Design, synthesis, and biological evaluation of N-acetyl-2- carboxybenzenesulfonamides: A novel class of cyclooxygenase-2 (COX-2) inhibitors

Article abstract of DOI:10.1016/j.bmc.2005.01.039

N-Acetyl-2-carboxybenzenesulfonamide (11), and a group of analogues possessing an appropriately substituted-phenyl substituent (4-F, 2,4-F ₂, 4-SO₂Me, 4-OCHMe₂) attached to its C-4, or C-5 position, were synthesized for ev

Full text of DOI:10.1016/j.bmc.2005.01.039

Bioorganic & Medicinal Chemistry 13 (2005) 2459–2468
Design, synthesis, and biological evaluation of
N-acetyl-2-carboxybenzenesulfonamides: a novel class of
cyclooxygenase-2 (COX-2) inhibitors
Qiao-Hong Chen, P. N. Praveen Rao and Edward E. Knaus*
Faculty of Pharmacy and Pharmaceutical Sciences, University of Alberta, Edmonton, Alberta, Canada T6G 2N8
Received 14 December 2004; revised 21 January 2005; accepted 21 January 2005
Abstract—N-Acetyl-2-carboxybenzenesulfonamide (11), and a group of analogues possessing an appropriately substituted-phenyl
substituent (4-F, 2,4-F2, 4-SO2Me, 4-OCHMe2) attached to its C-4, or C-5 position, were synthesized for evaluation as selective
cyclooxygenase-2(COX-)2 inhibitors. In vitro COX-1/COX-2inhibition studies showed that
11 is a more potent inhibitor
(COX-1 IC50 = 0.06 lM; COX-2IC 50 = 0.25 lM) than aspirin (COX-1 IC50 = 0.35 lM; COX-2IC 50 = 2 .4lM), and like aspirin
[COX-2selectivity index (S.I.) = 0.14], 11 is a nonselective COX-2 inhibitor (COX-2 S.I. = 0.23). Regioisomers having a 2,4-difluo-
rophenyl substituent attached to the C-4 (COX-2IC 50 = 0.087 lM; COX-2S.I. >1149), or C-5 (COX-2IC 50 = 0.77 lM, SI > 130),
position of 11 exhibited the most potent and selective COX-2inhibitory activity relative to the reference drug celecoxib (COX-1
IC50 = 33.1 lM; COX-2IC 50 = 0.07 lM; COX-2S.I. = 472). N-Acetyl-2-carboxybenzenesulfonamide (11, ED50 = 49 mg/kg), and
its C-4 2,4-difluorophenyl derivative (ED50 = 91 mg/kg), exhibited superior antiinflammatory activity (oral dosing) in a carra-
geenan-induced rat paw edema assay compared to aspirin (ED50 = 129 mg/kg). These latter compounds exhibited comparable anal-
gesic activity to the reference drug diflunisal, and superior analgesic activity compared to aspirin, in a 4% NaCl-induced abdominal
constriction assay. A molecular modeling (docking) study indicated that the SO2NHCOCH3 substituent present in N-acetyl-2-carb-
oxy-4-(2,4-fluorophenyl)benzenesulfonamide, like the acetoxy substituent in aspirin, is suitably positioned to acetylate the Ser530
hydroxyl group in the COX-2primary binding site. The results of this study indicate that the SO 2NHCOCH3 pharmacophore pres-
ent in N-acetyl-2-carboxybenzenesulfonamides is a suitable bioisostere for the acetoxy (OCOMe) group in aspirin.
ꢀ 2005 Elsevier Ltd. All rights reserved.
1. Introduction
F
The complex biological actions exhibited by the simple
salicylate class of compounds have attracted on-going
attention for more than 100 years. In this context, the
CO2H
CO2H
O
C
O
Me
F
moderately active antiinflammatory and nonnarcotic
analgesic agent acetylsalicylic acid (aspirin, 1) continues
to be a frequent first choice drug in the treatment of
some arthritic disorders (see structure in Fig. 1). How-
ever, these beneficial actions of aspirin may also be
accompanied by adverse effects that include tinnitus,
hypersensitization, and contraindicated gastrointestinal
irritation, bleeding and/or ulceration.1 The ability of
aspirin to inhibit blood platelet aggregation is now
viewed as a clinically useful prophylactic action that
OH
Diflunisal (2)
Aspirin (1)
SC
C(CH2)3Me
Me
MeSO2
SO2Me
4
3
O
C
O
2
O
C
O
Me
O
O
(4)
APHS (3)
R
R
N
Me
O
O
O
(7, R = SO2N--COEt Na+)
(8, R = SO2NH2)
Keywords: N-Acetyl-2-carboxybenzenesulfonamides; Cyclooxygenase-
1 and -2inhibition; Antiinflammatory and analgesic activities.
(5, R = SO2NHCOMe)
(6, R = SO2NH2)
*
Corresponding author. Tel.: +1 780 4925993; fax: +1 780 492
1217; e-mail: eknaus@pharmacy.ualberta.ca
Figure 1. Some representative cyclooxygenase (COX) inhibitors.
0968-0896/$ - see front matter ꢀ 2005 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2005.01.039

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Q.-H. Chen et al. / Bioorg. Med. Chem. 13 (2005) 2459–2468
can reduce the incidence of thrombus formation in indi-
viduals with cardiovascular disease. The search for a
clinical replacement for aspirin resulted in the develop-
ment of the nonacetylating salicyclic acid derivative
diflunisal (2) that is a more potent antiinflammatory
and analgesic agent with a longer duration of action that
is less ulcerogenic than aspirin.2 The subsequent discov-
ery3,4 that there are two cyclooxygenase isozymes COX-
1 and COX-2provided the basis for the drug design con-
appropriately substituted-phenyl substituent attached
to its C-4, or C-5, position that were designed to be po-
tential bioisosteres of aspirin.
2. Chemistry
N-Acetyl-2-carboxybenzenesulfonamide (11) was syn-
thesized using a two-step reaction sequence that in-
volved N-acetylation of 2-methylbenzenesulfonamide
(9) followed by oxidation of the aryl C-2methyl substi-
tuent using KMnO4 in 0.5 N aqueous NaOH as illus-
trated in Scheme 1. The target N-acetyl-2-
carboxybenzenesulfonamides (19a–d, 20a–e) having a
variety (R1 = H, F, SO2Me, OCHMe2; R2 = H, F) of
substituted-phenyl substituents at the C-4 or C-5 posi-
tions were prepared using a palladium-catalyzed Suzuki
cross-coupling reaction according to the reaction se-
quence shown in Scheme 2. Chlorosulfonation of 3-
bromotoluene (12a), and 4-bromotoluene (12b), at
0 ꢁC followed by amminolysis using aqueous ammo-
nium hydroxide in dioxane afforded the respective sul-
fonamide (14a,b) in good yield. The subsequent
acetylation of 14a,b yielded the corresponding
5
cept that selective COX-2inhibitors such as celecoxib
elicit effective antiinflammatory activity devoid of the
ulcerogenic effect associated with the use of nonsteroidal
antiinflammatory drugs (NSAIDs) such as aspirin that
inhibit both COX-1 and COX-2. Aspirin is a unique
nonselective COX inhibitor due to its ability to acetylate
the Ser530 hydroxyl group in the primary COX binding
site of COX-1 and COX-2. In this regard, aspirin is a
10- to 100-fold more potent inhibitor of COX-1 relative
to COX-2.6 Acetylation of the weakly nucleophilic OH
of Ser530 by aspirin is thought to result from initial bind-
ing of its COOH to the Arg120 residue near the mouth
of the COX binding site, which positions the ortho-acet-
oxy moiety in close proximity to the Ser530 OH, which
it acetylates. Some of aspirinꢀs beneficial therapeutic
effects arise from acetylation of COX-2, whereas its
antithrombotic and ulcerogenic effects result from
acetylation of COX-1. These observations were
exploited in the design of the aspirin analogue o-(acet-
oxyphenyl)hept-2-ynyl sulfide (APHS, 3) that is a selec-
tive COX-2inhibitor. 7 In an earlier study, we reported a
novel class of isomeric acetoxy analogues of rofecoxib
(4), which are potent and selective COX-2inhibitors
that, like aspirin, have the potential to acetylate the
CH3
CH3
CH3
3
4
4
5
4
5
a
b
Br
Br
Br
Br
SO2Cl
SO2NH2
12a, 3-Br
12b, 4-Br
14a, 4-Br
13a, 4-Br
13b, 5-Br
14b, 5-Br
2
c
R
R2
4
1
R
B(OH)
2
CH3
CH3
8
4
16
d
COX-2isozyme.
R1
5
5
SO2NHCOMe
SO2NHCOMe
It is known that the SO2NHCOCH3 moiety is a 105–106
more reactive acetylating agent of enzyme serine
hydroxyls than simple amides.9 In a recent study, it
was shown that the incorporation of a para-N-acetyl-
sulfonamido substituent on the C-3 phenyl ring of the
rofecoxib regioisomer (5) provided a highly potent and
15a, 4-Br
15b, 5-Br
17, 4-substituted-phenyl
18, 5-substituted-phenyl
e
17-20a, R1 = R2 = H
17-20b, R1 = F, R2 = H
R2
17-20c, R1 = R2 = F
CO2H
4
R1
17-18d, R1 = SMe, R2 = H
17-18e, R1 = SO2Me, R2 = H
19-20d, R1 = SO2Me, R2 = H
18f, 20e, R1 = OCHMe2, R2 = H
f
5
SO2NHCOMe
selective COX-2inhibitor that has the potential to acet-
10
19, 4-substituted-phenyl
20, 5-substituted-phenyl
ylate the COX-2isozyme.
COX-2Ser
After acetylation of the
OH by compound 5, compound (6) hav-
530
20d, R1 = SO2Me, R2 = H
g, h
ing a free SO2NH2 compound would be released that
could also exhibit COX-2inhibitory activity. This ratio-
nale is based on observation that the water soluble non-
narcotic analgesic agent parecoxib sodium (7)11 is a
prodrug to the selective COX-2inhibitor valdecoxib
(8).12 Accordingly, the SO2NHCOCH3 pharmacophore
could serve the dual role of acetylation agent and pro-
drug. As part of our on-going research program to de-
sign selective COX-2inhibitors, we describe herein the
synthesis and biological evaluation of a novel group of
N-acetyl-2-carboxybenzenesulfonamides possessing an
CO2Me
SO2NHCOMe
MeSO2
21
Scheme 2. Reagents and conditions: (a) ClSO3H, CHCl3, 0 ꢁC, 4 h; (b)
30% w/v NH4OH, dioxane, 0 ꢁC, 6 h; (c) Ac2O, DMAP, pyridine,
25 ꢁC, overnight; (d) Pd(PPh3)4, Na2CO3, THF, reflux, 5 h; (e)
KMnO4, 0.5 N NaOH, 60 ꢁC, 4 h; (f) Oxoneꢂ, THF, MeOH, H2O,
25 ꢁC, 2h; (g) MeOH, H 2SO4, 80 ꢁC, overnight; (h) Ac2O, pyridine,
DMAP, 25 ꢁC, overnight.
COOH
CH3
CH3
b
a
SO2NHCOMe
11
SO2NHCOMe
10
SO2NH2
9
Scheme 1. Reagents and conditions: (a) Ac2O, DMAP, pyridine, 25 ꢁC, overnight; (b) KMnO4, 0.5 N aqueous NaOH solution, 60 ꢁC, 6 h.

Q.-H. Chen et al. / Bioorg. Med. Chem. 13 (2005) 2459–2468
2461
N-acetyl-4-(or 5-)bromo-2-methylbenzenesulfonamide
(15a,b). The Suzuki cross-coupling reaction13,14 between
an aryl bromide (15a,b) and a substituted-phenylboronic
acid (16) in the presence of 2M aqueous sodium carbon-
ate in tetrahydrofuran, using tetrakis(triphenylphos-
(11) is a more potent inhibitor of COX-1 and COX-2
[COX-1 IC50 = 0.06 lM; COX-2IC 50 = 0.25 lM;
COX-2selectivity index (S.I.) = 03.2] than aspirin
(COX-1 IC50 = 0.35 lM; COX-2IC 50 = 2 .4lM; COX-
2S.I. = 0.14). Introduction of a C-4 phenyl substituent
(19a) increased COX-2inhibitory potency and selecti-
vity (COX-1 IC50 = 0.33 lM; COX-2IC 50 = 0.03 lM,
S.I. = 10). In contrast, incorporation of a C-5 phenyl
substituent (20a) did not appreciably change COX-1
inhibitory activity but COX-2inhibitory activity and
selectivity was decreased (COX-1 IC50 = 0.03 lM;
COX-2IC 50 = 1.2 lM; COX-2S.I. = 0.0)2. The point
of attachment of a 4-fluorophenyl substituent is a deter-
minant of selectivity since the C-4 compound (19b)
selectively inhibits COX-1, whereas the C-5 regioisomer
(20b) is a selective COX-2inhibitor. Similarly, the C-4 4-
methanesulfonylphenyl regioisomer (19d) was a selective
COX-1 inhibitor, while the C-5 regioisomer (20d) was a
selective COX-2inhibitor. On the other hand, placement
of a 2,4-difluorophenyl substituent at either the C-4 po-
phine)palladium(0) as
a
catalyst, afforded the
respective biaryl derivative (17, 18). Subsequent oxida-
tion of the C-2methyl aryl substituent present in 17
and 18 using KMnO4 in 0.5 N aqueous NaOH at
60 ꢁC for 6 h yielded the desired C-4 (19), or C-5 (20)
substituted-phenyl derivative of N-acetyl-2-carboxyben-
zenesulfonamide. Methylation of the 2-carboxy
compound 20d followed by reacetylation furnished 2-
methoxycarbonyl-5-(4-methylsulfonylphenyl)benzene-
sulfonamide (21).It was necessary to reacetylate the sul-
fonamide substituent since it undergoes N-deacetylation
during the acid catalyzed esterification reaction em-
ployed to convert the C-2carboxyl substituent to the
C-2methyl ester.
sition
(19c,
COX-2IC
50 = 0.087 lM;
COX-2
3. Results and discussion
S.I. = >1149), or C-5 position (20c, COX-2
IC50 = 0.77 lM; COX-2S.I. = >130) provided com-
pounds with superior COX-2selectivity with the C-4
difluorophenyl regioisomer (19c) being a ninefold more
potent and selective COX-2inhibitor than the C-5 regio-
isomer (20c). Accordingly, N-acetyl-2-carboxy-4-(2,4-
difluorophenyl)benzenesulfonamide (19c) (i) is a signifi-
cantly more potent and selective COX-2inhibitor than
the reference drug aspirin (COX-1 IC50 > 0.35 lM;
COX-2IC 50 = 2 .4lM; COX-2S.I. = 0.14), and (ii) a
slightly less potent but more selective COX-2inhibitor
than celecoxib (COX-1 IC50 = 33.1 lM; COX-2
IC50 = 0.07 lM, S.I. = 472). Other structure–activity
A group of N-acetyl-2-carboxybenzenesulfonamides
possessing an appropriately substituted-phenyl substitu-
ent attached to its C-4, or C-5, position were designed to
determine (i) whether the N-acetylsulfonamido moiety
(11) is a suitable bioisostere of the acetoxy substituent
in aspirin (1), and (ii) if a substituted-phenyl moiety at-
tached to the C-4 or C-5 position of the parent 2-car-
boxybenzenesulfonamido ring will provide the additional
steric size required to confer COX-2selectivity. In vitro
COX-1/COX-2inhibition studies (see data in Table 1)
showed that N-acetyl-2-carboxybenzenesulfonamide
Table 1. In vitro COX-1 and COX-2inhibition data for N-acetyl-2-carboxybenzenesulfonamides (11, 19, 20) and the 2-methoxycarbonyl derivative
(21)
R2
R2
COOR3
R1
COOH
COOH
R1
R1
SO2NHCOCH3
SO2NHCOCH3
19a-c, e
1 (Aspirin)
11
20a-e, 21
b
Compound
R1
R2
R3
IC50 (lM)a
COX-2S.I.
COX-1
COX-2
11
19a
SO2NHCOCH3
H
—
H
H
F
—
—
—
—
—
H
0.06
0.33
0.68
>100
0.17
0.03
>100
>100
2.17
>100
>100
0.35
33.1
>100
0.25
0.03
>100
0.087
>100
1.20.02
3.8
0.23
10.3
19b
19c
F
<0.007
>1149
<0.002
F
19d
20a
SO2CH3
H
H
H
H
F
20b
20c
F
H
>25
>130
7.4
F
H
0.77
0.3
20d
20e
SO2CH3
(CH3)2CHO
SO2CH3
OCOCH3
H
H
H
—
H
H
>100
>100
2.4
N/A
N/A
0.14
472
21
CH3
—
1 (Aspirin)
Celecoxib
Rofecoxib
0.07
0.50
>200
a Values are means of two determinations acquired using an ovine COX-1/COX-2assay kit (catalog no. 560101, Cayman Chemicals Inc., Ann Arbor,
MI, USA), and the deviation from the mean is <10% of the mean value.
b In vitro COX-2selectivity index (COX-1 IC 50/COX-2IC 50).

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Q.-H. Chen et al. / Bioorg. Med. Chem. 13 (2005) 2459–2468
relationships acquired show that (i) introduction of a C-
5 4-isopropoxyphenyl substituent (20e) abolishes both
acid residues Val523, Asp515, Arg513, Gln192, Thr94, and
His90 (Fig. 2). In this context, the distance between 4-flu-
oro atom of the 2,4-difluorophenyl ring and the NH2
COX-1 and COX-2inhibitory activity (IC
values
50
>100 lM), and (ii) a C-2carboxyl substituent is essential
since its elaboration (20d) to a C-2methoxycarbonyl
substituent (21) destroys both COX-1 and COX-2inhibi-
tory activity.
(guanidino group) of Arg513 is about 5.64 A, and it is
˚
positioned about 5.90 A from the NH2 of Gln192. The
˚
2-fluoro atom of the 2,4-difluoro-phenyl ring is posi-
tioned near Thr94, Gly354, and Tyr355 (distance < 5 A)
˚
close to the entrance of the COX-2secondary pocket.
A molecular modeling experiment was carried out to
determine the binding interactions of N-acetyl-2-carb-
oxy-4-(2,4-difluorophenyl)benzenesulfonamide (19c) in
the COX-2binding site ( Fig. 2). The parent aromatic ring
possessing the C-2carboxyl and N-acetylsulfonamido
substituents was oriented such that the carboxylic acid
moiety is positioned near the mouth of COX-2binding
site where it forms a salt bridge (electrostatic interaction)
Pharmacological studies were carried out to assess the in
vivo antiinflammatory and analgesic activities of N-acet-
yl-2-carboxybenzenesulfonamide (11), and some of the
most potent and selective COX-2inhibitors ( 19c, 20b,
and 20c), based on in vitro enzyme inhibition data (see
data in Table 2). In the carrageenan-induced rat paw
edema assay model, the parent compound 11 was the
most potent antiinflammatory agent (ED50 = 49 mg/kg)
within this group of compounds at 3 h postdrug admin-
istration (oral dose). This high in vivo antiinflammatory
activity shown by 11, relative to 19c, 20b, and 20c, is
attributed to the fact that 11 inhibits both COX-1 and
COX-2whereas the latter compounds inhibit only
COX-2. Credence for this explanation is based on obser-
vation that the more potent and selective in vitro COX-2
inhibitor N-acetyl-2-carboxy-4-(2,4-difluorophenyl)benz-
enesulfonamide (19c) is a less potent antiinflammatory
agent in vivo (ED50 = 91 mg/kg, oral dose) than 11
(ED50 = 49 mg/kg, oral dose). These structure–
activity data indicate that the SO2NHCOMe moiety
present in 11 is a suitable bioisostere, with respect to
antiinflammatory activity, of the acetoxy (OCOMe)
with the guanidino group of Arg120 (distance < 3 A). The
˚
N-acetylsulfonamido-substituent is located in a region
comprised of nonpolar amino acids such as Ala527
,
Val349, Leu359, Leu531, and Leu117. Interestingly, the
C@O of the SO2NHCOMe substituent forms a favorable
hydrogen bonding interaction with the OH of Tyr355
˚
close to the mouth of COX-2channel (distance = 1.7 A ).
The distance between the OH of Ser530, which is the acet-
ylation site for aspirin, and C@O of the SO2NHCOMe
moiety is about 7.03 A. These observations suggest that
˚
the SO2NHCOMe moiety present in 19c is suitably orient-
ated to potentially acetylate (covalent bond formation)
Ser530 present in the COX-2isozyme.
The 2,4-difluorophenyl ring present in 19c is oriented to-
wardthe COX-2secondary pocket in the vicinityof amino
Figure 2. Docking of N-acetyl-2-carboxy-4-(2,4-difluorophenyl)benzenesulfonamide (19c) (ball-and-stick) in the active site of murine COX-2.
Hydrogens atoms of the amino acid residues have been removed to improve clarity.

Q.-H. Chen et al. / Bioorg. Med. Chem. 13 (2005) 2459–2468
2463
Table 2. In vivo antiinflammatory and analgesic activities for N-acetyl-2-carboxybenzenesulfonamides
F
R2
COOH
SO2NHCOCH3
COOH
F
COOH
R1
SO2NHCOCH3
SO2NHCOCH3
19c
11
20b, R1 = F, R2 = H
20c, R1 = R2 = F
Compound
Antiinflammatory activitya
% Inhibition (50 mg/kg) ED50 (mg/kg)
Analgesic activityb
% Inhibition at 30 min
% Inhibition at 60 min
11
19c
51.1 5.249
41.7 5.291
Inactive
48.0 9.7
33.7 10.1
78.0 1.4
60.0 10.3
20b
20c
—
—
38.0 19.7
58.3 11.8
53.3 22.2
33.3 18.0
58.3 10.2
46.4 14.1
Inactive
60.8 0.9c
25.2 3.3
Diflunisal (2)
Aspirin (1)
17
129
52.8 20.7
29.7 10.7
a Inhibitory activity in a carrageenan-induced rat paw edema assay. The results are expressed as mean SEM (n = 4) at 3 h following a 50 mg/kg oral
dose of the test compound, or as the ED50 value when it was determined.
b Inhibitory activity in the rat 4% NaCl-induced abdominal constriction assay. The results are expressed as mean SEM (n = 4) following a 5 mg/kg
oral dose of the test compound.
c 30 mg/kg oral dose.
substituent present in aspirin (ED50 = 129 mg/kg, oral
dose).
let), q (quartet), m (multiplet), and br (broad). Micro-
analyses were performed for C, H, N (MicroAnalytical
Service Laboratory, Department of Chemistry, Univer-
sity of Alberta) and were within 0.4% of theoretical
values. Silica gel column chromatography was per-
formed using Merck silica gel 60 ASTM (70–230 mesh).
All reagents, purchased from the Aldrich Chemical
Company (Milwaukee, WI), were used without further
purification. Male Sprague–Dawley rats, used in the
antiinflammatory-analgesic screens, were purchased
from Animal Health Services at the University of Alber-
ta, and experiments were carried out using protocols ap-
proved by the Animal Welfare Committee, University of
Alberta.
In a rat model 4% NaCl-induced abdominal constriction
assay, a 5 mg/kg po dose of compounds 11, 19c, 20b,
and 20c exhibited good analgesic activities (33–78%
inhibition range) at 30 or 60 min postdrug administra-
tion relative to the reference drugs diflunisal (52–58%
inhibition) and aspirin (30–46% inhibition).
4. Conclusions
In vitro COX-1/COX-2isozyme inhibition, and in vivo
antiinflammatory and analgesic, data acquired for this
novel class of N-acetyl-2-carboxybenzenesulfonamides
showed that (i) the SO2NHCOCH3 moiety is a suitable
bioisostere of the OAc substituent present in aspirin, (ii)
incorporation of a 2,4-difluorophenyl substituent at the
C-4 position of N-acetyl-2-carboxybenzenesulfonamide
provided the most potent (IC50 = 0.087 lM) and selec-
tive (S.I. >1149) inhibition of COX-2, and that this com-
pound could serve as a useful probe to study the
function and catalytic activity of the COX-2isozyme,
and (iii) a compound, which inhibits both COX-1 and
COX-2such as N-acetyl-2-carboxybenzenesulfonamide
exhibits superior in vivo antiinflammatory activity rela-
tive to compounds that are more potent and selective
inhibitors of COX-2.
5.1. N-Acetyl-2-methylbenzenesulfonamide (10)
Acetic anhydride (1.7 mL, 18 mmol) and 4-dimethylami-
nopyridine (219 mg, 1.8 mmol) were added to a solution
of 2-methylbenzenesulfonamide (9, 1.03 g, 6 mmol) in
pyridine (3 mL) and the reaction was allowed to proceed
at 25 ꢁC with stirring for 6 h. EtOAc (300 mL) was
added and this solution was washed successively with
saturated aqueous NH4Cl (2 · 50 mL) and H2O
(2 · 50 mL). The organic fraction was dried (Na2SO4)
and the solvent was removed in vacuo to afford 10
(962mg, 60%) as colorless needles; mp 130–132 ꢁC; IR
(film) 1704 (C@O), 1465 (Ar), 1341 (SO2) cmÀ1 1H
;
NMR (CDCl3): d 2.09 (s, 3H, NHCOCH3), 2.68 (s,
3H, C-2, CH3), 7.35 (d, J = 7.7 Hz, 1H, H-3), 7.40 (t,
J = 7.7 Hz, 1H, H-5), 7.55 (t, J = 7.7 Hz, 1H, H-4),
8.15 (d, J = 7.7 Hz, 1H, H-6), 8.66 (br s, 1H, NH).
5. Experimental
Melting points were determined on a Thomas–Hoover
capillary apparatus and are uncorrected. Infrared (IR)
spectra were recorded on a Nicolet 550 Series II Magna
5.2. N-Acetyl-2-carboxybenzenesulfonamide (11)
KMnO4 (1.9 g, 12mmol) was added to a solution
of N-acetyl-2-methylbenzenesulfonamide (10, 426 mg,
2mmol) in aqueous NaOH (24 mL of 0.5 N), and the
reaction was allowed to proceed at 60 ꢁC with stirring
for 6 h prior to quenching with acetone. The insoluble
material was removed by filtration, and the filtrate was
1
FT-IR spectrometer. H NMR spectra were measured
on a Bruker AM-300 spectrometer in CDCl3 or
CDCl3 + DMSO-d6 with TMS as the internal standard,
where J (coupling constant) values are estimated in Hz.
Spin multiples are given as s (singlet), d (double), t (trip-

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Q.-H. Chen et al. / Bioorg. Med. Chem. 13 (2005) 2459–2468
diluted with H2O (150 mL) prior to acidification to pH 3
using 5% HCl. Extraction with CH2Cl2 (2 · 100 mL),
washing the combined CH2Cl2 extracts with water
(3 · 50 mL), drying the organic fraction (Na2SO4), and
removal of the solvent in vacuo afforded 11 (306 mg,
63%) as a pale yellow solid; mp 178–180 ꢁC; IR (CHCl3)
3669–2497 (COOH), 3273 (NH), 3157 (Ar–H), 1721
1H NMR (CDCl3): d 2.67 (s, 3H, CH3), 4.81 (br s, 2H,
NH2), 7.47 (d, J = 8.2Hz, 1H, H-5), 7.51 (s, 1H, H-3),
7.88 (d, J = 8.2Hz, 1H, H-6).
5.8. 5-Bromo-2-methylbenzenesulfonamide (14b)
Yield, 80%; white needles; mp 164–165 ꢁC (lit.15 164–
1
(C@O), 1620, 1470 (Ar), 1380 (SO2) cmÀ1; H NMR
165 ꢁC); IR (film) 3397, 3281 (NH2), 1291 (SO2) cmÀ1
;
1H NMR (CDCl3): d 2.63 (s, 3H, CH3), 4.79 (br s, 2H,
NH2), 7.21 (d, J = 8.0 Hz, 1H, H-3), 7.58 (dd, J = 8.0,
2.1 Hz, 1H, H-4), 8.15 (d, J = 2.1 Hz, 1H, H-6).
(CDCl3 + DMSO): d 1.95 (s, 3H, NHCOCH3), 7.50
(m, 2H, H-4, H-5), 7.66 (dd, J = 7.8, 1.6 Hz, 1H, H-3),
8.10 (dd, J = 7.3, 1.2Hz, 1H, H-6), 10.40 (br s, 1H,
NH). Anal. Calcd for C9H9O5NS: C, 44.44; H, 3.73;
N, 5.76. Found: C, 44.37; H, 3.51; N, 5.65.
Compounds 15a,b, for which the physical and spectro-
scopic data are listed below, were prepared using an
acetylation procedure similar to that described previ-
ously for the synthesis of compound 10.
5.3. General procedure for the synthesis of 4-bromo-2-
methylbenzenesulfonyl chloride (13a) and 5-bromo-2-
methylbenzensulfonyl chloride (13b)
5.9. N-Acetyl-4-bromo-2-methylbenzenesulfonamide
(15a)
Chlorosulfonic acid (2.5 mL, 4.38 g, 37.6 mmol) was
added slowly to a cold solution (0 ꢁC) of either 3-bromo-
toluene (12a, 1.03 g, 6 mmol), or 4-bromotoluene (12b,
1.03 g, 6 mmol), in CHCl3 (10 mL). The reaction was al-
lowed to proceed with stirring for 4 h at 0 ꢁC prior to
pouring onto crushed ice (250 mL), and then extraction
with CHCl3 (3 · 150 mL). The combined CHCl3 ex-
tracts were washed with water (3 · 100 mL), the organic
fraction was dried (Na2SO4), and the solvent was re-
moved in vacuo to yield the respective arylsulfonyl chlo-
ride product (13a or 13b). Some physical and
spectroscopic data for 13a,b are listed below.
Yield, 80%; pale yellow crystals; mp 150–152 ꢁC; IR
(film) 1704 (C@O), 1597, 1547, 1440 (Ar), 1349
(SO2) cmÀ1
; d 2.09 (s, 3H,
1H NMR (CDCl3):
NHCOCH3), 2.65 (s, 3H, C-2 CH3), 7.52(s, 1H, H-3),
7.54 (d, J = 8.5 Hz, 1H, H-5), 8.00 (d, J = 8.5 Hz, 1H,
H-6), 8.36 (br s, 1H, NH). Anal. Calcd for
C9H10BrNO3S: C, 37.00; H, 3.45; N, 4.79. Found: C,
37.28; H, 3.34; N, 4.62.
5.10. N-Acetyl-5-bromo-2-methylbenzenesulfonamide
(15b)
5.4. 4-Bromo-2-methylbenzenesulfonyl chloride (13a)
Yield, 82%; pale yellow crystals; mp 179–180 ꢁC; IR
Yield, 99%; white crystals; mp 63–64 ꢁC; IR (film) 1577,
(film) 1668 (C@O), 1473 (Ar), 1333 (SO2) cmÀ1 1H
;
1547, 1472(Ar), 1375 (SO ) cmÀ1; 1H NMR (CDCl3): d
2.77 (s, 3H, CH3), 7.57 (d, J = 8.5 Hz, 1H, H-5), 7.60 (s,
1H, H-3), 7.93 (d, J = 8.6 Hz, 1H, H-6).
2
NMR (CDCl3): d 2.12 (s, 3H, NHCOCH3), 2.62 (s,
3H, C-2, CH3), 7.22 (d, J = 8.3 Hz, 1H, H-3), 7.65 (dd,
J = 8.3, 2.1 Hz, 1H, H-4), 8.26 (d, J = 2.1 Hz, 1H, H-
6), 8.60 (br s, 1H, NH). Anal. Calcd for C9H10BrNO3S:
C, 37.00; H, 3.45; N, 4.79. Found: C, 37.13; H, 3.34; N,
4.68.
5.5. 5-Bromo-2-methylbenzenesulfonyl chloride (13b)
Yield, 78%; colorless liquid; IR (neat) 3091 (Ar–H),
1374 (SO2) cmÀ1 1H NMR (CDCl3): d 2.73 (s, 3H,
;
CH3), 7.31 (d, J = 8.2Hz, 1H, H-3), 7.72 (dd, J = 8.2,
1.8 Hz, 1H, H-4), 8.19 (d, J = 1.8 Hz, 1H, H-6).
5.11. General procedure for the synthesis of N-Acetyl-2-
methyl-4-(substituted-phenyl)benzenesulfonamides (17a–
d) and N-acetyl-2-methyl-5-(substituted-phenyl)benzene-
sulfonamides (18a–d,f)
5.6. General procedure for the synthesis of 4-bromo-2-
methylbenzenesulfonamide (14a) and 5-bromo-2-methyl-
benzenesulfonamide (14b)
The aryl bromide (15a or 15b, 0.58 g, 2.0 mmol) and the
appropriately substituted-phenylboronic acid (16,
3.0 mmol) were dissolved in THF (30 mL), and then
aqueous Na2CO3 (3.0 mL of 2M) followed by tetra-
kis(triphenylphosphine)palladium (70 mg, 0.06 mmol)
were added. The reaction was allowed to proceed at re-
flux for 3–5 h, cooled to 25 ꢁC, water was added
(150 mL), the mixture was acidified to pH 3 using 5%
w/v HCl, and the mixture was extracted with EtOAc
(3 · 100 mL). The combined EtOAc extracts were
washed with water (3 · 50 mL), the organic fraction
was dried (Na2SO4), and the solvent was removed
in vacuo to afford the crude product. Purification of
the product by silica gel column chromatography using
CHCl3–MeOH (100:3, v/v) as eluant furnished the
respective title compound (17a–d, 18a–d,f).
An aqueous solution of NH4OH (30 mL of 30% w/v)
was added to a cold (0 ꢁC) solution of the arylsulfonyl
chloride (13a or 13b, 0.59 g, 2.2 mmol) in dioxane
(15 mL) with vigorous stirring, and the reaction was al-
lowed to proceed for 6 h at 0 ꢁC with continued stirring.
The insoluble material was removed by filtration,
washed with water (3 · 10 mL), and recrystallized from
hexanes–acetone to yield the respective product (14a
or 14b).
5.7. 5-Bromo-2-methylbenzenesulfonamide (14a)
Yield, 78%; white needles; mp 176–177 ꢁC; IR (film)
3362, 3242 (NH2), 1592, 1547 (Ar), 1315 (SO2) cmÀ1
;

Q.-H. Chen et al. / Bioorg. Med. Chem. 13 (2005) 2459–2468
2465
5.12. N-Acetyl-2-methyl-4-phenylbenzenesulfonamide
(17a)
5.17. N-Acetyl-5-(2,4-difluorophenyl)-2-methylbenzene-
sulfonamide (18c)
Yield, 90%; white needles; mp 168–169 ꢁC; IR (CHCl3)
3393 (NH), 3155 (Ar–H), 1722 (C@O), 1603, 1474
Yield, 69%; pale yellow needles; mp 162–164 ꢁC; IR
(CHCl3) 3385 (NH), 3010 (Ar–H), 1720 (C@O), 1600,
1
(Ar), 1380, 1350 (SO2) cmÀ1
;
1H NMR (CDCl3): d
1490 (Ar), 1380 (SO2) cmÀ1; H NMR (CDCl3): d 2.12
2.13 (s, 3H, NHCOCH3), 2.74 (s, 3H, C-2, CH3),
7.40–8.27 (m, 8H, Ar–H), 8.62 (br s, 1H, NH). Anal.
Calcd for C15H15NO3S: C, 62.26; H, 5.23; N, 4.84.
Found: C, 62.20; H, 5.19; N, 4.69.
(s, 3H, NHCOCH3), 2.71 (s, 3H, C-2, CH3), 6.95 (m,
2H, difluorophenyl H-3, H-5), 7.42 (d, J = 8.2Hz, 1H,
H-3), 7.45 (m, 1H, difluorophenyl H-6), 7.70 (br d,
J = 8.2Hz, 1H, H-4), 8.28 (br s, 1H, H-6), 8.53 (br s,
1H, NH). Anal. Calcd for C15H13F2NO3S: C, 55.38;
H, 4.03; N, 4.31. Found: C, 55.45; H, 3.82; N, 4.21.
5.13. N-Acetyl-2-methyl-5-phenylbenzenesulfonamide
(18a)
5.18. N-Acetyl-2-methyl-4-(4-methylthiophenyl)benzene-
sulfonamide (17d)
Yield, 53.5%; pale yellow crystals; mp 183–185 ꢁC; IR
(film) 1682(C @O), 1480, 1435 (Ar), 1310 (SO2) cmÀ1
;
1H NMR (CDCl3): d 2.12 (s, 3H, NHCOCH3), 2.71 (s,
3H, C-2, CH3), 7.37–7.51 (m, 4H, H-3, phenyl H-3, H-
4, H-5), 7.62(dd, J = 8.4, 1.2 Hz, 2H, phenyl H-2, H-
6), 7.76 (dd, J = 8.0, 1.8 Hz, 1H, H-4), 8.33 (br s, 1H,
NH), 8.37 (d, J = 1.8 Hz, 1H, H-6). Anal. Calcd for
C15H15NO3SÆ1/4H2O: C, 61.31; H, 5.31; N, 4.77. Found:
C, 61.34; H, 5.31; N, 4.73.
Yield, 90%; white crystals; mp 162–163 ꢁC; IR (film)
1697 (C@O), 1600, 1442(Ar), 1300 (SO 2) cmÀ1 1H
;
NMR (CDCl3): d 2.12 (s, 3H, NHCOCH3), 2.54 (s,
3H, SCH3), 2.73 (s, 3H, C-2, CH3), 7.34 (d,
J = 8.4 Hz, 2H, methylthiophenyl H-3, H-5), 7.52–7.58
(m, 4H, H-3, H-5, methylthiophenyl H-2, H-6), 8.19
(d, J = 8.6 Hz, 1H, H-6), 8.46 (br s, 1H, NH). Anal.
Calcd for C16H17NO3S2: C, 57.29; H, 5.11; N, 4.18.
Found: C, 57.42; H, 5.08; N, 3.98.
5.14. N-Acetyl-4-(4-fluorophenyl)-2-methylbenzenesulf-
onamide (17b)
5.19. N-Acetyl-2-methyl-5-(4-methylthiophenyl)benzene-
sulfonamide (18d)
Yield, 87%; pale yellow crystals; mp 175–176 ꢁC; IR
(CHCl3) 3382(NH), 3019 (Ar–H), 1723 (C @O), 1602,
Yield, 89%; pale yellow solid; mp 173–175 ꢁC; IR (film)
1
1474 (Ar), 1387 (SO2) cmÀ1; H NMR (CDCl3): d 2.12
1696 (C@O), 1602, 1481 (Ar), 1347 (SO2) cmÀ1 1H
;
(s, 3H, NHCOCH3), 2.73 (s, 3H, C-2, CH3), 7.18 (t,
J = 8.5 Hz, 2H, fluorophenyl H-3, H-5), 7.50 (br s, 1H,
H-3), 7.58 (m, 3H, H-5, fluorophenyl H-2, H-6), 8.21
(d, J = 8.4 Hz, 1H, H-6), 8.57 (br s, 1H, NH). Anal.
Calcd for C15H14FNO3S: C, 58.62; H, 4.59; N, 4.56.
Found: C, 58.60; H, 4.34; N, 4.37.
NMR (CDCl3): d 2.10 (s, 3H, NHCOCH3), 2.53 (s,
3H, SCH3), 2.69 (s, 3H, C-2, CH3), 7.33 (d,
J = 8.2Hz, 2H, methylthiophenyl H-3, H-5), 7.40 (d,
J = 8.2Hz, 1H, H-3), 7.54 (d, J = 8.5 Hz, 2H, methylthio-
phenyl H-2, H-6), 7.73 (dd, J = 8.2, 1.8 Hz, 1H, H-4),
8.35 (d, J = 1.8 Hz, 1H, H-6), 8.58 (br s, 1H, NH). Anal.
Calcd for C16H17NO3S2: C, 57.29; H, 5.11; N, 4.18.
Found: C, 57.34; H, 4.93; N, 4.01.
5.15. N-Acetyl-5-(4-fluorophenyl)-2-methylbenzenesulf-
onamide (18b)
5.20. N-Acetyl-5-(4-isopropoxyphenyl)-2-methylbenzene-
sulfonamide (18f)
Yield, 75%; pale yellow solid; mp 120–122 ꢁC; IR
(CHCl3) 3388 (NH), 3130 (Ar–H), 1723 (C@O), 1620,
1
1461 (Ar), 1380 (SO2) cmÀ1; H NMR (CDCl3): d 2.10
Yield, 82%; white needles; mp 150–151 ꢁC; IR (CHCl3)
3388 (NH), 3031, 3024 (Ar–H), 1726 (C@O), 1602,
(s, 3H, NHCOCH3), 2.70 (s, 3H, C-2, CH3), 7.16 (t,
J = 8.4 Hz, 2H, fluorophenyl H-3, H-5), 7.41 (d,
J = 8.0 Hz, 1H, H-3), 7.57 (dd, J = 8.4, 5.2Hz, 2H, fluo-
rophenyl H-2, H-6), 7.70 (dd, J = 8.0, 1.8 Hz, 1H, H-4),
8.33 (d, J = 2.1 Hz, 1H, H-6), 8.34 (br s, 1H, NH). Anal.
Calcd for C15H14FNO3S: C, 58.62; H, 4.59; N, 4.56.
Found: C, 58.78; H, 4.48; N, 4.43.
1
1485 (Ar), 1205 (SO2) cmÀ1; H NMR (CDCl3): d 1.38
[d, J = 6.1 Hz, 6H, OCH(CH3)2], 2.10 (s, 3H,
NHCOCH3), 2.69 (s, 3 H, C-2, CH3), 4.61 [m, 1H,
OCH(CH3)2], 6.98 (d, J = 8.7 Hz, 2H, isopropoxyphenyl
H-3, H-5), 7.37 (d, J = 8.0 Hz, 1H, H-3), 7.53 (d,
J = 8.7 Hz, 2H, isopropoxyphenyl H-2, H-6), 7.71 (dd,
J = 8.2, 1.8 Hz, 1H, H-4), 8.32 (d, J = 1.8 Hz, 1H, H-
6), 8.62(br s, 1H, NH). Anal. Calcd for C18H21NO4S:
C, 62.23; H, 6.09; N, 4.03. Found: C, 62.34; H, 6.10;
N, 3.94.
5.16. N-Acetyl-4-(2,4-difluorophenyl)-2-methylbenzene-
sulfonamide (17c)
Yield, 86%; pale gray crystals; mp 146–147 ꢁC; IR
(CHCl3) 3382(NH), 3153 (Ar–H), 1716 (C @O), 1622
5.21. General procedure for the synthesis of N-acetyl-4-
(4-methanesulfonylphenyl)-2-methylbenzenesulfonamide
(17e) and N-acetyl-5-(4-methanesulfonylphenyl)-2-meth-
ylbenzenesulfonamide (18e)
1
(Ar), 1387 (SO2) cmÀ1; H NMR (CDCl3): d 2.13 (s,
3H, NHCOCH3), 2.73 (s, 3H, C-2, CH3), 6.95 (m, 2H,
difluorophenyl H-3, H-5), 7.38–7.53 (m, 2H, H-3, H-
5), 8.20 (d, J = 8.2Hz, 1H, H-6), 8.52(br s, 1H, NH).
Anal. Calcd for C15H13F2NO3S: C, 55.38; H, 4.03; N,
4.31. Found: C, 55.41; H, 3.96; N, 4.23.
An aqueous solution of Oxoneꢂ (1.9 g, 3.03 mmol, 15 mL)
was added to a stirred solution of the methylthiophenyl

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Q.-H. Chen et al. / Bioorg. Med. Chem. 13 (2005) 2459–2468
compound (17d or 18d, 574 mg, 1.71 mmol) in methanol
(6 mL) and THF (15 mL), and the reaction was allowed
to proceed with stirring at 25 ꢁC for 1.5 h. Addition of
H2O (100 mL), extraction with CH2Cl2 (3 · 80 mL),
drying the combined CH2Cl2 extracts (Na2SO4), and
removal of the solvent in vacuo afforded the crude
product. The 1H NMR of this product showed that
the N-acetyl group has undergone partial hydrolysis.
To circumvent this, the title compounds were isolated
following acetylation of the crude product employing
the same acetylation procedure described previously
for the synthesis of compound 10. The physical and
spectral data for 17–18e are summarized below.
5.25. N-Acetyl-2-carboxy-5-phenylbenzenesulfonamide
(20a)
Yield, 67%; pale yellow solid; mp 274–275 ꢁC; IR
(CHCl3) 3471–2513 (COOH), 1704 (C@O), 1638, 1473
1
(Ar), 1366 (SO2) cmÀ1; H NMR (CDCl3 + DMSO): d
2.01 (s, 3H, NHCOCH3), 7.35 (m, 3H, phenyl H-3, H-
4, H-5), 7.56 (d, J = 8.0 Hz, 2H, phenyl H-2, H-6),
7.75 (dd, J = 8.2, 1.5 Hz, 1H, H-4), 7.81 (d, J = 8.2Hz,
1H, H-3), 8.36 (d, J = 1.5 Hz, 1H, H-6), 10.30 (br s,
1H, NH). Anal. Calcd for C15H13NO5S: C, 56.42; H,
4.10; N, 4.39. Found: C, 56.10; H, 4.15; N, 4.30.
5.26. N-Acetyl-2-carboxy-4-(4-fluorophenyl)benzenesulf-
onamide (19b)
5.22. N-Acetyl-4-(4-methanesulfonylphenyl)-2-methyl-
benzenesulfonamide (17e)
Yield, 88%; white solid; mp 201–202 ꢁC; IR (CHCl3):
3409–2468 (COOH), 1709 (C@O), 1602, 1467 (Ar),
Yield, 89%; pale orange crystals; mp 206–208 ꢁC; IR
1
1380 (SO2) cmÀ1; H NMR (CDCl3 + DMSO): d 1.92
(CHCl3) 1716 (C@O), 1595, 1441 (Ar), 1313 (SO2) cmÀ1
;
1.84 (s, 3H,
1H NMR (CDCl3 + DMSO):
d
(s, 3H, NHCOCH3), 7.02(t, J = 8.5 Hz, 2H, fluorophe-
nyl H-3, H-5), 7.45 (m, 2H, fluorophenyl H-2, H-6), 7.60
(dd, J = 8.2, 1.2 Hz, 1H, H-5), 7.76 (d, J = 1.2Hz, 1H,
H-3), 8.13 (d, J = 8.2Hz, 1H, H-6), 10.69 (br s, 1H,
NH). Anal. Calcd for C15H12FNO5S: C, 53.41; H,
3.59; N, 4.15. Found: C, 53.44; H, 3.51; N, 4.02.
NHCOCH3), 2.56 (s, 3H, C-2, CH3), 2.94 (s, 3H,
SO2CH3), 7.35 (s, 1H, H-3), 7.39 (d, J = 8.2Hz, 1H,
H-5), 7.62(d, J = 8.2Hz, 2H, methanesulfonylphenyl
H-2, H-6), 7.85 (d, J = 8.2Hz, 2H, methanesulfonylphe-
nyl H-3, H-5), 8.04 (d, J = 8.2Hz, 1H, H-6), 11.7 (br s,
1H, NH). Anal. Calcd for C16H17NO5S2: C, 52.30; H,
4.66; N, 3.81. Found: C, 52.38; H, 4.38; N, 3.71.
5.27. N-Acetyl-2-carboxy-5-(4-fluorophenyl)benzenesulf-
onamide (20b)
5.23. N-Acetyl-5-(4-methanesulfonylphenyl)-2-methyl-
benzenesulfonamide (18e)
Yield, 78%; pale yellow solid; mp 250–252 ꢁC; IR
(CHCl3) 3493–2515 (COOH), 1712 (C@O), 1380
(SO2) cmÀ1 1H NMR (CDCl3 + DMSO): d 2.02 (s,
;
Yield, 57.5%; white crystals; mp 221–222 ꢁC; IR
(CHCl3) 3393 (NH), 3155 (Ar–H), 1713 (C@O), 1639,
3H, NHCOCH3), 7.09 (t, J = 8.5 Hz, 2H, fluorophenyl
H-3, H-5), 7.56 (dd, J = 8.5, 5.2Hz, 2H, fluorophenyl
H-2, H-6), 7.74 (dd, J = 8.0, 1.8 Hz, 1H, H-4), 7.82(d,
J = 8.0 Hz, 1H, H-3), 8.35 (d, J = 1.8 Hz, 1H, H-6),
10.27 (br s, 1H, NH). Anal. Calcd for C15H12FNO5S:
C, 53.41; H, 3.59; N, 4.15. Found: C, 53.08; H, 3.51;
N, 4.05.
1500
(Ar),
1380
(SO2) cmÀ1
;
1H
NMR
(CDCl3 + DMSO): d 1.98 (s, 3H, NHCOCH3), 2.67 (s,
3H, C-2, CH3), 3.05 (s, 3H, SO2CH3), 7.36 (d,
J = 8.2Hz, 1H, H-3), 7.67 (dd, J = 8.2, 2.2 Hz, 1H, H-
4), 7.76 (d, J = 8.2Hz, 2H, methanesulfonylphenyl H-
2, H-6), 7.96 (d, J = 8.2Hz, 2H, methanesulfonylphenyl
H-3, H-5), 8.36 (d, J = 2.2 Hz, 1H, H-6), 11.7 (br s, 1H,
NH). Anal. Calcd for C16H17NO5S2: C, 52.30; H, 4.66;
N, 3.81. Found: C, 52.49; H, 4.74; N, 3.66.
5.28. N-Acetyl-2-carboxy-4-(2,4-difluorophenyl)benzene-
sulfonamide (19c)
Yield, 81%; white solid; mp 189–190 ꢁC; IR (CHCl3)
3368–2509 (COOH), 1716 (C@O), 1615, 1461 (Ar),
The N-acetyl-2-carboxy-4-(substituted-phenyl)benzene-
sulfonamides (19a–d) and N-acetyl-2-carboxy-5-(substi-
1
1380 (SO2) cmÀ1; H NMR (CDCl3 + DMSO): d 1.87
tuted-phenyl)benzenesulfonamides
(20a–d)
were
(s, 3H, NHCOCH3), 6.83 (m, 2H, difluorophenyl H-3,
H-5), 7.26 (m, 1H, difluorophenyl H-6), 7.54 (br d,
J = 8.2Hz, 1H, H-5), 7.66 (br s, 1H, H-3), 8.08 (d,
J = 8.2Hz, 1H, H-6), 10.90 (br s, 1H, NH). Anal. Calcd
for C15H11F2NO5S: C, 50.70; H, 3.12; N, 3.94. Found:
C, 50.55; H, 2.86; N, 3.87.
prepared by oxidation of the C-2methyl substituent
using KMnO4 according to the procedure described pre-
viously for the preparation of compound 11.
5.24. N-Acetyl-2-carboxy-4-phenylbenzenesulfonamide
(19a)
5.29. N-Acetyl-2-carboxy-5-(2,4-difluorophenyl)benzene-
sulfonamide (20c)
Yield, 88%; white crystals; mp 195–196 ꢁC; IR (CHCl3)
3388–2475 (COOH), 1709 (C@O), 1595, 1467 (Ar), 1250
(SO2) cmÀ1; 1H NMR (CDCl3 + DMSO): d 2.00 (s, 3H,
NHCOCH3), 7.30–7.41 (m, 3H, phenyl H-3, H-4, H-5),
7.51 (d, J = 7.5 Hz, 2H, phenyl H-2, H-6), 7.70 (dd,
J = 8.4, 1.8 Hz, 1H, H-5), 7.89 (d, J = 1.8 Hz, 1H, H-
3), 8.19 (d, J = 8.4 Hz, 1H, H-6), 10.45 (br s, 1H, NH).
Anal. Calcd for C15H13NO5S: C, 56.42; H, 4.10; N,
4.39. Found: C, 56.32; H, 3.96; N, 4.23.
Yield, 69%; white solid; mp 220–221 ꢁC; IR (CHCl3)
3361–2515 (COOH), 1729 (C@O), 1629, 1467 (Ar),
1
1380 (SO2) cmÀ1; H NMR (CDCl3 + DMSO): d 2.01
(s, 3H, NHCOCH3), 6.90 (m, 2H, difluorophenyl H-3,
H-5), 7.43 (m, 1H, difluorophenyl H-6), 7.72(br d,
J = 8.0 Hz, 1H, H-4), 7.79 (d, J = 8.0 Hz, 1H, H-3),
8.28 (br s, 1H, H-6), 10.36 (br s, 1H, NH). Anal. Calcd

Q.-H. Chen et al. / Bioorg. Med. Chem. 13 (2005) 2459–2468
2467
for C15H11F2NO5S: C, 50.70; H, 3.12; N, 3.94. Found:
C, 50.66; H, 2.95; N, 3.85.
3H, SO2CH3), 3.86 (s, 3H, OCH3), 7.73 (d, J = 8.2Hz,
1H, H-3), 7.78 (d, J = 8.4 Hz, 2H, methanesulfonylphe-
nyl H-2, H-6), 7.80 (dd, J = 8.2, 1.5 Hz, 1H, H-4), 7.92
(d, J = 8.4 Hz, 2H, methanesulfonylphenyl H-3, H-5),
8.41 (d, J = 1.5 Hz, 1H, H-6), 11.40 (br s, 1H, NH).
Anal. Calcd for C17H17NO7S2: C, 49.62; H, 4.16; N,
3.40. Found: C, 49.55; H, 3.96; N, 3.26.
5.30. N-Acetyl-2-carboxy-4-(4-methanesulfonylphen-
yl)benzenesulfonamide (19d)
Yield, 70%; white crystals; mp 199–200 ꢁC; IR (CHCl3)
3382–2723 (COOH), 1716 (C@O), 1602, 1454 (Ar), 1306
(SO2) cmÀ1; 1H NMR (CDCl3 + DMSO): d 1.89 (s, 3H,
NHCOCH3), 2.93 (s, 3H, SO2CH3), 7.64 (dd, J = 8.2,
1.8 Hz, 1H, H-5), 7.64 (d, J = 8.2Hz, 2H, methanesulfon-
ylphenyl H-2, H-6), 7.80 (d, J = 1.8 Hz, 1H, H-3), 7.87
(d, J = 8.2Hz, 2H, methanesulfonylphenyl H-3, H-5),
8.16 (d, J = 8.2Hz, 1H, H-6), 11.0 (br s, 1H, NH). Anal.
Calcd for C16H15NO7S2: C, 48.35; H, 3.80; N, 3.52.
Found: C, 48.44; H, 3.66; N, 3.42.
5.34. Molecular modeling (docking) study
Docking experiments were performed using Insight II
software Version 2000.1 (Accelrys Inc.) running on a Sili-
con Graphics Octane 2R14000A workstation according
to a previously reported method.16
5.35. In vitro cyclooxygenase inhibition assays
5.31. N-Acetyl-2-carboxy-5-(4-methanesulfonylphen-
yl)benzenesulfonamide (20d)
The ability of the test compounds listed in Table 1 to in-
hibit ovine COX-1 and COX-2(IC
value, lM) was
50
determined using an enzyme immuno assay (EIA) kit
(catalog number 560101, Cayman Chemical, Ann
Arbor, MI, USA) according to our previously reported
method.16
Yield, 81%; white solid; mp >300 ꢁC; IR (CHCl3) 3409–
2468 (COOH), 1716 (C@O), 1615, 1454 (Ar), 1380
(SO2) cmÀ1 1H NMR (CDCl3 + DMSO): d 1.90 (s,
;
3H, NHCOCH3), 2.95 (s, 3H, SO2CH3), 7.71 (m, 4H,
H-3, H-4, methanesulfonylphenyl H-2, H-6), 7.89 (d,
J = 8.6 Hz, 2H, methanesulfonylphenyl H-3, H-5), 8.33
(d, J = 1.0 Hz, 1H, H-6), 11.0 (br s, 1H, NH). Anal.
Calcd for C16H15NO7S2: C, 48.35; H, 3.80; N, 3.52.
Found: C, 48.00; H, 3.71; N, 3.42.
5.36. Antiinflammatory assay
Antiinflammatory activity was performed using a meth-
od described by Winter et al.17
5.37. Analgesic assay
5.32. N-Acetyl-2-carboxy-5-(4-isopropoxyphenyl)benz-
enesulfonamide (20e)
Analgesic activity was determined using a 4% sodium
chloride-induced writhing (abdominal constriction assay
previously reported).18
Yield, 87%; white crystals; mp 206–208 ꢁC; IR (film)
3430–2845 (COOH), 1735, 1727 (C@O), 1592(Ar),
;
1240 (SO2) cmÀ1 1H NMR (CDCl3): d 1.06 [d,
J = 6.1 Hz, 6H, CH(CH3)2], 1.76 (s, 3H, NHCOCH3),
4.32[m, 1H, CH(CH3)2], 6.68 (d, J = 8.7 Hz, 2H, iso-
propoxyphenyl H-3, H-5), 7.28 (d, J = 8.7 Hz, 2H,
isopropoxyphenyl H-2, H-6), 7.48 (d, J = 8.0 Hz, 1H,
H-3), 7.52(dd, J = 8.0, 1.8 Hz, 1H, H-4), 8.09 (d,
J = 1.8 Hz, 1H, H-6), 11.0 (br s, 1H, NH). Anal. Calcd
for C18H19NO6SÆ1/4H2O: C, 56.61; H, 5.15; N, 3.67.
Found: C, 56.81; H, 5.10; N, 3.64.
Acknowledgements
We are grateful to (i) the Canadian Institutes of Health
Research (CIHR) (MOP-14712) for financial support of
this research, (ii) the Alberta Heritage Foundation for
Medical Research (AHFMR) for a postdoctoral fellow-
ship award (to Q.H.C.), and a graduate scholarship (to
P.R.), and to Rx&D-HRF/CIHR for a postdoctoral fel-
lowship (to Q.H.C.).
5.33. N-Acetyl-2-methoxycarbonyl-5-(4-methanesulfonyl-
phenyl)benzenesulfonamide (21)
References and notes
Concentrated H2SO4 (1.3 mL) was added dropwise at
ice-bath temperature to a stirred solution of 20d
(100 mg, 0.25 mmol) in methanol (15 mL). The reaction
mixture was refluxed for 24 h, cooled to 25 ꢁC, and
CH2Cl2 (100 mL) was added. This solution was washed
with water (30 mL), the organic fraction was dried
(Na2SO4), and the solvent was removed in vacuo to pro-
vide a white solid. This solid was acetylated in situ, fol-
lowing the procedure described previously for the
synthesis of compound 10, to afford a crude product,
which was crystallized from hexanes–acetone to yield
the target product 21 as pale yellow crystals (80 mg,
77%); mp 217–218 ꢁC; IR (film): 1721 (C@O), 1597,
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