Synthesis and antioxidant activity of a new class of mono- and bis-heterocycles

Article abstract of DOI:10.1002/ardp.201200353

A new class of mono- and bis-heterocycles, 2- arylsulfonylaminosulfonylmethyl-5-styrylsulfonylmethyloxadiazoles, pyrazolyl oxadiazoles, and isoxazolyl oxadiazoles, were synthesized and tested for their antioxidant activity. The styrylsulfonylmethyloxadiazole 5b showed good antioxidant activity when compared with the standard ascorbic acid. Copyright

Full text of DOI:10.1002/ardp.201200353

154
Arch. Pharm. Chem. Life Sci. 2013, 346, 154–162
Full Paper
Synthesis and Antioxidant Activity of a New Class of
Mono- and Bis-Heterocycles
Guda Mallikarjuna Reddy, Putta Ramachandra Reddy, Venkatapuram Padmavathi,
and Adivireddy Padmaja
Department of Chemistry, Sri Venkateswara University, Tirupati, Andhra Pradesh, India
A new class of mono- and bis-heterocycles, 2-arylsulfonylaminosulfonylmethyl-5-styrylsulfonylmethyl-
oxadiazoles, pyrazolyl oxadiazoles, and isoxazolyl oxadiazoles, were synthesized and tested for their
antioxidant activity. The styrylsulfonylmethyloxadiazole 5b showed good antioxidant activity when
compared with the standard ascorbic acid.
Keywords: 1,3-Dipolar cycloaddition / Antioxidant activity / Isoxazolyl oxadiazole / Pyrazolyl oxadiazole /
Styrylsulfonylmethyloxadiazole
Received: September 11, 2012; Revised: November 15, 2012; Accepted: November 22, 2012
DOI 10.1002/ardp.201200353
Introduction
natural products and pharmaceutical drugs based on the
pyrazole and isoxazole ring systems such as celecoxib, valde-
coxib, leflunomide, and cloxacillin have become very import-
ant areas of research in natural product and pharmaceutical
chemistry [11]. So far, extensive work has been generated
for the synthesis of pyrazoles and isoxazoles based on [2þ3]
cycloaddition of 1,3-dipoles to alkynes [12] and olefins
[13–15], condensation of hydrazine and hydroxylamine with
b-diketone equivalents such as propargylic ketones, enones,
and a,b-unsaturated nitriles [16]. As part of our continued
interest to develop biologically active heterocycles, we report
herein the synthesis and bioassay of a new class of mono- and
bis-heterocycles.
Heterocycles are ubiquitous in natural products, pharma-
ceuticals, organic materials, and numerous functional mol-
ecules. Therefore, the interest for developing new, versatile,
and efficient methods for the synthesis of heterocycles has
always been a thread in the synthetic community [1]. The
2,5-disubstituted 1,3,4-oxadiazole motif is of considerable
importance in different areas of chemistry viz., medicinal,
pesticide, polymer, and material science [2]. In drug discovery
and development, the compounds containing oxadiazole
moiety are in late stage clinical trials, including zibotentan
as an anticancer agent [3] and ataluren used for the
treatment of cystic fibrosis [4]. Raltegravir is an oxadiazole
containing antiretroviral drug used for the treatment of Results and discussion
HIV infection.
The 1,3,4-oxadiazoles are prepared by (a) oxidative cycliza-
tion of N-acylhydrazones with various oxidizing agents such
as chloramine T [5], ceric ammonium nitrate [6], FeCl3 [7],
KMnO4 under microwave irradiation [8], (b) cyclodehydration
of 1,2-diacylhydrazines with thionyl chloride, PPA, phos-
phorus oxychloride, H2SO4 [9] and (c) direct reaction of car-
boxylic acids or acyl chlorides with acid hydrazides or
hydrazines [10]. Additionally, a vast number of bioactive
Chemistry
A new series of 2-arylsulfonylaminosulfonylmethyl-5-styrylsul-
fonylmethyloxadiazoles, pyrazolyl oxadiazoles, and isoxazolyl
oxadiazoles were prepared from the simple, multifunctional
starting compounds, methyl 2-((arylsulfonyl)aminosulfonyl)-
acetate (2) and Z-styrylsulfonylacetic acid (4) (Scheme 1).
Compound 2 was obtained by the reaction of arylsulfonamide
(1) with chlorosulfonylmethylacetate in the presence of
Et3N. Treatment of compound 2 with hydrazine hydrate led
to the formation of 2-((arylsulfonyl)aminosulfonyl)acetohydr-
azide (3). The condensation between compounds 3 and 4 in the
presence of POCl3 produced 2-(((arylsulfonyl-)aminosulfonyl)-
methyl)-5-((styrylsulfonyl)methyl)-1,3,4-oxadiazoles (5). The IR
Correspondence: Dr. Adivireddy Padmaja, Department of Chemistry, Sri
Venkateswara University, Tirupati 517 502, Andhra Pradesh, India.
E-mail: adivireddyp@yahoo.co.in
Fax: þ91 877 2249532
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Arch. Pharm. Chem. Life Sci. 2013, 346, 154–162
Antioxidant Activity of New Mono- and Bis-Heterocycles
155
O
O
O
O
O
O
O
O
O
O
O
O
S
S
S
S
S
NH2
N
OMe
N
NHNH2
i
ii
H
H
R
R
R
3
1
2
R a = H
b = Me
c = Cl
(i) ClSO2CH2CO2Me / Et3N / Benzene
(ii) NH2NH2.H2O / Pyridine / MeOH
O
O
O
O
O
R
S
S
O
N
NHNH2
O
O
H
+
S
R
OH
3
4
i
R
N
2
N
5
O
O
O
O
O
O
4
3
1
S
S
S
N
O
H
HA
5
HB
R
O
iii
ii
R
R
R
N N
O
N
N
O
O
O
O
O
O
O
O
O
O
O
O
O
O
S
S
S
S
S
S
S
S
N
N
O
H
H
N
O
O
Ph
Ph
R
Ph
R
N
N
6
7
iv
iv
R
N
N
N
N
O
O
O
O
O
O
O
O
O
S
S
S
S
N
N
H
O
O
H
N
R
Ph
Ph
Ph
R
N
N
8
9
(i) POCl3
R a = H
b = Me
c = Cl
(ii) Ph-CH=NNHPh / Chloramine-T . 3H2O / MeOH
(iii) Ph-CH=NOH / Chloramine-T . 3H2O / MeOH
(iv) Chloranil / Xylene
Scheme 1. Synthesis of mono- and bis-heterocycles.
spectra of compound 5 exhibited absorption bands in the
proton HA displayed a signal in a more downfield region
and merged with aromatic protons. The coupling constant
J ¼ 9.6 Hz indicated that they are in cis geometry. The com-
pound 5a presented a broad singlet at d 10.59 ppm due to NH
and disappeared when D2O was added. The olefin moiety in
compounds 5 was exploited to develop pyrazole and isoxazole
rings by 1,3-dipolar cycloaddition. Thus, the cycloaddition of
regions 1149–1162 and 1302–1315 (SO2), 1560–1577 (CN),
1610–1625 (C C) and 3219–3230 cmꢀ1 (NH). The 1H NMR spec-
–
–
trum of compound 5a showed two singlets at d 5.16, 4.92 ppm
which were assigned to methylene protons attached to C-2 and
C-5, respectively. Apart from these, a doublet was observed at
d 6.72 ppm due to the olefin proton HB while the other olefin
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156
G. Mallikarjuna Reddy et al.
Arch. Pharm. Chem. Life Sci. 2013, 346, 154–162
nitrile imines generated from araldehyde phenylhydrazone in Biological results
the presence of chloramine-T to 5 resulted in tetrasubstituted
pyrazolinyl derivative 2-(((arylsulfonyl)aminosulfonyl)methyl)-
5-((40,50-dihydro-10,30-diphenyl-50-aryl-10H-pyrazol-40-ylsulfonyl)-
methyl)-1,3,4-oxadiazole (6). Likewise, the addition of nitrile
oxides generated from araldoximes in the presence of chlor-
amine-T to 5 gave 2-(((arylsulfonyl)aminosulfonyl)methyl)-5-
((40,50-dihydro-30-phenyl-50-arylisoxazol-40-ylsulfonyl)methyl)-
1,3,4-oxadiazole (7). In the IR spectra of compounds 6 and 7,
the absorption bands observed at 1140–1151 and 1329–1347,
Antioxidant activity
The compounds 5–9 were evaluated for antioxidant property
by 2,20,-diphenyl-1-picrylhydrazyl (DPPH) [17, 18], nitric oxide
(NO) [19, 20], and hydrogen peroxide (H2O2) [21] methods.
The observed data on the antioxidant activity of the
compounds and control drug are shown in Tables 1–3 and
Figs. 1–3. The aim of this study is to identify the potential
heterocyclic compound for antioxidant activity. The com-
pounds 5b, 8b, and 9b showed excellent radical scavenging
activity in all the three methods due to the presence of
electron donating group, Me, in benzene ring when com-
pared with the standard drug ascorbic acid. The compounds
5a, 8a, and 9a exhibited good activity whereas the com-
pounds 5c, 6b, 7b, 8c, and 9c displayed moderate activity.
However, the other compounds showed no activity. Amongst
bis-heterocyclic systems, the aromatized compounds 8 and 9
exhibited greater activity than the corresponding dihydro
compounds 6 and 7. It was also perceived that mono-hetero-
cyclic compound 5b displayed slightly higher activity than
the corresponding bis-heterocyclic systems 8b and 9b. This
may be due to extended conjugation in mono-heterocyclic
systems. However, the compound isoxazole in combination
with oxadiazole 9 exhibited greater activity which may be
due to the presence of two oxygen atoms than the com-
pounds having pyrazole and oxadiazole 8. The IC50 values
of the standard ascorbic acid in DPPH method was found to
be 59.65 mg/mL at 100 mg/mL whereas the IC50 values of the
1565–1585 and 3241–3263 cmꢀ1 were assigned to SO , C N
–
–
and NH, respectively. The H NMR spectra of compounds 6a
2
1
and 7a displayed two doublets at d 5.13, 5.17 and 5.42,
0
0
5.50 ppm due to C5 -H and C4 -H, two singlets at d 5.20,
5.22, and 4.83, 4.96 ppm due to methylene protons attached
to C-2 and C-5, respectively. Moreover, a broad singlet was
observed at d 10.54 in 6a and at 10.62 ppm in 7a due to NH,
which disappeared when D2O was added. The oxidation of
compounds 6 and 7 was carried out to afford the aromatized
compounds. Thus, 2-(((arylsulfonyl)aminosulfonyl)methyl)-5-
((10,30-diphenyl-50-aryl-10H-pyrazol-40-ylsulfonyl)methyl)-1,3,4-
oxadiazole (8) and 2-(((arylsulfonyl)-aminosulfonyl)methyl)-5-
((30-phenyl-50-arylisoxazol-40-ylsulfonyl)methyl)-1,3,4-oxadi-
azole (9) were prepared by the reaction of compounds 6
and 7 with chloranil in xylene. The absence of signals
due to methine protons of pyrazoline and isoxazoline
units confirmed their formation. The structures of the lead
compounds were further established by 13C NMR spectral
data.
Table 1. The in vitro antioxidant activity of 5–9 in the DPPH method.
Compound
Concentration
50 mg/mL
75 mg/mL
100 mg/mL
IC50 mmol/mL
5a
5b
5c
6a
68.19 ꢁ 0.82
75.57 ꢁ 1.06
50.42 ꢁ 0.54
–
70.11 ꢁ 0.42
78.24 ꢁ 0.25
52.37 ꢁ 0.16
–
72.91 ꢁ 0.71
82.45 ꢁ 1.01
57.40 ꢁ 0.33
–
0.075 ꢁ 0.04
0.064 ꢁ 1.08
0.089 ꢁ 0.69
–
6b
6c
55.15 ꢁ 0.36
59.57 ꢁ 1.17
61.85 ꢁ 1.26
0.064 ꢁ 1.32
–
–
–
–
7a
7b
7c
8a
8b
8c
9a
9b
–
–
–
–
58.41 ꢁ 1.87
62.28 ꢁ 1.32
64.76 ꢁ 1.41
0.067 ꢁ 1.86
–
–
–
–
60.48 ꢁ 0.15
70.23 ꢁ 1.38
44.38 ꢁ 0.91
65.38 ꢁ 0.12
73.57 ꢁ 1.03
48.33 ꢁ 1.73
77.15 ꢁ 0.45
–
63.18 ꢁ 0.42
72.08 ꢁ 0.49
46.70 ꢁ 1.07
68.67 ꢁ 0.61
76.24 ꢁ 0.52
50.36 ꢁ 0.78
80.95 ꢁ 0.39
–
66.72 ꢁ 0.96
75.61 ꢁ 1.07
49.81 ꢁ 0.09
71.50 ꢁ 1.42
80.45 ꢁ 1.54
52.17 ꢁ 1.88
83.82 ꢁ 0.81
–
0.061 ꢁ 0.45
0.050 ꢁ 1.66
0.075 ꢁ 1.06
0.063 ꢁ 0.07
0.054 ꢁ 0.22
0.077 ꢁ 1.13
0.183 ꢁ 1.20
–
9c
Ascorbic acid
Blank
(–) Showed no scavenging activity.
Values were the means of three replicates ꢁ SD.
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Arch. Pharm. Chem. Life Sci. 2013, 346, 154–162
Antioxidant Activity of New Mono- and Bis-Heterocycles
157
Table 2. The in vitro antioxidant activity of 5–9 in the nitric oxide
method.
Conclusion
In summary, we prepared a novel series of 2-arylsulfonylami-
nosulfonylmethyl-5-styrylsulfonylmethyloxadiazoles, pyrazolyl
oxadiazoles, and isoxazolyl oxadiazoles from simple com-
pounds 3 and 4 adopting versatile synthetic methodologies.
Among the tested compounds, the styrylsulfonylmethyloxadi-
azole derivative (5b) is a potential antioxidant agent.
Compound
Concentration
50 mg/mL
75 mg/mL
100 mg/mL
5a
5b
5c
6a
62.41 ꢁ 1.15
70.51 ꢁ 0.20
48.57 ꢁ 0.97
–
64.32 ꢁ 1.34
74.14 ꢁ 0.55
50.01 ꢁ 1.42
–
66.15 ꢁ 1.01
76.43 ꢁ 1.50
54.74 ꢁ 1.11
–
6b
6c
7a
7b
7c
8a
8b
8c
52.10 ꢁ 1.29
54.15 ꢁ 1.02
58.67 ꢁ 1.67
–
–
–
Experimental
–
–
–
55.24 ꢁ 1.30
57.37 ꢁ 1.72
60.14 ꢁ 0.47
Chemistry
–
–
–
Melting points were determined in open capillaries on a Mel-
Temp apparatus and are uncorrected. The purity of the com-
pounds was checked by TLC (silica gel H, BDH, ethyl acetate/
hexane, 1:3). The IR spectra were recorded on a Thermo Nicolet IR
200 FT-IR spectrometer as KBr pellets and the wavenumbers are
given in cmꢀ1. The 1H NMR spectra were recorded in DMSO-d6 on
a Bruker-400 spectrometer (400 MHz). The 13C NMR spectra were
recorded in DMSO-d6 on a Bruker spectrometer operating at
100 MHz. All chemical shifts are reported in d (ppm) using
TMS as an internal standard. The mass spectra were recorded
on Jeol JMS-D 300 and Finnigan Mat 1210 B at 70 eV with an
emission current of 100 mA. The microanalyses were performed
on a Perkin-Elmer 240C elemental analyzer. The antioxidant
property was determined by using a Shimadzu UV-2450 spectro-
photometer. The Z-styrylsulfonylacetic acid (4) was prepared by
the literature procedure [22, 23].
58.38 ꢁ 0.59
65.43 ꢁ 1.66
42.81 ꢁ 1.69
60.74 ꢁ 0.16
67.51 ꢁ 1.25
46.29 ꢁ 1.51
78.23 ꢁ 0.17
–
60.65 ꢁ 1.31
68.21 ꢁ 1.81
45.26 ꢁ 1.61
62.33 ꢁ 0.71
69.40 ꢁ 1.05
48.10 ꢁ 1.23
81.46 ꢁ 1.37
–
62.83 ꢁ 1.17
70.20 ꢁ 1.41
48.63 ꢁ 0.31
65.21 ꢁ 0.37
73.43 ꢁ 0.89
50.92 ꢁ 0.77
82.79 ꢁ 0.80
–
9a
9b
9c
Ascorbic acid
Blank
(–) Showed no scavenging activity.
Values were the means of three replicates ꢁ SD.
Table 3. The in vitro antioxidant activity of 5–9 in the H2O2 method.
Compound
Concentration
General procedure for the synthesis of methyl 2-
((arylsulfonyl)aminosulfonyl)acetate (2a–c)
50 mg/mL
75 mg/mL
100 mg/mL
To a solution of chlorosulfonylmethylacetate (1.71 g, 10 mmol)
in benzene (60 mL), arylsulfonamide (1) (10 mmol) and triethyl-
amine (15 mL) in benzene (150 mL) were added dropwise while
stirring. After addition was completed, the mixture was warmed
gently for 5 min. Then, it was cooled and filtered. The filtrate was
washed successively with water, dil. HCl, sat. NaHCO3 solution,
and brine solution. The organic layer was dried over an. Na2SO4
and the solvent was removed in vacuo. The resultant compound
was purified by recrystallization from benzene/cyclohexane.
5a
5b
5c
6a
6b
6c
7a
7b
7c
8a
8b
8c
9a
9b
63.59 ꢁ 1.54
71.42 ꢁ 1.48
49.12 ꢁ 0.81
–
64.72 ꢁ 1.76
75.23 ꢁ 1.25
52.37 ꢁ 1.63
–
69.21 ꢁ 1.85
77.67 ꢁ 1.68
56.01 ꢁ 1.92
–
50.63 ꢁ 1.04
53.47 ꢁ 1.81
55.92 ꢁ 1.96
–
–
–
–
–
–
57.83 ꢁ 0.45
59.08 ꢁ 1.63
61.18 ꢁ 1.45
–
–
–
59.76 ꢁ 1.17
66.70 ꢁ 1.60
43.16 ꢁ 1.10
61.30 ꢁ 1.55
69.27 ꢁ 0.38
46.46 ꢁ 0.79
77.68 ꢁ 0.51
–
60.91 ꢁ 0.73
68.84 ꢁ 1.74
46.48 ꢁ 0.60
63.19 ꢁ 1.86
70.56 ꢁ 0.19
49.79 ꢁ 1.15
79.27 ꢁ 1.29
–
62.15 ꢁ 0.38
70.62 ꢁ 1.89
50.43 ꢁ 0.11
65.77 ꢁ 1.30
72.68 ꢁ 0.21
51.14 ꢁ1.01
83.16 ꢁ 0.44
–
Methyl 2-((phenylsulfonyl)aminosulfonyl)acetate 2a
White solid in 66%; m.p.: 148–1508C; IR (KBr) ymax (cmꢀ1): 1124,
1318 (SO2), 1732 (CO2Me), 3230 (NH); 1H NMR (DMSO-d6) d (ppm):
3.60 (s, 3H, OCH3), 4.42 (s, 2H, CH2), 7.21–7.85 (m, 5H, Ar–H), 10.25
(bs, 1H, NH); 13C NMR (DMSO-d6) d (ppm): 50.2 (OCH3), 54.6 (CH2),
162.5 (CO), 126.2, 127.3, 129.5, 131.5 (aromatic carbons); MS (m/z):
293.33 [Mþ]. Anal. calcd. for C9H11NO6S2: C 36.85, H 3.78, N 4.77.
Found: C 36.47, H 3.89, N 4.82%.
9c
Ascorbic acid
Blank
(–) Showed no scavenging activity.
Values were the means of three replicates ꢁ SD.
Methyl 2-((4-methylphenylsulfonyl)aminosulfonyl)acetate
2b
White solid in 78%; m.p.: 135–1378C; IR (KBr) ymax (cmꢀ1): 1119,
1322 (SO2), 1727 (CO2Me), 3223 (NH); 1H NMR (DMSO-d6) d (ppm):
2.32 (s, 3H, Ar–CH3), 3.58 (s, 3H, OCH3), 4.37 (s, 2H, CH2), 7.19–7.68
(m, 4H, Ar–H), 10.21 (bs, 1H, NH); 13C NMR (DMSO-d6) d (ppm): 24.5
(Ar–CH3), 49.9 (OCH3), 56.7 (CH2), 163.2 (CO), 126.9, 128.4, 133.4,
134.1 (aromatic carbons); MS (m/z): 307.35 [Mþ]. Anal. calcd.
compounds 5b, 8b, and 9b were found to be 33.08, 35.47,
and 33.98 mg/mL. Besides, the perusal of Tables 1–3 indicated
that radical scavenging activity in DPPH, nitric oxide, and
hydrogen peroxide methods increases with increase in
concentration.
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158
G. Mallikarjuna Reddy et al.
Arch. Pharm. Chem. Life Sci. 2013, 346, 154–162
85
5a
80
75
70
65
60
55
50
45
40
5b
5c
6a
6b
6c
7a
7b
7c
8a
8b
8c
9a
9b
9c
Ascorbic acid
50μg/mL
75μg/mL
100μg/mL
Figure 1. The in vitro antioxidant activity of
5–9 in the DPPH method.
Concentration (μg/mL)
85
80
75
70
65
60
55
50
45
40
5a
5b
5c
6a
6b
6c
7a
7b
7c
8a
8b
8c
9a
9b
9c
Ascorbic acid
50μg/mL
75μg/mL
100μg/mL
Figure 2. The in vitro antioxidant activity of 5–9
Concentration (μg/mL)
in the nitric oxide method.
for C10H13NO6S2: C 39.07, H 4.26, N 4.55. Found: C 39.40, H 4.29, N
4.77%.
The solid separated was collected by filtration, dried, and recrys-
tallized from methanol.
Methyl 2-((4-chlorophenylsulfonyl)aminosulfonyl)acetate 2c
White solid in 80%; m.p.: 164–1658C; IR (KBr) ymax (cmꢀ1): 1137,
1327 (SO2), 1739 (CO2Me), 3241 (NH); 1H NMR (DMSO-d6) d (ppm):
3.64 (s, 3H, OCH3), 4.45 (s, 2H, CH2), 7.37–7.91 (m, 4H, Ar–H), 10.33
(bs, 1H, NH); 13C NMR (DMSO-d6) d (ppm): 51.5 (OCH3), 55.4 (CH2),
162.7 (CO), 123.2, 125.7, 130.6, 134.1 (aromatic carbons); MS (m/z):
327.77 [Mþ]. Anal. calcd. for C9H10ClNO6S2: C 32.98, H 3.07,
N 4.27. Found: C 33.39, H 3.28, N, 4.63%.
2-((Phenylsulfonyl)aminosulfonyl)acetohydrazide 3a
White solid in 75%; m.p.: 166–1688C; IR (KBr) ymax (cmꢀ1): 1150,
1321 (SO2), 1647 (CONH), 3242 (NH), 3335, 3441 (NH2); 1H NMR
(DMSO-d6) d (ppm): 3.91 (s, 2H, CH2), 4.34 (bs, 2H, NH2), 7.31–7.69
(m, 5H, Ar–H), 9.39 (bs, 1H, CO–NH), 10.45 (bs, 1H, NH–SO2);
13C NMR (DMSO-d6) d (ppm): 56.2 (CH2), 159.3 (CO), 124.5,
125.9, 127.4, 132.9 (aromatic carbons); MS (m/z): 293.33 [Mþ].
Anal. calcd. for C8H11N3O5S2: C 32.75, H 3.78, N 14.32. Found:
C 32.52, H 3.65, N, 14.72%.
General procedure for the synthesis of 2-((arylsulfonyl)-
aminosulfonyl)acetohydrazide (3a–c)
2-((4-Methylphenylsulfonyl)aminosulfonyl)acetohydrazide
3b
A
mixture of compound 2 (10 mmol), hydrazine hydrate
(0.53 mL, 11 mmol), methanol (6 mL), and three drops of pyr-
idine was refluxed for 5–7 h. The reaction mixture was cooled.
White solid in 71%; m.p.: 152–1548C; IR (KBr) ymax (cmꢀ1): 1144,
1316 (SO2), 1643 (CONH), 3237 (NH), 3329, 3435 (NH2); 1H NMR
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Arch. Pharm. Chem. Life Sci. 2013, 346, 154–162
Antioxidant Activity of New Mono- and Bis-Heterocycles
159
85
80
75
70
65
60
55
50
45
40
5a
5b
5c
6a
6b
6c
7a
7b
7c
8a
8b
8c
9a
9b
9c
Ascorbic acid
μ
μ
μ
100 g/mL
50 g/mL
75 g/mL
Figure 3. The in vitro antioxidant activity of 5–9
Concentration (μg/mL)
in the hydrogen peroxide method.
(DMSO-d6) d (ppm): 2.30 (s, 3H, Ar–CH3), 3.85 (s, 2H, CH2), 4.22
(bs, 2H, NH2), 7.23–7.37 (m, 4H, Ar–H), 9.34 (bs, 1H, CO–NH), 10.38
(bs, 1H, NH–SO2); 13C NMR (DMSO-d6) d (ppm): 23.2 (Ar–CH3), 54.3
(CH2), 157.6 (CO), 121.9, 123.2, 126.6, 129.5, 132.4 (aromatic
carbons); MS (m/z): 307.35 [Mþ]. Anal. calcd. for C9H13N3O5S2: C
35.17, H 4.26, N 13.67; Found: C 35.59, H 4.73, N 13.89%.
MS (m/z): 483.55 [Mþ]. Anal. calcd. for C18H17N3O7S3: C 44.71,
H 3.54, N 8.69. Found: C 44.85, H 3.59, N 8.99%.
2-(((4-Methylphenylsulfonyl)aminosulfonyl)methyl)-5-
((4-methylstyrylsulfonyl)methyl)-1,3,4-oxadiazole 5b
White solid in 61%; m.p.: 115–1178C; IR (KBr) ymax (cmꢀ1): 1149,
1
1309 (SO ), 1560 (C N), 1610 (C C), 3219 (NH); H NMR (DMSO-d )
–
–
–
–
2
6
2-((4-Chlorophenylsulfonyl)aminosulfonyl)acetohydrazide
d (ppm): 2.37 and 2.41 (s, 6H, Ar–CH3), 4.85 (s, 2H, CH2-(C-5)), 5.12
(s, 2H, CH2-(C-2)), 6.69 (d, 1H, HB, J ¼ 9.2 Hz), 7.15–7.62 (m, 9H, HA
and Ar–H), 10.58 (bs, 1H, NH); 13C NMR (DMSO-d6) d (ppm): 21.7
and 22.5 (Ar–CH3), 42.9 (CH2-(C-5)), 48.7 (CH2-(C-2)), 121.2 (C-HB),
138.5 (C-HA), 156.9 (C-5), 157.8 (C-2), 123.4, 124.6, 125.2, 127.4,
128.1, 129.3, 130.5, 131.7 (aromatic carbons); MS (m/z): 511.61
[Mþ]. Anal. calcd. for C20H21N3O7S3: C 46.95, H 4.11, N 8.21;
Found: C 46.57, H 4.45, N 8.33%.
3c
White solid in 79%; m.p.: 163–1658C; IR (KBr) ymax (cmꢀ1): 1158,
1324 (SO2), 1651 (CONH), 3248 (NH), 3341, 3450 (NH2); 1H NMR
(DMSO-d6) d (ppm): 3.98 (s, 2H, CH2), 4.42 (bs, 2H, NH2), 7.39–7.47
(m, 4H, Ar–H), 9.47 (bs, 1H, CO–NH), 10.52 (bs, 1H, NH–SO2);
13C NMR (DMSO-d6) d (ppm): 58.8 (CH2), 162.3 (CO), 124.1,
125.7, 128.4, 135.2 (aromatic carbons); MS (m/z): 327.77 [Mþ].
Anal. calcd. for C8H10ClN3O5S2: C 29.31, H 3.07, N 12.81.
Found: C 29.39, H 3.52, N 12.89%.
2-(((4-Chlorophenylsulfonyl)aminosulfonyl)methyl)-5-
((4-chlorostyrylsulfonyl)methyl)-1,3,4-oxadiazole 5c
White solid in 65%; m.p.: 139–1418C; IR (KBr) ymax (cmꢀ1): 1162,
General procedure for the synthesis of 2-(((arylsulfonyl)-
aminosulfonyl)methyl)-5-((styrylsulfonyl)methyl)-1,3,4-
oxadiazole (5a–c)
To an equimolar mixture of compounds 3 (10 mmol) and 4
(10 mmol), POCl3 (7 mL) was added and heated under reflux
for 6–8 h. The excess POCl3 was removed under reduced pressure
and the residue was poured onto crushed ice. The resulting
precipitate was filtered, washed with saturated sodium bicarbon-
ate solution and then with water. It was dried and recrystallized
from ethanol.
1
1315 (SO ), 1577 (C N), 1625 (C C), 3230 (NH); H NMR (DMSO-d )
–
–
–
–
2
6
d (ppm): 4.98 (s, 2H, CH2-(C-5)), 5.23 (s, 2H, CH2-(C-2)), 6.75
(d, 1H, HB, J ¼ 9.8 Hz), 7.36–7.89 (m, 9H, HA and Ar–H), 10.60
(bs, 1H, NH); 13C NMR (DMSO-d6) d (ppm): 48.3 (CH2-(C-5)), 51.5
(CH2-(C-2)), 123.5 (C-HB), 141.1 (C-HA), 157.5 (C-5), 159.2 (C-2), 127.9,
128.3, 129.1, 129.8, 130.4, 131.6, 133.8, 137.2 (aromatic carbons);
MS (m/z): 552.45 [Mþ]. Anal. calcd. for C18H15Cl2N3O7S3: C 39.13,
H 2.73, N 7.60. Found: C 38.82, H 2.98, N 7.41%.
General procedure for the synthesis of 2-(((arylsulfonyl)-
aminosulfonyl)methyl)-5-((40,50-dihydro-10,30-diphenyl-50-
aryl-10H-pyrazol-40-ylsulfonyl)methyl)-1,3,4-oxadiazole
(6a–c)
2-(((Phenylsulfonyl)aminosulfonyl)methyl)-5-
((styrylsulfonyl)methyl)-1,3,4-oxadiazole 5a
White solid in 63%; m.p.: 128–1308C; IR (KBr) ymax (cmꢀ1): 1154,
1
1302 (SO ), 1565 (C N), 1614 (C C), 3224 (NH); H NMR (DMSO-d )
–
–
–
–
The compound 5 (1 mmol), araldehyde phenylhydrazone
2
6
d (ppm): 4.92 (s, 2H, CH2-(C-5)), 5.16 (s, 2H, CH2-(C-2)), 6.72
(d, 1H, HB, J ¼ 9.6 Hz), 7.35–7.86 (m, 11H, HA and Ar–H), 10.59
(bs, 1H, NH); 13C NMR (DMSO-d6) d (ppm): 45.2 (CH2-(C-5)), 49.2
(CH2-(C-2)), 122.3 (C-HB), 141.3 (C-HA), 158.2 (C-5), 159.7 (C-2), 125.2,
126.6, 127.3, 128.9, 130.2, 131.4, 132.7, 133.1 (aromatic carbons);
(1.2 mmol) and chloramine-T (0.33 g, 1.2 mmol) in methanol
(20 mL) were refluxed for 20–22 h. The precipitated inorganic
salts were filtered off. The filtrate was concentrated and the
residue was extracted with dichloromethane. The organic layer
was washed with water, brine and dried (an. Na2SO4). The solvent
ß 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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160
G. Mallikarjuna Reddy et al.
Arch. Pharm. Chem. Life Sci. 2013, 346, 154–162
2-(((Phenylsulfonyl)aminosulfonyl)methyl)-5-((40,50-
was removed under vacuum. The resultant residue was purified
by column chromatography (silica gel, 60–120 mesh) using hex-
ane/ethyl acetate (4:1) as eluent.
dihydro-30-phenyl-50-phenylisoxazol-40-ylsulfonyl)methyl)-
1,3,4-oxadiazole 7a
White solid in 70%; m.p.: 161–1638C; IR (KBr) ymax (cmꢀ1): 1148,
2-(((Phenylsulfonyl)aminosulfonyl)methyl)-5-((40,50-
dihydro-10,30-diphenyl-50-phenyl-10H-pyrazol-40-
ylsulfonyl)methyl)-1,3,4-oxadiazole 6a
1336 (SO ), 1570 (C N), 3245 (NH); 1H NMR (DMSO-d6) d (ppm):
–
–
2
4.96 (s, 2H, CH2-(C-5)), 5.17 (d, 1H, C50-H, J ¼ 7.2 Hz), 5.22 (s, 2H,
CH2-(C-2)), 5.50 (d, 1H, C40-H, J ¼ 7.2 Hz), 7.34–7.81 (m, 15H, Ar–H),
10.62 (bs, 1H, NH); 13C NMR (DMSO-d6) d (ppm): 49.7 (CH2-(C-5)), 55.2
(CH2-(C-2)), 63.2 (C-50), 87.2 (C-40), 157.6 (C-30), 159.5 (C-2), 160.2 (C-5),
127.9, 129.5, 130.3, 131.1, 131.9, 132.3, 133.7, 134.4 (aromatic
carbons); MS (m/z): 602.68 [Mþ]. Anal. calcd. for C25H22N4O8S3: C
49.82, H 3.67, N 9.29. Found: C 49.66, H 3.83, N 9.50%.
Pale yellow solid in 64%; m.p.: 173–1758C; IR (KBr) ymax (cmꢀ1):
1145, 1332 (SO ), 1580 (C N), 3252 (NH); 1H NMR (DMSO-d6)
–
–
2
d (ppm): 4.83 (s, 2H, CH2-(C-5)), 5.13 (d, 1H, C50-H, J ¼ 7.3 Hz),
5.20 (s, 2H, CH2-(C-2)), 5.42 (d, 1H, C40-H, J ¼ 7.3 Hz), 7.28–7.82
(m, 20H, Ar–H), 10.54 (bs, 1H, NH); 13C NMR (DMSO-d6) d (ppm):
49.5 (CH2-(C-5)), 53.7 (CH2-(C-2)), 66.4 (C-50), 86.2 (C-40), 158.2 (C-30),
159.1 (C-5), 159.4 (C-2), 126.5, 127.6, 128.3, 128.9, 129.7, 130.8,
132.3, 133.5, 134.2, 135.7, 136.1, 136.9 (aromatic carbons): MS
(m/z): 677.78 [Mþ]. Anal. calcd. for C31H27N5O7S3: C 54.93, H 4.01,
N 10.33; Found: C 55.42, H 4.17, N 10.65%.
2-(((4-Methylphenylsulfonyl)aminosulfonyl)methyl)-5-
((40,50-dihydro-30-phenyl-50-(4-methylphenyl)isoxazol-40-
ylsulfonyl)methyl)-1,3,4-oxadiazole 7b
White solid in 68%; m.p.: 150–1528C; IR (KBr) ymax (cmꢀ1): 1140,
1
–
1343 (SO ), 1565 (C N), 3241 (NH); H NMR (DMSO-d ) d (ppm): 2.34
–
2
6
and 2.47 (s, 6H, Ar–CH3), 5.07 (s, 2H, CH2-(C-5)), 5.14 (d, 1H, C50-H,
J ¼ 6.9 Hz), 5.26 (s, 2H, CH2-(C-2)), 5.48 (d, 1H, C40-H, J ¼ 6.9 Hz),
7.28–7.88 (m, 13H, Ar–H), 10.57 (bs, 1H, NH); 13C NMR (DMSO-d6) d
(ppm): 23.4 and 25.1 (Ar–CH3), 48.6 (CH2-(C-5)), 54.8 (CH2-(C-2)), 62.7
(C-50), 85.6 (C-40), 157.9 (C-30), 158.2 (C-2), 160.8 (C-5), 126.2, 127.4,
139.7, 130.3, 131.5, 132.2, 132.9, 133.5 (aromatic carbons); MS (m/z):
630.74 [Mþ]. Anal. calcd. for C27H26N4O8S3: C 51.41, H 4.15, N 8.88.
Found: C 51.59, H 4.38, N 9.07%.
2-(((4-Methylphenylsulfonyl)aminosulfonyl)methyl)-5-
((40,50-dihydro-10,30-diphenyl-50-(4-methylphenyl)-10H-
pyrazol-40-ylsulfonyl)methyl)-1,3,4-oxadiazole 6b
Pale yellow solid in 60%; m.p.: 166–1688C; IR (KBr) ymax (cmꢀ1):
1142, 1329 (SO ), 1576 (C N), 3249 (NH); 1H NMR (DMSO-d6)
–
–
2
d (ppm): 2.32 and 2.41 (s, 6H, Ar–CH3), 4.79 (s, 2H, CH2-(C-5)),
5.09 (d, 1H, C50-H, J ¼ 7.1 Hz), 5.18 (s, 2H, CH2-(C-2)), 5.40 (d, 1H,
C40-H, J ¼ 7.1 Hz), 7.21–7.65 (m, 18H, Ar–H), 10.49 (bs, 1H, NH);
13C NMR (DMSO-d6) d (ppm): 22.5 and 23.2 (Ar–CH3), 48.2 (CH2-
(C-5)), 53.2 (CH2-(C-2)), 65.7 (C-50), 85.8 (C-40), 156.8 (C-30), 157.9
(C-2), 158.7 (C-5), 125.8, 126.1, 127.3, 127.9, 128.4, 130.1, 131.6,
132.5, 133.8, 134.2, 135.1, 135.9 (aromatic carbons); MS (m/z):
705.83 [Mþ]. Anal. calcd. for C33H31N5O7S3: C 56.15, H 4.42,
N 9.92. Found: C 56.37, H 4.59, N 10.03%.
2-(((4-Chlorophenylsulfonyl)aminosulfonyl)methyl)-5-
((40,50-dihydro-30-phenyl-50-(4-chlorophenyl)isoxazol-40-
ylsulfonyl)methyl)-1,3,4-oxadiazole 7c
White solid in 76%; m.p.: 179–1818C; IR (KBr) ymax (cmꢀ1): 1144,
1347 (SO ), 1572 (C N), 3250 (NH); 1H NMR (DMSO-d6) d (ppm):
–
–
2
5.21 (d, 1H, C50-H, J ¼ 7.4 Hz), 5.26 (s, 2H, CH2-(C-5)), 5.34 (s, 2H,
CH2-(C-2)), 5.60 (d, 1H, C40-H, J ¼ 7.4 Hz), 7.38–7.93 (m, 13H,
Ar–H), 10.65 (bs, 1H, NH); 13C NMR (DMSO-d6) d (ppm): 50.4
(CH2-(C-5)), 55.9 (CH2-(C-2)), 64.1 (C-40), 89.5 (C-50), 158.2 (C-30),
159.8 (C-2), 161.6 (C-5), 128.7, 129.9, 132.5, 133.7, 134.6, 136.5,
137.1, 137.8 (aromatic carbons); MS (m/z): 671.58 [Mþ]. Anal. calcd.
for C25H20Cl2N4O8S3: C 44.71, H 3.00, N 8.34. Found: C 45.01,
H 2.85, N 8.42%.
2-(((4-Chlorophenylsulfonyl)aminosulfonyl)methyl)-5-
((40,50-dihydro-10,30-diphenyl-50-(4-chlorophenyl)-10H-
pyrazol-40-ylsulfonyl)methyl)-1,3,4-oxadiazole 6c
Pale yellow solid in 65%; m.p.: 185–1868C; IR (KBr) ymax (cmꢀ1):
1151, 1337 (SO ), 1585 (C N), 3263 (NH); 1H NMR (DMSO-d6)
–
–
2
d (ppm): 4.85 (s, 2H, CH2-(C-5)), 5.18 (d, 1H, C50-H, J ¼ 7.6 Hz),
5.24 (s, 2H, CH2-(C-2)), 5. 45 (d, 1H, C40-H, J ¼ 7.6 Hz), 7.32–7.91
(m, 18H, Ar–H), 10.58 (bs, 1H, NH); 13C NMR (DMSO-d6) d (ppm):
51.2 (CH2-(C-5)), 54.5 (CH2-(C-2)), 68.1 (C-50), 86.9 (C-40), 158.7 (C-30),
159.9 (C-5), 160.5 (C-2), 126.5, 127.6, 128.3, 129.6, 130.7, 131.2,
132.7, 134.3, 135.9, 136.7, 137.2, 137.7 (aromatic carbons); MS
(m/z): 746.68 [Mþ]. Anal. calcd. for C31H25Cl2N5O7S3: C 49.86,
H 3.37, N 9.37. Found: C 49.96, H 3.82, N 9.71%.
General procedure for the synthesis of 2-(((arylsulfonyl)-
aminosulfonyl)methyl)-5-((10,30-diphenyl-50-aryl-10H-
pyrazol-40-ylsulfonyl)methyl)-1,3,4-oxadiazole (8a–c)/2-
(((arylsulfonyl)aminosulfonyl)methyl)-5-((30-phenyl-50-
arylisoxazol-40-ylsulfonyl)methyl)-1,3,4-oxadiazole (9a–c)
A solution of 6/7 (1 mmol) in xylene (10 mL) and chloranil
(0.29 g, 1.2 mmol) was refluxed for 25–30 h. Then, it was treated
with a 5% sodium hydroxide solution. The organic extract was
separated, repeatedly washed with water and dried (an. Na2SO4).
The solvent was removed in vacuo. The resultant solid was recrys-
tallized from 2-propanol.
General procedure for the synthesis of 2-(((arylsulfonyl)-
aminosulfonyl)methyl)-5-((40,50-dihydro-30-phenyl-50-
arylisoxazol-40-ylsulfonyl)methyl)-1,3,4-oxadiazole (7a–c)
A mixture of compound 5 (1 mmol), araldoxime (1.2 mmol),
chloramine-T (0.33 g, 1.2 mmol) and methanol (20 mL) was
refluxed for 16–18 h. The precipitated inorganic salts were fil-
tered off. The filtrate was concentrated and the residue was
extracted with dichloromethane. The organic layer was washed
with water, brine and dried (an. Na2SO4). The solvent was
removed under reduced pressure. The resultant residue was
purified by column chromatography (silica gel, 60–120 mesh)
using hexane/ethyl acetate (4:1) as eluent.
2-(((Phenylsulfonyl)aminosulfonyl)methyl)-5-((10,30-
diphenyl-50-phenyl-10H-pyrazol-40-ylsulfonyl)methyl)-
1,3,4-oxadiazole 8a
White solid in 67%; m.p.: 186–1878C; IR (KBr) ymax (cmꢀ1): 1135,
1
1335 (SO ), 1570 (C N), 1633 (C C), 3277 (NH); H NMR (DMSO-d )
–
–
–
–
2
6
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Arch. Pharm. Chem. Life Sci. 2013, 346, 154–162
Antioxidant Activity of New Mono- and Bis-Heterocycles
161
d (ppm): 5.25 (s, 2H, CH2-(C-5)), 5.36 (s, 2H, CH2-(C-2)), 7.13–7.77
(m, 20H, Ar–H), 10.59 (bs, 1H, NH); 13C NMR (DMSO-d6) d (ppm):
46.2 (CH2-(C-5)), 53.2 (CH2-(C-2)), 138.5 (C-40), 149.4 (C-30), 150.5
(C-50), 158.2 (C-5), 158.7 (C-2), 124.5, 125.0, 125.8, 126.2, 127.4,
128.1, 129.3, 130.7, 131.1, 132.8, 133.7, 134.3 (aromatic carbons);
MS (m/z): 675.77 [Mþ]. Anal. calcd. for C31H25N5O7S3: C 55.09,
H 3.73, N 10.36. Found: C 55.54, H 4.02, N 10.49%.
for C27H24N4O8S3: C 51.58, H 3.84, N 8.91. Found: C 51.93,
H 4.15, N 9.23%.
2-(((4-Chlorophenylsulfonyl)aminosulfonyl)methyl)-5-((30-
phenyl-50-(4-chlorophenyl)isoxazol-40-ylsulfonyl)methyl)-
1,3,4-oxadiazole 9c
White solid in 78%; m.p.: 182–1848C; IR (KBr) ymax (cmꢀ1): 1132,
1
1339 (SO ), 1590 (C N), 1628 (C C), 3283 (NH); H NMR (DMSO-d )
–
–
–
–
2
6
2-(((4-Methylphenylsulfonyl)aminosulfonyl)methyl)-5-
((10,30-diphenyl-50-(4-methylphenyl)-10H-pyrazol-40-
ylsulfonyl)methyl)-1,3,4-oxadiazole 8b
d (ppm): 5.42 (s, 2H, CH2-(C-5)), 5.56 (s, 2H, CH2-(C-2)), 7.36–7.97
(m, 13H, Ar–H), 10.76 (bs, 1 NH); 13C NMR (DMSO-d6) d (ppm): 49.3
(CH2-(C-5)), 54.9 (CH2-(C-2)), 143.8 (C-40), 148.4 (C-30), 154.3 (C-50),
160.3 (C-5), 161.1 (C-2), 127.9, 129.2, 130.3, 131.4, 133.2, 133.9,
134.5, 135.2 (aromatic carbons); MS (m/z): 669.56 [Mþ]. Anal. calcd.
for C25H18Cl2N4O8S3: C 44.84, H 2.70, N 8.36. Found: C 45.05,
H 3.14, N 8.23%.
White solid in 64%; m.p.: 173–1758C; IR (KBr) ymax (cmꢀ1): 1131,
1
1333 (SO ), 1573 (C N), 1629 (C C), 3272 (NH); H NMR (DMSO-d )
–
–
–
–
2
6
d (ppm): 2.43 and 2.51 (s, 6H, Ar–CH3), 5.15 (s, 2H, CH2-(C-5)), 5.29
(s, 2H, CH2-(C-2)), 6.97–7.65 (m, 18H, Ar–H), 10.57 (bs, 1H, NH);
13C NMR (DMSO-d6) d (ppm): 22.5 and 22.9 (Ar–CH3), 45.8 (CH2-
(C-5)), 53.8 (CH2-(C-2)), 138.1 (C-40), 149.2 (C-30), 150.8 (C-50), 157.3
(C-5), 158.4 (C-2), 123.9, 124.5, 125.2, 126.5, 127.2, 127.9, 128.4,
128.9, 129.3, 131.7, 132.5, 133.6 (aromatic carbons); MS (m/z):
703.82 [Mþ]. Anal. calcd. for C33H29N5O7S3: C 56.31, H 4.15,
N 9.94; Found: C 55.82, H 4.57, N 10.41%.
Biological assays
Antioxidant activity
The compounds 5–9 were tested for antioxidant property by
DPPH, nitric oxide, and H2O2 methods.
DPPH radical scavenging activity
2-(((4-Chlorophenylsulfonyl)aminosulfonyl)methyl)-5-
((10,30-diphenyl-50-(4-chlorophenyl)-10H-pyrazol-40-
ylsulfonyl)methyl)-1,3,4-oxadiazole 8c
The hydrogen atom or electron donation ability of the com-
pounds was measured from the bleaching of the purple colored
methanol solution of DPPH radical. The spectrophotometric
assay uses the stable radical DPPH as a reagent. To 4 mL of
0.004% w/v methanol solution of DPPH, 1 mL of various concen-
trations of the test compounds (50, 75, and 100 mg/mL) in meth-
anol were added. After 30 min incubation period at room
temperature, the absorbance was read against blank at
517 nm. Ascorbic acid was used as the standard. The percent
of inhibition (I%) of free radical production from DPPH was
calculated by the following equation
White solid in 71%; m.p.: 191–1928C; IR (KBr) ymax (cmꢀ1): 1147,
1
1340 (SO ), 1582 (C N), 1635 (C C), 3286 (NH); H NMR (DMSO-d )
–
–
–
–
2
6
d (ppm): 5.31 (s, 2H, CH2-(C-5)), 5.40 (s, 2H, CH2-(C-2)), 7.26–7.96
(m, 18H, Ar–H), 10.64 (bs, 1 NH); 13C NMR (DMSO-d6) d (ppm): 47.2
(CH2-(C-5)), 53.9 (CH2-(C-2)), 139.2 (C-40), 150.1 (C-30), 151.5 (C-50),
159.24 (C-5), 159.8 (C-2), 125.4, 126.1, 126.7, 127.5, 128.3, 130.3,
131.6, 132.2, 133.9, 134.8, 135.4, 136.5 (aromatic carbons);
MS (m/z): 744.66 [Mþ]. Anal. calcd. for C31H23 Cl2N5O7S3: C 50.00,
H 3.11, N 9.40. Found: C 50.17, H 3.34, N 9.67%.
ꢀ
ꢁ
Acontrol ꢀ Asample
I % ¼
ꢂ 100
2-(((Phenylsulfonyl)aminosulfonyl)methyl)-5-((30-phenyl-
Ablank
50-phenylisoxazol-40-ylsulfonyl)-methyl)-1,3,4-oxadiazole
9a
where Acontrol is the absorbance of the control reaction (containing
methanolic DPPH and ascorbic acid), Asample is the absorbance of
the test compound (containing methanolic DPPH and test com-
pound) and Ablank is the absorbance of the blank (containing only
methanolic DPPH). Tests were carried out in triplicate.
White solid in 74%; m.p.: 169–1718C; IR (KBr) ymax (cmꢀ1): 1129,
1
1330 (SO ), 1584 (C N), 1624 (C C), 3279 (NH); H NMR (DMSO-d )
–
–
–
–
2
6
d (ppm): 5.34 (s, 2H, CH2-(C-5)), 5.52 (s, 2H, CH2-(C-2)), 7.31–7.93
(m, 15H, Ar–H), 10.72 (bs, 1H, NH); 13C NMR (DMSO-d6) d (ppm):
48.5 (CH2-(C-5)), 54.1 (CH2-(C-2)), 142.5 (C-40), 147.2 (C-30), 153.7
(C-50), 159.1 (C-2), 159.7 (C-5), 126.4, 128.8, 129.2, 130.7, 131.5,
131.9, 132.3, 133.5 (aromatic carbons); MS (m/z): 600.67 [Mþ].
Anal. calcd. for C25H20N4O8S3: C 49.99, H 3.35, N 9.32. Found:
C 49.57, H 3.39, N 9.65%.
Nitric oxide (NO) scavenging activity
Nitric oxide scavenging activity was measured by slightly modified
methods of Green et al. [19] and Marcocci et al. [20]. Nitric oxide
radicals (NO) were generated from sodium nitroprusside. One
milliliter of sodium nitroprusside (10 mM) and 1.5 mL of phos-
phate buffer saline (0.2 M, pH 7.4) were added to different con-
centrations (50, 75, and 100 mg/mL) of the test compounds and
incubated at 258C for 150 min. After incubation, 1 mL of the
reaction mixture was treated with 1 mL of Griess reagent (1%
sulfanilamide, 2% H3PO4, and 0.1% naphthylethylenediamine
dihydrochloride). The absorbance of the chromatophore was
measured at 546 nm. Ascorbic acid was used as standard. Nitric
oxide scavenging activity was calculated by the following equation
2-(((4-Methylphenylsulfonyl)aminosulfonyl)methyl)-5-((30-
phenyl-50-(4-methylphenyl)isoxazol-40-ylsulfonyl)methyl)-
1,3,4-oxadiazole 9b
White solid in 72%; m.p.: 158–1608C; IR (KBr) ymax (cmꢀ1): 1124,
1
1327 (SO ), 1579 (C N), 1619 (C C), 3271 (NH); H NMR (DMSO-d )
–
–
–
–
2
6
d (ppm): 2.39 and 2.46 (s, 6H, Ar–CH3), 5.28 (s, 2H, CH2-(C-5)), 5.48
(s, 2H, CH2-(C-2)), 7.18–7.82 (m, 13H, Ar–H), 10.68 (bs, 1H, NH);
13C NMR (DMSO-d6) d (ppm): 23.9 and 24.9 (Ar–CH3), 48.1 (CH2-
(C-5)), 53.7 (CH2-(C-2)), 142.1 (C-40), 146.8 (C-30), 153.4 (C-50), 158.4
(C-2), 159.1 (C-5), 125.7 127.2, 128.4, 129.5, 130.6, 131.4, 131.8,
132.2 (aromatic carbons); MS (m/z): 628.72 [Mþ]. Anal. calcd.
ꢀ
ꢁ
Acontrol ꢀ Asample
% of scavenging ¼
ꢂ 100
Ablank
ß 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com

162
G. Mallikarjuna Reddy et al.
Arch. Pharm. Chem. Life Sci. 2013, 346, 154–162
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where Acontrol is the absorbance of the control reaction (containing
all reagents and Ascorbic acid), Asample is the absorbance of the test
compound (containing all reagents and test compound) and Ablank
is the absorbance of the blank (containing only reagents). Tests
were carried out in triplicate.
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Hydrogen peroxide (H2O2) scavenging activity
The H2O2 scavenging ability of the test compound was deter-
mined according to the method of Ruch et al. [21]. A solution
of H2O2 (40 mM) was prepared in phosphate buffer (pH 7.4). 10,
25, 50, 75, and 100 mg/mL concentrations of the test compounds
in 3.4 mL phosphate buffer were added to H2O2 solution (0.6 mL,
40 mM). The absorbance value of the reaction mixture was
recorded at 230 nm. The percent of scavenging of H2O2 was
calculated by the following equation
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ꢀ
ꢁ
ðAcontrol ꢀ Asample
Þ
% of scavenging ¼
ꢂ 100
Ablank
where Acontrol is the absorbance of the control reaction (contain-
ing all reagents and ascorbic acid), Asample is the absorbance of
the test compound (containing all reagents and test compound)
and Ablank is the absorbance of the blank (containing only
reagents). Tests were carried out in triplicate.
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The authors are grateful to the Council of Scientific and Industrial Research
(CSIR), New Delhi, for financial assistance under major research project.
One of the authors, P. Ramachandra Reddy, is thankful to CSIR, New Delhi,
India for the sanction of Junior Research Fellowship.
[14] V. Padmavathi, C. Prema kumari, B. C. Venkatesh, A. Padmaja,
Eur. J. Med. Chem. 2011, 46, 5317–5326.
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The authors have declared no conflict of interest.
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ß 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
www.archpharm.com