Synthesis of new sulfonamides as lipoxygenase inhibitors

Article abstract of DOI:10.1016/j.bmc.2012.02.055

The present study describes a convenient method for the synthesis of new lipoxygenase inhibitors, 4-(toluene-4-sulfonylamino)-benzoic acids from p-amino benzoic acid. Reaction of p-amino benzoic acid with p-toluenesulfonyl chloride provided thirteen N- and O-alkylation products 4a-4m in moderate to good yields. Lipoxygenase inhibition of newly formed sulfonamide derivatives was investigated and some of these compounds 4m, 4g, 4e, 4f and 4j showed good lipoxygenase inhibitory activities with IC₅₀ values ranged between 15.8 ± 0.57 and 91.7 ± 0.61 μmol whilst all other compounds exhibited mild anti-lipoxygenase activities with IC₅₀ values ranged between 139.2 ± 0.75 and 232.1 ± 0.78 μmol. N-alkylated products were more active against the enzyme than O-alkylated or both N- and O-alkylated ones. All synthesized sulfonamides were recrystallized in chloroform to give these title compounds which were characterized using FTIR, ¹H NMR, ¹³C NMR, elemental analysis and single crystal X-ray diffraction techniques.

Full text of DOI:10.1016/j.bmc.2012.02.055

Bioorganic & Medicinal Chemistry 20 (2012) 2535–2539
Contents lists available at SciVerse ScienceDirect
Bioorganic & Medicinal Chemistry
journal homepage: www.elsevier.com/locate/bmc
Synthesis of new sulfonamides as lipoxygenase inhibitors
Ghulam Mustafa a, , Islam Ullah Khan a, , Muhammad Ashraf b,c, Iftikhar Afzal c,
⇑
⇑
Sohail Anjum Shahzad d, Muhammad Shafiq a
a Materials Chemistry Laboratory, Department of Chemistry, Government College University, Lahore 54000, Pakistan
b Department of Biochemistry & Biotechnology, The Islamia University of Bahawalpur, Bahawalpur 63100, Pakistan
c Department of Pharmacy, The Islamia University of Bahawalpur, Bahawalpur 63100, Pakistan
d Department of Chemistry, COMSATS Institute of Information Technology, Abbottabad 22060, Pakistan
a r t i c l e i n f o
a b s t r a c t
Article history:
The present study describes a convenient method for the synthesis of new lipoxygenase inhibitors, 4-(tol-
uene-4-sulfonylamino)-benzoic acids from p-amino benzoic acid. Reaction of p-amino benzoic acid with
p-toluenesulfonyl chloride provided thirteen N- and O-alkylation products 4a–4m in moderate to good
yields. Lipoxygenase inhibition of newly formed sulfonamide derivatives was investigated and some of
these compounds 4m, 4g, 4e, 4f and 4j showed good lipoxygenase inhibitory activities with IC50 values
Received 1 January 2012
Revised 22 February 2012
Accepted 23 February 2012
Available online 3 March 2012
ranged between 15.8 0.57 and 91.7 0.61
genase activities with IC50 values ranged between 139.2 0.75 and 232.1 0.78
ucts were more active against the enzyme than O-alkylated or both N- and O-alkylated ones. All
synthesized sulfonamides were recrystallized in chloroform to give these title compounds which were
characterized using FTIR, 1H NMR, 13C NMR, elemental analysis and single crystal X-ray diffraction
techniques.
l
mol whilst all other compounds exhibited mild anti-lipoxy-
mol. N-alkylated prod-
Keywords:
Lipoxygenase
Lipoxygenase inhibitors
Sulfonamides
4-(Toluene-4-sulfonylamino)-benzoic acids
l
Ó 2012 Elsevier Ltd. All rights reserved.
1. Introduction
Such molecular architecture of sulfonamides attracted attention
and keeping in view of their biological activity, synthesis of new
Sulfonamide derivatives are well known pharmaceutical agents
since this group has been the main functional part of the most of
the drug structures due to stability and tolerance in human
beings.1 These molecules have gained much attention due to their
diverse biological activities in pharmaceutical2 as well as in agri-
cultural3 areas. These are used in urinary tract infections, meningi-
tis, streptococcal pharyngitis, bacillary dysentery, trachoma,
chancroid, malaria, toxoplasmosis, nocardiasis and conjunctivi-
tis.4–6 Sulfonamides have a number of biological activities such
as antibacterial,7–9 insulin releasing,10 carbonic anhydrase inhibi-
tory,11,12 anti-inflammatory,13 and antitumor14 activities. Antibac-
terial sulfonamides as sulfadiazinealone, and also diuretics, such as
hydrochlorothiazide, are being therapeutically used for many dec-
ades.15 Other commercial drugs with a sulfonamide structure are
the antihypertensive agents like bosentan,16 antiviral HIV protease
inhibitor, amprenavir,17 and the phosphodiesterase-5 inhibitor, sil-
denafil.18 Recently, sulfonamide group has been found to be the
key constituent of a new class of cyclooxygenase inhibitors such
as celecoxib19 and valdecoxib20 as in Figure 1. The sulfonamide
partial structure with versatile medicinal applications continues
to play a fundamental role in medicinal chemistry.21
diversely N- and O-alkylated 4-(toluene-4-sulfonylamino)-benzoic
acids was carried out in search for new lead compounds as poten-
tial inhibitors of lipoxygenase. The data shows that 4m, 4g, 4e, 4f
and 4j are good inhibitors of lipoxygenase enzyme.
2. Results
2.1. Chemistry
The present approach successfully combined the formation of
sulfonamide and its subsequent alkylation in the synthesis of a
range of sulfonamides as outlined in Schemes 1a and b.
NH2
S
O
N
O
N
O
N
CF3
CH3
H2N
O
S
H3C
O
⇑
Corresponding authors. Tel.: +92 3214557884 (G.M.); tel.: +92 3334046740
(I.U.K.).
Valdecoxib
Celecoxib
E-mail addresses: gmustafa884@yahoo.com (G. Mustafa), iuklodhi@yahoo.com
(I.U. Khan).
Figure 1. Chemical structures of celecoxib and valdecoxib.
0968-0896/$ - see front matter Ó 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2012.02.055

2536
G. Mustafa et al. / Bioorg. Med. Chem. 20 (2012) 2535–2539
O
OH
obtained as an ester of sulfonamide 3 under the given specific reac-
CH
3
O
OH
tion conditions. Consequently, the different product distribution
observed on increasing reaction time and/or temperature is indic-
ative of the reactivity of electrophile and stability of the product
which favored particular course of reaction. Steric and electronic
effects due to the larger groups were apparent in the reactions of 3.
Na CO
2
3
+
98 %
O
O
S
O
N
H
S
NH
2
Cl
O
2.2. Crystallography
CH
3
3
2
1
The suitable crystals for X-ray diffraction were grown under
slow evaporation at room temperature in chloroform. Single crys-
tal X-ray diffraction data were collected at 296 (2) K on a BRUKER
KAPPA diffractometer equipped with an APEX II CCD detector
Scheme 1a. Synthesis of precursor sulfonamide.
(Bruker-AXS) using Mo K radiation (0.71073 Å). The crystal struc-
O
OH
a
O
O
S
R2
ture was solved by direct methods using SHELXS, and all structural
refinements were conducted using either SHELXL-97.22 PLATON23
and WinGX24 were used for molecular graphics. All the non-hydro-
gen atoms were refined with anisotropic displacement parameters.
All the hydrogen atoms were placed at calculated positions or
located via difference map and were refined using a riding model
with co-ordinates and isotropic displacement parameters being
dependent upon the atoms to which they are attached.
NaH/DMF/RX
42-81%
O
S
O
N
N
H
R1
O
O
CH3
CH3
3
Crystal data: (4b) C18H21N1O4S1, M = 347.4 g molꢀ1, white, nee-
dle like, 0.34, 0.17, 0.17 mm3, monoclinic, space group P21/n,
a = 8.2114(6), b = 19.4939 (13), c = 11.3291(7) Å, b = t100.078(4)o,
4a-4m
Scheme 1b. N-alkylation and O-alkylation product.
V = 1785.49(13), Z = 4, Dc = 1.29 g cmꢀ3, F(000) = 735.9, Mo K
a
radiation, k = 0.71073 Å, T = 296 (2) K, 2hmax = 57.8o, 16948 reflec-
tion collected, 4565 unique (Rint = 0.086), Final GooF = 0.997,
R1 = 0.072, wR2 = 0.115, R indices based on 1724 reflections with
The synthesis of compound 3 was carried out under basic con-
dition from the reaction of p-amino benzoic acid with p-toluene-
sulfonyl chloride and subsequent reaction with various alkylating
or acylating agents that afforded new thirteen sulfonamide deriv-
atives in moderate to good yields. Compound 4-(toluene-4-sulfo-
nylamino)-benzoic acid 3 was subjected to alkylation in the
presence of sodium hydride using DMF (dimethyl formamide) as
solvent to produce fourteen various N- and O- alkylated sulfon-
amide derivatives 4a–4m.
Two reactive sites carboxylic acid and amino group in the pre-
cursor’s molecule are available towards alkylation. We began our
investigation by installing different substituents. Under described
reaction conditions, three kinds of products could be obtained.
After screening a number of conditions, sulfonamide 3 could be
then further functionalized, in a selective manner, to either O-
alkylation product or N-alkylation product by using slightly differ-
ent reaction conditions. We found that deprotonation of 3 with
2.0 equiv sodium hydride in the presence of DMF was followed
by the addition of electrophiles which successfully yielded alkyl-
ation products. Both amide and ester functionality could be in-
stalled simultaneously in 4a, 4b and 4i if the reaction time was
extended up to 15 hours. Smaller size of alkylating agents was
found to favor the reaction at room temperature towards both
functional group and resulted 4a and 4b in good yields, respec-
tively while 4i was formed in 65% yield when the reaction was per-
formed at 90 °C for 15 h.
I>2
rection applied,
r
(I) (refinement on F2) 220 parameters, Lp and absorption cor-
l
= 0.202 mmꢀ1
.
In the crystal structure of 4b (Fig. 2), two aromatic rings are
twisted at dihedral angle of 35.61(10)°. The ester group attached
to phenyl ring (C7–C13) is planar with the root mean square devi-
ation of 0.0092 Å and it is inclined at 5.06 (18)° with the ring (C7–
C13). No classical hydrogen bonding interactions have been ob-
served in the molecules. Only C–Hꢁ ꢁ ꢁO type interaction connects
the molecule with the symmetry operation (½ + x, ½ ꢀ y, ½ + z)
and generate six memebered ring motif which can be represented
mathematically as R12(6).25
2.3. Lipoxygenase assay
Lipoxygenase (LOX) activity was assayed according to the meth-
od of Tappel (1953) with minor modifications.26 A total volume of
200
lL lipoxygenase assay mixture contained 150
lL sodium phos-
phate buffer (100 mM, pH 8.0), 10
l
L test compound and 15 lL
The second type of products such as 4c–f, 4g, 4j–l and 4m were
obtained in which an alkylating agent was reacted with the amino
group to produce N-alkylated sulfonamides. Compound 4c was
formed by heating at 80 °C for 5 h while 4d and 4f were obtained
in moderate yields when reaction conducted at room temperature
for 3 h. Compound 4g was prepared by heating the reaction mix-
ture at 100 °C for 6 h while 4j and 4k were obtained when reaction
was carried out at 80–90 °C for 12–18 h. Compounds 4l and 4m
were obtained by simple heating at 60 °C. Acid halides were only
reacted with amine group and failed to react with the carboxylic
acid because the resulting anhydride was unstable. In general,
the reaction of larger size of alkyl halide with sulfonamide 3 was
found to occur slowly. The third type of product like 4h were also
Figure 2. ORTEP diagram of 4b, thermal ellipsoids drawn at 50% probability level.

G. Mustafa et al. / Bioorg. Med. Chem. 20 (2012) 2535–2539
2537
purified lipoxygenase enzyme (600 units wellꢀ1, Sigma Inc. USA).
The contents were mixed and pre-read at 234 nm and preincu-
bated for 10 min at 25 °C. The reaction was initiated by the addi-
Compound 4h was made as ester of sulfonamide 3 under the given
reaction conditions with increasing reaction time and temperature.
The reactivity of electrophile and stability of the product also had
impact in the synthesis of 4. Steric hindrance and electronic effects
due to the larger groups were apparent in the reactions of 3.
All synthesized compounds were tested for their ability to act as
inhibitors against lipoxygenase. Enzyme inhibition data is given in
Table 1 as percent inhibition at 0.5 mM and IC50 values (concentra-
tion to inhibit 50% enzyme activity); the lower the IC50 value, the
highest the inhibitory activity of the compound. Baicalein and
quercetin were used as standard inhibitors. The compound 4m
tion of 25 lL substrate solution of linoleic acid. The change in
absorbance was observed after 6 min at 234 nm using 96-well
plate reader Synergy HT, Biotek, USA. All reactions were performed
in triplicates. The positive and negative controls were included in
the assay. Baicalin and quercetin (0.5 mM wellꢀ1) were used as
standard inhibitors. The percentage inhibition was calculated by
the following formula. IC50 values of selected compounds exhibit-
ing >50% activity at 0.5 mM were calculated after suitable dilutions
using EZ–Fit Enzyme Kinetics software (Perrella Scientific Inc. Am-
herst, USA). All the measurements were taken in triplicate and sta-
tistical analysis was performed by Microsoft Excel 2003. Results
are presented as mean SEM.
showed the lowest IC50 value of 15.8 0.57
the standard inhibitor baicalein (22.4 1.3
(37.12 0.07 mol). This was the most active compound against
lmol compared with
l
mol) or quercetin
l
the enzyme and even better than the standard inhibitors. This
compound is N-alkylated with CH2CH@CH(CH3)2 alkyl group
(Table 1). N-alkylation with –CH2-Ph group (4g) was the second
abs of control ꢀ abs of test comp
Inhibition ð%Þ ¼
ꢂ 100
abs of control
most active compound with IC50 value of 59.1 0.87
values were recorded for another N-alkylated (–C5H11) compound
4f with IC50 value of 68.6 0.43 mol and 4e (IC50 value of
61.4 0.69 mol). Compound 4j, other N-alkylated product,
showed slightly increased IC50 values of 91.7 0.61 mol. These
lmol. Similar
l
3. Discussion
l
l
A series of structurally related sulfonamide derivatives (4a–4m)
were prepared according to Scheme 1a by reacting p-amino ben-
zoic acid with p-toluenesulfonyl chloride which on subsequent
reaction with various alkylating or acylating agents provided thir-
teen N- and O-alkylation products in moderate to good yields. All
reactions were carried out at varied temperatures (25–100 °C)
and reaction times (2–18 h). The new compounds were in yields
of 42–81%. Alkylation of 3 was carried out in the presence of so-
dium hydride using DMF as solvent at the two reactive sites of car-
boxylic acid and amino groups. Different reaction conditions
yielded either O-alkylation or N-alkylation products. Deprotona-
tion of 3 with sodium hydride in DMF in the presence of various
electrophiles gave alkylation products. Both amide and ester func-
tionality could be carried out simultaneously in 4a, 4b and 4i if the
reaction is carried out for 15 h. Smaller size of alkylating agents fa-
vored reactions at room temperature giving 4a and 4b in good
yields, 74 and 81%, respectively whilst 4i was formed at 90 °C for
15 h in 65% yield.
studies reveal that N-alkylation at R1 in the above compounds in-
creased their enzyme inhibition action compared to those com-
pounds which had both O- and N-alkylation (4a, 4b, 4i, increased
IC50 values) or N-alkylation with –C(O)-Ph-Cl (4k) or –CH2–
CH@CH2 (4l). N-alkylation with C2H4Cl (4c) or C3H7 (4d) abolished
the enzyme inhibition potential of the compounds. On the other
hand, N-alkylation at R1 with C4H9 (4e) had increased inhibitory
activity with IC50 value of 61.4 0.69
lmol compared with the
compound 4h, wherein substitution of CH2–CN at R2 site increased
value to 232.1 0.78 lmol.
4. Conclusion
The present work shows that N-alkylation at R1 yielded some
good enzyme inhibitors with IC50 values compared with the stan-
dard inhibitors. Addition of other alkylating agents at N-site may
give more compounds with lower IC50 values. This was found espe-
cially in butyl (e), pentyl (f), benzyl (g) wherein more enzyme inhi-
bition was found and in that of dimethylallyl (m). Substitution at R2
site with CH2–CN was the only active compound with O-ester bond.
Substitution at both O- and N-sites had little effect on the inhibitory
profile of these compounds. Work is in progress on these lines.
Alkylation at amino group gave N-alkylated sulfonamides, that
is, 4c, 4d, 4e, 4f, 4g, 4j, 4k, 4l and 4m. The reaction of larger size
of alkyl halide with sulfonamide 3 was occurred slowly. Acid ha-
lides only reacted with amine group and failed to react with the
carboxylic acid because the resulting anhydride was unstable.
Table 1
Reaction conditions and inhibition studies of N- and O-alkylated sulfonamides
Product
R1
R2
Alkyl/Acyl halide (R–X) Rec. Temp (°C) Rec. Time (Hrs.) Yield
Lipoxygenase
Inhibition at 0.5 mM (%) IC50 (lmol)
3
H
CH3
C2H5
C2H4Cl
C3H7
C4H9
C5H11
CH2–C6H5
H
CH2CH@CH–C6H5
COC6H5
COC6H4Cl
CH2CH@CH2
CH2CH@CH(CH3)2
H
CH3
C2H5
H
H
H
H
H
—
CH3–I
C2H5–I
Cl–C2H4–Cl
C3H7–I
25
25
25
80
25
25
25
100
80
90
80
80
60
60
2
3
3
5
3
4.5
5
6
3
98
74
81
66
68
58
55
63
55
65
42
45
63
57
99.44 0.95
88.50 0.87
97.62 0.93
21.88 1.09
40.01 0.99
99.42 0.88
98.60 0.94
85.13 0.79
97.05 0.84
26.88 0.95
99.03 1.03
98.08 0.97
96.19 0.81
98.71 0.68
139.2 0.75
189.1 0.62
231.3 0.81
>600
4a
4b
4c
4d
4e
4f
4g
4h
4i
>500
C4H9–I
61.4 0.69
68.6 0.43
59.1 0.87
232.1 0.78
>600
91.7 0.61
176.5 0.48
218.6 0.69
15.8 0.57
C5H11–I
Cl–CH2–C6H5
Cl–CH2–CN
CH2–CN
CH2CH@CH–C6H5 Cl–CH2CH@CH–C6H5
15
4j
4k
4l
H
H
H
H
Cl–COC6H5
Cl–COC6H4Cl
Br–CH2CH@CH2
Br–CH2CH@CH(CH3)2
15
18
5
4m
5
Quercetin
Baicalein
—
—
—
—
—
37.12 0.07
22.4 1.3
Enzyme inhibition assays are mean of three independent experiments (mean SEM, n = 3).

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G. Mustafa et al. / Bioorg. Med. Chem. 20 (2012) 2535–2539
3H, CH3), 2.39 (s, 3H. CH3), 3.50 (q, J = 7.2 Hz, 2H. CH2–N), 4.29
5. Experimental
5.1. General methods
(q, J = 6.9 Hz, 2H, CH2–O), 7.07 (d, J = 8.4 Hz, 2H, Ar-H), 7.14 (d,
J = 7.8 Hz, 2H, Ar-H), 7.62 (d, J = 7.8 Hz, 2H, Ar-H), 7.83 (d,
J = 8.4 Hz, 2H, Ar-H).
All the chemicals used were purchased from Merck and Fluka or
BDH and were used without purification except solvents which
were purified through distillation. 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 checked on an electro-
thermal (Griffin 1090) apparatus and are reported as uncorrected.
IR spectra were recorded on a Perkin Elmer 1600-FT spectrometer.
1H NMR and 13C NMR spectra were recorded on Bruker (300, 400
and 600 MHz) AMX spectrometer. Elemental analysis was done
on Vario Micro CHNS Analyzer.
5.3.3. 4-[(2-Chloro-ethyl)-(toluene-4-sulfonyl)-amino]-benzoic
acid (4c)
White crystalline powder; Yield 66%, ratio 1.0, mp 143–144 °C.
Anal. Calcd for C16H16ClNO4S: C, 54.31; H, 4.56; N, 3.96; S, 9.06.
Found: C, 54.19; H, 4.36; N, 3.81; S, 9.01. IR (KBr), cmꢀ1: 1157
(SO2), 1338 (SO2), 1701 (C@O), 3219 (OH). 1H NMR (300 MHz,
CDCl3: CD3OD): d (ppm) = 2.25 (s, 3H, CH3), 3.66 (t, J = 7.2 Hz, 2H,
CH2–Cl), 4.39 (t, J = 7.2 Hz, CH2–N), 7.03, (d, J = 8.4 Hz, 2H, Ar-H),
7.12 (d, J = 7.8 Hz, 2H, Ar-H), 7.59 (d, J = 8.1 Hz, 2H, Ar-H), 7.77
(d, J = 8.4 Hz, 2H, Ar-H).
5.2. Synthesis of 4-(toluene-4-sulfonylamino)-benzoic acid (3)
5.3.4. 4-[Propyl-(toluene-4-sulfonyl)-amino]-benzoic acid (4d)
Colorless crystals; Yield 67%, ratio 0.78, mp 149–150 °C (Lit. mp
147 °C).29 Anal. Calcd for C17H19NO4S: C, 61.24; H, 5.74; N, 4.20; S,
9.62. Found: C, 61.08; H, 5.82; N, 4.31; S, 9.42. IR (KBr), cmꢀ1: 1158
(SO2), 1338 (SO2), 1701 (C@O), 3252 (OH). 1H NMR (300 MHz,
CDCl3: CD3OD): d (ppm) = 0.96 (t, J = 7.2 Hz, 3H, CH3), 1.21–1.31
(m, 2H, CH2–CH3), 2.25 (s, 3H, CH3), 4.16–4.27 (m, 2H, CH2–N),
7.03 (d, J = 8.4 Hz, 2H, Ar-H), 7.12 (d, J = 7.8 Hz, 2H, Ar-H), 7.59
(d, J = 8.1 Hz, 2H, Ar-H), 7.75 (d, J = 8.7 Hz, 2H, Ar-H).
To a solution of p-amino benzoic acid (100 mmol, 13.71 g) and
water (50 mL), sodium carbonate (1 N) was added to adjust the
pH 8. Then added p-toluenesulfonyl chloride (120 mmol, 22.87 g)
and the mixture was stirred at room temperature keeping the pH
of the mixture up to 8.0 with occasional addition of sodium car-
bonate solution. Progress and completion of the reaction was con-
firmed by TLC and conversion of suspension into clear solution.
After 2 h, whole mixture was poured into a beaker and the pH
was adjusted to 2.0 by 1 N HCl. White precipitates were produced
which were filtered and washed with distilled water. Colorless
crystals were produced after recrystallization from methanol.
Yield 98%, mp 231 °C; (Lit. mp 230 °C).27 Anal. Calcd for
5.3.5. 4-[Butyl-(toluene-4-sulfonyl)-amino]-benzoic acid (4e)
Yellow crystals; Yield 57%, ratio 0.83, mp 127–128 °C. Anal.
Calcd for C18H21NO4S: C, 62.23; H, 6.09; N, 4.03; S, 9.23. Found:
C, 62.09; H, 6.11; N, 4.00; S, 9.19. IR (KBr), cmꢀ1: 1157 (SO2),
1339 (SO2), 1689 (C@O), 3487 (NH). 1H NMR (600 MHz, CDCl3): d
(ppm) = 0.96 (t, J = 7.8 Hz, 3H, CH3), 1.41–1.49 (m, 2H, CH2),
1.69–1.76 (m, 2H, CH2), 2.38 (s, 3H, CH3), 4.27 (t, J = 7.2 Hz, 2H,
CH2–N), 7.13 (d, J = 8.7 Hz, 2H, Ar-H), 7.25 (d, J = 8.4, 2H, Ar-H),
7.72 (d, J = 8.4 Hz, 2H, Ar-H), 7.91(d. J = 8.7 Hz, 2H, Ar-H); 13C
NMR (150 MHz, CDCl3): d (ppm) = 13.76, 19.23, 21.58, 30.70,
64.88, 118.95, 126.49, 127.24, 129.85, 131.02, 135.68, 140.82,
144.40, 166.03.
C
14H13NO4S: C, 57.72; H, 4.50; N, 4.81; S, 11.01. Found: C, 57.36;
H, 4.52; N, 4.83; S, 10.98. IR (KBr), cmꢀ1: 1117 (SO2), 1334(SO2),
1705 (C@O), 3215 (OH) 3585 (NH). 1H NMR (300 MHz, CDCl3:
CD3OD): d (ppm) = 2.24 (s, 3H, CH3), 7.02 (d, J = 8.4 Hz, 2H, Ar-H),
7.11 (d, J = 8.1 Hz, 2H, Ar-H), 7.58 (d, J = 8.1 Hz, 2H, Ar-H), 7.76
(d, J = 8.4 Hz, 2H, Ar-H), 9.43 (s, 1H, NH).
5.3. General procedure for N- and O-alkylation (4a–4n)
4-{[(4-Methylphenyl)sulfonyl]amino}benzoic acid (10 mmol,
2.91 g), DMF (10 mL) and n-hexane washed sodium hydride
(30 mmol, 0.72 g) were stirred at room temperature for 40 min fol-
lowed by the addition of alkylating reagent (alkyl iodide/bromide
or acid chloride, 10 mmol). The whole reaction mixture was stirred
till the completion of the reaction (Table 1 for reaction details) and
poured into crushed ice in a beaker. The pH of the mixture was ad-
justed to 4.0 with 1 N HCl. White precipitates were produced, fil-
tered and washed twice with distilled water.
5.3.6. 4-[Pentyl-(toluene-4-sulfonyl)-amino]-benzoic acid (4f)
White crystals; Yield 55%, ratio 0.88, mp 207–208 °C. Anal.
Calcd for C19H23NO4S: C, 63.13; H, 6.41; N, 3.88; S, 8.87. Found:
C, 62.79; H, 6.11; N, 3.64; S, 8.82. IR (KBr), cmꢀ1: 1157 (SO2),
1339 (SO2), 1689 (C@O), 3217 (OH). 1H NMR (300 MHz, CDCl3:
CD3OD): d (ppm) = 0.78 (t, J = 7.8 Hz, 3H, CH3), 1.16–1.28 (m, 4H),
1.60–1.64 (m, 2H, CH2), 2.26 (s, 3H, CH3), 4.14 (t, J = 7.2 Hz, 2H,
CH2–N), 7.04 (d, J = 7.8 Hz, 2H, Ar-H), 7.33 (d, J = 8.1, 2H, Ar-H),
7.60 (d, J = 8.1 Hz, 2H, Ar-H), 7.76 (d, J = 8.4 Hz, 2H, Ar-H).
5.3.1. 4-[Methyl-(toluene-4-sulfonyl)-amino]-benzoic acid
methyl ester (4a)
5.3.7. 4-[Benzyl-(toluene-4-sulfonyl)-amino]-benzoic acid (4g)
Light yellowish powder; Yield 63%, ratio 0.9, mp 107–108 °C.
Anal. Calcd for C21H19NO4S: C, 66.12; H, 5.02; N, 3.67; S, 8.41.
Found: C, 65.92; H, 4.62; N, 3.69; S, 8.37. IR (KBr), cmꢀ1: 1158
(SO2), 1314 (SO2), 1639 (C@O), 3231 (OH). 1H NMR (300 MHz,
CDCl3: CD3OD): d (ppm) = 2.28 (s, 3H, CH3), 5.22 (s, 2H, CH2–N),
7.01–7.31 (m, 7H, Ar-H), 7.42 (d, J = 7.8 Hz, 2H, Ar-H), 7.62 (d,
J = 8.1 Hz, 2H, Ar-H), 7.83 (d, J = 8.1 Hz, 2H, Ar-H).
White crystals; Yield 74%, ratio 1.0, mp 166–167 °C. Anal. Calcd
for C16H17NO4S: C, 60.17; H, 5.37; N, 4.39; S, 10.04. Found: C,
60.09; H, 5.41; N, 4.26; S, 10.01. IR (KBr), cmꢀ1: 1155 (SO2), 1338
(SO2), 1703 (C@O). 1H NMR (300 MHz, CDCl3: CD3OD):
d
(ppm) = 2.39 (s, 3H, CH3), 3.17 (s, 3H, CH3–N), 3.90 (s, 3H, CH3–
O), 7.10 (d, J = 8.7 Hz, 2H, Ar-H), 7.39 (d, J = 8.1 Hz, 2H, Ar-H),
7.69 (d, J = 8.1 Hz, 2H, Ar-H), 7.96 (d, J = 8.4 Hz, 2H, Ar-H).
5.3.8. 4-(Toluene-4-sulfonylamino)-benzoic acid cyanomethyl
ester (4h)
5.3.2. 4-[Ethyl-(toluene-4-sulfonyl)-amino]-benzoic acid ethyl
ester (4b)
Clay color crystals; Yield 55%, ratio 0.9, mp 169–170 °C. Anal.
Calcd for C16H14N2O4S: C, 58.17; H, 4.27; N, 8.48; S, 9.71. Found:
C, 58.03; H, 4.14; N, 8.38; S, 9.62. IR (KBr), cmꢀ1: 1156 (SO2),
1338 (SO2), 1638 (C@O), 3528 (NH). 1H NMR (600 MHz, CDCl3:
DMSO): d (ppm) = 2.37 (s, 3H, CH3), 4.93 (s, 2H, CH2–CN), 7.25 (d,
J = 8.4 Hz, 2H, Ar-H),7.25 (d, J = 8.7 Hz, 2H, Ar-H), 7.74 (d,
White crystals; Yield 81%, ratio 1.0, mp 126–127 °C; (Lit. mp
126 °C).28 Anal. Calcd for C18H21NO4S: C, 62.23; H, 6.09; N, 4.03;
S, 9.23. Found: C, 61.83; H, 6.01; N, 3.96; S, 9.16.IR (KBr), cmꢀ1
:
1091 (SO2), 1337 (SO2), 1690 (C@O). 1H NMR (300 MHz, CDCl3:
CD3OD): d (ppm) = 0.96 (t, J = 7.2 Hz, 3H, CH3), 1.24 (t, J = 6.9 Hz,

G. Mustafa et al. / Bioorg. Med. Chem. 20 (2012) 2535–2539
2539
J = 8.4 Hz, 2H, Ar-H), 7.86 (d, J = 8.7 Hz, 2H, Ar-H), 10.44 (s, 1H,
NH); 13C NMR (150 MHz, CDCl3: DMSO): d (ppm) = 21.10, 48.28,
114.33, 117.71, 121.81, 126.61, 129.26, 130.90, 136.04, 143.23,
143.39, 164.01.
Ar-H), 7.71 (d, J = 8.4 Hz, 2H, Ar-H), 7.92 (d, J = 8.7 Hz, 2H, Ar-H);
13C NMR (150 MHz, CDCl3): d (ppm) = 18.11, 21.57, 25.82, 61.91,
118.46, 119.00, 126.53, 127.24, 129.83, 131.08, 135.63, 139.35,
140.75, 144.41, 165.96.
5.3.9. 4-[(3-Phenyl-allyl)-(toluene-4-sulfonyl)-amino]-benzoic
acid 3-phenyl-allyl ester (4i)
Acknowledgment
Colorless crystals; yield 65%. ratio 0.82, mp 112–113 °C. Anal.
Calcd for C32H29NO4S: C, 73.40; H, 5.58; N, 2.67; S, 6.12. Found:
C, 73.29; H, 5.51; N, 2.64; S, 6.02. IR (KBr), cmꢀ1: 1157 (SO2),
Authors acknowledge Higher Education Commission of Pakistan
for financial support.
1343 (SO2), 1685 (C@O). 1H NMR (600 MHz, CDCl3):
d
Supplementary data
(ppm) = 2.43 (s, 3H, CH3), 4.37 (dd, J = 6.6, 1.2 Hz, 2H, CH2–N),
4.96 (dd, J = 6.6, 1.2 Hz, 2H, CH2–O), 6.05 (t, J = 6.6 Hz, 1H, CH),
6.37 (t, J = 6.00 Hz, 1H, CH), 6.39 (t, J = 6.6 Hz, 1H, CH), 6.73 (s,
1H, CH) 7.18–7.22 (m, 5H, Ar-H), 7.24–7.28 (m, 5H, Ar-H), 7.33
(t, J = 7.8 Hz, 2H, Ar-H), 7.42 (d, J = 7.8 Hz, 2H, Ar-H), 7.49 (d,
J = 8.4 Hz, 2H, Ar-H), 8.00 (d, J = 8.4 Hz, 2H, Ar-H); 13C NMR
(150 MHz, CDCl3): d (ppm) = 21.59, 52.75, 65.74, 122.94, 123.38,
126.42, 126.63, 127.63, 127.96, 128.10, 128.16, 128.52, 128.62,
129.07, 129.61, 130.36, 134.23, 134.51, 134.91, 135.98, 136.06,
143.46, 143.87, 165.65.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.bmc.2012.02.055. These data
include MOL files and InChiKeys of the most important compounds
described in this article.
References and notes
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5.3.10. 4-[Benzoyl-(toluene-4-sulfonyl)-amino]-benzoic acid
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White powder; Yield 42%, ratio 1.0, 218 °C. Anal. Calcd for
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C
21H17NO5S: C, 63.79; H, 4.33; N, 3.54; S, 8.11. Found: C, 62.57;
H, 4.37; N, 3.49; S, 7.03. IR (KBr), cmꢀ1: 1158 (SO2), 1285 (SO2),
1687 (C@O), 3216 (OH). 1H NMR (300 MHz, CDCl3: CD3OD): d
(ppm) = 2.28 (s, 3H, CH3), 7.04–7.08 (m, 3H, Ar-H), 7.15 (d,
J = 8.1 Hz, 2H, Ar-H), 7.34–7.45 (m, 2H, Ar-H), 7.62 (d, J = 8.1 Hz,
2H, Ar-H), 7.75 (d, J = 7.8 Hz, 2H, Ar-H), 7.81 (d, J = 8.7 Hz, 2H, Ar-
H).
5.3.11. 4-[(4-Chloro-benzoyl)-(toluene-4-sulfonyl)-amino]-
benzoic acid (4k)
Colorless crystals; Yield 45%, ratio 1.0, mp 198–200 °C. Anal.
Calcd for C21H16ClNO5S: C, 58.67; H, 3.75; N, 3.26; S, 7.46. Found:
C, 58.61; H, 3.77; N, 3.19; S, 7.45 IR (KBr), cmꢀ1: 1160 (SO2),
1334 (SO2), 1675 (C@O), 3224 (OH). 1H NMR (300 MHz, CDCl3:
CD3OD): d (ppm) = 2.25 (s, 3H, CH3), 7.03 (d, J = 8.7 Hz, 2H, Ar-H),
7.12 (d, J = 8.1 Hz, 2H, Ar-H), 7.30 (d, J = 8.4 Hz, 2H, Ar-H), 7.59
(d, J = 8.1 Hz, 2H, Ar-H), 7.77 (d, J = 8.7 Hz, 2H, Ar-H), 7.86 (d,
J = 8.4 Hz, 2H, Ar-H).
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S.; Graneto, M. J.; Lee, L. F.; Malecha, J. W.; Miyashiro, J. M.; Rogers, R. S.; Rogier,
D. J.; Yu, S. S.; Anderson, G. D.; Burton, E. G.; Cogburn, J. N.; Gregory, S. A.;
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5.3.12. 4-[Allyl-(toluene-4-sulfonyl)-amino]-benzoic acid (4l)
Yellowish brown thick paste; Yield 63%, ratio 0.93, mp 40 °C.
Anal. Calcd for C17H17NO4S: C, 61.61; H, 5.17; N, 4.23; S, 9.68.
Found: C, 61.43; H, 4.98; N, 4.19; S, 9.59. IR (KBr), cmꢀ1: 1158
(SO2), 1341 (SO2), 1695 (C@O), 3239 (OH). 1H NMR (300 MHz,
CDCl3: CD3OD): d (ppm) = 2.28 (s, 3H, CH3), 4.06 (d, J = 6.0 Hz, 2H,
CH2–N), 4.61 (d, J = 6.0 Hz, 1H), 4.66 (d, J = 6.0 Hz, 1H), 5.10–5.29
(m, 1H, CH), 7.09 (d, J = 8.4 Hz, 2H, Ar-H), 7.32 (d, J = 8.1 Hz, 2H,
Ar-H), 7.56 (d, J = 8.1 Hz, 2H, Ar-H), 7.74 (d, J = 8.4 Hz, 2H, Ar-H).
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5.3.13. 4-[(3-Methyl-but-2-enyl)-(toluene-4-sulfonyl)-amino]-
benzoic acid (4m)
Brown powder; Yield 57%, ratio 0.97, mp 172 °C. Anal. Calcd for
C
19H21NO4S: C, 63.49; H, 5.89; N, 3.90; S, 8.92. Found: C, 63.37; H,
5.97; N, 3.82; S, 8.91. IR (KBr), cmꢀ1: 1158 (SO2), 1383 (SO2), 1690
(C@O), 3234 (OH). 1H NMR (600 MHz, CDCl3): d (ppm) = 1.76 (s,
6H, CH3), 2.38 (s, 3H, CH3), 4.77 (d, J = 7.2 Hz, 2H), 5.42 (t,
J = 7.2 Hz, 1H), 7.11(d, J = 8.4 Hz, 2H, Ar-H), 7.24 (d, J = 8.7 Hz, 2H,
29. Piper, J. R.; McCaleb, G. S.; Montgomery, J. A.; Kisliuk, R. L.; Gaumont, Y.;
Sirotnaks, F. M. J. Med. Chem. 1982, 25, 877.