Synthesis and biological evaluation of novel indoloazepine derivatives as non-peptide vasopressin V2 receptor antagonists

Article abstract of DOI:10.1016/S0960-894X(02)01059-4

A series of novel 3,4,5,6-tetrahydro-1H-azepino[4,3,2-cd]indoles was synthesized and tested for vasopressin receptor antagonist activity. We identified compounds with high affinity for the human V2 receptor and good selectivity over the human V1a receptor

Full text of DOI:10.1016/S0960-894X(02)01059-4

Bioorganic & Medicinal Chemistry Letters 13 (2003) 753–756
Synthesis and Biological Evaluation of Novel Indoloazepine
Derivatives as Non-peptide Vasopressin V2 Receptor Antagonists
Jay M. Matthews,a,* Michael N. Greco,a Leonard R. Hecker,a William J. Hoekstra,a
Patricia Andrade-Gordon,a Lawrence de Garavilla,a Keith T. Demarest,b Eric Ericson,b
Joseph W. Gunnet,b William Hageman,a Richard Look,b John B. Mooreb and
Bruce E. Maryanoff a
aDrug Discovery, Johnson & Johnson Pharmaceutical Research & Development,y Spring House, PA 19477-0776, USA
bDrug Discovery, Johnson & Johnson Pharmaceutical Research & Development, Raritan, NJ 08869, USA
Received 20 June 2002; accepted 14 October 2002
Abstract—A series of novel 3,4,5,6-tetrahydro-1H-azepino[4,3,2-cd]indoles was synthesized and tested for vasopressin receptor
antagonist activity. We identified compounds with high affinity for the human V2 receptor and good selectivity over the human V1a
receptor. Compound 6c bound to V2 receptors with an IC50 value of 20 nM, had >100-fold selectivity over V1a receptors, and
inhibited cAMP formation in a cellular V2 functional assay with an IC50 value of 70 nM.
# 2003 Elsevier Science Ltd. All rights reserved.
Arginine vasopressin (AVP) is a peptide hormone that is
principally secreted from the posterior pituitary gland.
Its interaction with G-protein-coupled receptors results
in inter alia vasoconstriction and water reabsorption,
via V1a and V2 subtypes, respectively.1 The V2 recep-
tors located in the kidneys are responsible for control-
ling water reabsorption. Thus, there is potential to
develop a vasopressin V2 receptor antagonist for the
treatment of disorders such as congestive heart failure,
hypertension, renal disease, edema and hyponatremia.2
A V2 receptor antagonist would have a benefit of
exerting specific, electrolyte-sparing diuresis.
pino[4,3,2-cd]indole 3 was prepared in seven steps from
4-nitroindole 2,11ꢀ13 which was prepared from 2-methyl-
3-nitroaniline 1 in two steps.14,15 Acylation of 3 with a
4-nitroaroyl chloride (RNO2PhCOCl) provided 4,
which was subsequently reduced with zinc and ammo-
nium chloride to provide aniline 5. Acylation of 5 with
acyl acid chlorides (R1PhCOCl) provided compounds of
generic structure 6.
N-Substituted indoles of generic structure 9 (R2 varied)
were prepared according to Scheme 2. Alkylation of the
indole nitrogen with a variety of electrophiles provided
intermediates 7, which were converted to products 9 by
using the reduction/acylation steps mentioned above.
Many efforts to discover non-peptidic, orally active V2
selective antagonists for treating excessive renal reab-
sorption of water have been reported, exemplified by
compounds such as OPC-312603ꢀ6 and VPA-9857ꢀ10
(Fig. 1). Herein, we report on the synthesis and biolo-
gical activity of novel indoloazepine derivatives as
selective V2 receptor antagonists.
Results and Discussion
Scheme 1 shows the primary route used to prepare the
indoloazepine scaffold. The 3,4,5,6-tetrahydro-1H-aze-
*Corresponding author. Tel.: +1-215-628-5214; fax: +1-215-628-
3297; e-mail: jmatthew@prius.jnj.com
yFormerly The R. W. Johnson Pharmaceutical Research Institute.
Figure 1. Structures of OPC-31260 and VPA-985.
0960-894X/03/$ - see front matter # 2003 Elsevier Science Ltd. All rights reserved.
doi:10.1016/S0960-894X(02)01059-4

754
J. M. Matthews et al. / Bioorg. Med. Chem. Lett. 13 (2003) 753–756
For derivatization at R3 (Scheme 3), 6c was treated with
N-chlorosuccinimide at 23 ꢁC to provide a mixture of
indolinone 1016 and 2-chloroindole 11. Reaction of
derivatives 6c with chlorosulfonic acid provided sulfonic
acid product 12.
by measuring the accumulation of cAMP in HEK-293
transfected with the human V2 receptor; the respective
data is shown in Table 1.17
Ogawa4 reported that introduction of lipophilic groups,
such as an o-tolyl moiety, leads to compounds with
similar V1a and V2 receptor affinities. As shown in
Table 1, incorporation of a 2-methyl group in the indo-
loazepine scaffold (6a) has virtually no binding affinity.
On the other hand, replacing the o-tolyl group with 2-
methyl-5-fluorophenyl, as shown by Albright et al.,7 led
to 6b, which has modest binding affinity to the V2
receptor. Tanaka et al.18 described replacing the o-tolyl
group with an o-phenyl group, which led to compounds
with enhanced V2 potency. Indeed, replacing the o-tolyl
moiety (6a) with an o-phenyl moiety (6c) led to an
indoloazepine analogue with superior binding affinity.
Replacing the o-phenyl with a 2-(4-methyl)phenyl
resulted in a 2-fold increase in potency (6d). Com-
pounds 6c and 6d also demonstrate functional activity
with the human V2 receptor; their IC50 values are each a
respectable 70 nM (cf. result for VPA-985). Introduc-
tion of a chloro in the 3-position of the PABA ring (6e)
provided an analogue that is equipotent to unsub-
stituted 6c, while substitution of the C-2 position of the
PABA ring (6f) with a chloro led to a decrease in V2
affinity.
Compounds were assessed for their ability to displace
[3H]-AVP from human V1 or V2 receptors transfected
into HEK-293 cells; IC50 values are shown in Table 1.
Assays were run in duplicate with an assay variability of
20%. Vasopressin antagonist activity was determined
Substitution on the indole nitrogen (R2) suggested
that hydrogen substitution was optimal, as demon-
strated in the significant loss of activity when a methyl
group (9a) was substituted for the hydrogen, resulting
in a 14-fold decrease in activity compared to the
unsubstituted analogue 6d.
Compound 11 demonstrates that the introduction of a
lipophilic moiety (chloro) to the indole ring of 6c leads
to a slight decrease in V2 binding affinity (IC50=44
nM), while the addition of a polar sulfonate moiety to
the indole ring, 12 and 13, leads to analogues that are
equipotent to unsubstituted 6c.
Scheme 1. (a) CH2Cl2, Et3N, 4-NO2ArCOCl, 0 ꢁC; (b) Zn dust,
NH4Cl, MeOH, reflux; (c) CH2Cl2, Et3N, ArCOCl, 0 ꢁC.
Binding to the V1a receptor was also performed on all
compounds in Table 1 by using [3H]-AVP and recom-
binant human vasopressin V1a receptor. The com-
pounds demonstrated >100-fold selectivity for the V2
receptor over the V1a receptor. Three of the compounds
Scheme 2. (a) NaH (60%), DMF, R2X; (b) Zn dust, NH4Cl, MeOH,
reflux; (c) CH2Cl2, Et3N, 2-(4-MePh)COCl, 0 ꢁC.
Scheme 3. (a) CH2Cl2, NCS, rt; (b) CH2Cl2, ClSO3H, rt.

J. M. Matthews et al. / Bioorg. Med. Chem. Lett. 13 (2003) 753–756
Table 1. Vasopressin V2 and V1a binding data for indoloazepines
755
Compda
R
R1
R2
R3
V2 IC50, mMb
cAMP IC50, mMc
6a
6b
6c
6d
6e
6f
6g
9a
9b
9c
9d
9e
11
12
13
H
H
H
2-Me
2-Me, 5-F
2-Ph
2-(4-MePh)
2-Ph
2-Ph
2-Me, 3-F
2-(4-MePh)
2-(4-MePh)
2-(4-MePh)
2-(4-MePh)
2-(4-MePh)
2-Ph
H
H
H
H
H
H
H
Me
COMe
CH2Ph
Pr
H
H
H
H
H
H
H
H
H
H
H
H
Cl
SO3H
SO3H
IA
0.19
0.020
0.011
0.015
0.05
0.18
0.21
0.17
IA
0.070
0.070
H
3-Cl
2-Cl
H
H
H
H
H
H
H
0.33
IA
CH2CO2Et
H
0.55
0.044
0.013
0.012
0.005
H
3-Cl
2-Ph
2-Ph
H
H
VPA-985d
0.091
aTarget compounds were all purified by reverse-phase semi-prep HPLC. Purities were >95% as judged by reverse-phase HPLC/MS at 215 and 254
nm; all compounds were analyzed by 300-MHz 1H NMR.
bInhibition of [3H]-AVP binding to recombinant human vasopressin V2 receptor. IA=inactive, that is <30% inhibition of radioligand binding at a
concentration of 0.1 mM. All analogues demonstrated >100-fold selectivity for the V2 over V1a receptor.17
cFunctional activity of the human V2 receptor, assessed by the accumulation of cAMP in transfected HEK-293 cells.17
dReference standard. V1a binding IC50=0.15 mM.
exhibited V1a binding in excess of 30% at 1 mM: 6b—
58%; 6d—33%; 9a—49%.
References and Notes
1. Albright, J. D.; Chan, P. S. Curr. Pharm. Des. 1997, 3, 615.
2. Kondo, K.; Ogawa, H.; Shinohara, T.; Kurimura, M.;
Tanada, Y.; Kan, K.; Yamashita, H.; Nakamura, S.; Hirano,
T.; Yamamura, Y.; Mori, T.; Tominago, M.; Itai, A. J. Med.
Chem. 2000, 43, 4388.
3. Ogawa, H.; Yamamura, Y.; Miyamoto, H.; Kondo, K.;
Yamashita, H.; Nakaya, K.; Chihara, T.; Mori, T.; Tominaga,
M.; Yabuuchi, Y. J. Med. Chem. 1993, 36, 2011.
4. Ogawa, H.; Yamashita, H.; Kondo, K.; Yamamura, Y.;
Miyamoto, H.; Kan, K.; Kitano, K.; Tanaka, M.; Nakaya, K.;
Nakamura, S.; Mori, T.; Tominaga, M.; Yabuuchi, Y. J. Med.
Chem. 1996, 39, 3547.
5. Kondo, K.; Ogawa, H.; Yamashita, H.; Miyamoto, H.;
Tanaka, M.; Nakaya, K.; Kitano, K.; Yamamura, Y.; Naka-
mura, S.; Onogawa, T.; Mori, T.; Tominago, M. Bioorg. Med.
Chem. 1999, 7, 1743.
Compound 6c was viewed with particular interest, given
its functional V2 antagonist activity of 70 nM. The IC50
value for V1a binding for 6c was found to be 3.1 mM,
giving it a V1a/V2 selectivity of 155. Compound 6c also
demonstrated potent rat V2 receptor binding, with an
IC50 of 1 nM. Compound 6c was subjected to an in vivo
evaluation in Sprague–Dawley rats by measuring urine
output and osmolality following oral administration.
Unfortunately, although 6c is a potent V2 antagonist in
vitro, it lacked in vivo activity when dosed orally at 10
mg/kg. Given the potency of compound 6c in rodents,
the lack of in vivo activity may relate to low oral
absorption of the compound.
In summary, we have identified a novel series of vaso-
pressin V2 receptor antagonists that contain an indo-
loazepine tricyclic nucleus. Some of the analogues, such
as indoloazepine 6c, show excellent binding affinities
and high selectivity for the recombinant human vaso-
pressin V2 receptor.
6. Matsubara, J.; Morita, S.; Yamashita, H.; Otsubo, K.;
Kitano, K.; Ohtani, T.; Kawano, Y.; Bando, M.; Kido, M.;
Uchida, M.; Tabusa, F. Heterocycles 2001, 54, 131.
7. 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.
8. Venkatesan, A. M.; Albright, J. D.; Grosu, G. T.; Chan,
P. S.; Coupet, J.; Saunders, T.; Ru, X.; Mazandarani, H.
Bioorg. Med. Chem. Lett. 1999, 9, 1737.
Acknowledgements
9. Albright, J. D.; Delos Santos, E. F.; Dusza, J. P.; Chan,
P. S.; Coupet, J.; Ru, X.; Mazandarani, H. Bioorg. Med.
Chem. Lett. 2000, 10, 695.
We thank Dr. Gary Caldwell, Dr. John Masucci and
Mr. Pat Sasso for technical assistance and advice.
10. Ashwell, M. A.; Bagli, J. F.; Caggiano, T. J.; Chan, P. S.;

756
J. M. Matthews et al. / Bioorg. Med. Chem. Lett. 13 (2003) 753–756
Molinari, A. J.; Palka, C.; Park, C. H.; Rogers, J. F.; Sher-
man, M.; Trybulski, E. J.; Williams, D. K. Bioorg. Med.
Chem. Lett. 2000, 10, 783.
11. Hester, J. B. J. Org. Chem. 1964, 29, 1158.
12. Hester, J. B. J. Org. Chem. 1967, 32, 4095.
13. Nagasaka, T.; Ohki, S. Chem. Pharm. Bull. 1977, 25,
3023.
14. Bergman, J.; Sand, P. Org. Synth. 1987, 65, 146.
15. Quick, J.; Saha, B. Tetrahedron. Lett. 1994, 35, 8553.
16. Compound 10 gave a V2 IC50 value of 8 nM with >100-
fold selectivity over the V1a receptor.
17. Rigas, A.; Levine, L. J. Pharmacol. Exp. Ther. 1984, 231, 230.
18. Matsuhisa, A.; Tanaka, A.; Kikuchi, K.; Shimada, Y.;
Yatsu, T.; Yanagisawa, I. Chem. Pharm. Bull. 1997, 45, 1870.