N-methylbenzanilide derivatives as a novel class of selective V1A receptor antagonists

Article abstract of DOI:10.1016/S0960-894X(01)00723-5

During our efforts to develop a novel class of selective V_1A receptor antagonists, the N-methylbenzanilide structure was applied to a 4,4-difluoro-1-benzazepine derivative, 4, which is a selective V_1A receptor antagonist. Further str

Full text of DOI:10.1016/S0960-894X(01)00723-5

Bioorganic & Medicinal Chemistry Letters 12 (2002) 229–232
N-Methylbenzanilide Derivatives as a Novel Class of Selective
V1A Receptor Antagonists
Akio Kakefuda,a,* Junko Tsukada,b Toshiyuki Kusayama,a Atsuo Taharaa
and Shin-ichi Tsukamotoa
aInstitute for Drug Discovery Research, Yamanouchi Pharmaceutical Co. Ltd., 21 Miyukigaoka, Tsukuba, Ibaraki 305-8585, Japan
bClinical Development Dept., Yamanouchi Pharmaceutical Co. Ltd., 3-17-1 Hasune, Itabashi, Tokyo 174-8612, Japan
Received 25 September 2001; accepted 27 October 2001
Abstract—During our efforts to develop a novel class of selective V1A receptor antagonists, the N-methylbenzanilide structure was
applied to a 4,4-difluoro-1-benzazepine derivative, 4, which is a selective V1A receptor antagonist. Further structural modifications
gave 16a with high V1A affinity and V2/V1A selectivity (Ki=5.71nM, V /V1A=140) and potent V1A receptor antagonist activity
2
(ID50=0.0080 mg/kg iv). # 2002 Elsevier Science Ltd. All rights reserved.
Introduction
hydro-1H-1-benzazepine derivative, 3 (V1A Ki=0.160
nM, V2 Ki=0.770 nM), was discovered as a V1A and V2
receptor dual antagonist.8 We moved into the next
research program which addressed the development of
selective V1A receptor antagonists. Extensive study of
the 4,4-difluoro-1-benzazepine derivatives afforded a
series of compounds with the selectivity for the V1A
receptor versus the V2 receptor, such as the 2-methyl-3-
furyl derivative, 4 (V1A Ki=0.102 nM, V2 Ki=33.9 nM,
V2/V1A=330).9 On the other hand, Ohkawa et al.
reported the N-methylbenzanilide derivative, FR179544
(5), as a V1A and V2 receptor dual antagonist.10 This
report prompted us to apply the N-methylbenzanilide
structure to 4, which might afford a novel class of
selective V1A receptor antagonists. Subsequently, we
attempted modifications of the tether linking the N-
methylbenzanilide template with the terminal amide
part, and the 2-methyl-3-furyl part. In this paper, we
describe the synthesis and pharmacological evaluation
of N-methylbenzanilide derivatives.
Arginine vasopressin (AVP) is a peptide hormone which
is released from the posterior pituitary and exerts a
variety of biological effects in mammals. So far, two
AVP receptor subtypes (V1A and V2) have been identi-
fied, in periphery.1 The V1A receptor mediates phos-
pholipase
C activation and intracellular calcium
mobilization, which causes various known AVP actions,
such as vasoconstriction, platelet aggregation, and
growth of vascular smooth muscle cell.1 The V2 receptor
is positively coupled to adenylate cyclase and plays a
predominant role in the antidiuretic response to AVP
which promotes water reabsorption.2
AVP may play a role in several diseases and disorders,
such as heart failure, hypertension, coronary renal
vasospasm, hyponatremia, and dysmenorrhea.3,4
Therefore, the development of subtype selective AVP
receptor antagonists is essential to investigate the
pathophysiological roles of AVP and could lead to new
therapeutic tools. Recently, two nonpeptide selective
V1A receptor antagonists, OPC-21268 (1)5,6 and
SR49059 (2)7 have been reported (Fig. 1). They have
undergone clinical testing.
Chemistry
The basic structure of the novel compounds was con-
structed by condensation of a N-methylaniline with a 4-
acylaminobenzoyl chloride (Scheme 1) or condensation
of a N-methyl-40-aminobenzanilide with a substituted
benzoyl chloride (Scheme 2). Scheme 1shows the pre-
paration of compounds 9a–c and 12a–d. The N-methyl-
In the course of the search for AVP antagonists at our
laboratories, the 4,4-difluoro-5-methylene-2,3,4,5-tetra-
aniline (6) was coupled with
furyl)carboxamido]benzoyl chloride to afford the N-
a
4-[(2-methyl-3-
*Corresponding author. Tel.:+81-298-54-1545; fax: +81-298-53-
5387; e-mail: kakefuda@yamanouchi.co.jp
0960-894X/02/$ - see front matter # 2002 Elsevier Science Ltd. All rights reserved.
PII: S0960-894X(01)00723-5

230
A. Kakefuda et al. / Bioorg. Med. Chem. Lett. 12 (2002) 229–232
Figure 1. Known AVP antagonists.
Scheme 1. (a) 4-[(2-Methylfuran-3-yl)carboxamido]benzoyl chloride, pyridine, Cl(CH2)2Cl; (b) Br(CH2)5CO2Et, K2CO3, CH3CN, reflux; (c)
4-BrCH2C6H4CO2Me, K2CO3, CH3CN, reflux: (d) 1N NaOH aq, EtOH; (e) N-methylpiperazine or 4-(piperidino)piperidine, EDC.HCl, HOBt,
Cl(CH2)2Cl.
Scheme 2. (a) 4-O2NC6H4COCl, pyridine, Cl(CH2)2Cl; (b) H2, Pd/C or PtO2, EtOH–THF; (c) 2-(2-ethyl-1-imidazolyl)benzoyl chloride, pyridine,
Cl(CH2)2Cl; (d) 1N NaOH aq, EtOH; (e) N-methylpiperazine, EDC.HCl, HOBt, Cl(CH2)2Cl.
methylbenzanilide (7). The anilide 7 was finally trans-
Results and Discussion
formed to the target compounds, 9a–c, by O-alkylation,
hydrolysis, and condensation with amines. Compounds
12a–d were synthesized from N-methylanilines (10a–d)
by a similar procedure described for 9a–c. The synthesis
of 16a–b was illustrated in Scheme 2. The N-methylani-
line (13a–b) was converted to the N-methyl-4-amino-
benzanilide (14a–b) by benzoylation followed by
hydrogenation. Compounds 14a–b were coupled with 2-
(2-ethyl-1-imidazolyl)benzoyl chloride11 to give 15a–b.
Compounds 15a–b were transformed to the target com-
pounds, 16a–b, by hydrolysis and condensation with
amines.12
The synthesized compounds were primarily evaluated
for their binding affinities for the V1A and V2 receptors
on membranes using [3H]AVP (rat liver for V1A and rat
kidney for V2).13 The results were expressed as Ki values
and selectivity (Ki ratio, V2/V1A) in Table 1.
Initially, we examined the 2-methyl-3-furyl derivative
(9a). Compound 9a showed high V1A affinity (Ki=8.77
nM) and moderate V2/V1A selectivity (V2/V1A=8.4).
The structure–activity relationships (SAR) of 3 and its

A. Kakefuda et al. / Bioorg. Med. Chem. Lett. 12 (2002) 229–232
Table 1. Binding affinities of N-methylbenzanilide derivatives for V1A and V2 receptors
231
Compd
R1R2
R3
Kia (nM)
Selectivity
Ki ratio V2/V1A
V1A
V2
9a
Me
8.77ꢀ0.66
73.4ꢀ11
8.4
9b
Me
H
4.97ꢀ0.73
1140ꢀ230
491ꢀ34
94.5ꢀ20
2250ꢀ160
1360ꢀ270
168ꢀ22
19
2.0
2.8
2.1
6.1
14
12a
12b
12c
12d
9c
H
H
78.6ꢀ11
H
335ꢀ93
2040ꢀ420
41.5ꢀ9.3
782ꢀ110
Me
Me
2.93ꢀ0.24
5.71ꢀ0.83
16a
140
16b
Me
7.59ꢀ0.48
445ꢀ36
59
1
3
4
23.5ꢀ4.39
0.620ꢀ0.23
0.102b
>10,000
1.19ꢀ0.02
33.9b
>430
1.9
330
aKi values were obtained from two or more independent experiments. Each value indicates mean ꢀ SEM.
bMean from two experiments.
derivatives revealed that the 4-aminopiperidine ring as
the terminal basic part is superior to the 4-alkylpiper-
azine ring with respect to the V2/V1A selectivity.14 Thus,
we utilized these results to 9a having a 4-methylpiper-
azine to obtain the 4-piperidinopiperidine derivative
(9b). As a result, compound 9b exhibited improved V1A
affinity and V2/V1A selectivity (Ki=4.97 nM, V2/
V1A=19) in comparison to 9a. This result was similar to
the SAR of 3 and its derivatives.
substitution pattern. Therefore, we examined another
aromatic tethers with 1,4-substitution pattern. The
phenyl derivative (12d) showed considerably weak V1A
affinity. In contrast, the benzyloxy derivative (9c)
exhibited high V1A affinity (Ki=2.93 nM), being better
than that of 9b. These results suggested that the distance
between the terminal basic moiety and the N-methyl-
benzanilide template might be important to exert high
V1A affinity and that the 4-benzyloxy moiety might be
suitable for the tether.
We then modified the tether linking the N-methylbenz-
anilide template with the terminal amide of 9b. The
comparison of the binding results of the phenoxy deri-
vatives (12a–c) demonstrated that the rank of order of
potency in their V1A affinities was 1,4- > 1,3- > 1,2-
Next, we converted the 2-methyl-3-furyl part of 9 into
another heterocycle utilizing the SAR of 3.14 The 2-(2-
ethyl-1-imidazolyl)phenyl derivatives (16a–b) showed
similar V1A affinities, but reduced V2 affinities compared

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A. Kakefuda et al. / Bioorg. Med. Chem. Lett. 12 (2002) 229–232
Analysis and Metabolism Laboratories for performing
spectral measurements.
Table 2. In vivo activities of N-methylbenzanilide derivatives
a
Compd
ID50 (mg/kg iv)
n
9a
9c
16a
16b
1
0.11ꢀ0.013
0.038ꢀ0.002
0.0080ꢀ0.002
0.015ꢀ0.005
0.34ꢀ0.05
4
4
4
6
References and Notes
1. Michel, R. H.; Kirk, C. J.; Billah, M. M. Biochem. Soc.
Trans. 1979, 7, 861.
2. Jard, S. Kidney Int., Supp. 1988, 26, 38.
3. Laszlo, F. A.; Laszlo, F.; De Wied, D. Pharmacol. Rev.
1991, 43, 73.
aID50 represents the dose of the compounds required to inhibit AVP-
induced pressor response in pithed rats by 50%. Each value indicates
meanꢀSEM.
4. Mah, S. C.; Hofbauer, K. G. Drugs Future 1987, 12,
1055.
5. Yamamura, Y.; Ogawa, H.; Chihara, T.; Kondo, K.; Ono-
gawa, T.; Nakamura, S.; Mori, T.; Tominaga, M.; Yabuuchi,
Y. Science 1991, 252, 572.
to 9a, which resulted in an improvement of V2/V1A
selectivity. Especially, compound 16a had high V2/V1A
selectivity (V2/V1A=140).
6. Ogawa, H.; Yamamura, T.; Miyamoto, H.; Kondo, K.;
Yamashita, H.; Nakaya, K.; Chihara, T.; Mori, T.; Tominaga,
M.; Yabuuchi, Y. J. Med. Chem. 1993, 36, 2011.
7. Serradeil-Le Gal, C.; Wagnon, J.; Garcia, C.; Lacour, C.;
Guiraudou, P.; Christophe, B.; Villanova, G.; Nisato, D.;
Maffrand, J. P.; Le Fur, G.; Guillon, G.; Cantau, B.; Barberis,
C.; Trueba, M.; Ala, Y.; Jard, S. J. Clin. Invest. 1993, 92, 224.
8. Shimada, Y.; Taniguchi, N.; Matsuhisa, A.; Sakamoto, K.;
Yatsu, T.; Tanaka, A. Chem. Pharm. Bull. 2000, 48, 1644.
9. Shimada, Y.; Taniguchi, N.; Matsuhisa, A.; Akane, H.;
Kawano, N.; Yatsu, T.; Tanaka, A. Abstracts of Papers, Part
1, 214th National Meeting of the American Chemical Society,
Las Vegas, NV, Sep 7–11, 1997; American Chemical Society:
Washington, DC, 1997; MEDI 203.
Thus, application of N-methylbenzanilide structure to 4
and further structural modifications utilizing the SAR
of 3 led to novel compounds which had high V1A affi-
nity and V2/V1A selectivity.
From the results of the binging assay, some compounds
were selected for in vivo evaluation13 (Table 2). All the
tested compounds dose-dependently antagonized an
increase in DBP induced by AVP (30 mU/kg iv) via the
V1A receptor. In particular, compound 16a, which had
the highest V2/V1A selectivity in this series, exhibited
potent V1A receptor antagonist activity with an ID50
value of 0.0080 mg/kg, which was 43-fold more potent
than that of 1.
10. Ohkawa, T.; Zenkoh, T.; Setoi, H.; Hemmi, K.; Tanaka,
H. Abstracts, 18th Symposium on Medicinal Chemistry,
Kyoto, Nov 25–27, 1998; The Pharmaceutical Society of
Japan: Tokyo, 1998; 1-P-25.
11. Taniguchi, N.; Tanaka, A.; Matsuhisa, A.; Sakamoto, K.;
Koshio, H.; Yatsu, T. WO9506035 Chem. Abstr. 1995, 58550,
125.
Conclusion
Application of the N-methylbenzanilide structure to a
selective V1A receptor antagonist, 4, gave the novel 2-
methyl-3-furyl derivative (9a) which showed high V1A
affinity and moderate V2/V1A selectivity. Further mod-
ifications utilizing the SAR of 3 gave novel compounds
which exhibit high V1A affinity and high V2/V1A selec-
tivity, such as the 2-(2-ethyl-1-imidazolyl)phenyl deriv-
ative (16a). Compound 16a showed potent V1A receptor
antagonist activity in vivo and was 43-fold more potent
than 1. This study would provide a novel approach to
selective V1A receptor antagonists, which might be use-
ful in the treatment of diseases in which AVP is involved
via the V1A receptor.
12. Satisfactory analytical data were obtained for all the tar-
get compounds. For example, 16a: colorless amorphous pow-
der: 1H NMR (400 MHz, DMSO-d6) d 1.16 (3H, t, J=7.6 Hz),
1.43–1.47 (2H, m), 1.53–1.61 (2H, m), 1.69–1.76 (2H, m), 2.22
(3H, s), 2.39 (2H, t, J=7.6 Hz), 2.73 (5H, br s), 3.02–3.51(8H,
m), 3.15 (3H, s), 3.87–3.93 (2H, m), 6.63 (1H, d, J=8.0 Hz),
6.79 (1H, s), 6.99 (1H, d, J=8.0 Hz), 7.19 (2H, d, J=8.0 Hz),
7.42 (2H, d, J=8.0 Hz), 7.71–7.81 (5H, m), 7.93–7.95 (1H, m),
10.81 (1H, s), 11.41 (1H, br s), 15.05 (1H, br s); MS (FAB) m/z
+
.
.
651(MH ). Anal. calcd for C38H46N6O4 2HCl 1.8H2O: C,
60.36, H, 6.88, N, 11.11; Cl, 9.38. Found: C, 60.32, H, 7.15, N,
11.00, Cl, 9.45.
13. Tahara, A.; Tomura, Y.; Wada, K.; Kusayama, T.; Tsu-
kada, J.; Takanashi, M.; Yatsu, T.; Uchida, W.; Tanaka, A. J.
Pharmacol. Exp. Ther. 1997, 282, 301.
14. Shimada, Y.; Taniguchi, N.; Matsuhisa, A.; Akane, H.;
Kawano, N.; Yatsu, T.; Tanaka, A. Abstracts, 17th Sym-
posium on Medicinal Chemistry, Tsukuba, Nov 19–21,
1997; The Pharmaceutical Society of Japan: Tokyo, 1997;
1-P-18.
Acknowledgements
We thank Drs. S. Sakamoto and T. Suzuki for their
critical reading of the manuscript, and the staff of