Synthesis and evaluation of nonpeptide substituted spirobenzazepines as potent vasopressin antagonists

Article abstract of DOI:10.1016/j.bmcl.2004.04.016

A series of substituted spirobenzazepines was prepared and evaluated as V_1a and V₂ dual vasopressin receptor antagonists. Compounds 7p and 7q have been shown to be not only potent inhibitors of vasopressin receptors, but also have exhibited an excellent overall pharmaceutical suitability profile.

Full text of DOI:10.1016/j.bmcl.2004.04.016

Bioorganic & Medicinal Chemistry Letters 14 (2004) 3143–3146
Synthesis and evaluation of nonpeptide substituted
spirobenzazepines as potent vasopressin antagonists
Min Amy Xiang, Robert H. Chen,*, Keith T. Demarest, Joseph Gunnet,
Richard Look, William Hageman, William V. Murray, Donald W. Combs,
Philip J. Rybczynski and Mona Patel*
Endocrine Therapeutics and Metabolic Disorders, Johnson and Johnson Pharmaceutical Research and Development,
L.L.C., 1000 Route 202, Bldg: PCC, Room: PC110, Raritan, NJ 08869, USA
Received 17 March 2004; accepted 7 April 2004
Abstract—A series of substituted spirobenzazepines was prepared and evaluated as V1a and V2 dual vasopressin receptor antago-
nists. Compounds 7p and 7q have been shown to be not only potent inhibitors of vasopressin receptors, but also have exhibited an
excellent overall pharmaceutical suitability profile.
ꢀ 2004 Elsevier Ltd. All rights reserved.
Arginine vasopressin (AVP), a cyclic peptide hormone
released from the posterior pituitary, plays an important
role in the homeostasis of fluid osmolality and volume
status.1 The hormone exerts its actions by interacting
with three well characterized G-protein mediated
receptor sub-types: vascular V1a, hormone releasing V1b
(V3) and renal V2 receptors. V1 receptors antagonists are
potentially useful for the treatment of arterial hyper-
tension, congestive heart failure and peripheral arterial
disease.2 V2 receptor antagonists would be useful for the
treatment of congestive heart failure, liver cirrhosis,
nephritic syndrome and any state of excessive retention
of water.2
Conivaptan and Lixivaptan (Fig. 1) are known AVP
antagonists amongst others that are currently undergo-
ing clinical trials. Both clinical candidates are based on
the benzazepine scaffold, with Conivaptan being a dual
V1a/V2 receptor antagonist and Lixivaptan being a
selective V2 receptor antagonist.3 During the course of
our research efforts directed towards the discovery of a
dual V1a/V2 vasopressin receptor antagonist, a series of
spirobenzazepines was identified as potent V1a selective
and V1a/V2 dual antagonists.4 Although the initial data
for spirocyclohexenes was promising, a poor solubility
profile as well as a poor metabolic stability profile
precluded additional preclinical studies. Further
HN
N
N
N
N
N
O
O
F
O
O
O
O
R
Cl
N
H
Lixivaptan
N
H
N
H
Conivaptan
Figure 1. V1a/V2 antagonists.
* Corresponding authors. Tel.: +1-908-707-3558; fax: +1-908-203-8109; e-mail: mpatel5@prdus.jnj.com
Current address: Ace Chemicals and Pharmaceutical, M. L. King, Jr. Boulevard, Newark, NJ 07102, USA.
0960-894X/$ - see front matter ꢀ 2004 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2004.04.016

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M. A. Xiang et al. / Bioorg. Med. Chem. Lett. 14 (2004) 3143–3146
development of the spirobenzazepine scaffold led to the
discovery of the spiropentene framework. The prepara-
tion and evaluation of this series of compounds is
described herein. The preparation of compound 1 has
been previously described.5 Compound 1 was acylated
with para nitrobenzoyl chloride in dichloromethane to
provide 2 in good yield. Ring contraction of the six
membered cyclohexyl ring (2) to the five membered
cyclopentene ring with a pendant carboxaldehyde group
(3) was accomplished by ozonolysis of the double bond
followed by recyclization.6 The conversion of the formyl
group in compound 3 to the corresponding ester was
accomplished in a two step process involving first, an
oxidation of the aldehyde to the acid using sodium
chlorite, followed by Fischer esterification to provide the
ester. The nitro group was reduced by treatment with
tin(II) chloride in refluxing ethanol to provide amino
ester 4. Acylation of the aniline moiety with an appro-
priately substituted benzoyl chloride resulted in com-
pound 5. Base hydrolysis of the ester provided acid (6).
Coupling of acid (6) with a variety of amines using EDC
and HOBt in dichloromethane afforded 7a–o (Table 1).7
Compounds 7a and 7e required the use of a tBDMS
protected alcohol, which resulted in an additional final
step of deprotection with TBAF in tetrahydrofuran in
quantitative yields. Furthermore, for the preparation of
compound 7c, coupling was carried with a methyl ester
protected glycine, which was deprotected under basic
conditions to give the carboxylic acid in good yield
(Scheme 1).
Table 1 details the in vitro potency of the spiro-
benzazepines. The development of SAR on the ben-
zazepine scaffold involved variations at both the alkyl
amido side chain (R1) and substitution on the phenyl
ring (R2). The first set of compounds prepared were 7a–
d, wherein a phenyl substituent was introduced as R2
and a variety of side chains were explored at the R1
position.3d;e These compounds were observed to be dual
V1a/V2 receptor antagonists. Next, we sought to intro-
duce a 2-fluoro substituent at the R2 position and
retained previously explored R1 groups. Compounds 7e
and 7f demonstrate selectivity for the V1a receptor as
compared to compounds 7a and 7b. It seems that a
2-fluoro substituent imparts V1a selectivity. In vitro
activity observed for compounds 7g–i, wherein variation
at R1 was introduced while retaining a 2-fluoro sub-
stituent at R2 validates this conclusion.
Table 1. In vitro potency of the spirobenzazepines
CONHR1
N
O
O
N
H
R2
Compound # R1
R2
V1a binding8
IC50 (nM)
V1a functional8
IC50 (nM)
V2 binding8
IC50 (nM)
V2 functional8
IC50 (nM)
7a
7b
7c
7d
7e
7f
(CH2)2OH
(CH2)2N(CH3)2
CH2COOH
2-Ph
2-Ph
2-Ph
2-Ph
2-F
6
5
5
4
11
11
170
100
24
5
78
29
99
126
18
16
350
20
(CH2)3N(CH3)2
(CH2)2OH
(CH2)2N(CH3)2
4
>1000
>1000
>1000
>1000
2-F
8
7g
7h
7i
2-F
2-F
2-F
4
7
8
227
950
155
>1000
>1000
>1000
ndb
(CH2)2N
(CH2)2N
(CH2)2N
O
>1000
>1000
7j
(CH2)2N(CH3)2
(CH2)3N(CH3)2
CH2COOCH3
2-CH3, 5-F
2-CH3, 5-F
2-CH3, 5-F
5
5
7
65
4
20
23
10
105
31
7k
7l
135
440
7m
7n
7o
2-CH3, 5-F
2-CH3, 5-F
2-CH3, 5-F
10
19
16
48
29
71
39
39
8
48
48
9
(CH2)2N
(CH2)2N
(CH2)2N
7pa
7qa
(CH2)2N(CH3)2
(CH2)2N(CH3)2
2-Ph
2-F
2
4
45
78
8
341
36
646
a Compound is a single enantiomer (R).
b nd ¼ not determined.

M. A. Xiang et al. / Bioorg. Med. Chem. Lett. 14 (2004) 3143–3146
3145
CHO
c, d
b
a
N
N
H
N
1
3
2
O
O
NO2
CO2CH3
NO2
CO2CH3
e
O
R2
N
N
Ar =
N
H
4
5
O
O
Ar
NH2
CONHR1
COOH
f
g
N
N
7
6
O
Ar
O
Ar
Scheme 1. Reagents and conditions: (a) 4-nitrobenzoyl chloride, TEA, DCM, 70–90%; (b) ozone, DMS; TsOH–H2O, DCM, 60–75%; (c) NaClO2,
DMSO, NaH2PO4, H2O; concd H2SO4, ethanol, 80–90% over two steps. (d) SnCl2, ethanol, 60–90%. (e) ArCOCl, TEA, DCM, 60–70%. (f) LiOH,
THF–H2O, 60–70%; (g) HOBt, EDC, RNH2, DCM, 60–65%.
Next, we sought to introduce a known substitution
pattern in a 2-CH3-5-F moiety at the R2 position.3a;b;c
Compounds 7j–o appear to be dual V1a/V2 antagonists.
Again, we observe in compounds 7j, 7k, 7m, 7n and 7o
that selectivity is determined by substituents at R2 rather
than by R1 substituents. Therefore, we concluded R1
substituents may be utilized to adjust the pharmaceuti-
cal suitability profile of this series of compounds.
Compounds bearing a three carbon linker in R1 such as
compounds 7d and 7k as well as those bearing a mor-
pholine (7g), pyrrolidine (7i, 7n and 7o) and piperidine
(7h and 7m) moiety had observed pKa values in the range
of 9–10 and were deemed to have poor absorption
potential as they would likely be protonated at physio-
logical pH. As compounds 7b and 7f were of interest, the
racemic mixtures of each were chromatographically
resolved and active enantiomer (R) identified as com-
pounds 7p and 7q, respectively.9 Compound 7p was
recognized as a dual V1a/V2 antagonist and 7q as a V1a
selective antagonist, and as a result were subjected to
additional assays (Table 2). The solubility profiles of
both compounds were satisfactory as were the pKa and
log P values. Human liver microsome stability assays
were carried out to determine half-life values for possi-
ble Phase I oxidative metabolism. The t1=2 values for
both 7p and 7q were higher than our acceptable mini-
mum of 30 min. Encouraged by this data, we embarked
on additional key assays to determine Caco-2 perme-
ability potential, cytochrome P450 inhibition profile as
well as the Ames mutagenicity tests.
Both compound 7p and 7q subjected to Caco-2 perme-
ation assay and were considered to have high absorption
potential (Papp[A to B] P 1.0 · 10ꢀ6 cm/s). As drug–
drug interactions are often the result of cytochrome
P450 inhibition, we sought to profile 7p and 7q through
a series of cytochrome P450 isozymes. Compounds 7p
and 7q had IC50 values significantly higher than 10 lM
and were therefore not considered potential inhibitors.
In the Ames test both compounds were negative. Due to
good intrinsic activity and a good pharmaceutical suit-
ability profile, compounds 7p and 7q were selected for
pharmacokinetic studies in rats (Table 3). To explore
possible species differences, the antagonistic activities of
Table 2. Pharmaceutical suitability properties of 7p and 7q
Compound #
Solubility (mg/mL)
@ pH 2
Solubility (mg/mL)
@ pH 7.4
pKa
Log P
HLM stability (t1=2)
minutesa
7p
7q
0.16
0.32
0.04
0.07
8.36
8.18
3.63
2.45
65
43
a Human liver microsomal stability assay was run at a concentration of 5 lM for the compounds. Studies were conducted by Absorption Systems,
Exton, PA.

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M. A. Xiang et al. / Bioorg. Med. Chem. Lett. 14 (2004) 3143–3146
Table 3. Pharmacokinetic profiles for 7p and 7q in rats
Compound #
Route
Dose (mg/kg)
AUC (lM h)
Cmax (lM)
Tmax (h)
t1=2 (h)
F (%)
7p
Oral
IV
30
3
4.57
2.06
7.04
1.68
0.79
2.66
1.1
4
6.47
1.68
4.15
4.35
22
NAa
4.67
NAa
NAa
42
7q
Oral
IV
30
3
1.8
NAa
a NA ¼ not applicable.
Biochem. Soc. Trans. 1979, 7, 861; (c) Jard, S. Kidney Int.,
Supp. 1988, 26, 38; (d) Thibonnier, M. Regul. Pep. 1992, 38,
1.
7p and 7q were evaluated in cells transfected with rat V1a
and V2 cells. 7p had IC50 values of 33 and 5 nM in rat
V1a and V2 binding assay, respectively. 7q had IC50
values of 433 and 444 nM in rat V1a and V2 binding
assay, respectively.
2. (a) Laszlo, F. A.; Laszlo, F., Jr.; De Wied, D. Pharmacol.
Rev. 1991, 43, 73; (b) Mah, S. C.; Hofbauer, K. G. Drugs
Fut. 1987, 12, 1055; (c) Paranjape, S. B.; Thibonnier, M.
Exp. Opin. Invest. Drugs 2001, 10, 825; (d) Trybulski, E. J.
In Annual Reports in Medicinal Chemistry; Doherty, A. H.,
Ed.; Academic: San Diego, 2001; Vol. 36, pp 159–168; (e)
Albright, J. D.; Chan, P. S. Curr. Pharm. Des. 1997, 3, 615.
3. Lixivaptan: (a) Martinez-Castelao, A. Curr. Opin. Investig.
Drugs 2001, 2, 525; (b) Albright, J. D.; Reich, M. F.; Delos
Santos, E. G.; Dusza, J. P.; Sum, F.-W.; Venkatesan, A.
M.; Coupet, J.; Chan, P. S.; Ru, X.; Mazandarani, H.;
Bailey, T. J. Med. Chem. 1998, 41, 2442; (c) Albright, J. D.;
Delos Santos, E. G.; Dusza, J. P.; Chan, P. S.; Coupet, J.;
Ru, X.; Mazandarani, H. Bioorg. Med. Chem. Lett. 2000,
10, 695; (d) Conivaptan: Norman, P.; Leeson, P. A.;
Rabasseda, X.; Castaner, J.; Castaner, R. M. Drugs Fut.
2000, 25, 1121; (e) Matsushita, A.; Taniguchi, N.; Koshio,
H.; Yatsu, T.; Tanaka, A. Chem. Pharm. Bull. 2000, 48, 21.
4. Xiang, M. A.; Chen, R. H.; Demarest, K. T.; Gunnet, J.;
Look, R.; Hageman, W.; Murray, W. V.; Combs, D. W.;
Patel, M. Bioorg. Med. Chem. Lett. 2004, 14, 2987.
5. Chen, R. H.; Xiang, M. A. WO 02/02531 A1, 2002.
6. Chen, R. H; Xiang, M.; Moore, J. B., Jr.; Beavers, M. P.
U.S. Patent 5,972,939, 1999.
Following a single oral dose of 7p (30 mg/kg) in rats, a
Cmax of 0.79 lM and a Tmax of 4 h was observed. The
compound was moderately eliminated as evidenced by a
terminal half-life of 6.47 h and the absolute oral bio-
availability was determined to be 22%. Following an
intravenous administration of 7p (3 mg/kg), the appar-
ent volume of distribution (6836 mL/kg) was greater
than the total body water for the species, indicating
extensive distribution of 7p outside of the plasma. Fol-
lowing a single oral dose of 7q (30 mg/kg) in rats, a mean
Tmax value of 4.67 h was observed and was moderately
eliminated based on a terminal half-life of 4.15 h. The
absolute oral bioavailability was determined to be 42%.
Following an intravenous dose of 7q (3 mg/kg), the
apparent volume of distribution (6675 mL/kg) exceeded
total body water indicating distribution of 7q outside of
the plasma. Compounds 7p and 7q have demonstrated
an overall balance of good permeability, oral bioavail-
ability and a long terminal half-life.
7. All compounds provided satisfactory spectral data (1H
NMR, CI-MS/ESI/MS and were homogeneous by TLC).
8. Rigas, A.; Levine, L. J. Pharmacol. Exp. Ther. 1984, 231,
230. Binding affinities were determined by measuring the
inhibition of 3[H] AVP binding to cloned human V1a and V2
receptors. Functional activity was determined by (a) the
accumulation of cAMP was measured in transfected HEK-
293 cells expressing human V2 receptors and (b) the
intracellular calcium mobilization was measured in HEK-
293 cells transfected to express human V1a receptors.
9. The absolute stereochemistry (R enantiomer) of com-
pounds 7p and 7q was assigned via crystal structure
analysis of an intermediate prepared by H. Marlon Zhong
and co-workers of the Chemical Development Group,
Johnson and Johnson Pharmaceutical Research and Devel-
opment, L.L.C.
Optimization of our spirobenzazepine template led to
the discovery of highly potent dual V1a/V2 (7p) and
selective V1a (7q) vasopressin receptor antagonists. Both
compounds have not only shown good in vitro and in
vivo activity, but have also shown good pharmaceutical
suitability profiles.
References and notes
1. (a) Laszlo, F. A.; Laszlo, F., Jr. Drug News Perspect. 1993,
6, 591; (b) Michel, R. H.; Kirk, C. J.; Billah, M. M.