/2 inhibitors are reported. Com-
pounds 13i and 13j displayed excellent potency as non-selective
ACC1/2 inhibitors through our structure-based approach. This
work is expected to provide helpful information for the discovery
of novel structural ACC inhibitors.
6. Isler, O.; Gutmann, H.; Straub, O.; Fust, B.; Böhni, E.; Studer, A. Helv. Chim. Acta
1955, 118, 1033.
7. Typical procedure. In a glass vial was placed 2-methyl-3-cyano-5-bromoindole
(331 mg, 1.41 mmol), bis(pinacolate)diboron (536 mg, 2.11 mmol), Pd(dppf)Cl2
(115 mg, 0.141 mmol), potassium acetate (414 mg, 4.22 mmol) and DMSO
(1.50 mL) under Ar atmosphere. The sealed vial was heated at 90 °C for 24 h
and allowed to cool to ambient temperature. The insoluble material was
removed by filtration and washed with CHCl3. The filtrate was concentrated in
vacuo and the residue was purified by silica gel column chromatography (0–
40% AcOEt/n-hexane) to afford 2-methyl-3-cyano-5-indole boronic acid
pinacol ester (250 mg, 0.89 mmol) as a colorless powder. 1H NMR (200 MHz,
CDCl3) d 1.37 (s, 12H), 2.63 (s, 3H), 7.29–7.37 (m, 1H), 7.64–7.73 (m, 1H), 8.19
(s, 1H), 8.49 (br s, 1H). MS ESI/APCI Dual m/z 283 [M+H]+.
8. Anne, M.; William, J. R. J. Clin. Invest. 1987, 79, 59.
Acknowledgments
The authors thank Yoshiki Fukasawa for collecting DMPK data.
The authors also thank Drs. Nagaaki Sato and Shigeru Tokita for
editing this manuscript.
9. (a) Zhang, H.; Yang, Z.; Shen, Y.; Tong, L. Science 2003, 299, 2064; (b) PDB ID:
1OD2.
References and notes
10. Metabolic stability in liver microsomes. 5
37 °C in 1 mg/mL human or rat microsomes supplemented with 1.5 mM
glucose-6-phosphate, 0.16 mM b-nicotinamide-adenine dinucleotide
lM of compound was incubated at
1. (a) Harwood, H. J., Jr.; Petras, S. F.; Shelly, L. D.; Zaccaro, L. M.; Perry, D. A.;
Makowski, M. R.; Hargrove, D. M.; Martin, K. A.; Tracey, W. R.; Chapman, J. G.;
Magee, W. P.; Dalvie, D. K.; Soliman, V. F.; Martin, W. H.; Mularski, C. J.;
Eisenbeis, S. A. J. Biol. Chem. 2003, 278, 37099; (b) Harwood, H. J., Jr. Exp. Opin.
Cardiovasc. Renal. 2005, 9, 267; (c) Corbett, J. W.; Harwood, H. J., Jr. Rec. Pat.
Cardiovasc. Drug Discov. 2007, 2, 162.
phosphate, 1 U/mL glucose-6-phosphate dehydrogenase, 250 mM phosphate
buffer, 2.4 mM magnesium chloride and 69 mM potassium chloride.
Concentrations of the test compound were determined by LC-MS/MS.
Metabolic stability was calculated from the ratio of the test compound
concentration at 0 min to its concentration after a 15-min incubation.