Sulfonamide derivatives of styrylheterocycles as a potent inhibitor of COX-2-mediated prostaglandin E2 production

Article abstract of DOI:10.1016/j.bmcl.2010.09.136

The overproduction of prostaglandin E₂ (PGE₂) plays an important role in a variety of pathophysiological processes including inflammation and carcinogenesis. Therefore, the modulation of PGE₂ production is a promising targ

Full text of DOI:10.1016/j.bmcl.2010.09.136

Bioorganic & Medicinal Chemistry Letters 20 (2010) 6938–6941
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry Letters
journal homepage: www.elsevier.com/locate/bmcl
Sulfonamide derivatives of styrylheterocycles as a potent inhibitor
of COX-2-mediated prostaglandin E2 production
Chaemin Lim a, Minhee Lee a, Eun-Jung Park b, Ran Cho a, Hyen-Joo Park a, Seong Jin Lee c,
a,
Heeyeong Cho c, Sang Kook Lee a, , Sanghee Kim
⇑
⇑
a College of Pharmacy, Seoul National University, San 56-1, Shilim, Kwanak, Seoul 151-742, Republic of Korea
b College of Pharmacy, Ewha Womans University, 11-1 Daehyun, Seodaemun, Seoul 120-750, Republic of Korea
c Pharmacology Research Center, Korea Research Institute of Chemical Technology, Sinseongno 19, Yuseong, Daejeon 305-343, Republic of Korea
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 13 July 2010
Revised 16 September 2010
Accepted 28 September 2010
Available online 20 October 2010
The overproduction of prostaglandin E2 (PGE2) plays an important role in a variety of pathophysiological
processes including inflammation and carcinogenesis. Therefore, the modulation of PGE2 production is a
promising target in the design of chemotherapeutic agents. In the present study, the inhibitory effects of
a series of styrylheterocycles having either a p-SO2NH2 or p-SO2Me group on the production of cyclooxygen-
ase-2-mediated PGE2 were evaluated in lipopolysaccharide-stimulated RAW264.7 murine macrophages.
Among the series of styrylheterocycle derivatives, (E)-4-(2-(thiophen-3-yl)vinyl)benzenesulfonamide
exhibited a potent inhibitory activity, with an IC50 value of 0.013 lM. The inhibitory activity against the
overproduction of PGE2 by the active compound was found to be due in part to the suppression of COX-2
mRNA expression.
Keywords:
COX-2 inhibitors
Styrylheterocycles
PGE2 production
Structure–activity relationships
Ó 2010 Elsevier Ltd. All rights reserved.
Accumulating evidence suggests that the overproduction of
prostaglandins (PGs) influences a variety of pathophysiological
processes, including inflammation, Alzheimer’s disease, hyperten-
sion, heart failure, and carcinogenesis.1–5 Consequently, inhibition
of PG synthesis has been investigated as a means of developing
new therapeutic agents for the treatment of numerous diseases
mediated by PGs.6–8
p-SO2Me substituent on one of the phenyl rings represent a major
class of selective COX-2 inhibitors. Extensive structure–activity
studies indicate that the SO2NH2 or SO2Me substituents interact
with the COX-2 side pocket through tight-binding kinetics, provid-
ing COX-2 selectivity and potency.15 Typical examples of this class
of the selective COX-2 inhibitors are Coxibs such as celecoxib and
rofecoxib. However, the recent market withdrawal of rofecoxib
due to its increase risk of cardiovascular side effects with its long-
term use in clinic16 clearly depicts the need to explore new class of
compounds having reduced cardiovascular adverse effects.17,18 Sev-
eral natural compounds have been shown to inhibit COX without
causing cardiac toxicities, probably by acting on other pathways that
compensate for the cardiac toxicity of pure COX inhibition.18 The
dual inhibition of COX and LOX enzymes was suggested as potential
therapeutic approaches for anti-inflammatory agents with reduced
GI and cardiovascular side effects.18
The rate limiting step in PG biosynthesis is the conversion of ara-
chidonic acid to PGH2, which is the precursor of primary PGs.1,9,10
This necessary step is catalyzed by the enzyme cyclooxygenase
(COX). Two isoforms of the COX enzyme, which are encoded by
two different genes, have been identified. COX-1 is constitutively ex-
pressed in virtually all tissues, whereas COX-2 is expressed only in
response to growth factors, tumor promoters, or various physiolog-
ical and inflammatory stimuli.11,12 Because COX-2-mediated metab-
olites, including PGE2, are involved in the induction of inflammation,
pain, and carcinogenesis,1–3 COX-2 inhibitors have received much
attention as effective anti-inflammatory or cancer chemopreventive
agents. In addition, selective COX-2 inhibitors are postulated to be
beneficial in the prophylactic treatment of neurodegenerative
disorders.13
Several compounds with acylic central systems have been sug-
gested as potential COX-2 modulators.19 It has also been shown that
stilbenoids exhibit COX inhibitory activity. Synthetic cis-stilbene
derivatives that possess a p-SO2NH2 or p-SO2Me pharmacophore
exhibit COX-2 inhibitory activities with appreciable potency.20
A
Several classes of COX-2 inhibitors have been reported.14 Of
these, vicinal diaryl heterocycles that contain a p-SO2NH2 or
number of naturally occurring and synthetic trans-stilbenoids were
also revealed as inhibitors of COX, although this compound class was
somewhat less active than the representative COX inhibitors.21
Recently, we reported on the preparation of a series of trans-
stilbenoids, including styrylheterocycles, and evaluated their
inhibitory effects on the production of COX-2 mediated PGE2.22
⇑
Corresponding authors. Tel.: +82 2 880 2475; fax: +82 2 762 8322 (S.K.L.); tel.:
+82 2 880 2487; fax: +82 2 888 0649 (S.K.).
E-mail addresses: sklee61@snu.ac.kr (S.K. Lee), pennkim@snu.ac.kr (S. Kim).
0960-894X/$ - see front matter Ó 2010 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmcl.2010.09.136

C. Lim et al. / Bioorg. Med. Chem. Lett. 20 (2010) 6938–6941
6939
Table 1
Inhibitory effects of styrylheterocycles on the PGE2 production in LPS-
stimulated RAW264.7 cellsa
Figure 1. Chemical structures of compounds 1 and 2.
b
Compd
R
IC50 (lM)
We found that styrylheterocycles 1 (Fig. 1) containing a para-
methoxy group on the phenyl ring showed submicromolar inhibi-
tory activity against the overproduction of the inflammatory medi-
ator PGE2 in LPS-stimulated RAW264.7 cells. This result led us to
consider styrylheterocycles 1 as a new lead compound for further
chemical optimization. As part of our ongoing program to develop
inhibitors of PG production, we now describe the synthesis and
biological evaluation of styrylheterocycles of general structure 2
(Fig. 1) that possess a p-SO2NH2 or p-SO2Me COX-2 pharmacophore
on the phenyl ring.
6a
6b
6c
6d
8a
8b
8c
8d
Me
Me
Me
Me
NH2
NH2
NH2
NH2
1.18
>50
0.38
0.52
18.27
>50
0.013
0.44
The activities were measured as described previously.22,25
The IC50 values were determined from triplicate tests.
a
b
The designed compounds were synthesized from the commer-
cially available 4-methylthiobenzaldehyde (3), as shown in
Scheme 1. A Wittig reaction was performed with phosphonium
bromides 4a–d and aldehyde 3 in the presence of n-BuLi to yield
a mixture of olefins 5a–d with an E/Z ratio of ca. 2:1. The E/Z mix-
ture 5 was converted to the E-isomer by heating with catalytic
amounts of iodine in refluxing heptane. Oxidation of the SMe sub-
stituent of E-isomer 5 using an aqueous Oxone solution23 afforded
the methylsulfone products 6a–d. Conversion of the methylsulfone
substituent to the corresponding sulfonamide group was accom-
plished according to a previously reported two-step process.24
Treatment of 6a–d with LDA and (iodomethyl)trimethylsilane led
to the formation of the trimethylsilylethyl sulfone intermediate
7. Desilylation with TBAF and subsequent treatment of the result-
ing sulfinic acid salts with hydroxylamine-O-sulfonic acid provided
the desired sulfonamides (8a–d) in moderate yields.
sulfone analogue 6b, which contains a 3-furyl group, did not show
any inhibitory activities up to 50 M, while its parent styrylhetero-
cycle (1b) had an IC50 of 0.5
compound 6c, which contains a 2-thienyl group, exhibited the
most appreciable inhibitory activity (IC50 = 0.38 M).
lM. Among these sulfone analogues,
l
The effects of styrylheterocycles with a p-SO2NH2 group were
revealed to also be highly dependent on the structure of the het-
erocyclic ring. The sulfonamide analogue possessing a 3-thienyl
group 8d was approximately equipotent to its corresponding sul-
fone analogue 6d in this assay. The sulfonamide analogue possess-
ing a 3-furyl group 8b was not effective. The inhibitory activity of
the 2-furyl containing compound 8a was significantly decreased
compared to the 2-furyl sulfone analogue 6a. On the other hand,
the 2-thienyl sulfonamide analogue 8c exhibited the most potent
inhibitory activity, with an IC50 value of 0.013 lM. This potency
The prepared compounds, 6a–d and 8a–d, were evaluated for
their inhibitory activities on the PGE2 production in LPS-stimulated
RAW264.7 cells.25 As shown in Table 1, the replacement of the
p-OMe substituent with a p-SO2Me group resulted in a loss in
inhibitory activity. For example, aryl sulfones 6a and 6d were
found to be almost three or five times less potent than their corre-
sponding parent compounds 1a and 1c, respectively (Fig. 1). The
was 30-fold greater than that of the corresponding sulfone ana-
logue 6c and approximately 8- to 40-fold greater than that of the
p-OMe substituted styrylheterocycles 1.
We performed molecular modeling studies on the interaction of
COX-2 with the most promising analogue 8c.25 A docking study
with compound 8c and COX-2 (Protein Data Bank code 1CX2)
showed that the spatial location of the sulfonamide groups on 8c
Scheme 1. A solution phase synthetic approach was employed for the preparation of the trans-stilbenoids as described in Table 1. Reagents and conditions: (a) n-BuLi, THF, rt;
aqueous workup (5a, E/Z = 2:1, 68%; 5b, E/Z = 2.1:1, 65%; 5c, E/Z = 2.2:1, 75%; 5d, E/Z = 2.3:1, 70%); (b) I2, heptane, reflux; (c) Oxone, THF, rt; isolation (6a, 75%; 6b, 70%; 6c,
100%; 6d, 80%); (d) LDA, (iodomethyl)trimethylsilane, THF, À78 °C to rt; aqueous workup (7a, 42%; 7b, 42%; 7c, 50%; 7d, 51%); (e) TBAF, THF, reflux; (f) H2NOSO3H, rt (8a, 52%;
8b, 48%; 8c, 60%; 8d, 48%).

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C. Lim et al. / Bioorg. Med. Chem. Lett. 20 (2010) 6938–6941
and SC-558 (a celecoxib analogue) are partially overlapped, and
their benzenesulfonamide groups are nearly superimposed
(Fig. 2). The Ar-SO2NH2 group of 8c interacts with the amino acid
residues lining the COX-2 binding site (Gly519, Phe518, Ala516,
Gln192, Arg513, and His90). The two oxygen atoms of the SO2NH2
group form two hydrogen bonds with the backbone NHs of His90
and Arg513 (distance = 2.87 Å). In addition, other possible hydro-
gen bonds are observed between the nitrogen of the SO2NH2 moi-
ety and the backbone carbonyl in Gln192 (distance = 3.72 Å)/
Phe518 (distance = 3.84 Å)/Leu352 (distance = 4.12 Å). These
observations suggest that styrylheterocyclic sulfonamides interact
favorably within the COX-2 binding site.
To understand the underlying molecular mechanisms that lead
to the inhibition of PGE2 production, the suppressive effect of 8c on
the COX-2 mRNA expression was investigated using reverse tran-
scription-polymerase chain reaction (RT-PCR) analysis.25 Treat-
ment with LPS for 5 h dramatically increased the expression of
the COX-2 mRNA levels, and the induction was suppressed by
the treatment of 8c in a concentration-dependent manner as de-
picted in Figure 3. Based on our observations, we hypothesize that
the inhibitory effects of styrylheterocycles 8c against LPS-stimu-
lated PGE2 production may in part be correlated with the suppres-
sion of COX-2 mRNA expression. However, because the suppressive
effect of 8c on the COX-2 mRNA expression was not reached com-
pletely at the IC50 value of PGE2 production, other mechanisms
such as direct COX-2 inhibitory activity could not be excluded.
Therefore, the inhibition of PGE2 production in LPS-activated
RAW264.7 cells by styrylheterocyles might be due to either sup-
pression of COX-2 expression or direct inhibition of COX-2 enzyme
activity.
In summary, although the caution with the cardiovascular side
effect by vicinal diaryl heterocycle class compounds targeting
COX-2 activity was recently raised, studies are still required to ex-
plore new templates having reduced cardiovascular adverse ef-
fects. In this study, a series of styrylheterocycle derivatives have
been prepared and evaluated as to their effects on COX-2-mediated
PGE2 production, with the goal of identifying a potent modulator.
Our previous lead compound 1 was optimized by the incorporation
of a p-SO2NH2 COX-2 pharmacophore. We found that (E)-4-(2-
(thiophen-3-yl)vinyl)benzenesulfonamide (8c) exhibited a potent
inhibitory activity against the overproduction of the inflammatory
mediator PGE2 and could serve as a new therapeutic agent for the
treatment of diseases mediated by PGs. We have also gained in-
sight into the structure–activity relationship of styrylheterocycles
that is valuable in the design and development of new class of
inhibitors of PG synthesis. Further studies are currently in progress,
including a more detailed biological evaluation and chemical
optimizations.
Acknowledgments
This study was supported by a grant KRF-2007-313-E00617
(S.K.L.), and WCU program(R32-2008-000-10098-0) (S.K.), Republic
of Korea.
Supplementary data
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmcl.2010.09.136.
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