Discovery of new chromone containing sulfonamides as potent inhibitors of bovine cytosolic carbonic anhydrase

Article abstract of DOI:10.1016/j.bmc.2011.04.040

Series of chromone containing sulfonamides were prepared by the reaction of (un)substituted 3-formylchromones with 3-aminobenzenesulfonamide and 4-aminobenzenesulfonamide. Bovine carbonic anhydrase (bCA) inhibitory activity of these newly synthesized comp

Full text of DOI:10.1016/j.bmc.2011.04.040

Bioorganic & Medicinal Chemistry 19 (2011) 3367–3371
Contents lists available at ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Discovery of new chromone containing sulfonamides as potent inhibitors
of bovine cytosolic carbonic anhydrase
Mariya al-Rashida a, , Muhammad Ashraf b, Bushra Hussain b, Saeed Ahmad Nagra a, Ghulam Abbas a
⇑
a Institute of Chemistry, University of the Punjab, Lahore 54590, Pakistan
b Department of Pharmacy, The Islamia University of Bahawalpur, Bahawalpur 63100, Pakistan
a r t i c l e i n f o
a b s t r a c t
Article history:
Series of chromone containing sulfonamides were prepared by the reaction of (un)substituted 3-form-
ylchromones with 3-aminobenzenesulfonamide and 4-aminobenzenesulfonamide. Bovine carbonic
anhydrase (bCA) inhibitory activity of these newly synthesized compounds was determined. All com-
pounds were active and possessed excellent bCA inhibitory activities with IC50 values ranged between
Received 7 March 2011
Revised 19 April 2011
Accepted 20 April 2011
Available online 22 April 2011
4.31 0.001 and 29.12 0.008
most active.
lmol. Compounds derived from 6-fluoro-3-formylchromones were the
Keywords:
Ó 2011 Elsevier Ltd. All rights reserved.
Carbonic anhydrase
Carbonic anhydrase inhibitors
Formylchromones
Sulfonamides
1. Introduction
disorders.15–18 There are 16 currently known isozymes of CA in hu-
mans. It is thus of critical importance to synthesize and assay CA
inhibitors from diverse classes of substances, in order to identify
compounds with specificity towards specific isozymes.
Chromones are a group of naturally occurring oxygen contain-
ing heterocyclic compounds. They are widely distributed in plant
kingdom and form the basic nucleus of important compounds such
as anthocyanin and flavonoids. Chromones are also well known for
their antimicrobial,1,2 antitumor,3,4 and antiviral5,6 activities. 3-
Formylchromones are important synthons in synthetic chemistry
for incorporating chromone moieties into other heterocyclic sys-
tems or for creating new heterocyclic systems based on chromone
ring.7,8 They are widely used due to their ease of preparation and
modification via Vilsmeier Haack reaction.9,10 The synthetic utility
of 3-formylchromones can be explored by exploiting three electron
deficient centers; the (keto) carbonyl carbon, carbon atom C2 and
the aldehyde carbon atom C3.11
The clinical and medicinal importance of sulfonamides is well
documented. The sulfonamide moiety (–SO2NH2) is an active phar-
macophore, exhibiting a wide variety of pharmacological activities
such as antimicrobial, antimalarial, insulin-releasing antidiabetic,
anti-HIV, high ceiling diuretic, antithyroid, and antitumor.12–14
Among the broad spectrum of activities exhibited by sulfonamides,
their role as inhibitors of the zinc containing metalloenzyme
carbonic anhydrase (CA) is probably most widely studied. Many
sulfonamide CA inhibitors have been used as therapeutic agents
against various diseases including glaucoma, gastro-duodenal
ulcers, acid–base disequilibria, and various neurological
Over the years, a lot of development has been made in this area
and new classes of compounds that can act as CA inhibitors are
continuously being emerged in hopes of finding isozyme specific
inhibitors. In this regard, the efforts of research group of Supuran
are worth mentioning.19–23 In 2005, Puccetti et al.24 reported sul-
fonamides containing chromone moieties as a new class of CA
inhibitors for the first time. The compounds reported were Schiff
bases obtained by the reaction of 3-formylchromone with various
aminobenzene sulfonamides. In the present work, we have ex-
panded this new class of inhibitors by synthesizing novel sulfona-
mides containing chromone moieties and determined their
inhibition activity against bCA.
2. Results
2.1. Chemistry
Two series of sulfonamide containing chromone moieties
(1a–1e and 2a–2e) were synthesized by simple and facile conden-
sation reaction of equimolar quantities of 6-(un)substituted 3-
formylchromones with 3- and 4-amino benzenesulfonamide using
ethanol in the presence of catalytic amount of p-toluenesulfonic
acid (p-TsOH). Reaction mixture was refluxed for 3.5 h and kept
overnight. Solid product was obtained by filtration and purified
by recrystallization. The substituted 3-formylchromones used
⇑
Corresponding author. Tel.: +92 3432106432; fax: +92 42 99231269.
E-mail address: maria_al_rashida@hotmail.com (M. al-Rashida).
0968-0896/$ - see front matter Ó 2011 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2011.04.040

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M. al-Rashida et al. / Bioorg. Med. Chem. 19 (2011) 3367–3371
were 6-fluoro-3-formylchromone, 6-bromo-3-formylchromone,
6,8-dibromo-3-formylchromone and 6-ethyl-3-formylchromone.
The general pathway leading to the synthesis of compounds
(1a–1e and 2a–2e) is given in Scheme 1. The structures of newly
synthesized compounds were ascertained via IR, MS, 1H NMR
and 13C NMR spectroscopic techniques. Single crystal XRD analysis
of one of the compounds (1a)25 further confirms the structural
elucidation.
test comp/abs of control) ꢁ 100)]. IC50 values of selected com-
pounds exhibiting >50% activity at 0.5 mM were calculated after
suitable dilutions.
3. Discussion
A
series of structurally related sulfonamide enamines
containing chromone moieties (1a–1e and 2a–2e) were prepared
according to Scheme 1 by reacting 3-formylchromone, 6-fluoro-
3-formylchromone, 6-bromo-3-formylchromone, 6,8-dibromo-3-
formylchromone and 6-ethyl-3-formylchromone with 3- and
4-aminobenzene sulfonanmides. All reactions were carried out in
ethanol in the presence of catalytic amount of p-toluenesulfonic
acid (p-TsOH). The molecule of 3-formylchromone has a very reac-
tive electron deficient centre at C2 position. Ethanol (solvent) acts
as a nucleophile and is added into the C2-C3 olefinic bond of the
chromone yielding an enamine product. This enamine product is
sufficiently stable and is not converted to Schiff base. Similar addi-
tions of ethanol to the molecule of 3-formylchromone have been
studied in detail by Stankovicova et al.27–29 Analogous results were
obtained by Dziewulska-Kułaczkowska and Mazur30 for the prepa-
ration of related compound 3-(anilinomethylene)-2-methoxychro-
man-4-one, in which a molecule of methanol has been added into
the C2 position of chromone ring. One of the reasons for the stabil-
ity of this sulfonamide enamine is the N–HꢂꢂꢂO intramolecular
hydrogen bond. The presence of this hydrogen bond has been con-
firmed via single crystal X-ray diffraction of one of the compounds
1a reported here (Fig 1).25
2.2. Carbonic anhydrase assay
CA activity was determined by the method of Pocker and
Stone26 after standardization of reaction conditions like enzyme
conc., substrate conc., buffer pH, duration of reaction etc. The
method is based on the principle that p-nitrophenyl acetate is
hydrolyzed by CA to form p-nitrophenol which is determined spec-
trophotometrically. Reaction mixture contained 50 mM Tris–sul-
fate buffer pH 7.6 containing 0.1 mM ZnCl2, 5
lL (0.5 mM) test
compound in DMSO and 10 L (0.35 U, with activity units of
l
700 U/g) bovine enzyme per well. Contents were mixed and pre-
incubated at 25 °C for 10 min. Plates were pre-read at 348 nm
using a 96 well plate reader. Substrate, p-nitrophenyl acetate was
prepared (3 mM stock using <5% acetonitrile in buffer and used
fresh) and 20
lL was added per well to achieve 0.6 mM concentra-
tion per well. Total reaction volume was made to 100
lL. After
30 min incubation at 25 °C, contents were mixed and read at
348 nm. Suitable controls with DMSO and known inhibitor aceta-
zolamide were included in the assay. Results reported are mean
of three independent experiments ( sem) and expressed as percent
inhibitions calculated by the formula, Inhibition (%) = [100ꢀ(abs of
All synthesized compounds were tested for their ability to act as
CA inhibitors against bovine cytosolic CA containing CA-I and CA-II
R2
R2
NH2
O
O
O
CH3
O
EtOH
p-TsOH
SO2NH2
+
R1
R1
O
O
HN
SO2NH2
1a-1e; 4-SO2NH2
2a-2e; 3-SO2NH2
1a, 2a; R1 = H; R2 = H
1b, 2b; R1 = F; R2 = H
1c, 2c; R1 = Br; R2 = H
1
1d, 2d; R = Br; R2 = Br
1e, 2e; R1 = CH2CH3; R2 = H
Scheme 1.
Figure 1. Stabilization of the enamine product via N–HꢂꢂꢂO intramolecular hydrogen bond in 1a.

M. al-Rashida et al. / Bioorg. Med. Chem. 19 (2011) 3367–3371
5. Experimental
3369
Table 1
Percent inhibition and IC50 values (lmol) of compounds
Compounds
Bovine carbonic anhydrase
Inhibition at 0.5 mM (%)
5.1. General methods
IC50 (lmol)
All reactants were purchased from either Sigma or Aldrich and
were used without further purification. Commercially available sol-
vents were used. Ethanol was distilled and dried using standard
methods and stored over molecular sieves. Reaction progress and
product purity was checked by precoated TLC silica gel plates
(0.2 mm, 60 HF254, Merck). Spots were visualized under short and
long wavelength UV light. Melting points were taken on a Gallenk-
amp melting point apparatus and are not corrected. IR spectra were
recorded on Perkin Elmer Spectrum BX-II. 1H NMR and 13C NMR
spectra were recorded on Bruker (300, 400 and 500 MHz) AMX
Spectrometer. Chemical shift values are reference against TMS.
DMSO-d6 was used as solvent for NMR spectroscopy. Mass Spectra
were recorded on Finnigan MAT 312 Spectrometer. Bovine enzyme,
carbonic anhydrase (bCA), was purchased from Calzyme Lab Inc.
USA, Cat No 147 A2000 (700 U/g). The enzyme was 98.9% pure as
given by the suppliers. A 96 well plate reader from Synergy HT Bio-
Tek, USA was used. For the calculation of IC50 values, data was com-
puted using EZ-Fit5 Perrella Scientific Inc. Amherst USA software.
1a
1b
1c
1d
1e
2a
2b
2c
64.00 0.01
71.22 0.03
65.16 0.07
67.34 0.03
69.65 0.02
67.60 0.01
66.83 0.05
68.75 0.01
61.18 0.05
65.29 0.02
91.32 0.01
19.21 0.002
4.31 0.001
16.12 0.002
21.12 0.006
16.63 0.002
17.72 0.001
11.37 0.003
18.27 0.005
29.12 0.008
11.71 0.003
1.13 0.001
2d
2e
Acetazolamide
Results are mean of 3-independent determinations (mean sem, n = 3)
isozymes. CA inhibition data for these compounds is given in
Table 1. CA activities of these compounds were tested against the
standard clinically used inhibitor acetazolamide. The compounds
1a–1e and 2a–2e differ only in the relative position of the sulfon-
amide group on the benzene ring. In general, compounds contain-
ing sulfonamide group at p-position of the benzene ring (1a–1e)
were more active than compounds having sulfonamide group at
the m-position (2a–2e). Compound 1b was the most active having
5.2. General method for the synthesis of compounds (1a–1e and
2a–2e)
IC50 value of 4.31 0.001
least active with IC50 value of 29.12 0.008
tuted compounds were the most active, followed by 6-bromo
substituted and un-substituted compounds (which had almost
comparable activity 16.12 0.002 and 19.21 0.002
lowest CA inhibition was shown by 6,8-dibromo substituted com-
pounds with IC50 values of 21.12 0.006 and 29.12 0.008 mol
l
mol, whereas compound 2d was the
mol. 6-Fluoro substi-
A solution containing 0.001 mol 6-(un)substituted 3-formyl-
chromone in 5–7 mL ethanol was stirred with heating until dis-
solved. Then catalytic amount of p-toluenesulfonic acid (p-TsOH)
was added followed by the addition of 0.001 mol of 3- and 4-ami-
nobenzene sulfonamide in equal volumes of ethanol. Reaction mix-
ture was refluxed for 3.5 h and kept overnight. Solid product was
obtained by filtration and purified by recrystallization from a mix-
ture of hot ethanol and acetone (1:1).
l
lmol). The
l
(Table 1). It has been demonstrated31 that C-6 substitution of chro-
mone ring with electron withdrawing groups enhances the biolog-
ical activity. The difference in activity of these compounds can be
explained, in part, due to the difference in nature of halogen sub-
stituent attached at 6 position of the chromone ring. In general,
fluorine containing compounds have been found to be very active
biologically. For instance, methanesulfonamide (CH3SO2NH2) is a
weak inhibitor of CA (KI = 10ꢀ4 M), whereas its fluoro analog, triflu-
oromethanesulfonamide (CF3SO2NH2) is an excellent inhibitor of
CA (KI = 2 ꢁ 10ꢀ9 M)32, due to the strong electron withdrawing ef-
fect of fluorine. Similar trend in activity has been observed here
(F > Br > H ꢃ Et). However, when 6 and 8 positions of chromone
ring are substituted simultaneously, as in 6,8-dibromo compounds
(1d and 2d), a significant decrease in activity is observed.
5.2.1. 4-{[(2-Ethoxy-4-oxo-2H-chromen-3(4H)-ylidene)methyl]
amino}benzenesulfonamide (1a)
Yield: 85%; Mp 158–160 °C. IR (m
, cmꢀ1): 1646 (C@O), 3400
(NH2), 1152 (SO2sym), 1376 (SO2asym). EI–MS m/z (rel. int.%):
328.0 (23), 171.9 (93), 156.0 (57), 92.0 (90), 65 (100). 1H NMR
(400 MHz, DMSO) d: 11.81 (1H, d, J = 12.4 Hz, NH), 8.17 (1H, d,
J = 12.3 Hz, CH enamine), 7.85–7.80 (3H, m, H-5, ArH), 7.56–7.51
(3H, m, H-7, ArH benzene), 7.28 (2H, br s, SO2NH2), 7.16–7.06
(2H, m, ArH chromome), 5.94 (1H, s, H-2), 3.74 (2H, q, J = 7.1 Hz,
CH2), 1.10 (3H, t, J = 7.1 Hz, CH3). 13C NMR (300 MHz, DMSO)
d: 14.94 (CH3), 63.07 (CH2), 180.56 (C-4), 155.69 (C-9), 142.41
(C-10), 138.78 (C-40), 127.56 (C-10), 104.84 (C-3), 144.08 (C-11),
127.41 (C-30, C-50), 116.39 (C-20, C-60), 99.92 (C-2), 134.78 (C-7),
118.09 (C-8), 125.67 (C-5), 121.96 (C-6).
4. Conclusions
Chromone containing sulfonamide enamines were prepared via
reaction of 3-formylchromone, 6-fluoro-3-formylchromone,
6-bromo-3-formylchromone, 6,8-dibromo-3-formylchromone and
6-ethyl-3-formylchromone with 3- and 4-aminobenzene sulfonan-
mides. Keeping in view CA inhibitory role of sulfonamides, the
compounds were assayed as inhibitors of bCA and all compounds
exhibited excellent CA inhibition activity (IC50 values 4.31 0.001
5.2.2. 4-{[(2-Ethoxy-6-fluoro-4-oxo-2H-chromen-3(4H)-
ylidene)methyl]amino}benzenesulfonamide (1b)
Yield: 80%. Mp 158–160 °C. IR (m
, cmꢀ1): 1654 (C@O), 3319
(NH2), 1154 (SO2sym). EI–MS m/z (rel. int.%): 346.1 (100), 265.1
(15), 190.1 (78), 164.1 (62), 138.1 (23), 106.1 (58), 78.1 (56). 1H
NMR (500 MHz, DMSO), d: 11.78 (1H, d, J = 12.5 Hz, NH), 8.20
(1H, d, J = 12.5 Hz, CH enamine), 7.81 (2H, d, J = 8.5 Hz, H-30, H-
50), 7.55 (2H, d, J = 8.6 Hz, H-20, H-60), 7.52 (1H, dd, J = 3.0 Hz,
J = 8.3 Hz, H-5), 7.43 (1H, ddd, J = 3 Hz, J = 8.6 Hz, H-7), 7.29 (2H,
br s, SO2NH2), 7.15 (1H, dd, J = 3 Hz, J = 8.8 Hz, H-8), 5.95 (1H, s,
H-2), 3.74 (2H, q, J = 7 Hz, CH2), 1.09 (3H, t, J = 7.0 Hz, CH3). 13C
NMR (400 MHz, DMSO) d: 63.15 (CH2), 14.90 (CH3), 179.42 (C-4),
158.23 (C-9), 155.86 (C-6), 151.85 (C-10), 142.34 (C-40), 139.04
(C-10), 104.39 (C-3), 144.77 (C-11), 127.38 (C-30, C-50), 116.62 (C-
20, C-60), 99.94 (C-2), 121.88 (C-7), 120.03 (C-8), 110.90 (C-5).
to 29.12 0.008 lmol). Compounds containing fluorine showed
the most activity, whereas the lowest activity was exhibited by
6,8-dibromo substituted compounds. Compounds derived from
4-aminobenzene sulfonanmides were more active than those
derived from 3-aminobenzene sulfonanmides. Based on the results
we propose that there is a need for these compounds to be tested
against a wide range of CA isozymes, that is, CA-IV, CA-IX and
CA-XII etc. which are important drug targets in drug development
program.

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M. al-Rashida et al. / Bioorg. Med. Chem. 19 (2011) 3367–3371
5.2.3. 4-{[(6-Bromo-2-ethoxy-4-oxo-2H-chromen-3(4H)-
ylidene)methyl]amino}benzenesulfonamide (1c)
5.2.7. 3-{[(6-Fluoro-2-ethoxy-4-oxo-2H-chromen-3(4H)-
ylidene)methyl]amino}benzenesulfonamide (2b)
Yield: 87%. Mp 174–176 °C. IR (
m
, cmꢀ1): 1660 (C@O), 3324
Yield: 88%. Mp 168–170 °C. IR (m
, cmꢀ1): 1645 (C@O), 3300
(NH2), 1159 (SO2sym), 1340 (SO2asym). EI–MS m/z (rel. int.%):
406.0 (32), 327.0 (39), 251.9 (60), 224.0 (100), 172.1 (36), 156.0
(51), 92.0 (48), 64.1 (50). 1H NMR (400 MHz, DMSO) d: 11.78
(1H, d, J = 12.7 Hz, NH), 8.23 (1H, d, J = 12.8 Hz, CH enamine),
7.90 (1H, s, H-5), 7.83 (2H, d, J = 8.6 Hz, H-30, H-50), 7.72 (1H, dd,
J = 2.4 Hz, J = 8.7 Hz, H-7), 7.58 (2H, d, J = 8.7 Hz, H-20, H-60), 7.31
(2H, br s, SO2NH2), 7.11 (1H, d, J = 8.6 Hz, H-8), 5.99 (1H, s, H-2),
3.69 (2H, q, J = 7.1 Hz, CH2), 1.11 (3H, t, J = 7.1 Hz, CH3). 13C NMR
(400 MHz, DMSO) d: 178.88 (C-4), 154.74 (C-9), 142.30 (C-10),
139.12 (C-40), 124.10 (C-10), 113.69 (C-6), 104.26 (C-3), 144.94
(C-11), 137.02 (C-7), 128.13 (C-5), 127.38 (C-30, C-50), 121.54 (C-
8), 116.69 (C-20, C-60), 100.09 (C-2), 63.27 (CH2), 14.90 (CH3).
(NH2), 1157 (SO2sym), 1377 (SO2asym). EI–MS m/z (rel. int.%):
346.1 (8), 164.1 (16), 265.1 (100), 190.1 (42), 76.1 (23). 1H NMR
(500 MHz, DMSO) d: 1.08 (3H, t, J = 7.08 Hz, CH3), 3.75–3.66 (2H,
m, CH2), 5.98 (1H, s, H-2), 7.15 (1H, dd, J = 4.2 Hz, J = 9.0 Hz, H-8),
7.42–7.38 (3H, m, H-7, SO2NH2), 7.50–7.61 (4H, m, H-5, ArH ben-
zene), 7.81 (1H, s, H-20), 8.19 (1H, d, J = 12.5 Hz, H-11), 11.88 (1H,
d, J = 12.5 Hz, NH). 13C NMR (400 MHz, DMSO) d: 15.16 (CH3),
63.14 (CH2), 179.29 (C-4), 158.25 (C-9), 155.87 (C-6), 151.81 (C-
10), 145.59 (C-30), 110.68 (C-10).
5.2.8. 3-{[(6-Bromo-2-ethoxy-4-oxo-2H-chromen-3(4H)-
ylidene)methyl]amino}benzenesulfonamide (2c)
Yield: 88%. Mp 168–170 °C. IR (m
, cmꢀ1): 1643 (C@O), 3231
(NH2), 1150 (SO2sym), 1336 (SO2asym). EI–MS m/z (rel. int.%):
406.0 (16), 325.0 (14), 250.0 (25), 172.1 (74), 92.1 (100), 65.1
(93). 1H NMR (300 MHz, DMSO) d: 1.10 (3H, t, J = 7.1 Hz, CH3),
3.77–3.65 (2H, m, CH2), 6.01 (1H, s, H-2), 7.09 (1H, d, J = 8.7 Hz,
H-8), 7.40 (2H, br s, SO2NH2), 7.54–7.60 (3H, m, ArH benzene),
7.66 (1H, dd, J = 2.4 Hz, J = 8.7 Hz, H-7), 7.81 (1H, s, H-20), 7.88
(1H, s, H-5), 8.21 (1H, d, J = 12.6 Hz, H-11), 11.86 (1H, d,
J = 12.6 Hz, NH). 13C NMR (300 MHz, DMSO) d: 63.25 (CH2), 14.95
(CH3), 178.77 (C-4), 154.74 (C-9), 145.61 (C-10), 128.15 (C-30),
124.18 (C-10), 119.59 (C-3), 103.89 (C-6), 145.33 (C-11), 140.04
(C-7), 136.93 (C-5), 130.42 (C-50), 127.73 (C-60), 120.73 (C-40),
120.17 (C-8), 113.65 (C-20), 100.10 (C-2).
5.2.4. 4-{[(6,8-Dibromo-2-ethoxy-4-oxo-2H-chromen-3(4H)-
ylidene)methyl]amino}benzenesulfonamide (1d)
Yield: 87%. Mp 215–217 °C. IR (m
, cmꢀ1): 1651 (C@O), 3321
(NH2), 1155 (SO2sym), 1336 (SO2asym). EI–MS m/z (rel. int.%):
420.8 (20), 404.8 (53), 329.8 (69), 303.8 (100), 172 (38), 92 (51),
156 (59). 1H NMR (400 MHz, DMSO) d: 1.11 (3H, t, J = 7.2 Hz,
CH3), 3.78 (2H, q, J = 7.2 Hz, CH2), 6.11 (1H, s, H-2), 7.30 (2H, br s,
SO2NH2), 7.58 (2H, d, J = 8.4 Hz, H-20, H-60), 7.82 (2H, d, J = 8.4 Hz,
H-30, H-50), 7.88 (1H, s, H-7), 8.0 (1H, s, H-5), 8.27 (1H, d,
J = 12.8 Hz, CH enamine), 11.76 (1H, d, J = 12.8 Hz, NH). 13C NMR
(300 MHz, DMSO) d: 177.85 (C-4), 151.45 (C-9), 142.14 (C-8),
139.41 (C-10), 124.96 (C-40), 113.86 (C-10), 113.01 (C-6), 103.58
(C-3), 145.70 (C-7), 138.86 (C-11), 138.74 (C-5), 127.53 (C-30, C-
50), 116.95 (C-20, C-60), 100.63 (C-2), 63.57 (CH2), 14.74 (CH3).
5.2.9. 3-{[(6,8-Dibromo-2-ethoxy-4-oxo-2H-chromen-3(4H)-
ylidene)methyl]amino}benzenesulfonamide (2d)
Yield: 85%. Mp 196–198 °C. IR (m
, cmꢀ1): 1641 (C@O), 3301
(NH2), 1158 (SO2sym), 1343 (SO2asym). EI–MS m/z (rel. int.%):
329.8 (17), 172 (100), 92 (31), 65 (27), 485.9 (15), 404.9 (14),
329.8 (17). 1H NMR (400 MHz, DMSO) d: 1.11 (3H, t, J = 7.2 Hz,
CH3), 3.84–3.70 (2H, m, CH2), 6.14 (1H, s, H-2), 7.42 (2H, s,
SO2NH2), 7.57–7.62 (3H, m, ArH benzene), 7.83 (1H, s, H-7), 7.85
(1H, s, H-5), 8.06 (1H, s, H-5), 8.26 (1H, d, J = 12.8 Hz, H-11),
11.86 (1H, d, J = 12.8 Hz, NH). 13C NMR (300 MHz, DMSO) d:
14.77 (CH3), 63.53 (CH2), 177.70 (C-4), 145.58 (C-9), 139.86
(C-10), 127.84 (C-30), 125.02 (C-10), 114.12 (C-6), 112.97 (C-3),
103.19 (C-8), 146.05 (C-7), 138.76 (C-11), 130.41 (C-5), 127.41
(C-50), 121.21 (C-60), 120.42 (C-40), 113.82 (C-20), 100.61 (C-2).
5.2.5. 4-{[(6-Ethyl-2-ethoxy-4-oxo-2H-chromen-3(4H)-
ylidene)methyl]amino}benzenesulfonamide (1e)
Yield: 77%. Mp 225–227 °C. IR (m
, cmꢀ1): 1647 (C@O), 3341
(NH2), 1158 (SO2sym), 1345 (SO2asym). EI–MS m/z (rel. int.%):
355.8 (13), 274.9 (78), 199.9 (100), 158.9 (48), 77.0 (62), 52.0
(24). 1H NMR (400 MHz, DMSO) d: 1.09 (3H, t, J = 7.6 Hz, -CH2CH3),
1.20 (3H, t, J = 7.2 Hz, -OCH2CH3), 2.64 (2H, q, J = 7.6 Hz, -CH2CH3),
3.72 (2H, q, J = 7.2 Hz, -OCH2CH3), 5.91 (1H, s, H-2), 7.28 (2H, s,
SO2NH2), 7.00 (1H, d, J = 8.4 Hz, H-8), 7.40 (1H, dd, J = 2.0 Hz,
J = 8.4 Hz, H-7), 7.53 (2H, d, J = 8.4 Hz, H-20, H-60), 7.64 (1H, s,
H-5), 7.80 (2H, d, J = 8.8 Hz, H-30, H-50), 8.15 (1H, d, J = 12.0 Hz,
H-11), 11.80 (1H, d, J = 12.4 Hz, NH). 13C NMR (400 MHz, DMSO)
d: 14.94 (CH3 ethyl), 15.55 (CH3 ethoxy), 64.57 (–OCH2), 27.23
(CH2), 180.77 (C-4), 146.99 (C-9), 142.21 (C-10), 137.21 (C-40),
127.36 (C-10), 105.00 (C-3), 143.89 (C-11), 127.42 (C-30, C-50),
116.31 (C-20, C-60), 99.83 (C-2), 134.47 (C-7), 117.98 (C-8), 125.17
(C-5), 132.26 (C-6).
5.2.10. 3-{[(6-Ethyl-2-ethoxy-4-oxo-2H-chromen-3(4H)-
ylidene)methyl]amino}benzenesulfonamide (2e)
Yield: 73%. Mp 215–217 °C. IR (m
, cmꢀ1): 1643 (C@O), 3325
(NH2), 1156 (SO2sym), 1343 (SO2asym). EI–MS m/z (rel. int.%):
356.0 (3), 308.8 (2), 275.0 (100), 200 (40), 132.9 (20), 91.0 (10),
75.9 (31). 1H NMR (400 MHz, DMSO) d: 1.09 (3H, t, J = 7.2 Hz,
-CH2CH3), 1.20 (3H, t, J = 7.6 Hz, -OCH2CH3), 2.62 (2H, q,
J = 7.6 Hz, -CH2CH3), 3.78–3.63 (2H, m, -OCH2CH3), 5.94 (1H, s,
H-2), 7.58 = 7.51 (4H, m, H-7, ArH benzene), 7.43–7.37 (2H, m,
SO2NH2), 7.00 (1H, d, J = 8.4 Hz, H-8), 7.64 (1H, S, H-5), 7.77 (1H,
s, H-20), 8.14 (1H, d, J = 12.0 Hz, H-11), 11.89 (1H, d, J = 12.4 Hz,
NH). 13C NMR (400 MHz, DMSO) d: 15.16 (CH3 ethoxy), 15.00
(CH3 ethyl), 62.94 (–OCH2), 27.27 (CH2), 180.44 (C-4), 155.65
(C-9), 145.58 (C-10), 140.20 (C-30), 121.89 (C-6), 121.88 (C-10),
104.41 (C-3), 144.25 (C-11), 134.35 (C-7), 130.40 (C-5), 124.13
(C-50), 120.50 (C-60), 119.79 (C-40), 117.92 (C-8), 113.21 (C-20),
99.78 (C-2).
5.2.6. 3-{[(2-Ethoxy-4-oxo-2H-chromen-3(4H)-ylidene)methyl]
amino}benzenesulfonamide (2a)
Yield: 87%. Mp 150–152 °C. IR (m
, cmꢀ1): 1642 (C@O), 3429
(NH2), 1157 (SO2sym), 1377 (SO2asym). EI–MS m/z (rel. int.%):
328.0 (16), 247.1 (14), 172.0 (95), 146.0 (20), 92.0 (91), 65.0
(100). 1H NMR (400 MHz, DMSO) d: 1.08 (3H, t, J = 7.2 Hz, CH3),
3.76 (2H, q, J = 7.1 Hz, CH2), 5.98 (1H, s, H-2), 7.08 (1H, d,
J = 8.0 Hz, H-8), 7.15 (1H, t, J = 7.6 Hz, H-7), 7.39 (2H, br s, SO2NH2),
7.51–7.59 (4H, m, ArH benzene, H-6), 7.79 (1H, s, H-20), 7.84 (1H,
dd, J = 1.2 Hz, J = 7.8 Hz, H-5), 8.15 (1H, d, J = 12.4 Hz, H-11),
11.90 (1H, d, J = 12.0 Hz, NH). 13C NMR (300 MHz, DMSO) d:
15.16 (CH3), 63.16 (CH2), 180.44 (C-4), 155.65 (C-9), 145.58
(C-10), 140.20 (C-30), 121.88 (C-10), 104.41 (C-3), 144.44 (C-11),
134.64 (C-7), 130.44 (C-5), 125.64 (C-50), 121.89 (C-6), 120.58
(C-60), 119.99 (C-40), 118.04 (C-8), 113.30 (C-20), 99.89 (C-2).
Acknowledgments
Authors acknowledge HEJ Research Institute of Chemistry, Uni-
versity of Karachi, Karachi, Pakistan for spectroscopic analyses.

M. al-Rashida et al. / Bioorg. Med. Chem. 19 (2011) 3367–3371
3371
12. Stokstad, E. L. R.; Jukes, T. H. J. Nutr. 1987, 117, 1335.
13. Hong, Y. L.; Hossler, P. A.; Calhoun, D. H.; Meshnic, S. R. Antimicrob. Agents
Chemother. 1995, 39, 1756.
14. Nalam, M. N. L.; Peeters, A.; Jonckers, T. H. M.; Dierynck, I.; Schiffer, C. A. J. Virol.
2007, 81, 9512.
Mariya-al-Rashida gratefully acknowledges Higher Education
Commission, Pakistan, for the award of Indigenous Scholarship
for PhD.
15. Santos, M. A.; Marques, S.; Vullo, D.; Innocenti, A.; Scozzafava, A.; Supuran, C. T.
Bioorg. Med. Chem. Lett. 2007, 17, 1538.
A. Supplementary data
16. Nishimori, I.; Minakuchi, T.; Kohsaki, T.; Onishi, S.; Takeuchi, H.; Vullo, D.;
Scozzafava, A.; Supuran, C. T. Bioorg. Med. Chem. Lett. 2007, 17, 3585.
17. Ilies, M. A.; Scozzafava, A.; Supuran, C. T. Met. Based Drugs 2000, 7, 57.
18. Zareef, M.; Iqbal, R.; De Dominguez, N. G.; Rodrigues, J.; Zaidi, J. H.; Arfan, M.;
Supuran, C. T. J. Enzyme Inhib. Med. Chem. 2007, 22, 301.
19. Supuran, C. T.; Scozzafava, A. Bioorg. Med. Chem. 2007, 15, 4336.
20. Supuran, C. T. Therapy 2007, 4, 355.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmc.2011.04.040.
References and notes
21. Supuran, C. T. Bioorg. Med. Chem. Lett. 2010, 12, 3467.
22. Supuran, C. T. Nat. Rev. Drug Disc. 2008, 7, 168.
23. Ozensoy, O.; Puccetti, L.; Fasolis, G.; Arslan, O.; Scozzafava, A.; Supuran, C. T.
Med. Chem. Lett. 2005, 15, 4862.
24. Puccetti, L.; Fasolis, G.; Vullo, D.; Chohan, Z. H.; Scozzafava, A.; Supuran, C. T.
Bioorg. Med. Chem. Lett. 2005, 15, 3096.
25. al-Rashida, M.; Tahir, M. N.; Nagra, S. A.; Imran, M.; Iqbal, J. Acta Crystallogr.
2009, E65, 01818.
1. el-Shaaer, H. M.; Foltinova, P.; Lacova, M.; Chovancova, J.; Stankovicova, H.
Farmaco 1998, 53, 224.
2. Chohan, Z. H.; Rauf, A.; Naseer, M. M.; Somra, M. A.; Supuran, C. T. J. Enzyme
Inhib. Med. Chem. 2006, 21, 173.
3. Nam, D. H.; Lee, K. Y.; Moon, C. S.; Lee, Y. S. Eur. J. Med. Chem. 2010, 45, 4288.
4. Huang, W.; Ding, Y.; Miao, Y.; Liu, M. Z.; Li, Y.; Yang, G. F. Eur. J. Med. Chem.
2009, 44, 3687.
5. Desideri, N.; Mastromarino, P.; Conti, C. Antiviral Chem. Chemother. 2003, 14,
195.
6. Houghton, P. J.; Woldemariam, T. Z.; Khan, A. I.; Burke, A.; Mahmood, N.
Antiviral Res. 1994, 25, 235.
7. Kaspentakis, G. C.; Tsoleridis, C. A.; Stephanatou, J. S. J. Heterocycl. Chem. 2007,
44, 425.
8. Sosnovskikh, V.; Moshkin, V. Russ. Chem. Bull. 2010, 59, 1056.
9. Nohara, A.; Umetani, T.; Sanno, Y. Tetrahedron 1974, 30, 3553.
10. Nohara, A.; Umetani, T.; Sanno, Y. Tetrahedron Lett. 1973, 22, 1995.
11. Ishiki, H. M.; Donate, P. M.; Galembeck, S. E. J. Mol. Struc-Theochem 1998, 423,
235.
26. Pocker, Y.; Stone, J. T. Biochemistry 1967, 6, 668.
27. Stankovicova, H.; Fabian, W. M. F.; Lacova, M. Molecules 1996, 1, 223.
28. Stankovicova, H.; Gasparova, R.; Lacova, M.; Chovancova, J. Collect. Czech. Chem.
Commun. 1997, 62, 781.
29. Stankovicova, H.; Lacova, M.; Gaplovsky, A.; Chovancova, J.; Pronayova, N., II-
International Electronic Conference on Synthetic Organic Chemistry (ECSOC-2),
1998 http://www.mdpi.org/ecsoc.
30. Dziewulska-Kułaczkowska, A.; Mazur, L. J. Mol. Struct. 2011, 985, 233.
31. Gajbhiye, A.; Mallareddy, V.; Achaiah, G. Indian J. Pharm. Sci. 2008, 70, 118.
32. Maren, T. H.; Conroy, C. W. J. Biol. Chem. 1993, 268, 26233.