Synthesis, structure-activity relationship, and pharmacological studies of novel melanin-concentrating hormone receptor 1 antagonists 3- aminomethylquinolines: Reducing human ether-a-go-go-related gene (hERG) associated liabilities

Article

pubs.acs.org/jmc

Synthesis, Structure−Activity Relationship, and Pharmacological

Studies of Novel Melanin-Concentrating Hormone Receptor 1

Antagonists 3-Aminomethylquinolines: Reducing Human Ether-a-go-

go-Related Gene (hERG) Associated Liabilities

Shizuo Kasai,* Makoto Kamata, Shinichi Masada, Jun Kunitomo, Masahiro Kamaura, Tomohiro Okawa,

Kazuaki Takami, Hitomi Ogino, Yoshihide Nakano, Shuntarou Ashina, Kaoru Watanabe, Tomoko Kaisho,

Yumi N. Imai, Sunghi Ryu, Masaharu Nakayama, Yasutaka Nagisa, Shiro Takekawa, Koki Kato,

Toshiki Murata, Nobuhiro Suzuki, and Yuji Ishihara

Pharmaceutical Research Division, Takeda Pharmaceutical Co., Ltd., 26-1, Muraoka-Higashi 2-Chome, Fujisawa, Kanagawa 251-8555,

Japan

S

* Supporting Information

ABSTRACT: Recently, we discovered 3-aminomethylquinoline derivative 1, a selective, highly potent, centrally acting, and

orally bioavailable human MCH receptor 1 (hMCHR1) antagonist, that inhibited food intake in F344 rats with diet-induced

obesity (DIO). Subsequent investigation of 1 was discontinued because 1 showed potent hERG K⁺channel inhibition in a patch-

clamp study. To decrease hERG K⁺channel inhibition, experiments with ligand-based drug designs based on 1 and a docking

study were conducted. Replacement of the terminal p-ﬂuorophenyl group with a cyclopropylmethoxy group, methyl group

introduction on the benzylic carbon at the 3-position of the quinoline core, and employment of a [2-(acetylamino)ethyl]amino

group as the amine portion eliminated hERG K⁺channel inhibitory activity in a patch-clamp study, leading to the discovery of N-

{3-[(1R)-1-{[2-(acetylamino)ethyl]amino}ethyl]-8-methylquinolin-7-yl}-4-(cyclopropylmethoxy)benzamide (R)-10h. The com-

pound (R)-10h showed potent inhibitory activity against hMCHR1 and dose-dependently suppressed food intake in a 2-day

study on DIO-F344 rats. Furthermore, practical chiral synthesis of (R)-10h was performed to determine the molecule’s absolute

conﬁguration.

in metabolic rate.⁶Transgenic mice overexpressing the prepro-

INTRODUCTION

The World Health Organization has declared obesity a

■

MCH gene exhibit hyperphagia, mild obesity, and insulin

resistance.⁷Moreover, MCHR1-deﬁcient (MCH1r−/−) mice

worldwide epidemic; more than 1 billion adults are overweight,

and at least 300 million are obese.¹The healthcare burden for

are lean (similar to prepro-MCH-deﬁcient mice) but are

hyperphagic when maintained on regular chow. MCH1r−/−

treating obesity is signiﬁcantly high because obesity causes

mice are less susceptible to diet-induced obesity because of

secondary chronic diseases such as type 2 diabetes, hyper-

their hyperactivity and increased energy expenditure.^8a,b

tension, stroke, cardiovascular disease, and certain forms of

MCHR1 antagonism suppresses food intake and fat accumu-

cancer. Although many molecular targets have been studied,

lation,⁹indicating that MCHR1 is an essential receptor for

antiobesity drugs remain an unmet medical need.

regulating body weight and composition. These ﬁndings

Melanin-concentrating hormone (MCH) is a disulﬁde-linked

suggest that MCHR1 antagonists may provide a new class of

cyclic nonadecapeptide expressed in the lateral hypothalamus,

antiobesity agents that act by inducing an anorexigenic eﬀect

and it is the natural ligand for seven-transmembrane G-protein-

and enhanced energy expenditure.^10a−c

coupled receptors MCHR1 and MCHR2.²⁻⁴

Small MCHR1 antagonists have been found to be promising

agents for treating obesity. Although many pharmaceutical and

biotechnology companies have been heavily examining small

MCHR1 is primarily expressed in the central nervous system

in mammals, but MCHR2 is not expressed in rats and mice;

thus, little is known about its physiological function.

MCH acutely stimulates feeding behavior in rats when

injected intracerebroventricularly,⁵and MCH knockout mice

show reduced body weight due to hypophagia and an increase

Received: February 6, 2012

Published: April 10, 2012

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Figure 1. Structure of MCHR1 antagonist 1 and synthetic strategy.

a

Scheme 1

a

i

Reagents and conditions: (a) (i) PrOH, reﬂux, (ii) 1 M HCl, 70 °C, (iii) K₂CO₃, AcOEt−H₂O, 90 °C; (b) pyrrolidine, NaBH(OAc)₃,

dichloroethane, rt; (c) (i) R²COOH, oxalyl chloride, DMF (cat.), THF, rt, (ii) triethylamine, THF, rt.

molecule MCHR1 antagonists for more than 10 years,^11a−cfew

compounds have been evaluated in clinical trials, and none of

these compounds are available commercially.^12a−cA major

hurdle in the use of MCHR1 antagonists in clinical settings

includes human ether-a-go-go-related gene (hERG) associated

cardiovascular risks.¹³Despite attractive in vivo proﬁles, further

development of many MCHR1 antagonists has been

discontinued because of signiﬁcant hERG K⁺channel binding,

which can induce QTc interval prolongation frequently

associated with potential lethal arrhythmias known as torsades

de pointes. The hERG blockade of MCHR1 antagonists can be

explained by two common structural elements between a

signiﬁcant number of reported MCHR1 antagonists and well-

known hERG-binding agents: a positively charged group and at

least one distal aromatic/lipophilic region.¹³

In previous reports, we described eﬀorts undertaken in the

ﬁeld of medicinal chemistry to improve upon a lead

compound^14a,band to study its relationship with MCHR1

antagonistic activity, pharmacokinetic properties, and selectivity

over serotonin 5-HT_2creceptor, which culminated in the

discovery of 3-aminomethylquinoline-based compound 1.¹⁵

Although compound 1 displayed excellent in vitro and in vivo

activities and selectivity over other enzymes and receptors,

including the 5HT_2creceptor,¹⁵1 was identiﬁed as a potent

hERG K⁺channel blocker in an in vitro patch-clamp study.

Herein, we report the structure−activity relationship (SAR) of

3-aminomethylquinoline-based MCHR1 antagonists and de-

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a

Scheme 2

a

Reagents and conditions: (a) MeMgBr, THF, 0 °C to rt; (b) SOCl₂, rt; (c) 4-cyclopropylmethoxybenzoyl chloride, triethylamine, THF, 0 °C to rt;

(d) amine, K₂CO₃, KI, DMF, 70 °C; (e) amine, DIPEA, NMP, 60 °C.

a

Scheme 3

a

Reagents and conditions: (a) chiral column separation by HPLC; (b) conc HCl, 100 °C; (c) 3-bromobenzoyl chloride, triethylamine, THF, 0 °C to

rt.

scribe pharmacological studies performed to address the issue

of hERG K⁺channel blocking.

introduction of methyl group(s) at the α-position of the basic

nitrogen atom to prevent the cation−π and/or CH−π

interaction by steric hindrance, and (iii) replacement of

pyrrolidine with bulky and/or a hydrophilic amine to reduce

the cation−π or CH−π interaction. For (ii), we also tested

ethyl, isopropyl, cyclopropyl, phenyl, and benzyl groups instead

of a methyl group. However, these replacements resulted in a

loss of MCH antagonistic activity (data not shown).

Furthermore, to support these strategies, we carried out a

docking study of a key compound with the hERG K⁺channel.²²

DRUG DESIGN

■

Several reports^16a,b,17,18indicated that some aromatic amino

acid residues constructing the hERG K⁺channel, such as

Tyr652 and Phe656, play a key role in creating a π-related or

hydrophobic interaction^19,20with various types of drugs that

block hERG K⁺channel with high aﬃnity. An eﬀective method

of reducing the hERG K⁺channel binding aﬃnity may be to

reduce lipophilicity and/or introduce hydrophilic substituents.

Indeed, there are a number of reports that describe decreasing

hERG liabilities by lowering the lipophilicity of the

compound.²¹On the basis of these ﬁndings, we adopted the

following strategies (Figure 1): (i) replacement of one aromatic

ring in the biphenyl group with a nonaromatic substituent

aimed to reduce the lipophilic and/or π−π interaction, (ii)

CHEMISTRY

■

First, we replaced one of the two benzene rings at the terminal

biphenyl moiety of 1. Scheme 1 depicts the synthesis of the key

intermediate 7-amino-3-formyl-8-methylquinoline 4 and pro-

posed quinoline derivatives 6a−j. Condensation and cyclization

of commercially available 2,6-diaminotoluene 2 with “vinami-

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dinium” bis-tetraﬂuoroborate salt 3 followed by a hydrolysis

reaction yielded the 3-formylquinoline derivative 4.²³Sub-

sequent reductive amination of 4 with pyrrolidine or 2-

methylpyrrolidine provided 3-pyrrolidinylmethylquinoline de-

rivatives 5a and 5b, respectively. A condensation reaction of 5a

or 5b with benzoic acids gave the desired amide compounds

6a−j.

Scheme 2 describes the synthesis of 1-(8-methylquinolin-3-

yl)ethanamine derivatives 10a−h (racemate). Compound 4 was

reacted with methylmagnesium bromide to give alcohol 7,

which was chlorinated to provide the key intermediate 3-(1-

chloroethyl)-8-methylquinolin-7-amine (8). Compound 8 was

coupled with 4-(cyclopropylmethoxy)benzoyl chloride pre-

pared from the corresponding acid to provide amide 9. Finally,

9 was reacted with amines to yield proposed racemic

compounds 10a−h.

Scheme 3 shows the chiral separation of 10a and 10h and the

determination of the absolute conﬁguration. Optical resolution

of 10a by chiral HPLC provided the less polar compound LP-

10a and the polar compound P-10a, respectively. LP-10a or P-

10a was hydrolyzed to aﬀord 7-aminoquinoline derivative 11a

or 11b, which was subsequently converted to 3-bromobenzoate

12a or 12b, respectively, without racemization. Since the

structure of 12a, which was derived from LP-10a, was

determined using X-ray crystallographic analysis to be an S-

conﬁguration (Figure 2), the structure of P-10a was

hydrogenated in the presence of [RuCl₂{(R)-xylbinap}{(R)-

daipen}] (substrate-to-catalyst molar ratio (S/C) of 1000)

under a 0.7 MPa hydrogen atmosphere in DMF and 2-propanol

solution to produce the prerequisite chiral alcohol (S)-14 with

98% ee. In the next step, we examined Thompson’s conditions

(diphenylphosphorylazide (DPPA), DBU, in toluene or in

THF, at −30 °C or at 0 °C to room temperature). Although

these reaction conditions provided the corresponding azide 16

in moderate to good yield (43−76%), the enantiomeric excess

was insuﬃcient (<90% ee, data not shown). We focused on the

optimization of the reaction conditions, and ﬁnally the

conversion of the chiral alcohol (S)-14 (98% ee) to the

corresponding chiral azide 16 was successfully achieved (90%,

98% ee) using DPPA under an excess of DIPEA as a solvent.

Catalytic hydrogenation of azide 16 quantitatively yielded

chiral primary amine 17 with 98% ee. We conﬁrmed the

absolute conﬁguration of 17 by synthesis of (R)-10a: the

reaction of 17 with 1,4-dibromobutane provided solely (R)-10a

in 61%. These results suggest that conversion of 15 to (S)-14

and inversion of (S)-14 to 16 were successfully achieved

without racemization.

Nosylation of the amino group of 17 gave 18 in excellent

yield. The Mitsunobu reaction with N-Boc-protected amino-

ethanol followed by acid-catalyzed removal of the Boc

protecting group was achieved in a one-pot reaction. Primary

amine 19 was puriﬁed by acid−basic extraction without column

chromatography. Reaction with acetyl chloride followed by

deprotection of the nosyl group aﬀorded the desired compound

(R)-10h in high yield. The overall yield of (R)-10h from

ketone 15 was 82% without racemization. Chiral HPLC

analysis showed that LP-10h is identical to (R)-10h; the

absolute stereochemistry of the eutomer of compound 10h was

determined to be an R-conﬁguration.

Scheme 5 shows the synthesis of 3-(1-methyl-1-pyrrolidin-1-

ylethyl)quinoline derivative 22, which bears two methyl groups

on the benzylic carbon. The formyl group of compound 13 was

converted to methyl ester using N-iodosuccinimide (NIS) in

the presence of K₂CO₃to give 20.²⁶A reaction of the methyl

ester of 20 with excess methyllithium yielded tertiary alcohol

21. Finally, compound 21 was chlorinated and successively

coupled with pyrrolidine to aﬀord the desired dimethyl

compound 22.

RESULTS AND DISCUSSION

■

Compounds synthesized in this study were tested for their

binding aﬃnities to the human MCH receptor 1 (hMCHR1)

and rat MCH receptor 1 (rMCHR1) by using a stably

transfected Chinese hamster ovary (CHO) cell line. Binding

assays of the test compounds were performed in the presence

of [¹²⁵I]MCH (4−19) as a ligand. Secondary functional cell-

based assays for the inhibition of MCH-stimulated arachidonic

acid release from CHO cells were also performed, and the test

compounds were found to be antagonists. In our previous study

for a MCHR1 antagonist,^14bwe conﬁrmed that the acachidonic

acid release inhibition represented the MCHR1 antagonistic

activity. The MCHR1 antagonist showed the binding aﬃnity

for MCHR1, reversed the MCH-mediated inhibition of

intracellular cAMP accumulation, inhibited the MCH-induced

intracellular Ca²⁺increase, and inhibited the MCH-induced

arachidonic acid release. Furthermore, we performed Ca²⁺

inﬂux assays for the key two compounds ((R)-10a and (R)-

10h) and conﬁrmed their antagonistic activities against

hMCHR1 (Supporting Information Figure S1).

Figure 2. Structure of 12a.

determined to be an R-conﬁguration. Optical resolution of

10h using chiral HPLC provided a less polar compound LP-

10h and a more polar compound P-10h, and the absolute

conﬁguration of LP-10h was determined to be R using the

chiral synthesis described in Scheme 4.

Compound 4 was coupled with 4-cyclopropylmethoxyben-

zoic acid to give amide 13, and a subsequent Grignard reaction

aﬀorded racemic alcohol (rac)-14. Oxidation of (rac)-14 with

manganese(IV) oxide aﬀorded ketone 15. To achieve the

asymmetric synthesis of (R)-10h, we designed the synthetic

route via Noyori asymmetric hydrogenation^24a−eof ketone 15

followed by inversion to optically active azide 16 under

Mitsunobu conditions reported by Thompson et al.²⁵Ohkuma

et al. reported a practical method for asymmetric hydrogenation

of heteroaromatic ketones, in which [RuCl₂{(R)-xylbinap}-

{(R)-daipen}] provides S-chiral alcohols.^24eKetone 15 was

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a

Scheme 4

a

Reagents and conditions: (a) 4-cyclopropylmethoxybenzoyl chloride, pyridine, 0 °C to rt; (b) MeMgBr, THF, 0 °C to rt, 4 h; (c) MnO₂, THF,

reﬂux, 24 h; (d) KO^tBu, DMF−2-propanol, RuCl₂{(R)-xylbinap}{(R)-daipen} (S/C = 1000), then H₂(0.7 MPa), rt, 24 h, quant, 98% ee; (e) DPPA,

DIPEA, rt, 96 h, 98% ee; (f) H₂(balloon), Pd/C, EtOH, rt, 2 h, 98% ee; (g) 1,4-dibromobutane, Na₂CO₃, DMF, 60 °C, 99% ee; (h) NsCl,

triethylamine, THF, 0 °C to rt, 4 h; (i) (i) HO(CH₂)₂NHBoc, DIAD, PPh₃, THF, 0 °C to rt, 2.5 h, (ii) HCl−AcOEt, rt, 15 h, one-pot reaction; (j)

AcCl, triethylamine, THF, 0 °C, 10 min; (k) HSCH₂CO₂H, LiOH·H₂O, DMF, rt, 4 h, 99% ee.

a

Scheme 5

a

Reagents and conditions: (a) NIS, K₂CO₃, MeOH, rt; (b) MeLi, THF, 0 °C to rt; (c) (1) SOCl₂, 0 °C, (2) pyrrolidine, 60 °C.

The test compounds were evaluated for their inhibitory

activities against the hERG K⁺channel by using a high

throughput nonradioactive rubidium (Rb⁺) eﬄux assay (Rb

assay).²⁷The Rb assay was performed using CHO cells

expressing the hERG K⁺channel in which astemizole was used

as a positive control. The results are expressed as relative

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Table 1. In Vitro Pharmacological and Physicochemical Data for MCHR1 Antagonists

a

b

c

IC₅₀values are calculated with one experiment performed in duplicate, with a standard deviation of 3-fold. Binding aﬃnity for hMCHR1. Binding

d

aﬃnity for rMCHR1. Antagonistic activity against hMCHR1, inhibition of MCH-stimulated arachidonic acid release from CHO cells expressing

e

f

hMCHR1. Relative activity of inhibition of Rb⁺eﬄux from CHO cells expressing the hERG channel (positive control is 0, vehicle is 1.0). Measured

g

at pH 7.4. Not tested.

activity (Rb value) to astemizole (positive control is 0) and

vehicle (control is 1). The criterion for the Rb value was set to

be >0.8, which was determined in an in-house study. Further

evaluation of cardiovascular safety was conducted using an in

vitro patch-clamp study.²²

These results imply that the π-property confers reduced

lipophilicity on the cyclopropane ring, aiding binding to the

MCHR1 receptor and contributing to a decrease in hERG

inhibition.

Introduction of a more polar substituent such as sulfone

(6e), ketone (6h), or amide (6g) improved the Rb value

(0.85−0.99), whereas that of the ketone derivative 6f did not

(Rb value of 0.48). A good correlation between the Rb value

and log D (pH 7.4) value was observed in these compounds:

log D values of 6e, 6g, and 6h are in the range 2.10−2.31,

whereas that of 6f is 3.50. The ketone derivative 6h (Rb value

of 0.85) showed a high binding aﬃnity for hMCHR1 (IC₅₀of

4.3 nM); however, 6e and 6g showed signiﬁcantly decreased

aﬃnities (7- to 370-fold decrease).

We previously discussed the SAR of the biphenyl moiety of

the compound 1 analogue in a docking study performed using a

homology model of hMCHR1.^14aIn this model, the biphenyl

group was bound to the lipophilic binding pocket of MCHR1;

however, a hydrophilic space was also observed in the same

binding site. On the basis of this observation, we believe that

The results of replacement of one of the benzene rings in the

4′-ﬂuorobiphenyl moiety of 1 are shown in Table 1. An n-

butoxyphenyl (6a) or a 4-ﬂuorophenylbutyl (6i) analogue

maintained in vitro activities (hMCHR1 IC₅₀of 2.0 and 3.2

nM, arachidonic acid release IC₅₀of 2.6 and 3.9 nM,

respectively) with slight improvement in the Rb value (0.38−

0.41). Replacement of the n-butyl group of 6a with a

cyclopropylmethyl (6b) or a cyclopropylethyl (6c) group led

to an improvement of the Rb value with a high in vitro binding

aﬃnity. Compound 6b showed 2-fold weaker antagonistic

activity than 6c (4.3 nM vs 2.0 nM); however, 6b showed a

better Rb value than 6c did (0.90 vs 0.72). The cyclopropyl

derivative 6b showed more potent in vitro binding aﬃnity (1.8

nM) with an improved Rb value than the corresponding

isopropyl analogue 6d (IC₅₀of 4.4 nM, Rb value of 0.70).

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Table 2. In Vitro Pharmacological and Physicochemical Data for MCHR1 Antagonists

a

b

c

IC₅₀values are calculated with one experiment performed in duplicate, with a standard deviation of 3-fold. Binding aﬃnity for hMCHR1. Binding

d

aﬃnity for rMCHR1. Antagonistic activity against hMCHR1, inhibition of MCH-stimulated arachidonic acid release from CHO cells expressing

e

f

hMCHR1. Relative activity of inhibition of Rb⁺eﬄux from CHO cells expressing the hERG channel (positive control is 0, vehicle is 1.0). Measured

g

at pH 7.4. Not tested.

the binding mode of the alkyl-linked analogue 6i is probably

diﬀerent from that of 6h; potent in vitro activity of 6i can be

achieved through a lipophilic interaction with MCHR1, and the

ketone group of 6h may form a hydrogen bond with a

hydrophilic amino acid residue.

introduced to the benzylic carbon of 6b and 6c attenuates

cation−π and/or CH−π interaction(s) with the hERG K⁺

channel through steric hindrance. In contrast, 2-methylpyrro-

lidine derivative 6j (racemate) decreased the Rb value (0.62).

Furthermore, introduction of an additional methyl group on

the benzylic carbon of 10a to yield the dimethyl compound 22

resulted in a loss of aﬃnity (hMCHR1 IC₅₀of 7.8 nM) as well

as a decrease in the Rb value (0.62). The methyl group at the 2-

position of the pyrrolidine ring or the second methyl group

introduced into the benzylic carbon increased lipophilicity and

may show new CH−π interaction with the hERG K⁺channel.

The patch-clamp study of (R)-10a, however, revealed that the

hERG K⁺inhibitory activity was only minimally improved from

that of compound 1 (88.1% vs 93.8%, Table 3).

We also performed a docking study of (R)-10a to the hERG

K⁺channel by characterizing the binding site and binding

mode.²²Brieﬂy, the number and relative position of selected

residues involved in (R)-10a binding to the hERG K⁺channel

were determined using site-directed mutagenesis combined

with a tandem approach: a tandem dimer of the hERG K⁺

Among the compounds in Table 1, we chose the cyclo-

propylmethoxy derivative 6b for further optimization. Table 2

displays the eﬀects of the methyl group(s) at the α-position of

the nitrogen atom of pyrrolidine. The 6b analogues, 10a (and

its S- and R-isomers (S)-10a and (R)-10a), 10b, 10c, 6j, and 22

showed nanomolar in vitro activities with moderate to excellent

Rb values (0.62−1.11). Among these, the optically active

pyrrolidine derivative (R)-10a showed the highest Rb value

(1.11) with potent in vitro activities (hMCHR1 IC₅₀of 1.1 nM,

arachidonic acid release of 2.9 nM). Considering the inﬂuence

of the methyl group on the benzylic carbon, Rb values of 10a

and 10b (1.02 and 0.80) were equal to or higher than those of

6b and 6c (0.90 and 0.72), although the log D values of 10a

and 10b (3.00 and 3.49) were higher than those of 6b and 6c

(2.77 and 3.40). These results imply that the methyl group

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Table 3. In Vitro Pharmacological and Physicochemical Data for MCHR1 Antagonists

a

b

c

IC₅₀values are calculated with one experiment performed in duplicate, with a standard deviation of 3-fold. Binding aﬃnity for hMCHR1. Binding

d

aﬃnity for rMCHR1. Antagonistic activity against hMCHR1, inhibition of MCH-stimulated arachidonic acid release from CHO cells expressing

hMCHR1. % of inhibition. Measured at pH 7.4. Not tested.

e

f

g

channel was constructed, where mutation was introduced into

one subunit to determine the residues that bind to (R)-10a.

The results revealed that at least two Tyr652 molecules in the

neighboring subunits are simultaneously involved in (R)-10a

binding (Supporting Information Figure S2). On the basis of

the topological information of the binding mode, a docking

study of (R)-10a was performed against an hERG homology

model. Multiple drug binding modes were generated for (R)-

10a, and binding modes satisfying the above results were

selected. Final docking models were generated after energy

minimizations were performed using MOE (Chemical

Computing Group, Canada).²⁸

Figure 3. Proposed hERG K⁺channel binding mode for compound

(R)-10a (black) and hypothetical modiﬁcation to avoid hERG binding

(blue). The number in parentheses after the residue name represents

the subunit number.

The conclusions from these studies are summarized in Figure

3. All ring substructures of (R)-10a were involved in the

interaction with the hERG channel. Two Tyr652 side chains in

adjacent subunits interacted with the terminal benzene ring and

pyridine in the quinoline ring of (R)-10a via π−π interactions

(red circle), and a terminal pyrrolidine ring was recognized by

Phe656, which constitutes a shallow pocket on the surface of

the pore (yellow circle). The cyclopropane moiety was

accommodated by a small pocket located in the back of the

selectivity ﬁlter, and two nitrogen atoms in the amide and in the

quinoline ring formed hydrogen bonds with Ser624 molecules.

Recommended approaches to attenuate the hERG inhibition

of (R)-10a are described in Figure 3 (blue): (i) introduction of

a bulky and/or hydrophilic moiety near the terminal amine

group; (ii) introduction of an sp²bond on the benzylic carbon;

(iii) removal of the nitrogen atom from the quinoline core; (iv)

reversal of the amide bond from CONH to NHCO; (v)

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a

Table 4. In Vivo Pharmacokinetic Proﬁle of (R)-10h

iv (1 mg/kg)

po (3 mg/kg)

b

c

d

e

f

g

Cpd

F

(%)

43

CL_total(L h⁻¹kg⁻¹))

V_ss(L kg⁻¹

)

C_max(ng mL⁻¹

)

T_max(h)

AUC_0−24h(ng h mL⁻¹

)

(R)-10 h

0.69

1.21

274

4.0

1940

a

b

c

d

e

f

n = 3; SD rats (male, 8 W). Rat bioavailability. Total clearance. Volume of distribution at the steady state. Maximal plasma concentration. Time

g

of maximal concentration. Area under the blood concentration time curve (0−24 h).

replacement of the terminal cyclopropylmethyl group with a

bulky and/or hydrophilic substituent.

In the SAR and docking study, replacement of the

pyrrolidine with a bulky and/or hydrophilic amine appeared

to be an ideal design, and the results are described in Table 3.

Replacement of the pyrrolidine with piperazine (10d)

decreased hMCHR1 binding aﬃnity. Introduction of a hydroxyl

group at the 3-position of the pyrrolidine ring provided 10e,

which showed potent hMCHR1 binding aﬃnity (IC₅₀= 5.5

nM) with attenuated hERG K⁺inhibition in a patch-clamp

study (58.4%). We also introduced a hydroxyl group at the 3-

position of pyrrolidine in compound 1; however, hERG

inhibitory activity remained potent (97%, data not shown).

Figure 4. Eﬀect of (R)-10 h on 2-day food intake study in DIO-F344

These results suggest that replacement of terminal benzene

with a cyclopropylmethoxy group and introduction of a

hydroxyl group in the amine moiety act additively to decrease

hERG potential. The (2-hydroxy-2-methylpropyl)amine deriv-

ative 10g displayed more potent in vitro MCHR1 aﬃnity than

the hydroxyethylamine derivative 10f. Interestingly, although

the log D of compound 10g was higher than that of the “less

bulky” compound 10f (2.67 vs 2.06), 10g showed decreased

hERG K⁺channel inhibitory activity in a patch-clamp study

(63.3% vs 84.8%). Moreover, replacement of the pyrrolidine

with [2-(acetylamino)ethyl]amine to provide 10h dramatically

decreased hERG potency (29.3%) without a signiﬁcant loss of

MCHR1 aﬃnity. Between the two enantiomers of 10h, the R-

isomer (R)-10h showed 3.5-fold more potent hMCHR1

binding aﬃnity (IC₅₀= 1.5 nM) than (S)-10h without

signiﬁcant hERG K⁺channel inhibition in a patch clamp

study (33.2%).

The pharmacokinetic proﬁle of (R)-10h described in Table 4

suggests that (R)-10h is orally available and could penetrate the

brain. Subsequently, the pharmacological eﬀect of compound

(R)-10h was evaluated using DIO-F344 rats fed high fat diet ad

libitum. The compound (R)-10h (1, 3, 5, and 10 mg/kg) was

orally administered to DIO-F344 rats daily at the beginning of

the dark cycle (at 5:00 p.m., 0 and 24 h), and the food intake

from initial administration to 1 and 2 days later was measured.

The results of a 2-day in vivo study of (R)-10h are shown in

Figure 4. Compound (R)-10h signiﬁcantly and dose-depend-

ently suppressed food intake in DIO-F344 rats from 1 mg/kg.

Recently, we reported SAR and pharmacological studies of a

potent and selective MCHR1 antagonist 1, an analogue of (R)-

10h. An MCHR1-deﬁcient mice study revealed that the

anorectic eﬀect of 1 was provoked by MCHR1 antagonism.¹⁵

Compound (R)-10h showed negligible activity for other

receptors, transporters, and enzymes (data not shown),

suggesting that the MCHR1 antagonistic activity of (R)-10h

exerted the anorectic eﬀect observed in this study. Taken

together, these data suggest that (R)-10h is an orally

bioavailable MCHR1 antagonist that exhibits excellent in vivo

eﬃcacy in a DIO rat model while maintaining a safety proﬁle

with respect to QTc prolongation.

rats: inhibition of cumulative food intake on days 1 and 2 in DIO-F344

rats. Compound was dosed once daily (at 5:00 p.m., 0 and 24 h).

Cumulative food intake inhibition rate was calculated by dividing

average food intake of each compound administered group by average

food intake of the control group at each measured point. The values

shown are a ratio of the control: (∗) p < 0.025 vs control group

(Williams test, n = 6 for each group).

CONCLUSION

■

We conducted a SAR study both for MCHR1 antagonistic

activity and for hERG K⁺channel inhibitory activity using 3-

aminomethylquinoline-based MCHR1 antagonists related to

compound 1. In parallel with the ligand-based SAR study, the

docking study of the key compound (R)-10a with the hERG K⁺

channel was conducted to support the optimization study. We

achieved the following: (i) replacement of the terminal p-

ﬂuorophenyl moiety with a cyclopropylmethoxy group,

introduction of a methyl group onto the benzylic carbon, and

employment of a [2-(acetylamino)ethyl]amino group as an

amine to synergistically reduce inhibitory activity against the

hERG K⁺channel allowed us to identify the optically active

compound (R)-10h as a novel, potent MCHR1 antagonist

(binding IC₅₀= 1.5 nM, antagonistic activity IC₅₀= 4.7 nM);

(ii) a docking study was conducted to support a design for

reducing hERG K⁺channel inhibition; (iii) practical asym-

metric synthesis of (R)-10h was achieved to determine the

absolute conﬁguration. (R)-10h did not show signiﬁcant hERG

K⁺channel inhibitory activity in a patch-clamp study.

Furthermore, (R)-10h (1, 3, 5, and 10 mg/kg) dose-

dependently and signiﬁcantly suppressed food intake in a 2-

day DIO-F344 rat study. In conclusion, (R)-10h is an orally

active MCHR1 antagonist with reduced hERG-associated

cardiovascular liabilities.

EXPERIMENTAL SECTION

Melting points (mp) were determined on a Yanagimoto micromelting

■

point apparatus or a Buchi melting point B545 apparatus and are

̈

uncorrected. Proton nuclear magnetic resonance (¹H NMR) spectra

were recorded on a Varian Gemini 200 or Varian Mercury 300 NMR

spectrometer. Chemical shifts were reported in δ value (ppm) with

tetramethylsilane as an internal standard. Splitting patterns are

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designated as follows: s, singlet; d, doublet; t, triplet; dd, double

doublet; q, qualtet; quint, quintet; sext, sextet; m, multiplet; br, broad.

Coupling constants (J) are reported in hertz (Hz). LC/MS (ESI

positive) spectra were recorded on a Waters Micromass ZQ 2000.

Elemental analysis (C, H, N) to determine the purity of test

compounds was conducted by the Analytical Department of Takeda

Pharmaceutical Co., and the results were within 0.4% of theoretical

values. Purity of compounds was >95%, as established by elemental

analysis. The data from elemental analysis are in Supporting

Information. Thin-layer chromatography (TLC) analyses were

performed with silica gel 60 F₂₅₄plate (Merck no. 5715) and alumina

60 F₂₅₄plate (type E). Chromatographic separations were performed

with Merck silica gel 60 (Merck no. 7734), ICN alumina B, Akt. I

(activity grade III), and NH-silica gel (Fuji Sylysia).

3.98 (2H, s), 4.08−4.16 (1H, m), 6.99 (1H, d, J = 8.7 Hz), 7.49 (1H,

d, J = 8.7 Hz), 7.91 (1H, d, J = 2.1 Hz), 8.77 (1H, d, J = 2.1 Hz).

4-Butoxy-N-[8-methyl-3-(pyrrolidin-1-ylmethyl)quinolin-7-

yl]benzamide (6a). The title compound was prepared in 20% yield

starting from 5a using the procedure described for 6d: mp 161 °C. ¹H

NMR (300 MHz, CDCl₃) δ 0.99 (3H, t, J = 7.3 Hz), 1.51 (2H, m),

1.80 (6H, m), 2.55 (4H, m), 2.80 (3H, s), 3.80 (2H, s), 4.03 (2H, t, J =

6.5 Hz), 6.98 (2H, m), 7.68 (1H, d, J = 9.0 Hz), 7.89 (3H, m), 8.04

(1H, d, J = 2.2 Hz), 8.22 (1H, d, J = 8.8 Hz), 8.87 (1H, d, J = 2.2 Hz).

Anal. (C₂₆H₃₁N₃O₂·0.3H₂O) C, H, N.

4-(Cyclopropylmethoxy)-N-[8-methyl-3-(pyrrolidin-1-

ylmethyl)quinolin-7-yl]benzamide (6b). The title compound was

prepared in 50% yield starting from 5a using the procedure described

for 6d: mp 168 °C. ¹H NMR (300 MHz, CDCl₃) δ 0.39 (2H, m), 0.69

(2H, m), 1.30 (1H, m), 1.81 (4H, m), 2.56 (4H, m), 2.80 (3H, s), 3.80

(2H, s), 3.88 (2H, d, J = 6.8 Hz), 7.00 (2H, m), 7.68 (1H, d, J = 8.6

Hz), 7.90 (3H, m), 8.05 (1H, d, J = 2.0 Hz), 8.23 (1H, d, J = 8.8 Hz),

8.87 (1H, d, J = 2.0 Hz). Anal. (C₂₆H₂₉N₃O₂·0.2H₂O) C, H, N.

4-(2-Cyclopropylethoxy)-N-[8-methyl-3-(pyrrolidin-1-

ylmethyl)quinolin-7-yl]benzamide (6c). The title compound was

prepared in 58% yield starting from 5a using the procedure described

7-Amino-8-methylquinoline-3-carboxaldehyde (4). (a) 2-

Dimethylaminomethylene-1,3-bis(dimethylimmonio)propane

Bis(tetraﬂuoroborate) (3).²³During 1.5 h, to an ice-cooled mixture

of bromoacetic acid (100 g, 0.72 mol) and phosphoryl chloride (200

mL, 2.15 mol) was added DMF (336 mL, 4.36 mol), maintaining

below 15 °C. The mixture was stirred at 110 °C for 3 h and then

cooled to 0 °C. (Caution: While heating, gaseous CO₂is evolved

vigorously and the temperature rose quickly to 150 °C.) To the

resulting solution was added a mixture of 48% aqueous solution of

HBF₄(500 g, 3.83 mol) and MeOH (200 mL) dropwise over a period

of 1 h. (Caution: The reaction is exothermic, and the cooled solution

becomes a viscous liquid.) To this mixture was added 2-propanol

(1000 mL), and the mixture was stirred at 0 °C for 2 h. The precipitate

was ﬁltered, rinsed with ice-cooled 2-propanol, quickly air-dried, and

dried at 60 °C under reduced pressure to give the title compound (207

g, 81%) as pale yellow crystals. (Caution: The crystals are

1

for 6d: mp 147−148 °C. H NMR (300 MHz, CDCl₃) δ 0.12−0.18

(2H, m), 0.48−0.55 (2H, m), 0.81−0.95 (1H, m), 1.73 (2H, q, J = 6.8

Hz), 1.78−1.85 (4H, m), 2.54−2.60 (4H, m), 2.81 (3H, s), 3.81 (2H,

s), 4.12 (2H, t, J = 6.7 Hz), 6.99−7.05 (2H, m), 7.70 (1H, d, J = 8.9

Hz), 7.89−7.96 (3H, m), 8.06 (1H, d, J = 2.1 Hz), 8.25 (1H, d, J = 8.9

Hz), 8.89 (1H, d, J = 2.1 Hz). Anal. (C₂₇H₃₁N₃O₂·H₂O) C, H, N.

4-(2-Methylpropoxy)-N-[8-methyl-3-(pyrrolidin-1-ylmethyl)-

quinolin-7-yl]benzamide (6d). To a mixture of 4-isobutoxybenzoic

acid (0.12 g, 0.62 mmol) and oxalyl chloride (0.16 mL, 1.85 mmol) in

THF (3 mL) were added 3 drops of DMF. The mixture was stirred at

room temperature for 2 h and then concentrated under reduced

pressure. The resulting residue was dissolved in THF (3 mL), and the

solution was added to a mixture of 5a (0.12 g, 0.52 mmol) and

triethylamine (0.14 mL, 1.03 mmol) in THF (3 mL). After being

stirred at room temperature for 15 h, the reaction mixture was

concentrated under reduced pressure and the residue was partitioned

between AcOEt and water. The organic layer was washed with brine,

dried over MgSO₄, ﬁltered, and concentrated under reduced pressure.

The resulting residue was puriﬁed by column chromatography (NH-

silica gel, hexane/AcOEt/CHCl₃= 2/1/1, AcOEt) and the resulting

solid was recrystallized from isopropyl ether and AcOEt to give 6d

(0.11 g, 0.26 mmol, 51% yield) as a pale yellow solid: mp 138−139 °C.

¹H NMR (300 MHz, CDCl₃) δ 1.06 (6H, d), 1.77−1.85 (4H, m),

1

hygroscopic.) H NMR (300 MHz, DMSO-d₆) δ 3.37 (9H, s), 3.53

(9H, s), 8.40 (9H, s).

(b) 7-Amino-8-methylquinoline-3-carboxaldehyde (4). A

mixture of 2-methyl-1,3-benzenediamine (2, 30.0 g, 246 mmol) and

vinamidinium bis-tetraﬂuoroborate (3, 263 g, 737 mmol) in 2-

propanol (500 mL) was stirred for 16 h under reﬂux. The reaction

mixture was allowed to cool to room temperature, and to this mixture

was added 1 M HCl (500 mL). Then the mixture was stirred at 70 °C

for 5 h. The reaction mixture was cooled to room temperature, and the

resulting precipitate was collected by ﬁltration. The precipitate was

washed with water, MeCN, and isopropyl ether, successively. A

mixture of the precipitate (61.6 g) and K₂CO₃(170 g, 1.23 mol) in

AcOEt (500 mL)−H₂O (500 mL) was stirred vigorously at 90 °C for

16 h and then cooled to room temperature. The organic layer was

separated, washed with brine, and dried over Na₂SO₄. This was ﬁltered

through a pad of silica gel (100 g), and the ﬁltrate was concentrated

under reduced pressure to give an orange solid. This solid was

triturated with isopropyl ether to give 4 (35.4 g, 77%) as an orange

powder: ¹H NMR (300 MHz, DMSO-d₆) δ 2.43 (3H, s), 6.17 (2H, br

s), 7.15 (1H, t, J = 8.7 Hz), 7.71 (1H, d, J = 8.7 Hz), 8.51 (1H, d, J =

2.4 Hz), 9.04 (1H, d, J = 2.4 Hz), 10.0 (1H, s).

2.06−2.21 (1H, m), 2.52−2.61 (4H, m), 2.81 (3H, s), 3.79−3.83 (4H,

m), 6.97−7.04 (2H, m), 7.70 (1H, d, J = 8.9 Hz), 7.88−7.95 (3H, m),

8.06 (1H, d, J = 2.1 Hz), 8.25 (1H, d, J = 8.9 Hz), 8.89 (1H, d, J = 2.3

Hz). Anal. (C₂₆H₃₁N₃O₂) C, H, N.

4-Butylsulfonyl-N-[8-methyl-3-(pyrrolidin-1-ylmethyl)-

quinolin-7-yl]benzamide (6e). The title compound was prepared in

36% yield starting from 5a using the procedure described for 6d: mp

211 °C. ¹H NMR (300 MHz, CDCl₃) δ 0.90 (3 H, t, J = 7.3 Hz), 1.38

(2H, m), 1.67 (2H, m), 1.81 (4H, m), 2.56 (4H, m), 2.81 (3H, s), 3.12

(2H, m), 3.81 (2H, s), 7.72 (1H, d, J = 8.4 Hz), 8.07 (7H, m), 8.90

(1H, d, J = 2.2 Hz). Anal. (C₂₆H₃₁N₃O₃S·0.2H₂O) C, H, N.

4-Hexanoyl-N-[8-methyl-3-(pyrrolidin-1-ylmethyl)quinolin-

7-yl]benzamide (6f). The title compound was prepared in 36% yield

starting from 5a using the procedure described for 6d: mp 175 °C. ¹H

NMR (300 MHz, CDCl₃) δ 0.93 (3H, m), 1.39 (4H, m), 1.82 (6H,

m), 2.57 (4H, m), 2.82 (3H, s), 3.02 (2H, t, J = 7.5 Hz), 3.82 (2H, s),

7.72 (1H, d, J = 9.2 Hz), 8.02 (1H, d, J = 2.2 Hz), 8.09 (5H, m), 8.19

(1H, d, J = 8.8 Hz), 8.91 (1H, d, J = 2.2 Hz). Anal.

(C₂₈H₃₃N₃O₂·0.1H₂O) C, H, N.

8-Methyl-3-(pyrrolidin-1-ylmethyl)quinolin-7-amine (5a). To

a suspension of 4 (21.0 g, 113 mmol) and pyrrolidine (28.3 mL, 145

mmol) in dichloroethane (210 mL) was added sodium triacetoxybor-

ohydride (35.8 g, 169 mmol). After the mixture was stirred at room

temperature for 4.5 h, to this mixture was added aqueous NaHCO₃

and the organic layer was separated. The organic layer was

concentrated under reduced pressure and the residue was chromato-

graphed on NH-silica gel (AcOEt) to give 5a (25.7 g, 94%) as a

1

viscous oil. H NMR (300 MHz, CDCl₃) δ 1.79 (4H, m), 2.54 (4H,

m), 2.59 (3H, s), 3.74 (2H, s), 3.98 (2H, s), 6.98 (1H, d, J = 8.6 Hz),

7.47 (1H, d, J = 8.6 Hz), 7.91 (1H, d, J = 2.2 Hz), 8.76 (1H, d, J = 2.2

Hz).

N-[8-Methyl-3-(pyrrolidin-1-ylmethyl)quinolin-7-yl]-4-

(pentanoylamino)benzamide (6g). The title compound was

prepared in 16% yield starting from 5a using the procedure described

for 6d: mp 193−194 °C. ¹H NMR (300 MHz, CDCl₃) δ 0.97 (3H, t, J

= 7.2 Hz), 1.44 (2H, m) 1.73 (2H, m), 1.81 (4H, m), 2.41 (2H, m),

2.57 (4H, m), 2.81 (3H, s), 3.81 (2H, s), 7.30 (1H, s), 7.69 (3H, m),

8-Methyl-3-[(2-methylpyrrolidin-1-yl)methyl]quinolin-7-

amine (5b). The title compound was prepared in 66% yield starting

1

from 4 using the procedure described for 5a. H NMR (300 MHz,

CDCl₃) δ 1.21 (3H, d, J = 6.0 Hz), 1.39−1.53 (1H, m), 1.55−1.79

(2H, m), 1.88−2.00 (1H, m), 2.15 (1H, q, J = 8.9 Hz), 2.37−2.50

(1H, m), 2.59 (3H, s), 2.85−2.95 (1H, m), 3.31 (1H, d, J = 13.2 Hz),

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7.92 (3H, m), 8.05 (1H, d, J = 2.2 Hz), 8.21 (1H, d, J = 8.8 Hz), 8.88

(1H, d, J = 2.4 Hz). Anal. (C₂₇H₃₂N₄O₂·0.4H₂O) C, H, N.

(3H, s), 3.89 (2H, d, J = 6.9 Hz), 5.31 (1H, q, J = 6.8 Hz), 7.01 (2H, d,

J = 8.8 Hz), 7.73 (1H, d, J = 8.8 Hz), 7.90−7.93 (3H, m), 8.12 (1H, d,

J = 2.4 Hz), 8.34 (1H, d, J = 8.8 Hz), 8.98 (1H, d, J = 2.4 Hz).

4-(Cyclopropylmethoxy)-N-[8-methyl-3-(1-pyrrolidin-1-

ylethyl)quinolin-7-yl]benzamide (10a). A mixture of 9 (21.9 g,

50.8 mmol), pyrrolidine (12.6 mL, 152 mmol), K₂CO₃(8.43 g, 61.0

mmol), and KI (10.1 g, 61.0 mmol) in DMF (300 mL) was stirred at

70 °C for 3 h. The reaction mixture was partitioned between AcOEt

and water. The organic layer was washed with water and brine and

dried over MgSO₄. After removal of the solvent under reduced

pressure, the residue was chromatographed on NH-silica gel (hexane/

AcOEt = 1/1) and silica gel (hexane/AcOEt = 1/1, AcOEt, AcOEt/

MeOH = 4/1) to give a pale yellow solid. This was dissolved in

AcOEt, and the solution was washed with 10% NaHCO₃and brine

and dried over MgSO₄. After removal of the solvent under reduced

pressure, the resulting residue was triturated with Et₂O to give 10a

5-(4-Fluorophenyl)-N-[8-methyl-3-(pyrrolidin-1-ylmethyl)-

quinolin-7-yl]-5-oxopentanamide (6h). The title compound was

prepared in 10% yield starting from 5a using the procedure described

1

for 6d: mp 172−173 °C. H NMR (300 MHz, CDCl₃) δ 1.79 (4H,

m), 2.23 (2H, m), 2.57 (6H, m), 2.73 (3H, s), 3.15 (2H, t, J = 6.7 Hz),

3.78 (2H, s), 7.12 (2H, t, J = 8.8 Hz), 7.48 (1H, s), 7.64 (1H, d, J = 8.8

Hz), 8.03 (4H, m), 8.85 (1H, d, J = 2.0 Hz). Anal. (C₂₆H₂₈F N₃O₂) C,

H, N.

5-(4-Fluorophenyl)-N-[8-methyl-3-(pyrrolidin-1-ylmethyl)-

quinolin-7-yl]pentanamide (6i). The title compound was prepared

in 12% yield starting from 5a using the procedure described for 6d:

1

mp 138−139 °C. H NMR (300 MHz, CDCl₃) δ 1.76 (2H, m), 1.88

(4H, m), 2.04 (3H, m), 2.50 (2H, t, J = 6.7 Hz), 2.67 (6H, m), 2.71

(3H, s), 3.91 (2H, s), 6.97 (2H, t, J = 8.7 Hz), 7.15 (1H, m), 7.24 (1H,

s), 7.67 (1H, d, J = 8.8 Hz), 8.10 (1H, d, J = 9.1 Hz), 8.16 (1H, s),

8.88 (1H, d, J = 1.9 Hz). Anal. (C₂₆H₃₀FN₃O) C, H, N.

1

(15.8 g, 72%) as a pale yellow powder: mp 189−190 °C. H NMR

(300 MHz, CDCl₃) δ 0.39 (2H, m), 0.69 (2H, m), 1.21−1.38 (1H,

m), 1.50 (3H, d, J = 6.6 Hz), 1.79 (4H, m), 2.31−2.49 (2H, m), 2.53−

2.66 (2H, m), 2.81 (3H, s), 3.37−3.49 (1H, m), 3.89 (2H, d, J = 6.9

Hz), 7.01 (2H, d, J = 8.8 Hz), 7.69 (1H, d, J = 8.8 Hz), 7.90−7.93

(3H, m), 8.05 (1H, d, J = 2.2 Hz), 8.24 (1H, d, J = 8.8 Hz), 8.92 (1H,

d, J = 2.2 Hz). Anal. (C₂₇H₃₁N₃O₂·0.1 H₂O) C, H, N.

4-(Cyclopropylmethoxy)-N-{8-methyl-3-[(2-methylpyrroli-

din-1-yl)methyl]quinolin-7-yl}benzamide (6j). The title com-

pound was prepared in 72% yield starting from 5b using the

procedure described for 6d: mp 159 °C. ¹H NMR (300 MHz, CDCl₃)

δ 0.36−0.43 (2H, m), 0.65−0.73 (2H, m), 1.22 (3H, d, J = 6.0 Hz),

1.25−1.38 (1H, m), 1.41−1.55 (1H, m), 1.61−1.81 (2H, m), 1.90−

2.04 (1H, m), 2.17 (1H, q, J = 8.9 Hz), 2.42−2.54 (1H, m), 2.81 (3H,

s), 2.88−2.96 (1H, m), 3.36 (1H, d, J = 13.4 Hz), 3.89 (2H, d, J = 7.0

Hz), 4.19 (1H, d, J = 13.4 Hz), 6.98−7.04 (2H, m), 7.70 (1H, d, J =

8.9 Hz), 7.88−7.95 (3H, m), 8.05 (1H, d, J = 2.1 Hz), 8.24 (1H, d, J =

8.9 Hz), 8.89 (1H, d, J = 2.1 Hz). Anal. (C₂₇H₃₁N₃O₂·0.2H₂O) C, H,

N.

Optical Resolution of 10a. A 200 mL solution of 10a (2.0 g) in

ethanol was loaded onto Chiralpak AD (50 mm i.d. × 500 mm)

through an injection line. Preparative HPLC was run at a ﬂow of 80

mL/min ethanol at 35 °C (UV 254 nm). Fractions eluting at 17 min

(tR1, LP-10a) and at 32 min (tR2, P-10a) were collected and

concentrated. To the resulting residue was added hexane, and the

mixture was concentrated under reduced pressure to aﬀord LP-10a

(1.0 g, >99.9% ee) and P-10a (1.0 g, >99.9% ee), respectively.

4-(Cyclopropylmethoxy)-N-{8-methyl-3-[(1S)-1-pyrrolidin-1-

ylethyl]quinolin-7-yl}benzamide (LP-10a = (S)-10a). White solid,

1-(7-Amino-8-methylquinolin-3-yl)ethanol (7). To an ice-

cooled solution of methylmagnesium bromide (3 M in Et₂O, 71.6

mL, 214.8 mmol) in THF (200 mL) was added dropwise a solution of

4 (10.0 g, 53.7 mmol) in THF (200 mL). After being stirred at room

temperature for 3 h, the reaction mixture was poured into 10% NH₄Cl

(1000 mL) and the mixture was extracted with AcOEt (500 mL). The

extract was washed with brine and dried over MgSO₄. After removal of

the solvent under reduced pressure, the residue was chromatographed

on NH-silica gel (AcOEt) to give 7 as an orange amorphous (8.45 g,

mp 189−190 °C. [α]²⁵−37.25 (c 0.996, MeOH). Anal.

D

(C₂₇H₃₁N₃O₂) C, H, N.

4-(Cyclopropylmethoxy)-N-{8-methyl-3-[(1R)-1-pyrrolidin-1-

ylethyl]quinolin-7-yl}benzamide (P-10a = (R)-10a). White solid,

mp 189−190 °C. [α]²⁵_D+39.32 (c 1.00, MeOH). Anal. (C₂₇H₃₁N₃O₂)

C, H, N.

Synthesis of 4-(Cyclopropylmethoxy)-N-{8-methyl-3-[(1R)-1-

pyrrolidin-1-ylethyl]quinolin-7-yl}benzamide ((R)-10a) from

17. A mixture of 17 (6.00 g, 16.0 mmol, 99% ee), 1,4-dibromobutane

(4.14 g, 19.2 mmol), and Na₂CO₃(5.10 g, 48.0 mmol) in DMF (150

mL) was stirred at 60 °C for 14 h. After the reaction was completed,

water (200 mL) was added to the reaction mixture and the mixture

was extracted with AcOEt (500 mL). The extract was washed with

brine, dried over MgSO₄, ﬁltered, and concentrated under reduced

pressure. The resulting residue was chromatographed on silica gel

(AcOEt/MeOH = 5/1) to give (R)-10a as colorless crystals (4.20 g,

61%, 98% ee by chiral HPLC analysis).

1

78%). H NMR (300 MHz, CDCl₃) δ 1.57 (3H, d, J = 6.4 Hz), 2.57

(3H, s), 4.01 (2H, br s), 5.04 (1H, q, J = 6.4 Hz), 6.98 (2H, d, J = 8.7

Hz), 7.45 (2H, d, J = 8.7 Hz), 7.91 (2H, d, J = 2.4 Hz), 8.78 (2H, d, J

= 2.4 Hz).

3-(1-Chloroethyl)-8-methylquinolin-7-amine Dihydrochlor-

ide (8). A mixture of 7 (8.45 g, 41.8 mmol) and thionyl chloride

(100 mL) was stirred at room temperature for 16 h. After removal of

an excess amount of thionyl chloride under reduced pressure, the

resulting residue was triturated with THF to give 8 (10.7 g, 87%) as a

1

brown powder. H NMR (300 MHz, CDCl₃) δ 2.05 (3H, d, J = 6.9

Hz), 3.19 (3H, s), 5.43 (1H, q, J = 6.9 Hz), 8.04 (1H, d, J = 8.7 Hz),

8.58 (1H, d, J = 8.7 Hz), 8.90 (1H, d, J = 2.0 Hz), 9.50 (1H, d, J = 2.0

Hz).

4-(Cyclopropylmethoxy)-N-[8-methyl-3-(1-piperidin-1-

ylethyl)quinolin-7-yl]benzamide (10b). The title compound was

prepared in 73% yield starting from 9 using the procedure described

1

N-[3-(1-Chloroethyl)-8-methylquinolin-7-yl]-4-

(cyclopropylmethoxy)benzamide (9). To a mixture of 4-cyclo-

propylmethoxybenzoic acid (1.44 g, 7.49 mmol) and DMF (0.02 mL,

0.34 mmol) in THF (40 mL) was added a solution of oxalyl chloride

(0.70 mL, 8.17 mmol) in THF (10 mL) under ice-cooling. After being

stirred at room temperature for 1 h, the reaction mixture was

concentrated under reduced pressure and the resulting residue was

dissolved in THF (20 mL). This mixture was added to a solution of 8

(2.0 g, 6.81 mmol) and triethylamine (4.7 mL, 34.3 mmol) in THF

(40 mL), and the mixture was stirred at room temperature for 16 h.

The reaction mixture was ﬁltered through a glass ﬁlter, and the ﬁltrate

was concentrated under reduced pressure. The resulting residue was

partitioned between AcOEt and water. The AcOEt layer was washed

with brine and dried over MgSO₄. After removal of the solvent under

reduced pressure, the residue was puriﬁed by column chromatography

(NH-silica gel, hexane/AcOEt = 4/1 to 1/1) to give 9 (0.91 g, 34%) as

for 10a: mp 184−186 °C. H NMR (300 MHz, CDCl₃) δ 0.34−0.47

(2H, m), 0.62−0.77 (2H, m), 1.19−1.45 (3H, m), 1.48 (3H, d, J = 6.8

Hz), 1.52−1.65 (4H, m), 2.29−2.55 (4H, m), 2.82 (3H, s), 3.68 (1H,

q, J = 6.8 Hz), 3.89 (2H, d, J = 7.0 Hz), 7.01 (2H, d, J = 8.7 Hz), 7.71

(1H, d, J = 8.9 Hz), 7.86−8.00 (4H, m), 8.26 (1H, d, J = 8.9 Hz), 8.93

(1H, d, J = 2.1 Hz). Anal. (C₂₈H₃₃N₃O₂·0.1 H₂O) C, H, N.

N-[3-(1-Azepan-1-ylethyl)-8-methylquinolin-7-yl]-4-

(cyclopropylmethoxy)benzamide (10c). The title compound was

prepared in 71% yield starting from 9 using the procedure described

1

for 10a: mp 169−171 °C. H NMR (300 MHz, CDCl₃) δ 0.34−0.46

(2H, m), 0.62−0.76 (2H, m), 1.21−1.39 (1H, m), 1.47 (3H, d, J = 6.6

Hz), 1.59 (8H, br s), 2.66 (4H, br s), 2.82 (3H, s), 3.89 (2H, d, J = 7.0

Hz), 4.03 (1H, q, J = 6.6 Hz), 7.01 (2H, d, J = 8.9 Hz), 7.70 (1H, d, J

= 8.9 Hz), 7.85−8.05 (4H, m), 8.24 (1H, d, J = 8.9 Hz), 9.05 (1H, d, J

= 2.3 Hz). Anal. (C₂₉H₃₅N₃O₂·0.2 H₂O) C, H, N.

4-(Cyclopropylmethoxy)-N-{8-methyl-3-[1-(4-methylpipera-

zin-1-yl)ethyl]quinolin-7-yl}benzamide (10d). The title com-

pound was prepared in 66% yield starting from 9 using the procedure

1

a yellow solid. H NMR (300 MHz, CDCl₃) δ 0.37−0.42 (2H, m),

0.66−0.73 (2H, m), 1.26−1.34 (1H, m), 1.98 (3H, d, J = 6.9 Hz), 2.81

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1

described for 10a: mp 168−169 °C. H NMR (300 MHz, CDCl₃) δ

3-Bromo-N-[8-methyl-3-(1-pyrrolidin-1-ylethyl)quinolin-7-

yl]benzamide (12a). A mixture of LP-10a (2.50 g, 5.82 mmol) and

concentrated HCl (40 mL) was stirred at 100 °C for 16 h. After

removal of the solvent under reduced pressure, the residue was

dissolved in water and the mixture was basiﬁed with 10% NaHCO₃

under ice-cooling. The mixture was extracted with AcOEt by the

salting out technique to give 11a as a pale brown oil (1.33 g, 90%). To

a mixture of 11a (0.17 g, 0.65 mmol) and triethylamine (0.09 mL, 0.65

mmol) in THF (10 mL) was added 3-bromobenzoyl chloride (0.14 g,

0.65 mmol) at 0 °C. After being stirred at room temperature for 16 h,

the reaction mixture was poured into water and the mixture was

extracted with AcOEt. The extract was washed with 10% NaHCO₃and

brine and dried over MgSO₄. After removal of the solvent under

reduced pressure, 12a (0.23 g, 81%) was obtained as a pale yellow

0.31−0.45 (2H, m), 0.58−0.77 (2H, m), 1.19−1.39 (1H, m), 1.47

(3H, d, J = 6.8 Hz), 2.27 (3H, s), 2.45 (8H, m), 2.82 (3H, s), 3.63

(1H, q, J = 6.6 Hz), 3.90 (2H, d, J = 7.0 Hz), 7.01 (2H, d, J = 8.9 Hz),

7.70 (1H, d, J = 8.9 Hz), 7.85−7.96 (3H, m), 7.99 (1H, d, J = 2.1 Hz),

8.27 (1H, d, J = 8.9 Hz), 8.94 (1H, d, J = 2.1 Hz). Anal.

(C₂₈H₃₄N₄O₂·0.2 H₂O) C, H, N.

4-(Cyclopropylmethoxy)-N-(3-{1-[(3S)-3-hydroxypyrrolidin-

1-yl]ethyl}-8-methylquinolin-7-yl)benzamide (10e). The title

compound was prepared in 72% yield starting from 9 using the

procedure described for 10a: mp 168 °C. ¹H NMR (300 MHz,

DMSO-d₆) δ 0.28−0.45 (2 H, m), 0.53−0.69 (2 H, m), 1.13−1.36 (1

H, m), 1.42 (3H, d, J = 6.4 Hz), 1.49−1.65 (1H, m), 1.88−2.09 (1H,

m), 2.17−2.46 (1H, m), 2.63 (3H, s), 2.68−2.95 (2H, m), 3.42−3.64

(1H, m), 3.92 (2H, d, J = 7.0 Hz), 4.10−4.30 (1H, m), 4.59−4.76

(1H, m), 7.07 (2H, d, J = 8.7 Hz), 7.58 (1H, d, J = 8.7 Hz), 7.80 (1H,

d, J = 8.9 Hz), 8.02 (2H, d, J = 8.9 Hz), 8.19 (1H, d, J = 2.0 Hz), 8.90

(1H, s), 10.05 (1H, s). Anal. (C₂₇H₃₁N₃O₃·0.1H₂O) C, H, N.

4-(Cyclopropylmethoxy)-N-(3-{1-[(2-hydroxyethyl)amino]-

ethyl}-8-methylquinolin-7-yl)benzamide (10f). The title com-

pound was prepared in 59% yield starting from 9 using the procedure

solid. This was recrystallized from hexane−AcOEt to give pale yellow

1

crystals: mp 123−124 °C. [α]²⁵−34.65° (c 1.00, MeOH). H NMR

D

(300 MHz, CDCl₃) δ 1.51 (3H, d, J = 6.6 Hz), 1.69−1.87 (4 H, m),

2.42 (2H, dd, J = 1.8, 6.9 Hz), 2.52−2.70 (2H, m), 2.82 (3H, s), 3.45

(1H, q, J = 6.6 Hz), 7.41 (1H, t, J = 7.9 Hz), 7.62−7.77 (2H, m),

7.81−7.95 (2H, m), 8.01−8.24 (3H, m), 8.94 (1H, d, J = 2.3 Hz).

Anal. (C₂₃H₂₄BrN₃O·1.0 H₂O) C, H, N.

1

described for 10a: mp 158 °C. H NMR (300 MHz, DMSO-d₆) δ

X-ray Crystallography Analysis of 12a. Results are as follows:

compound formula C₂₃H₂₄BrN₃O·H₂O, M_r= 456.38, triclinic, P1, a =

7.4429(9) Å, b = 13.6860(12) Å, c = 20.469(2) Å, α = 90.422(3)°, β =

90.138(4)°, γ = 90.044(4)°, V = 2085.0(4) Å³, Z = 4, D_calc= 1.454 g/

cm³, monochromatized radiation λ(Mo Kα) = 0.710 75 Å, μ = 2.002

mm⁻¹, F(000) = 944, T = 93 K. Data were collected on a Rigaku

RAXIS RAPID imaging plate to a θ limit of 27.49° which yielded

16 908 reﬂections. There are 12 512 unique reﬂections with 8788

observed at the 2σ level. The structure was solved by direct methods

(SIR92)²⁹and reﬁned using full-matrix least-squares on F²(SHELXL-

97).³⁰The ﬁnal model was reﬁned using 648 parameters and all 12 512

data. All non-hydrogen atoms were reﬁned with isotropic thermal

displacements. The ﬁnal agreement statistics are as follows: R = 0.0788

(based on 8788 reﬂections with I > 2σ(I)), wR = 0.1856, S = 1.025.

The maximum peak height in a ﬁnal diﬀerence Fourier map is 0.975 e

Å³, and this peak is without chemical signiﬁcance. The absolute

conﬁguration was determined based on the Flack parameter,³¹

0.038(13), reﬁned using 4052 Friedel pairs. CCDC 859003 contains

the supplementary crystallographic data for this paper. These data can

be obtained free of charge from The Cambridge Crystallographic Data

Centre via www.ccdc.cam.ac.uk/data_request/cif.

0.31−0.42 (2H, m), 0.53−0.67 (2H, m), 1.18−1.35 (1H, m), 1.40

(3H, d, J = 6.6 Hz), 2.35−2.47 (1, m), 2.52−2.59 (1H, m), 2.63 (3H,

s), 3.45 (2H, q, J = 5.5 Hz), 3.92 (2H, d, J = 7.2 Hz), 3.95−4.09 (1H,

m), 4.50 (1H, t, J = 5.4 Hz), 7.07 (2H, d, J = 8.9 Hz), 7.58 (1H, d, J =

8.7 Hz), 7.78 (1H, d, J = 8.9 Hz), 8.02 (2H, d, J = 8.9 Hz), 8.20 (1H,

d, J = 2.1 Hz), 8.93 (1H, d, J = 2.3 Hz), 10.05 (1 H, s). Anal.

(C₂₅H₂₉N₃O₃·0.5H₂O) C, H, N.

4-(Cyclopropylmethoxy)-N-(3-{1-[(2-hydroxy-2-

methylpropyl)amino]ethyl}-8-methylquinolin-7-yl)benzamide

(10g). A mixture of 9 (0.44 g, 1.02 mmol), 1-amino-2-methylpropan-

2-ol (0.91 g, 10.2 mmol), and DIPEA (0.45 mL, 2.58 mmol) in NMP

(10 mL) was stirred at 60 °C for 5 h. The reaction mixture was

partitioned between AcOEt and water. The organic layer was washed

with brine, dried over Na₂SO₄, ﬁltered, and concentrated in vacuo.

The residue was chromatographed on NH-silica gel (AcOEt/MeOH =

95/5) followed by recrystallization from AcOEt and diisopropyl ether

to obtain 10g (0.22 g, 0.71 mmol, 70%) as a colorless crystalline solid,

mp 124−125 °C. ¹H NMR (300 MHz, CDCl₃) δ 0.36−0.43 (2H, m),

0.65−0.74 (2H, m), 1.15 (3H, s), 1.18 (3H, s), 1.25−1.39 (1H, m),

1.51 (3H, d, J = 6.6 Hz), 2.38 (1H, d, J = 11.7 Hz), 2.54 (1H, d, J =

11.7 Hz), 2.76 (1H, br), 2.82 (3H, s), 3.90 (2H, d, J = 7.0 Hz), 4.00

(1H, q, J = 6.6 Hz), 7.01 (2H, d, J = 8.7 Hz), 7.71 (1H, d, J = 8.9 Hz),

7.87−7.96 (3H, m), 8.00 (1H, d, J = 2.1 Hz), 8.27 (1H, d, J = 8.9 Hz),

8.91 (1H, d, J = 2.1 Hz). Anal. (C₂₇H₃₃N₃O₃) C, H, N.

3-Bromo-N-[8-methyl-3-(1-pyrrolidin-1-ylethyl)quinolin-7-

yl]benzamide (12b). The title compound was prepared in 79% yield

starting from P-10a using the procedure described for 12a: mp 123−

124 °C. [α]²⁵+34.65° (c 1.00, MeOH); ¹H NMR (300 MHz,

D

N-[3-(1-{[2-(Acetylamino)ethyl]amino}ethyl)-8-methylquino-

lin-7-yl]-4-(cyclopropylmethoxy)benzamide (10h). The title

compound was prepared in 68% yield starting from 9 using the

CDCl₃) δ 1.51 (3H, d, J = 6.6 Hz), 1.69−1.87 (4 H, m), 2.42 (2H, dd,

J = 1.8, 6.9 Hz), 2.52−2.70 (2H, m), 2.82 (3H, s), 3.45 (1H, q, J = 6.6

Hz), 7.41 (1H, t, J = 7.9 Hz), 7.62−7.77 (2H, m), 7.81−7.95 (2H, m),

8.01−8.24 (3H, m), 8.94 (1H, d, J = 2.3 Hz).

HPLC Analysis of 12a and 12b. Column, Chiralpak AD-H

FA031, 4.6 mm i.d. × 250 mmL; mobile phase, hexane/ethanol = 500/

500 (v/v); ﬂow rate of 1.0 mL/min; temperature 30 °C; detection, UV

254 nm; concentration, 0.1 mg/mL; injection, 0.010 mL. 12a: >99.9%

ee (tR1). 12b: 99.9% ee (tR2).

1

procedure described for 10g: mp 169−170 °C. H NMR (300 MHz,

CDCl₃) δ 0.36−0.43 (2H, m), 0.65−0.73 (2H, m), 1.26−1.36 (1H,

m), 1.48 (3H, d, J = 6.8 Hz), 1.97 (3H, s), 2.51−2.62 (1H, m), 2.71−

2.82 (1H, m), 2.81 (3H, s), 3.31 (2H, q, J = 6.0 Hz), 3.90 (2H, d, J =

7.0 Hz), 4.00 (1H, q, J = 6.6 Hz), 5.86 (1H, s), 7.02 (2H, d, J = 8.9

Hz), 7.70 (1H, d, J = 8.9 Hz), 7.91 (1H, s), 7.92 (2H, d, J = 8.9 Hz),

7.99 (1H, d, J = 2.3 Hz), 8.27 (1H, d, J = 8.9 Hz), 8.91 (1H, d, J = 2.3

Hz). Anal. (C₂₇H₃₂N₄O₃·0.2H₂O) C, H, N.

4-(Cyclopropylmethoxy)-N-(3-formyl-8-methylquinolin-7-

yl)benzamide (13). To an ice-cooled solution of cyclopropylmethox-

ybenzoic acid (20.0 g, 107 mmol) and DMF (0.40 mL, 5.37 mmol) in

THF (350 mL) was added dropwise a solution of oxalyl chloride (10.1

mL, 118 mmol) in THF (50 mL). After being stirred at room

temperature for 1 h, the reaction mixture was concentrated under

reduced pressure and the resulting residue was dissolved in pyridine

(200 mL). This solution was added to a solution of 4 in pyridine (200

mL) under ice-cooling and then stirred at room temperature for 16 h.

The reaction mixture was diluted with THF (400 mL), and the

mixture was ﬁltered through a Celite pad. The ﬁltrate was

concentrated under reduced pressure and the resulting residue was

chromatographed on silica gel (CH₂Cl₂, AcOEt) to give a yellow solid.

This was triturated with Et₂O to give 13 (20.1 g, 55%) as a yellow

Optical Resolution of 10h. The optical resolution of 10h was

carried out using a method similar to the one described for 10a:

Chiralpak AD (50 mm i.d. × 500 mm), hexane/EtOH/DIPEA = 50/

50/0.1, UV 220 nm, 60 mL/min, 30 °C. Less polar LP-10h (84 mg,

>99.9% ee) and polar P-10h (85 mg, >99.9% ee) were collected from

10h (174 mg).

N-{3-[(1R)-1-{[2-(Acetylamino)ethyl]amino}ethyl]-8-methyl-

quinolin-7-yl}-4-(cyclopropylmethoxy)benzamide (LP-10h =

(R)-10h). White solid:, mp 169−170 °C. [α]²⁵+52.60° (c 0.1980,

D

MeOH). Anal. (C₂₇H₃₂N₄O₃·0.2H₂O) C, H, N.

N-{3-[(1S)-1-{[2-(Acetylamino)ethyl]amino}ethyl]-8-methyl-

quinolin-7-yl}-4-(cyclopropylmethoxy)benzamide (P-10h = (S)-

10h). White solid, mp 169−170 °C. [α]²⁵_D−52.60° (c 0.20, MeOH).

Anal. (C₂₇H₃₂N₄O₃) C, H, N.

1

powder. H NMR (300 MHz, CDCl₃) δ 0.37−0.41 (2H, m), 0.66−

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0.73 (2H, m), 1.20−1.33 (1H, m), 2.86 (3H, s), 3.90 (2H, d, J = 6.9

Hz), 6.93 (1H, d, J = 9.0 Hz), 7.03 (2H, d, J = 9.3 Hz), 7.93 (2H, d, J

= 9.3 Hz), 8.05 (1H, s), 8.57−8.60 (2H, m), 9.35 (1H, d, J = 2.1 Hz),

10.25 (1H, s).

Hz), 7.01 (2H, d, J = 8.8 Hz), 7.71 (1H, d, J = 8.8 Hz), 7.89−7.93

(3H, m), 8.08 (1H, d, J = 2.0 Hz), 8.26 (1H, d, J = 8.8 Hz), 8.93 (1H,

d, J = 2.0 Hz). [α]_D+26.50° (c 0.20, CHCl₃). 98% ee by HPLC

(SumiChiral OA 8000, n-hexane/EtOH/CF₃COOH = 750/25/1, 1.2

mL/min, 35 °C).

25

4-(Cyclopropylmethoxy)-N-[3-(1-hydroxyethyl)-8-methyl-

quinolin-7-yl]benzamide ((rac)-14). The title compound was

prepared in 97% yield starting from 13 using the procedure described

4-(Cyclopropylmethoxy)-N-{8-methyl-3-[(1R)-1-{[(2-

nitrophenyl)sulfonyl]amino}ethyl]quinolin-7-yl}benzamide

(18). A solution of 2-nitrobenzenesulfonyl chloride (7.15 g, 32.3

mmol) in THF (100 mL) was added to a solution of 17 (>99.9% ee,

10.1 g, 26.9 mmol) and triethylamine (5.6 mL, 40.2 mmol) in THF

(300 mL) at 0 °C. The mixture was stirred at room temperature for 12

h. The reaction mixture was concentrated in vacuo, and the residue

was partitioned between AcOEt and water. The mixture was washed

with brine, dried over Na₂SO₄, ﬁltered, and concentrated under

reduced pressure. The residue was puriﬁed by recrystallization from

1

for 7. H NMR (300 MHz, DMSO-d₆) δ 0.36 (2H, td, J = 5.23, 4.24

Hz), 0.60 (2H, m), 1.27 (1H, m), 1.48 (3H, d, J = 6.41 Hz), 2.64 (3H,

s), 3.92 (2H, d, J = 6.97 Hz), 5.00 (1H, dt, J = 9.80, 6.22 Hz), 5.49

(1H, d, J = 4.14 Hz), 7.07 (2H, d, J = 8.85 Hz), 7.59 (1H, d, J = 8.85

Hz), 7.81 (1H, d, J = 8.67 Hz), 8.02 (2H, d, J = 8.85 Hz), 8.23 (1H, d,

J = 2.07 Hz), 8.94 (1H, d, J = 2.26 Hz), 10.06 (1H, s).

N-(3-Acetyl-8-methylquinolin-7-yl)-4-(cyclopropylmethoxy)-

benzamide (15). A solution of (rac)-14 (10.0 g, 26.6 mmol) and

MnO₂(40.0 g, 460 mmol) in THF (1000 mL) was heated at reﬂux for

24 h. The reaction mixture was passed through a Celite and

concentrated in vacuo. The residue was crystallized from AcOEt to

give 15 (9.4 g, 94%) as a white powder. ¹H NMR (300 MHz, DMSO-

d₆) δ 0.34−0.39 (2H, m), 0.57−0.63 (2H, m), 1.24−1.29 (1H, m),

2.68 (3H, s), 2.74 (3H, s), 3.93 (2H, d, J = 7.0 Hz), 7.08 (2H, d, J =

8.9 Hz), 7.78 (1H, d, J = 8.7 Hz), 8.02 (3H, d, J = 8.9 Hz), 9.00 (1H,

d, J = 2.1 Hz), 9.35 (1H, d, J = 2.1 Hz), 10.13 (1H, s).

1

AcOEt to obtain 18 (14.6 g, 26.0 mmol, 97%) as white crystals. H

NMR (300 MHz, CDCl₃) δ 0.36−0.44 (2H, m), 0.65−0.74 (2H, m),

1.26−1.36 (1H, m), 1.67 (3H, d, J = 7.2 Hz), 2.71 (3H, s), 3.90 (2H,

d, J = 6.8 Hz), 4.92 (1H, quint, J = 7.2 Hz), 5.89 (1H, d, J = 8.3 Hz),

7.02 (2H, d, J = 8.7 Hz), 7.17 (1H, td, J = 7.8, 1.1 Hz), 7.40 (1H, td, J

= 7.8, 1.5 Hz), 7.53 (1H, d, J = 8.7 Hz), 7.59 (1H, dd, J = 7.8, 1.3 Hz),

7.67 (1H, dd, J = 8.0, 1.1 Hz), 7.87 (1H, d, J = 2.7 Hz), 7.88 (1H, s),

7.91 (2H, d, J = 9.1 Hz), 8.23 (1H, d, J = 9.1 Hz), 8.70 (1H, d, J = 2.3

Hz).

4-(Cyclopropylmethoxy)-N-{3-[(1S)-1-hydroxyethyl]-8-meth-

ylquinolin-7-yl}benzamide ((S)-14). In a stainless autoclave (1000

mL) that was ﬁlled with argon were added 15 (10.3 g, 27.5 mmol),

potassium tert-butoxide (25 g, 220.0 mmol), and 2-propanol (200

mmol) in DMF (440 mL). After the mixture was stirred at room

temperature for 30 min under an argon atmosphere, RuCl₂{(R)-

xylbinap}{(R)-daipen} (33.6 mg, S/C = 1000) was added to the

reaction mixture. The reduction was performed at room temperature

under 0.7 MPa of hydrogen for 24 h. After the reaction was ﬁnished,

hydrogen was released carefully and the solvent was removed by rotary

evaporation. The crystals were washed with 1 M HCl (220 mL), water

(300 mL) and dried in vacuo to provide brown crystals (10.4 g,

quant). ¹H NMR (400 MHz, DMSO-d₆) δ: 0.35−0.38 (2H, m), 0.59−

0.61 (2H, m), 1.25 (1H, m), 1.47 (3H, d, J = 6.3 Hz), 2.64 (3H, s),

3.92 (2H, d, J = 7.0 Hz), 4.98 (1H, q, J = 6.3 Hz), 7.06 (2H, d, J = 8.5

Hz), 7.58 (1H, d, J = 8.5 Hz), 7.80 (1H, d, J = 8.5 Hz), 8.01 (2H, d, J

= 8.5 Hz), 8.22 (1H, d, J = 2.0 Hz), 8.93 (1H, d, J = 2.0 Hz), 10.04

N-{3-[(1R)-1-{(2-Aminoethyl)[(2-nitrophenyl)sulfonyl]-

amino}ethyl]-8-methylquinolin-7-yl}-4-(cyclopropylmethoxy)-

benzamide (19). A solution of tert-butyl N-(2-hydroxyethyl)-

carbamate (28.8 g, 179 mmol) in THF (65 mL) was added to a

suspension of 18 (50.0 g, 89.2 mmol) and triphenylphosphine (46.8 g,

178 mmol) in THF (850 mL) at 0 °C. A solution of diisopropyl

azodicarboxylate (DIAD, 90%, 40.1 g, 178 mmol) in THF (65 mL)

was added at 0 °C for 45 min. The mixture was stirred at room

temperature for 2.5 h. A solution of 4 M HCl in AcOEt (334 mL) was

added to the above reaction mixture at 0 °C for 15 min. The mixture

was stirred at room temperature for 15 h. The reaction mixture was

concentrated under reduced pressure. AcOEt was added. The mixture

was extracted with 2 M HCl (aq)/DMSO = 5/3. The aqueous layers

were treated with sodium carbonate to adjust the pH to 9. The mixture

was extracted with AcOEt. The organic layer was washed with brine,

dried over Na₂SO₄, ﬁltered, and concentrated under reduced pressure

to obtain 19 (63.9 g) as pale yellow foam. This foam was used for the

next step without further puriﬁcation. ¹H NMR (300 MHz, CDCl₃) δ

0.36−0.44 (2H, m), 0.65−0.74 (2H, m), 1.27−1.38 (3H, m), 1.70

(3H, d, J = 6.8 Hz), 2.44 (1H, dt, J = 12.9, 7.2 Hz), 2.64 (1H, dt, J =

13.1, 7.2 Hz), 2.78 (3H, s), 3.29 (2H, t, J = 7.2 Hz), 3.90 (2H, d, J =

7.2 Hz), 5.49 (1H, q, J = 7.2 Hz), 7.02 (2H, d, J = 8.7 Hz), 7.62−7.76

(4H, m), 7.92 (2H, d, J = 8.7 Hz), 7.92 (1H, s), 8.02 (1H, d, J = 1.9

Hz), 8.05−8.11 (1H, m), 8.31 (1H, d, J = 9.1 Hz), 8.90 (1H, d, J = 2.3

Hz).

25

(1H, s). [α]_D−35.60° (c 0.20, DMF). 98% ee by HPLC (Chiralcel

OD-RH, H₂O/CH₃CN = 60/40, 1.0 mL/min, 35 °C).

N-{3-[(1R)-1-Azidoethyl]-8-methylquinolin-7-yl}-4-

(cyclopropylmethoxy)benzamide (16). DPPA (34 mL, 100

mmol) was added to a mixture of (S)-14 (9.9 g, 26.3 mmol, 98.0%

ee) and N, N-diisoproylethylamine (300 mL) at −40 °C. The reaction

mixture was stirred at room temperature for 4 days. Water (200 mL)

was added to the reaction mixture, and the solution was extracted with

AcOEt (500 mL). The extracts were washed with brine and dried

(MgSO₄). The solvent was evaporated in vacuo, and the residue was

passed through a silica gel plug, eluting with AcOEt/hexane = 1/3.

Solvent was removed under vacuum to yield the chiral azide 16 as

N-{3-[(1R)-1-{[2-(Acetylamino)ethyl]amino}ethyl]-8-methyl-

quinolin-7-yl}-4-(cyclopropylmethoxy)benzamide ((R)-10h). A

solution of acetyl chloride (10.5 g, 134 mmol) in THF (30 mL) was

added to a solution of 19 (63.9 g, all amounts from above-mentioned

reaction) and triethylamine (18.6 mL, 133 mmol) in THF (450 mL)

at 0 °C. The mixture was stirred at 0 °C for 10 min. AcOEt was added.

The mixture was washed with water, Na₂CO₃aqueous solution, and

brine. The organic layer was dried over Na₂SO₄, ﬁltered through a

silica gel plug, and concentrated under reduced pressure to obtain

acetamide intermediate as a yellow foam (61.0 g). The above

acetamide intermediate (all amount) was dissolved with DMF (250

mL). Lithium hydroxide monohydrate (29.9 g, 713 mmol) was added.

A solution of mercaptoacetic acid (90%, 36.5 g, 357 mmol) in DMF

(40 mL) was added dropwise at 0 °C over 10 min. The mixture was

stirred at room temperature for 4 h. AcOEt was added. The mixture

was washed with 2.5% NaHCO₃aqueous solution and brine. The

organic layer was dried over Na₂SO₄, ﬁltered, and concentrated under

reduced pressure. The residue was puriﬁed by recrystallization from

AcOEt to obtain (R)-10h (39.2 g, 85.1 mmol, 95% from 18) as white

1

yellow crystals (9.5 g, 90% yield). H NMR (400 MHz, CDCl₃) δ:

0.38−0.42 (2H, m), 0.67−0.70 (2H, m), 1.31 (1H, m), 1.68 (3H, d, J

= 6.8 Hz), 2.82 (3H, s), 3.89 (2H, d, J = 7.1 Hz), 4.86 (1H, q, J = 6.8

Hz), 7.02 (2H, d, J = 8.8 Hz), 7.74 (1H, d, J = 8.8 Hz), 7.91−7.93

(3H, m), 8.06 (1H, d, J = 2.2 Hz), 8.34 (1H, d, J = 8.8 Hz), 8.90 (1H,

25

d, J = 2.2 Hz). [α]_D+71.30° (c 0.20, CHCl₃). 98% ee by HPLC

(Chiralcel OJ-RH, 0.1 M KPF₆/CH₃CN = 50/50, 0.6 mL/min, 30

°C).

N-{3-[(1R)-1-Aminoethyl]-8-methylquinolin-7-yl}-4-

(cyclopropylmethoxy)benzamide (17). A mixture of 16 (6.70 g,

16.7 mmol, 98% ee) and palladium−carbon (1.70 g, 5%) in ethanol

(1100 mL) was stirred at room temperature under hydrogen

atmosphere for 2 h. After the reaction was ﬁnished, hydrogen was

released carefully and the reaction mixture was passed through Celite,

eluting with methanol. Solvent was removed under vacuum to yield 17

as pale yellow crystals (6.27 g, quant). ¹H NMR (400 MHz, CDCl₃) δ

0.38−0.42 (2H, m), 0.67−0.70 (2H, m), 1.29 (1H, m), 1.51 (3H, d, J

= 6.8 Hz), 2.81 (3H, s), 3.89 (2H, d, J = 6.8 Hz), 4.37 (1H, q, J = 6.8

25

crystals, 99.6% ee: mp 169−170 °C. [α]_D+52.6° (c 0.1980 in

1

MeOH). H NMR (300 MHz, CDCl₃) δ 0.36−0.43 (2H, m), 0.65−

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0.73 (2H, m), 1.26−1.36 (1H, m), 1.48 (3H, d, J = 6.8 Hz), 1.97 (3H,

s), 2.51−2.62 (1H, m), 2.71−2.82 (1H, m), 2.81 (3H, s), 3.31 (2H, q,

J = 6.0 Hz), 3.90 (2H, d, J = 7.0 Hz), 4.00 (1H, q, J = 6.6 Hz), 5.86

(1H, s), 7.02 (2H, d, J = 8.9 Hz), 7.70 (1H, d, J = 8.9 Hz), 7.91 (1H,

s), 7.92 (2H, d, J = 8.9 Hz), 7.99 (1H, d, J = 2.3 Hz), 8.27 (1H, d, J =

calculated by nonlinear logistic regression analysis in GraphPad

Prism software (GraphPad Software Inc.).

Measurement of Arachidonic Acid Release. CHO cells

expressing the human MCHR1 were plated in 24-well plates at a

density of 50 000 cells/well and cultured for 1 day. The cells were

incubated with [³H]arachidonic acid (0.2 μCi/well) for 16 h and

washed twice with 500 μL of Dulbecco’s modiﬁed Eagle’s medium

(DMEM) supplemented with 20 mM N-(2-hydroxyethyl)piperazine-

N′-ethanesulfonic acid (HEPES) (pH 7.4) and 0.2% bovine serum

albumin. The cells were then preincubated with compounds at various

concentrations at 37 °C for 30 min, and the reaction was started by

addition of MCH. After incubation for 45 min, the radioactivity in the

medium was measured with a liquid scintillation counter.

8.9 Hz), 8.91 (1H, d,

J = 2.3 Hz). Anal. Calcd for

C₂₇H₃₂N₄O₃·0.1H₂O: C, 70.14; H, 7.02; N, 12.12. Found: C, 69.98;

H, 7.17; N, 12.08.

Methyl 7-{[4-(Cyclopropylmethoxy)benzoyl]amino}-8-meth-

ylquinoline-3-carboxylate (20). To a solution of 13 (3.75 g, 10.4

mmol) in MeOH (200 mL) was added NIS (6.0 g, 26.9 mmol) and

K₂CO₃(3.7 g, 26.9 mmol). The resulting dark mixture was stirred for

16 h, at which time LC/MS analysis indicated complete consumption

of starting material. Water (5 mL) and Na₂S₂O₃·5H₂O (5.0 g) were

added to destroy remaining NIS or hypoiodite species. The resulting

mixture was extracted with Et₂O−hexane (1:1). The combined organic

extract was washed with brine (50 mL), and the solvent was removed

under reduced pressure to give 20 (3.92 g, quant) as a yellow powder.

This compound was used for the next reaction without further

puriﬁcation or identiﬁcation.

4-(Cyclopropylmethoxy)-N-[3-(1-hydroxy-1-methylethyl)-8-

methylquinolin-7-yl]benzamide (21). To a solution of methyl-

lithium (1.0 M ethereal solution, 50 mL, 50 mmol) in THF (300 mL)

was added 20 (3.92 g, 10.4 mmol) at 0 °C. The reaction mixture was

stirred at room temperature for 2 h. The reaction mixture was

partitioned between AcOEt and water. The AcOEt layer was washed

with brine and dried over MgSO₄. The solution was concentrated

under reduced pressure to aﬀord 21 (4.06 g, quant) as a pale brown

powder. This compound was used for the next reaction without further

puriﬁcation or identiﬁcation.

Rubidium (Rb⁺) Eﬄux Assay. HMZ/CHO.8B4 cells, which

stably expressed the hERG K⁺channel, were established by Takeda

Pharmaceutical Company. HMZ/CHO.8B4 cells were cultured in F-

12 nutrient mixture [Ham] (Invitrogen, Carlsbad, CA) containing

10% fetal bovine serum (FBS; Trace Scientiﬁc Ltd., Melbourne,

Australia), 500 μg/mL Geneticin (Invitrogen) in a humidiﬁed

atmosphere in 5% CO₂at 37 °C. For the Rb⁺eﬄux assay, HMZ/

CHO.8B4 cells (4 × 10⁴cells/well) were seeded on a collagen-coated

96-well assay plate (Becton Dickinson, Billerica, MA). After 24 h

culture, assay plates were washed with phosphate-buﬀered saline to

remove supplemented medium. Cells were then incubated (37 °C in

5% CO₂) with Rb-loading buﬀer containing the following: 150 mM

NaCl, 5.4 mM RbCl, 150 mM NaCl, 2 mM CaCl₂, 0.8 mM NaH₂PO₄,

1 mM MgCl₂, 5 mM glucose, 25 mM HEPES, 20% FBS, pH 7.4. After

3 h of incubation, each well was spiked to give a test compound and

incubated for an additional 30 min (n = 7). Wells were then washed

with minimum essential medium (MEM, Invitrogen) containing 10

mM HEPES to remove excess Rb loading buﬀer. To activate the

opening of hERG channels, cells were stimulated with buﬀer

containing MEM containing 50 mM KCl and 10 mM HEPES for an

additional 5 min. Finally, the supernatant was collected in a separate

assay plate, while cells were lysed with the addition 1% Triton X-100

to each well. To determine fractional Rb⁺eﬄux, the supernatant and

lysate from each experiment were run separately through the ICR8000

ﬂame atomic absorption spectrometer (Aurora Biomed Inc.,

Vancouver, BC, Canada). Rb⁺eﬄux was represented as the ratio of

the Rb⁺content of the supernatant with respect to the total Rb⁺in

each well. Each sample was measured twice. Data were then

normalized to account for variation in total Rb⁺eﬄux between

multiple experiments using the following equation: remaining acivity =

([Rb⁺]_sample− [Rb⁺]_bkgd)/([Rb⁺]_max− [Rb⁺]_bkgd), where [Rb⁺]_sampleis

the fractional eﬄux, [Rb⁺]_bkgdis the unstimulated eﬄux, and [Rb⁺]_max

is the maximum eﬄux.

4-(Cyclopropylmethoxy)-N-[8-methyl-3-(1-methyl-1-pyrroli-

din-1-ylethyl)quinolin-7-yl]benzamide (22). A mixture of 21

(4.06 g, 10.4 mmol) and thionyl chloride (30 mL) was stirred at 0 °C

for 30 min and at room temperature for 2 h. After removal of the

excess amount of thionyl chloride under reduced pressure, to the

resulting residue was added pyrrolidine (30 mL). The mixture was

stirred at 60 °C for 3 h. The reaction mixture was partitioned between

AcOEt and water. The AcOEt layer was washed with brine and

concentrated under reduced pressure. The resulting residue was

chromatographed on silica gel (AcOEt/MeOH = 5/1) to give 22 (1.20

1

g, 27%) as a pale brown powder: mp 161−163 °C. H NMR (300

MHz, CDCl₃) δ 0.37 (2H, m), 0.68 (2H, m), 1.32 (1H, m), 1.54 (6H,

s), 1.72 (4H, m), 2.01 (3H, s), 2.56 (4H, m), 3.89 (2H, d, J = 6.9 Hz),

7.00 (2H, d, J = 8.4 Hz), 7.25 (1H, s), 7.69 (1H, d, J = 8.7 Hz), 7.90

(2H, m), 8.07 (1H, s), 8.23 (1H, d, J = 8.7 Hz), 9.19 (1H, d, J = 2.1

Hz). Anal. (C₂₈H₃₃N₃O₂·0.3H₂O) C, H, N.

In Vivo Pharmacological Study (2-Day Assay). All animal

experiments were performed in compliance with the Guidelines for the

Care and Use of Laboratory Animals of Takeda Pharmaceutical

Company.

Measurement of Binding Aﬃnities. The MCHR1 binding

assays were based on the method of Takekawa et al.^14bwith minor

modiﬁcation. CHO cells stably expressing human MCHR1 and rat

MCHR1 were prepared.^2,14bThe frozen cell homogenate was thawed,

suspended in assay buﬀer (25 mM Tris-HCl, 1 mM EDTA, 0.1% BSA,

0.5 mM phenylmethylsulfonyl ﬂuoride, 1 μg/mL pepstatin A, 10 μg/

mL phosphoramidon, and 20 μg/mL leupeptine, pH 7.5), and used for

the binding assay. The membrane fraction was diluted to 2 μg/mL

(human MCHR1) or 4 μg/mL (rat MCHR1) with the assay buﬀer,

and then 175 μL/well aliquot was dispensed into polypropylene 96-

well plate (type 3363, Corning). Then 2 μL of DMSO solution of a

test compound was mixed with homogenates and [¹²⁵I]MCH (4−19)

peptide in a total volume of 200 μL/well and incubated at room

temperature for 60 min. The binding reaction was terminated by rapid

ﬁltration using FilterMate harvester (PerkinElmer) followed by three

300 μL/well washes with 50 mM Tris-HCl buﬀer (pH 7.5).

Nonspeciﬁc binding was deﬁned in the presence of 0.3 μM MCH

(1−19) peptide. GF/C ﬁlter plates were dried, and radioactivity was

determined after addition of 25 μL/well Microscint-0 (PerkinElmer)

using TopCount liquid scintillation counter (PerkinElmer). MCH (4−

19) peptide and MCH (1−19) peptide were purchased from Peptide

Institute. MCH (4−19) peptide was labeled with ¹²⁵I by the Bolton−

Hunter method. The 50% inhibitory concentration (IC₅₀) was

Male F344/Jcl rats (32-week-old, CLEA Japan, Inc.) loaded with a

high-fat diet (Research Diets, Inc., D12451) from 5 weeks of age were

used (DIO-F344 rats). Before the start of experiment, the rats were

independently raised (light cycle 7:00 a.m. to 7:00 p.m.), were allowed

access to a powder high-fat diet (D12451M, Research Diets) and tap

water ad libitum, and were administered tap water (0.5 mL) orally for

acclimation to oral dosing. Thereby the rats were habituated. The food

intake from evening of the day before the start of experiment to

morning of the next day was measured, and the rats were grouped

based on the food intake and the body weight of the previous day as

indices (mean body weight of 438.7 g, n = 6 for each group). On the

day of the start of experiment and the next day at 5:00 p.m., after body

weight measurement, 0.5% methylcellulose solution (vehicle) was

administered orally to the control group, and 0.5% methylcellulose

suspension (1, 3, 5, and 10 mg/kg) of the compound was administered

orally to the compound administration group at 2 mL/kg based on the

body weight of each day (volume range actually used was 0.79−0.94

mL). The food intake from the initial administration to 1 day and 2

days later was measured manually. The food intake inhibition rate of

each compound administration group to the control group was

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dx.doi.org/10.1021/jm300167z | J. Med. Chem. 2012, 55, 4336−4351

Journal of Medicinal Chemistry

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calculated. Food intake data were analyzed by Williams test, and values

of P < 0.025 were considered statistically signiﬁcant.

Subtype of the Melanin-Concentrating Hormone Receptor. Biochem.

Biophys. Res. Commun. 2001, 283, 1013−1018. (b) Hill, J.; Duckworth,

M.; Murdock, P.; Rennie, G.; Sabido-David, C.; Ames, R. S.; Szekeres,

P.; Wilson, S.; Berqsma, D. J.; Gloger, I. S.; Levy, D. S.; Chambers, J.

K.; Muir, A. I. Molecular Cloning and Functional Characterization of

MCH2, a Novel Human MCH Receptor. J. Biol. Chem. 2001, 276,

20125−20129. (c) Sailer, A. W.; Sano, H.; Zeng, Z.; McDonald, T. P.;

Pan, J.; Pong, S. S.; Feighner, S. D.; Tan, C. P.; Fukami, T.; Iwaasa, H.;

Hreniuk, D. L.; Morin, N. R.; Sadowski, S. J.; Ito, M.; Bansal, A.; Ky,

B.; Figueroa, D. J.; Jiang, Q.; Austin, C. P.; MacNeil, D. J.; Ishihara, A.;

Ihara, M.; Kanatani, A.; Van Der Ploeg, L. H.; Howard, A. D.; Liu, Q.

Identiﬁcation and Characterization of a Second Melanin-Concentrat-

ing Hormone Receptor, MCH-2R. Proc. Natl. Acad. Sci. U.S.A. 2001,

98, 7564−7569. (d) An, S.; Cutler, G.; Zhao, J. J.; Huang, S. G.; Tian,

H.; Li, W.; Liang, L.; Rich, M.; Bakleh, A.; Du, J.; Chen, J. L.; Dai, K.

Identiﬁcation and Characterization of a Melanin-Concentrating

Hormone Receptor. Proc. Natl. Acad. Sci. U.S.A. 2001, 98, 7576−

7581. (e) Rodriguez, M.; Beauverger, P.; Naime, I.; Rique, H.; Ouvry,

C.; Souchaud, S.; Dromaint, S.; Nagel, N.; Suply, T.; Audinot, V.;

Boutin, J. A.; Galizzi, J. P. Cloning and Molecular Characterization of

the Novel Human Melanin-Concentrating Hormone Receptor MCH2.

Mol. Pharmacol. 2001, 60, 632−639. (f) Wang, S.; Behan, J.; O’Neill,

K.; Weig, B.; Fried, S.; Laz, T.; Bayne, M.; Gustafson, E.; Hawes, B. E.

Identiﬁcation and Pharmacological Characterization of a Novel

Human Melanin-Concentrating Hormone Receptor, MCH-R2. J.

Biol. Chem. 2001, 276, 34664−34670.

ASSOCIATED CONTENT

* Supporting Information

■

S

Synthesis of starting materials, elemental analysis results of ﬁnal

compounds, MCHR1 Ca²⁺inﬂux assays for (R)-10a and (R)-

10h, binding of (R)-10a to wild type, monomer mutant

(Y652A) and tandem dimer mutant (Y652A) hERG, and eﬀect

of (R)-10h on 2-day food intake study in DIO-F-344 rats. This

material is available free of charge via the Internet at http://

pubs.acs.org.

AUTHOR INFORMATION

Corresponding Author

*Phone: +81-466-32-1052. Fax: +81-466-29-4468. E-mail:

Kasai_Shizuo@takeda.co.jp.

■

Notes

The authors declare no competing ﬁnancial interest.

ACKNOWLEDGMENTS

■

The authors thank Hisako Yoshida for the pharmacokinetic

study and Sumie Yoshitomi for the Rb⁺eﬄux assay. The

authors thank Keiko Higashikawa and Motoo Iida for X-ray

crystallography analyses. The authors thank Dr. Shin-ichi Niwa

for preparation of Supporting Information about the binding of

hERG currents by compound (R)-10a.

(5) Rossi, M.; Choi, S. J.; O’Shea, D.; Miyoshi, T.; Ghatei, M. A.;

Bloom, S. R. Melanin-Concentrating Hormone Acutely Stimulates

Feeding, but Chronic Administration Has No Eﬀect on Body Weight.

Endocrinology 1997, 138, 351−355.

(6) Shimada, M.; Tritos, N. A.; Lowell, B. B.; Flier, J. S.; Maratos-

Flier, E. Mice Lacking Melanin-Concentrating Hormone Are

Hypophagic and Lean. Nature 1998, 396, 670−674.

(7) Ludwig, D. S.; Tritos, N. A.; Mastaitis, J. W.; Kulkarni, R.;

Kokkotou, E.; Elmquist, J.; Lowell, B.; Flier, J. S.; Maratos-Flier, E.

Melanin-Concentrating Hormone Overexpression in Transgenic Mice

Leads to Obesity and Insulin Resistance. J. Clin. Invest. 2001, 107,

379−386.

(8) (a) Chen, Y.; Hu, C.; Hsu, C.-K.; Zhang, Q.; Bi, C.; Asnicar, M.;

Hsiung, H. M.; Fox, N.; Slieker, L. J.; Yang, D. D.; Heiman, M. L.; Shi,

Y. Targeted Disruption of the Melanin-Concentrating Hormone

Receptor-1 Results in Hyperphagia and Resistance to Diet-Induced

Obesity. Endocrinology 2002, 143, 2469−2477. (b) Marsh, D. J.;

Weingarth, D. T.; Novi, D. E.; Chen, H. Y.; Trumbauer, M. E.; Chen,

A. S.; Guan, X.-M.; Jiang, M. M.; Feng, Y.; Camacho, R. E.; Shen, Z.;

Frazier, E. G.; Yu, H.; Metzger, J. M.; Kuca, S. J.; Shearman, L. P.;

Gopal-Truter, S.; MacNeil, D. J.; Strack, A. M.; Maclntyre, D. E.; Van

der Ploeg, L. H. T.; Qian, S. Melanin-Concentrating Hormone 1

Receptor-Deﬁcient Mice Are Lean, Hyperactive, and Hyperphagic and

Have Altered Metabolism. Proc. Natl. Acad. Sci. U.S.A. 2002, 99, 3240−

3245.

ABBREVIATIONS USED

■

MCH, melanin-concentrating hormone; hERG, human ether-a-

go-go-related gene; DIO, diet-induced obesity; SAR, structure−

activity relationship; S/C, substrate-to-catalyst molar ratio;

DPPA, diphenylphosphorylazide; DIPEA, N,N-diisopropyle-

thylamine; NIS, N-iodosuccinimide; CHO, Chinese hamster

ovary; DIAD, diisopropyl azodicarboxylate

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dx.doi.org/10.1021/jm300167z | J. Med. Chem. 2012, 55, 4336−4351

Article Doi

Synthesis, structure-activity relationship, and pharmacological studies of novel melanin-concentrating hormone receptor 1 antagonists 3- aminomethylquinolines: Reducing human ether-a-go-go-related gene (hERG) associated liabilities

DOI: 10.1021/jm300167z

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