Identification of ortho-amino benzamides and nicotinamides as MCHr1 antagonists

Article abstract of DOI:10.1016/j.bmcl.2005.06.089

Several potent and efficacious MCHr1 antagonists containing an ortho-amino benzamide or nicotinamide chemotype have been identified, exemplified by 28 and 50.

Full text of DOI:10.1016/j.bmcl.2005.06.089

Bioorganic & Medicinal Chemistry Letters 15 (2005) 4174–4179
Identification of ortho-amino benzamides and nicotinamides
as MCHr1 antagonists
b,
b
Anil Vasudevan,a,* Matthew J. LaMarche, Christopher Blackburn,
*
Jennifer Lee Che,b Courtney A. Luchaco-Cullis,b Sujen Lai,b Thomas H. Marsilje,b
Michael A. Patane,b Andrew J. Souers,a Derek Wodka,a Bradley Geddes,b
Sumiao Chen,b Seven Brodjian,a Doug H. Falls,a Brian D. Dayton,a
Eugene Bush,a Michael Brune,a Robin D. Shapiro,a Kennan C. Marsh,a
Lisa E. Hernandez,a Hing L. Sham,a Christine A. Collinsa and Philip R. Kyma
aMetabolic Diseases Research, Global Pharmaceutical Research and Development, Abbott Laboratories, Abbott Park, IL 60064, USA
bMillennium Pharmaceuticals, Inc., 40 Landsdowne St. Cambridge, MA 02139, USA
Received 6 May 2005; revised 27 June 2005; accepted 29 June 2005
Abstract—Several potent and efficacious MCHr1 antagonists containing an ortho-amino benzamide or nicotinamide chemotype
have been identified, exemplified by 28 and 50.
Ó 2005 Published by Elsevier Ltd.
Melanin concentrating hormone (MCH) is an orexigenic
neuropeptide found in the lateral hypothalamus.1,2 ICV
injection of MCH stimulates food intake in mice and
rats, and mice lacking MCH are lean, hypophagic, and
have an increased metabolic rate.3 Furthermore, the
murine MCH receptor knockout displayed a normal
body weight with reduced fat mass, was hyperphagic
on regular chow, and was less susceptible to diet-in-
duced obesity.4,5 Infusion (ICV) of MCH did not induce
food intake or obesity in the knockout mice. The phar-
macological validation from these studies suggests that
MCHr1 antagonists may provide a novel therapy for
obesity.6
significant diminution of MCHr1 inhibition.8 However,
working under the assumption that 1 and 2 should inter-
act with MCHr1 in similar orientations, we hypothe-
sized that introduction of an ortho-amino group on
the benzamide scaffold (2 ! 3) should allow for confor-
mational restriction via intramolecular hydrogen bond-
ing between the amine N–H (donor) and the carbonyl
(acceptor). Not only should such compounds adopt a
similar binding motif to MCHr1 as 1, the ensuing struc-
tural simplification would allow for an additional syn-
thetic handle and increased ease of chemical
manipulation. These efforts are described in this letter.
O
O
O
O
N
N
We have previously reported the identification of cou-
marin and quinolone-containing MCHr1 antagonists,
1.7 Optimization of a distinct series of compounds orig-
inating from a high throughput screening hit led to the
identification of potent MCHr1 antagonists of general
structure 2.8 During the SAR investigation leading to
the identification of 2, introduction of hydrophobic sub-
stituents at the ortho position of the phenyl ring led to a
HN
HN
O
R
R
X
O
1
2
R = alkyl, halogen
X = O, NH, NR1
N
R1
HN
N
O
H
R
Keywords: MCH; Obesity; Benzamides; Nicotinamides; Melanin con-
centrating hormone.
X
R2
*
Corresponding authors. Tel.: +1 847 938 6594; fax: +1 847 935
0310; e-mail: Anil.Vasudevan@abbott.com
3
0960-894X/$ - see front matter Ó 2005 Published by Elsevier Ltd.
doi:10.1016/j.bmcl.2005.06.089

A. Vasudevan et al. / Bioorg. Med. Chem. Lett. 15 (2005) 4174–4179
4175
Table 1. MCHr1 binding affinity (IC50) and functional activity (IC50), in lM, of benzamide analogsa
N
R1
HN
R
O
R3
No.
R
R1
R3
IMR32 binding
0.11
IMR32 FLIPRTM
O
O
O
O
O
O
O
O
O
O
O
O
78
Cl
H
—
8
Cl
OH
0.08
0.009
0.68
0.56
0.26
0.16
0.22
0.01
0.05
0.02
0.009
0.07
0.02
0.09
0.39
0.07
0.41
0.01
0.02
0.02
0.002
0.006
0.02
0.51
0.20
—
9
Cl
NH2
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
Cl
NHCH3
Cl
NHSO2CH3
NHSO2CH3
—
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
OCH3
H
—
NHSO2CH3
—
Cl
O
—
HN
HN
N
H
Cl
O
O
O
O
O
O
O
O
O
O
O
O
O
O
0.09
1.06
0.04
0.07
0.22
0.05
0.10
1.94
0.10
—
HN
HN
HN
O
N
N
H
N
HN
HN
N
H
N
N
N
HN
HN
HN
HN
N
H
N
N
H
N
N
O
N
H
N
O
N
H
N
HN
HN
Cl
0.24
0.07
0.37
0.016
0.04
0.03
COCH3
N
O
O
O
N
OCH3
Cl
O
N
S
HN
HN
O
O
O
Cl
N
N
N
S
S
HN
HN
Cl
Cl
N
a Values are means of three experiments.

4176
A. Vasudevan et al. / Bioorg. Med. Chem. Lett. 15 (2005) 4174–4179
The synthesis of the compounds containing an ortho-
amino benzamide scaffold was accomplished via ring
opening of a substituted isatoic anhydride by a suitably
functionalized 4-amino-piperidine followed by reductive
amination with various alkyl and aryl groups using sodi-
um triacetoxyborohydride as shown in Scheme 1.
aminated compounds, though the functional potency
was compromised (27 and 26, respectively). Introduc-
tion of a 2-thiazolyl moiety afforded 28, with the best
combination of MCHr1 inhibition and functional activ-
ity. The 2-thiazolyl moiety was well tolerated with vari-
ous other R1 substituents as well, illustrated by
compounds 29 and 30.
Using these synthetic strategies, several ortho-amino
benzamide analogs were synthesized. MCHr1 binding
data for selected analogs, determined using methods de-
scribed previously,9 are shown in Table 1. Compounds
demonstrating MCHr1 binding affinity less than
100 nM were evaluated in an IMR32 FLIPR-based assay9
for functional activity. Introduction of a hydroxy or ami-
no moiety to afford 8 (MCHr1 IC50 = 80 nM) and 9
(MCHr1 IC50 = 9 nM), respectively, at the ortho position
to the benzamide resulted in an improvement in MCHr1
binding affinity compared to 7 (MCHr1 IC50 = 110 nM)8.
However, the functional potency for both analogs was
weaker than 200 nM. N-methylation of 9 resulted in a sig-
nificant reduction in MCHr1 binding affinity. Sulfonyla-
tion and urea formation at the amino group of 9 also
decreased MCHr1 binding affinity, illustrated by pipero-
nyl and para-chloro phenyl substituted analogs 11–14.
Functionalization of the ortho-amino group with alkyl
substituents larger than methyl afforded potent MCHr1
antagonists, with 15 and 17 demonstrating MCHr1 func-
tional antagonism less than 100 nM. Introduction of het-
eroaryl moieties at this position afforded interesting
results. In general, it was observed that a variety of hetero-
cyclic substituents such as imidazoles, pyrimidines, and
thiazoles afforded potent MCHr1 inhibitors, though the
nature of the R1 substituent played a major role in the
inhibitory potency of these analogs. The pyrimidine
substituted analog 18 was as potent as 9 in binding activ-
ity, though the functional potency was improved approx-
imately 3-fold. Imidazole substituted analogs were in
general less potent than 18—however, significant differ-
ences in MCHr1 binding affinity and functional antago-
nism were observed depending on the nature of the R1
substituent (20, 22, 23, and 25).
The effect of introduction of a nitrogen atom in the
benzamide scaffold to afford nicotinamide analogs was
also investigated. It was postulated that if potent
MCHr1 antagonists could be realized from this series,
they would afford different brain:plasma distribution
compared to the benzamide analogs.10 The synthesis
of these nicotinamide analogs was accomplished as
shown in Scheme 2. Acylation of 4-amino-piperidine-
1-carboxylic acid tert-butyl ester with a suitably substi-
tuted nicotinic acid, followed by nucleophilic displace-
ment, deprotection, and reductive amination afforded
the desired analogs.
The biological activities of some of the nicotinamide
analogs synthesized in this study are shown in Table 2,
and indicate that several potent MCHr1 antagonists,
some of which were also active in the FLIPR assay, were
attainable with these ortho-amino substituted nicotin-
amide analogs. Two trends were apparent in the analysis
of MCHr1 binding affinity of these nicotinamide ana-
logs—the importance of the ortho amine functionality,
as well as the influence of the R1 substituent. The latter
effect is especially apparent in the comparison of 38 with
39 and 40 with 41. Alkyl, aryl, and heteroaryl amine
moieties were generally well tolerated at R2, depending
on the R1 substituent. Similar to the benzamide scaffold,
functionalization of the ortho-amino group with thiazole
and imidazole moieties afforded potent MCHr1 inhibi-
tion and functional antagonism. Additionally, alkyl
ether substituted analogs such as 50 afforded excellent
MCHr1 inhibition and FLIPR activity. Replacement
of the chloro functionality at R with aryl moieties result-
ed in a diminution of MCHr1 affinity. Further, moving
Acylation of the ortho-amino group afforded
compounds comparable in potency to the reductively
Boc
O
N
O
R
R
N
OH
a
1
H
N
R
O
N
Cl
N
31
Cl
HN
R
a
32
O
R
O
N
R1
b
N
H
O
NH2
N
5
H2N
4
Boc
O
N
O
N
R1
R1
R
R
N
c
N
H
HN
H
N
R2
N
R2
R
b
O
33
34
NH
R2
Scheme 2. Reagents and conditions: (a) 4-amino-piperidine-1-carbox-
ylic acid tert-butyl ester, PS-DCC,11 HOBt, N,N-dimethylformamide,
25 °C (72–90%); (b) R2, N-methylpyrrolidone, lwave, 200 °C, 20 min,
(42–65%); (c) i—4 N HCl/dioxane, 25 °C, 4 h, (quantitative);
ii—R1CHO, MP-BH3CN12, 1:1 1,2-dichloroethane:CH3OH, 50 °C
(51–69%).
6
Scheme 1. Reagents and conditions: (a) Et3N, N,N-dimethylformam-
ide, 100 °C, 62–90% (b) R2CHO, NaB(OAc)3H, N,N-dimethylform-
amide, 50 °C, 12 h, 52–75%.

A. Vasudevan et al. / Bioorg. Med. Chem. Lett. 15 (2005) 4174–4179
4177
the R2 substituent to the 5-position of the nicotinamide
nucleus resulted in abrogation of MCHr1 binding affin-
ity (data not shown), consistent with the proposed bind-
ing mode alluded to above.
ortho-amino benzamide and nicotinamide analogs, we
next sought to characterize the series further in vivo, uti-
lizing murine pharmacokinetic (PK) analysis and
weight-loss efficacy studies. Accordingly, several analogs
were evaluated in a diet-induced obesity (DIO) mouse
model using methods described before,9 and selected
data are shown in Table 3.
Having successfully demonstrated potent MCHr1 bind-
ing affinity and functional antagonism with these novel
Table 2. MCHr1 binding affinity (IC50) and functional activity (IC50), in lM, of nicotinamide analogsa
N
R1
HN
2
3
R
O
4
2
5
1
N
R
No.
R
R1
R2
IMR32 binding
2.01
IMR32 FLIPRTM
—
O
O
O
O
35
Cl
Cl
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
Cl
HN
0.02
0.07
0.07
1.98
0.02
0.16
0.02
0.41
0.06
0.01
0.02
0.009
0.004
0.006
0.01
0.007
0.05
0.19
0.14
0.03
0.07
0.03
—
HN
HN
O
O
O
HN
HN
Cl
O
0.05
—
O
F
HN
HN
HN
O
O
0.02
—
O
Cl
Cl
O
HN
HN
1.22
0.03
0.07
0.02
0.008
0.009
0.02
0.06
0.02
—
OCH3
H
N
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
O
HN
HN
N
N
NH
N
HN
HN
S
N
O
S
HN
HN
HN
O
O
O
O
HN
HN
S
N
—
a Values are means of three experiments.

4178
A. Vasudevan et al. / Bioorg. Med. Chem. Lett. 15 (2005) 4174–4179
Table 3. Plasma and brain exposure of 28 and 50 in DIO mice after
10 mg/kg oral dose
50 (10)
50 (30)
Dex (10)
Vehicle
2
1
0
28
50
Plasma AUC (ng h/ml)
Brain AUC (ng h/ml)
Plasma T1/2 (h)
4104
2860
677
570
-1
3.8
7.8
2032
814
0.7
2.3
1.4
283
276
0.84
*
**
Brain T1/2 (h)
-2
-3
-4
-5
-6
**
**
**
Plasma Cmax (ng/ml)
Brain Cmax (ng/ml)
Brain/plasma AUC
**
**
**
**
**
28 (10)
Dex (10)
Vehicle
6
12
0
4
10
14
2
8
2
0
28 (30)
Time (Days)
Figure 2. Effect of compound 50 (dosed at 10 and 30 mg/kg, b.i.d.,
p.o., in 1% Tween 80 in water) on the body weight of DIO mice.
**
**
**
-2
have been designed, synthesized, and evaluated for the
treatment of obesity. The intramolecular hydrogen-
bonding network effectively mimics amino-piperidine
coumarin and amino-piperidine quinolone MCHr1
antagonists, providing a simplified scaffold amenable
to extensive SAR development. Compounds from both
these series exhibit dose-dependent sustained efficacy
in an obese murine weight-loss model.
**
**
**
**
**
-4
-6
-8
**
**
**
0
2
4
8
10 12
14
6
Time (Days)
Figure 1. Effect of compound 28 (dosed at 10 and 30 mg/kg, b.i.d.,
p.o., in 1% Tween 80 in water) on the body weight of DIO mice.
Acknowledgments
The authors thank Christopher Ogiela and Dennis Fry
for preparing the IMR-32 cells and aiding with the exe-
cution of the binding and functional assays, Paul Rich-
ardson and J. J. Jiang for MCH peptide synthesis.
Compound 28 provided high plasma concentrations,
with a Cmax of 2032 ng/ml and a half-life of ꢀ4 h. Peak
brain concentrations averaged 814 ng/ml, with a brain to
plasma AUC ratio of 0.7. In the case of 50, peak plasma
and brain concentrations were very similar (ꢀ280 ng/
ml), with plasma elimination half life averaged ꢀ2 h,
and a brain to plasma AUC ratio of 0.8.
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on ortho-amino benzamide and nicotinamide scaffolds

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