Benzo[b]thiophene-2-carboxamide derivatives as potent urotensin-II receptor antagonists

Article abstract of DOI:10.1016/j.bmcl.2016.08.049

Members of a series of benzo[b]thiophene-2-carboxamide derivatives, possessing an N-(1-(3-bromo-4-(piperidin-4-yloxy)benzyl)piperidin-4-yl) group, were synthesized and evaluated as urotensin-II receptor antagonists. The results show that these substances have potent UT binding affinities. Observations made in a systematic SAR investigation of the effects of a variety of substituents (R¹and R²) at the 5- and 6-positions in the benzo[b]thiophene-2-carboxamide moiety on UT binding affinities led to identification of the 5-cyano analog 7f as a highly potent UT antagonist with an IC₅₀value of 25?nM. Despite having a good metabolic stability, 7f is a potent inhibitor of CYP isozyme and displays an unsuitable PK profile.

Full text of DOI:10.1016/j.bmcl.2016.08.049

Bioorganic & Medicinal Chemistry Letters 26 (2016) 4684–4686
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Benzo[b]thiophene-2-carboxamide derivatives as potent urotensin-II
receptor antagonists
Chae Jo Lim a,b, , Seong Eun Woo a,b, Su Ik Ko a,c, Byung Ho Lee a, Kwang-Seok Oh a,b, Kyu Yang Yi a,b,
⇑
⇑
a Bio & Drug Discovery Division, Korea Research Institute of Chemical Technology, Yuseong-gu, Daejeon 34114, Republic of Korea
b Department of Medicinal Chemistry and Pharmacology, University of Science and Technology, Yuseong-gu, Daejeon 34113, Republic of Korea
c Department of Chemistry, Mokpo National University, Muan-gun, Jeonnam 58554, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Members of a series of benzo[b]thiophene-2-carboxamide derivatives, possessing an N-(1-(3-bromo-4-
(piperidin-4-yloxy)benzyl)piperidin-4-yl) group, were synthesized and evaluated as urotensin-II receptor
antagonists. The results show that these substances have potent UT binding affinities. Observations made
in a systematic SAR investigation of the effects of a variety of substituents (R1 and R2) at the 5- and 6-
positions in the benzo[b]thiophene-2-carboxamide moiety on UT binding affinities led to identification
of the 5-cyano analog 7f as a highly potent UT antagonist with an IC50 value of 25 nM. Despite having
a good metabolic stability, 7f is a potent inhibitor of CYP isozyme and displays an unsuitable PK profile.
Ó 2016 Elsevier Ltd. All rights reserved.
Received 3 June 2016
Revised 12 August 2016
Accepted 18 August 2016
Available online 26 August 2016
Keywords:
Urotensin-II receptor
Antagonists
Benzo[b]thiophene carboxamide
Cardiovascular disease
Cardiac hypertrophy is an adaptive response to pressure over-
load in the heart that assists in maintaining cardiac function. How-
ever, prolonged stresses promote an increase in cardiac size and a
loss of cardiovascular function, leading to heart failure.1 Among
many targets, urotensin-II receptor (UT) has attracted considerable
recent attention as a therapeutic target for treatment of heart fail-
ure.2 Urotensin-II (U-II), a cysteine-linked cyclic peptide, is mainly
expressed in a variety of tissues, including blood vessels, heart,
liver, kidney, skeletal muscle and lung.3 It is known to be the most
potent vasoconstrictor, displaying a 10 times greater potency than
that of endothelin.4 The effects of this peptide are mediated
through its interaction with a G protein-coupled receptor known
as a GPR14 or the urotensin-II receptor.5 Activation of UT by bind-
ing with U-II results in several cardiovascular responses including
vasoconstriction, vasodilation, cell proliferation and hypertrophy.6
Specifically, the cardiovascular roles of UT also are to modulate
cardiac contractility, cardiomyocyte hypertrophy and fibrosis.
These findings suggest that U-II and its receptor system are
involved in the pathogenesis of cardiovascular disease.7 Further-
more, the results of previous studies demonstrate that the expres-
sion of UT is low or undetectable in normal myocardium, whereas
elevated U-II plasma levels and increased levels of UT expression
are associated with numerous cardiorenal and metabolic diseases,
including hypertension,8 heart failure,9 atherosclerosis,10
diabetes11 and renal failure.12 In addition, several UT antagonists
have been found to have antihypertrophic effects in animal mod-
els.13 Therefore, UT has emerged as one of the most promising
therapeutic targets for treatment of heart failure as well as a broad
range of other cardiovascular maladies.14
Although a great effort by scientists at numerous pharmaceuti-
cal companies has been devoted to this issue, the development of
potent UT antagonists for the treatment of heart failure remains
a highly desirable endeavor.15 In continuing efforts to our drug dis-
covery program aimed at the development of novel and potent UT
antagonists,16 we carried out an initial structure activity relation-
ship (SAR) study with 5- or 6-heteroaryl substituted carboxamide
derivatives, possessing N-(1-(3-bromo-4-(piperidin-4-yloxy)ben-
zyl)piperidin-4-yl) group.17 The results, summarized in Table 1,
show that the thiophene derivative 1 has a moderate UT binding
activity with an IC50 value of 130 nM. In contrast, other 5-mem-
bered heteroaryl carboxamide derivatives, such as furan 2, isoxa-
zole
3 and thiazole 4, have much lower binding affinities.
Furthermore, the pyridine moiety 5 was observed to have a slightly
higher binding activity than does 1. Moreover, replacement of the
pyridine group (5) with a pyrazine moiety (6) led to a large loss in
binding activity. Among the substances tested, benzo[b]thiophene
derivative 7 was found to have the most potent UT binding activity.
These results indicate that the position of heteroatom and size of
heteroaryl group on carboxamide derivatives play a significant role
in UT binding. The observations made in this preliminary SAR
study encouraged us to carry out a further effort in this area, in
⇑
Corresponding authors. Tel.: +82 42 860 7143.
E-mail addresses: chemlcj@krict.re.kr (C.J. Lim), kyyi@krict.re.kr (K.Y. Yi).
http://dx.doi.org/10.1016/j.bmcl.2016.08.049
0960-894X/Ó 2016 Elsevier Ltd. All rights reserved.

C. J. Lim et al. / Bioorg. Med. Chem. Lett. 26 (2016) 4684–4686
4685
bromo intermediate 9c, employing previously reported methods.18
Subsequently, hydrolysis of esters using 5 N NaOH in methanol
produced the corresponding carboxylic acids 10. In a parallel
sequence, 3-bromo-4-hydroxy benzaldehyde 12 was coupled with
1-N-Boc-4-hydroxypiperidine under Mitsunobu conditions to form
the ether 13, which underwent reductive amination reaction with
the Fmoc-protected 4-aminopiperidine using sodium triacetoxy-
borohydride in dichloromethane to form the amine analog 14.
Fmoc removal in 14 using 3 M NaOH in MeOH, afforded the free
amine derivative 15. Finally, simple amide forming reactions
between the substituted benzo[b]thiophene-2-carboxylic acids 10
and 4-aminopiperidine derivative 15 using bis(2-oxo-3-oxazo-
lidinyl)phosphonic chloride (BOP-Cl) produced amides 11, which
were converted through N-Boc removal with conc. HCl in 1,4-diox-
ane to the corresponding targets 7.
Table 1
UT binding affinities of 5- and 6-heteroaryl carboxamide derivatives
Br
O
N
NH
Ar
N
H
O
Compound
Ar
UT
IC50 (nM)a,b
S
1
2
3
130
770
340
O
O
N
N
4
5
970
120
S
N
An SAR study was carried out to explore the effects on binding
affinities of substituents (R1 and R2) at the 5- and 6-positions of the
benzo[b]thiophene moiety of 7. Affinities for binding of the benzo
[b]thiophene-2-carboxamide derivatives to membranes of HEK293
cells expressing human UT receptor were determined by using a
competitive binding assay with Eu-labeled U-II and a time-
resolved fluorometric (TRF) assay.19 Inspection of the results
(Table 2) shows that the unsubstituted derivative 7 has a moderate
UT binding activity (IC50 = 63 nM) and that introduction of a 5-flu-
oro group (7a) results in a slight increase in binding activity. In
addition, 5-chloro (7b) and 5-nitro (7d) substituted analogs display
potent UT binding activities. Among the substances tested, 5-cyano
substituted analog 7f has the most potent UT binding activity with
an IC50 value of 25 nM. Furthermore, repositioning the cyano sub-
stitutent from the 5- (7f) to the 6-position (7g) results in a 3.2-fold
decrease in binding activity. The 4- and 7-cyano substituted
derivatives also have similar low binding affinities (data not
shown). Other substances, including the 5-bromo (7c), 5-trifluo-
romethyl (7e), 5-methyl (7h), 5-ethyl (7i), 5-methoxy (7j) and 5-
phenyl (7k) derivatives were found to have reduced binding affini-
ties. Interestingly, moving the sterically bulky phenyl group from
the 5- (7k) to the 6-position (7l) position leads to a large increase
in binding activity. The effects of various substituents on the 6-aryl
group of the benzo[b]thiophene-2-carboxamides were also
N
N
6
7
610
63
S
a
UT binding affinities were determined by using a competitive binding assay
with Eu-U-II and a TRF.
b
Values are means of at least two measurements.
which a number of benzo[b]thiophene-2-carboxamide derivatives
were prepared and subjected to an evaluation of their UT antago-
nist properties.
The general synthetic route employed for the preparation of
substituted benzo[b]thiophene-2-carboxamide derivatives
outlined in Scheme 1. In these pathways, commercially available
substituted 2-fluoro benzaldehydes 8 were reacted with methyl
thioglycolate in the presence of sodium hydride to give benzo[b]
thiophene-2-carboxylic acid methyl esters 9 including the fluoro
(9a), chloro (9b), bromo (9c), nitro (9d), trifluoromethyl (9e) and
methoxy (9f) analogs. In addition, cyano (9f–g), methyl (9h), ethyl
(9i) and aryl (9k–r) substituted benzo[b]thiophene-2-carboxylic
acid methyl esters 9 were synthesized with the corresponding
7 is
O
O
S
F
S
O
(c)
OMe
OH
(a)
(b)
R2
R2
R2
H
R1
R1
R1
S
8
9
10
Br
boc
Br
O
N
N
O
N
NH
S
(d)
N
O
N
H
O
H
R2
R2
R1
R1
11
7
boc
NH
N
Fmoc
N
H
O
HO
O
Br
boc
Br
H
(e)
(f)
H
N
OH
O
12
13
boc
Br
boc
Br
N
N
(g)
N
N
Fmoc
N
H
O
H2N
O
14
15
Scheme 1. Reagents and conditions: (a) methyl thioglycolate, NaH, DMF, rt; (b) 3 N NaOH, MeOH, rt; (c) 15, bis(2-oxo-3-oxazolidinyl)phosphonic chloride (BOP-Cl), Et3N,
DMF, rt; (d) conc. HCl, 1,4-dioxane, rt; (e) diethyl azodicarboxylate (DEAD), triphenylphosphine, THF, rt; (f) NaBH(OAc)3, dichloromethane, rt; (g) 3 N NaOH, MeOH, rt.

4686
C. J. Lim et al. / Bioorg. Med. Chem. Lett. 26 (2016) 4684–4686
Table 2
Supplementary data
Effects of substituents on UT binding affinities of benzo[b]thiophene-2-carboxamide
derivatives
Supplementary data associated with this article can be found, in
the online version, at http://dx.doi.org/10.1016/j.bmcl.2016.08.
049.
Br
O
N
NH
S
N
H
O
R2
References and notes
R1
7
1. (a) McKinsey, T. A.; Olson, E. N. J. Clin. Invest. 2005, 115, 538; (b) Onan, D.;
Pipolo, L.; Yang, E.; Hannan, R. D.; Thomas, W. G. Mol. Endocrinol. 2004, 18,
2344.
Compound
R1
R2
UT
IC50 (nM)a,b
2. (a) Russell, F. D. Pharmacol. Ther. 2004, 103, 223; (b) Gilbert, R. E.; Douglas, S. A.;
Krum, H. Curr. Opin. Inverstig. Drugs 2004, 5, 276.
3. Maguire, J. J.; Kuc, R. E.; Davenport, A. P. Br. J. Pharmacol. 2000, 131, 441.
4. (a) Bohm, F.; Pernow, J. Br. J. Pharmacol. 2002, 135, 25; (b) Douglas, S. A.;
Ohlstein, E. H. Trends Cardiovasc. Med. 2000, 10, 229.
7
H
F
Cl
H
H
H
H
H
H
H
CN
H
H
H
H
Ph
63
53
51
86
49
100
25
80
74
180
100
310
90
560
87
49
140
74
7a
7b
7c
7d
7e
7f
7g
7h
7i
7j
7k
7l
7m
7n
7o
7p
7q
7r
Br
NO2
CF3
CN
H
Me
Et
OMe
Ph
H
H
H
H
H
H
H
5. Ames, R. S.; Sarau, H. M.; Chambers, J. K.; Willette, R. N.; Aiyar, N. V.; Romanic,
A. M.; Louden, C. S.; Foley, J. J.; Sauermelch, C. F.; Coatney, R. W.; Ao, Z.; Disa, J.;
Holmes, S. D.; Stadel, J. M.; Martin, J. D.; Liu, W.-S.; Glover, G. I.; Wilson, S.;
McNulty, D. E.; Ellis, C. E.; Elshourbagy, N. A.; Shabon, U.; Trill, J. J.; Hay, D. W.
P.; Ohlstein, E. H.; Bergsma, D. J.; Douglas, S. A. Nature 1999, 401, 282.
6. Ong, K. L.; Lam, K. S. L.; Cheung, B. M. Y. Cardiovasc. Drugs Ther. 2005, 19, 65.
7. (a) Quaile, M. P.; Kubo, H.; Kimbrough, C. L.; Douglas, S. A.; Margulies, K. B. Circ.
Heart Fail. 2009, 2, 39; (b) Tzanidis, A.; Hannan, R. D.; Thomas, W. G.; Onan, D.;
Autelitano, D. J.; See, F.; Kelly, D. J.; Gilbert, R. E.; Krum, H. Circ. Res. 2003, 93,
246; (c) Johns, D. G.; Ao, Z.; Naselsky, D.; Herold, C. L.; Maniscalco, K.; Sarov-
Blat, L.; Steplewski, K.; Aiyar, N.; Douglas, S. A. Arch. Pharmacol. 2004, 370, 238.
8. (a) Matsushita, M.; Shichiri, M.; Imai, T.; Iwashina, M.; Tanaka, H.; Takasu, N.;
Hirata, Y. J. Hypertens. 2001, 19, 2185; (b) Krum, H.; Kemp, W. Curr. Hypertens.
Rep. 2007, 9, 53.
9. (a) Bousette, N.; Patel, L.; Douglas, S. A.; Ohlstein, E. H.; Giaid, A. Atherosclerosis
2004, 176, 117; (b) Loirand, G.; Rolli-Derkinderen, M.; Pacaud, P. Peptides 2008,
29, 778.
10. (a) Douglas, S. A.; Tayara, L.; Ohlstein, E. H.; Halawa, N.; Giaid, A. Lancet 2002,
359, 1990; (b) Tolle, M.; van der Giet, M. Peptides 2008, 29, 743.
11. (a) Totsune, K.; Takahashi, K.; Arihara, Z.; Sone, M.; Ito, S.; Murakami, O. Clin.
Sci. 2003, 104, 1; (b) Wenyi, Z.; Suzuki, S.; Hirai, M.; Hinokio, Y.; Tanizawa, Y.;
Matsutani, A.; Satoh, J.; Oka, Y. Diabetologia 2003, 46, 972.
2-OMe-Ph
3-OMe-Ph
4-OMe-Ph
4-Me-Ph
4-F-Ph
4-Cl-Ph
140
a
UT binding affinities were determined by using a competitive binding with Eu-
U-II and a TRF assay.
b
Values are means of at least two measurements.
12. (a) Totsune, K.; Takahashi, K.; Arihara, Z.; Sone, M.; Satoh, F.; Ito, S.; Kimura, Y.;
Sasano, H.; Murakami, O. Lancet 2001, 358, 810; (b) Langham, R. G.; Kelly, D. J.;
Gow, R. M.; Zhang, Y.; Dowling, J. K.; Thomson, N. M.; Gilbert, R. E. Am. J. Kidney
Dis. 2004, 44, 826.
13. (a) Bousette, N.; Hu, F.; Ohlstein, E. H.; Dhanak, D.; Douglas, S. A.; Giaid, A. J.
Mol. Cell. Cardiol. 2006, 41, 285; (b) Esposito, G.; Perrino, C.; Cannavo, A.;
Schiattarella, G. G.; Borgia, F.; Sannino, A.; Pironti, G.; Gargiulo, G.; Di Serafino,
L.; Franzone, A.; Scudiero, L.; Grieco, P.; Indolfi, C.; Chiariello, M. Basic Res.
Cardiol. 2011, 106, 577.
explored. While the substance having a p-methoxy group (7o) has
a potent UT binding affinity, which is higher than that of 7, analogs
in which this group is located at ortho (7m) and meta (7n) positions
have significantly decreased binding affinities. In addition, the p-
methyl (7p), p-fluoro (7q) and p-chloro (7r) aryl substituted
derivatives display low binding activities. Additional properties
of the 5-cyano substituted benzo[b]thiophene-2-carboxamide 7f
were evaluated. This substance was found to display good meta-
bolic stability in human and rat liver microsomes (85% and 74%
for 30 min, respectively). However, 7f shows potent inhibition of
cytochrome P450 enzymes, CYP2D6 and CYP3A4 (55% and 75%
14. (a) Maryanoff, B. E.; Kinney, W. A. J. Med. Chem. 2010, 53, 2695; (b) Lescot, E.;
Bureau, R.; Rault, S. Peptides 2008, 29, 680.
15. (a) Jin, J.; Douglas, S. A. Expert Opin. Ther. Pat. 2006, 16, 467; (b) Carotenuto, A.;
Grieco, P.; Rovero, P.; Novellino, E. Curr. Med. Chem. 2006, 13, 267; (c) Hilfiker,
M. A.; Zhang, D.; Dowdell, S. E.; Goodman, K. B.; McAtee, J. J.; Dodson, J. W.;
Viet, A. Q.; Wang, G. Z.; Sehon, C. A.; Behm, D. J.; Wu, Z.; Carballo, L. H.; Douglas,
S. A.; Neeb, M. J. Bioorg. Med. Chem. Lett. 2008, 18, 4470; (d) Lawson, E. C.; Luci,
D. K.; Ghosh, S.; Kinney, W. A.; Reynolds, C. H.; Qi, J.; Smith, C. E.; Wang, Y.;
Minor, L. K.; Haertlein, B. J.; Parry, T. J.; Damiano, B. P.; Maryanoff, B. E. J. Med.
Chem. 2009, 52, 7432; (e) Wang, Y.; Wu, Z.; Gioda, B. F.; Lawrence, S. K.; Neeb,
M. J.; Rivero, R. A.; Douglas, S. A.; Jin, J. Bioorg. Med. Chem. Lett. 2008, 18, 4936;
(f) Taylor, S. J.; Soleymanzadeh, F.; Muegge, I.; Akiba, I.; Taki, N.; Ueda, S.;
Mainolfi, E.; Eldrup, A. B. Bioorg. Med. Chem. Lett. 2013, 23, 2177.
16. (a) Lee, B. H.; Yi, K. Y.; Oh, K.-S.; Lim, C. J.; Kim, N. J.; Suh, J. H.; Lee, J. H.; Seo, H.
W. Korean Patent Application No. 2014–0042228, 2014.; (b) Lim, C. J.; Jang, J.
Y.; Kim, S. H.; Lee, B. H.; Oh, K.-S.; Yi, K. Y. Bull. Korean Chem. Soc. 2015, 36,
2549; (c) Oh, K.-S.; Lee, J. H.; Yi, K. Y.; Lim, C. J.; Lee, S.; Park, C. H.; Seo, H. W.;
Lee, B. H. Br. J. Pharmacol. 2015, 172, 2618; (d) Lim, C. J.; Oh, S. A.; Lee, B. H.; Oh,
K.-S.; Yi, K. Y. Bioorg. Med. Chem. Lett. 2014, 24, 5832; (e) Kim, S.-K.; Goddard,
W. A., III; Yi, K. Y.; Lee, B. H.; Lim, C. J.; Trzaskowski, B. ChemMedChem 2014, 9,
1732.
17. (a) Jin, J.; An, M.; Sapienza, A.; Aiyar, N.; Naselsky, D.; Sarau, H. M.; Foley, J. J.;
Salyers, K. L.; Knight, S. D.; Keenan, R. M.; Rivero, R. A.; Dhanak, D.; Douglas, S.
A. Bioorg. Med. Chem. Lett. 2008, 18, 3950; (b) Jin, J.; Dhanak, D.; Knight, S. D.;
Widdowson, K.; Aiyar, N.; Naselsky, D.; Sarau, H. M.; Foley, J. J.; Schmidt, D. B.;
Bennett, C. D.; Wang, B.; Warren, G. L.; Moore, M. L.; Keenan, R. M.; Rivero, R.
A.; Douglas, S. A. Bioorg. Med. Chem. Lett. 2005, 15, 3229.
18. (a) Lee, S.; Lee, H.; Yi, K. Y.; Lee, B. H.; Yoo, S.-E.; Lee, K.; Cho, N. S. Bioorg. Med.
Chem. Lett. 2005, 15, 2998; (b) Mukumoto, F.; Tamaki, H.; Kusaka, S.; Iwakoshi,
M. WO 2014/073623 A1.
at 10 lM, respectively). Furthermore, the results of an iv
pharmacokinetic study (10 mg/kg) demonstrate that 7f has both
a high clearance (Cl = 104 mL/min/kg) and volume of distribution
(Vss = 39 L/kg).
In summary, this SAR study led to the identification of benzo[b]
thiophene-2-carboxamide derivatives that serve as novel UT
antagonists. Observations made in a systematic optimization
study, probing the effects of a variety of substituents on the
benzo[b]thiophene moiety, resulted in the identification of the 5-
cyano substituted benzo[b]thiophene-2-carboxamide 7f as
a
highly potent UT antagonist. Although this substance displays good
metabolic stability, it is a potent inhibitor of the P450 enzymes
(CYP2D6 and CYP 3A4). Further studies concentrating on improv-
ing of CYP inhibitory and PK properties of the heteroaryl carbox-
amide derivatives are now in progress.
Acknowledgments
This research was financially supported by a grant from the
Ministry of Science, ICT & Future Planning (2011-0019397) and
the KRICT (SI1607-02), Republic of Korea.
19. Oh, K.-S.; Lee, S.; Lee, B. H. Assay Drug Dev. Technol. 2011, 9, 514.