Synthesis, antimicrobial and cytotoxic activities of 1,3,4-oxadiazoles, 1,3,4-thiadiazoles and 1,2,4-triazoles

Article abstract of DOI:10.1016/j.ejmech.2008.10.012

A new class of 1,3,4-oxadiazoles were prepared from acid hydrazides on treatment with different carboxylic acids in the presence of phosphorus oxychloride. Interconversion of oxadiazoles to thiadiazoles and triazoles was carried out with appropriate reagents. The antimicrobial and cytotoxic activities of compounds 7a-d to 12a-d were tested. Compounds 10d and 12d showed pronounced antimicrobial activity. Further, compound 10d exhibited maximum cytotoxicity.

Full text of DOI:10.1016/j.ejmech.2008.10.012

European Journal of Medicinal Chemistry 44 (2009) 2106–2112
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis, antimicrobial and cytotoxic activities of 1,3,4-oxadiazoles,
1,3,4-thiadiazoles and 1,2,4-triazoles
,
a
a
b
b
V. Padmavathi a , G. Sudhakar Reddy , A. Padmaja , P. Kondaiah , Ali-Shazia
*
a Department of Chemistry, Sri Venkateswara University, Tirupati 517 502, Andhra Pradesh, India
b Department of Molecular Reproduction, Development and Genetics, Indian Institute of Science, Bangalore 560 012, Karnataka, India
a r t i c l e i n f o
a b s t r a c t
Article history:
A new class of 1,3,4-oxadiazoles were prepared from acid hydrazides on treatment with different
carboxylic acids in the presence of phosphorus oxychloride. Interconversion of oxadiazoles to thiadia-
zoles and triazoles was carried out with appropriate reagents. The antimicrobial and cytotoxic activities
of compounds 7a–d to 12a–d were tested. Compounds 10d and 12d showed pronounced antimicrobial
activity. Further, compound 10d exhibited maximum cytotoxicity.
Received 10 July 2008
Received in revised form
15 October 2008
Accepted 17 October 2008
Available online 1 November 2008
Ó 2008 Elsevier Masson SAS. All rights reserved.
Keywords:
1,3,4-Oxadiazoles
1,3,4-Thiadiazoles
1,2,4-Triazoles
Antimicrobial activity
Cytotoxicity
1. Introduction
present communication deals with the synthesis of 2,5-diary-
loxadiazoles and their conversion to thiadiazoles and triazoles and
In the past years considerable evidence has been accumulated
to demonstrate the efficacy of substituted 1,3,4-oxadiazoles in
antibacterial, antifungal and HIV activities [1,2]. The advent of
sulfur drugs and the later discovery of mesoionic compounds in
fact accelerated the rate of progress in the field of sulfur containing
heterocycles. Substituted oxadiazole and thiadiazole derivatives
are potent cyclooxygenase/5-lipooxygenase inhibitors [3–7]. This
novel dual inhibitory activity of the enzyme pathways hold
promise as antiinflammatory agents with an improved efficacy.
Symmetrical oxadiazoles were found to be effective insecticides
towards houseflies, faceflies and hornflies [8]. The therapeutic
effects of 1,2,4-triazole derivatives have been studied for a number
of pathological conditions including inflammation, cancer, pain,
tuberculosis and hypertension [9–17]. In fact, remarkable progress
has been made by our group in the development of biologically
potent heterocycles [18–22]. Replacement of –O– by –S– or –NH–
in some heterocycles was reported viz., Bordners [23] preparation
of pyrroles from furan and the transformation of epoxides to
episulfides by the action of thiocyanates or thiourea [24–26].
However, reports about the conversion of 1,3,4-oxadiazoles to
1,3,4-thiadiazoles and 1,2,4-triazoles are relatively less [27,28]. The
also the biological evaluation for antimicrobial and cytotoxic
activities.
2. Chemistry
The arylsulfonylacetic acid methyl esters 3a–d and benzylsul-
fonylacetic acid methyl esters 4a–d were prepared from arylsulfo-
nylacetic acids 1a–d and benzylsulfonylacetic acids 2a–d by
esterification. The corresponding acid hydrazides 5a–d and 6a–
d were obtained by the reaction of 3/4 with hydrazine hydrate in
the presence of pyridine. The acid hydrazides on treatment with
different carboxylic acids in the presence of phosphorus oxy-
chloride afforded 2-(arylsulfonylmethyl)-5-aryl-1,3,4-oxadiazoles
7a–d and 2-(arylmethanesulfonylmethyl)-5-aryl-1,3,4-oxadiazoles
8a–d (Scheme 1). Compounds 7a–d and 8a–d were treated with
two-fold excess thiourea in tetrahydrofuran. The reaction mixture
indicated two spots on TLC which were separated and identified as
2-(arylsulfonylmethyl)-5-aryl-1,3,4-thiadiazoles 9a–d and 2-(aryl-
methanesulfonylmethyl)-5-aryl-1,3,4-thiadiazoles 10a–d as major
products apart from 7a–d and 8a–d as minor ones, respectively.
On the other hand, the reaction of 7a–d and 8a–d with excess
hydrazine produced 3-(arylsulfonylmethyl)-5-phenyl-4H-1,2,4-tri-
azol-4-amines 11a–d and 3-(arylmethanesulfonylmethyl)-5-
phenyl-4H-1,2,4-triazol-4-amines 12a–d (Scheme 1).
* Corresponding author. Tel.: þ91 877 2289303; fax: þ91 877 2249532.
E-mail address: vkpuram2001@yahoo.com (V. Padmavathi).
0223-5234/$ – see front matter Ó 2008 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2008.10.012

V. Padmavathi et al. / European Journal of Medicinal Chemistry 44 (2009) 2106–2112
2107
O
O
O
O
R
R
i
ii
S
CO2Me
S
CO2H
( )n
( )n
1/2
3/4
N
O
N
iii
R
O
O
O
R
S
S
CONHNH2
( )
( )n
O
n
R'
5/6
7/8
v
iv
N
N
N
O
N
R
O
O
R
O
S
S
( )
( )
N
S
n
n
NH2
R'
R'
11/12
9/10
n = 0 (1,3,5,7,9,11) n = 1 (2,4,6,8,10, 12)
a: R = H,
b: R = H,
c: R = 4-Cl, R' = H
R' = H
R' = 2-Cl
i. H2SO4 / MeOH
ii. H2NNH2·H2O / pyridine / MeOH
iii. POCl3 / R'C6H4COOH
d: R = 4-Cl, R' = 2-Cl
iv. Thiourea / THF
v. H2NNH2·H2O / n-butanol
Scheme 1.
3. Biology
3.1. Antimicrobial activity
were incubated further for 4 h. Blue formazan crystals were seen in
well when checked under microscope. Media was removed and 200
of DMSO was added per well. The absorbance was measured using
microtiter plate reader. Control treatments were performed with
ml
Compounds 7a–d to 12a–d were tested for in vitro antimicrobial
activity against the Gram-positive bacteria Staphylococcus aureus
(NCIM No. 5021), Bacillus subtilis (NCIM No. 2063), the Gram-
negative bacteria Klebsiella pneumoniae (NCIM No. 2957), Proteus
vulgaris (NCIM No. 2027) and fungi Fusarium solani (NCIM No.
1330), Curvularia lunata (NCIM No. 716) and Aspergillus niger (NCIM
No. 596). The primary screen was carried out by agar disc-diffusion
method [29] using nutrient agar medium. The minimum inhibitory
concentration for the most active compounds 10d and 12d against
the same microorganisms used in the preliminary screening was
carried out using microdilution susceptibility method [30]. Chlor-
amphenicol and ketoconazole were used as control drugs. The
observed data on the antimicrobial activity of compounds and
control drugs are given in Tables 1–3.
DMSO. The % viability was then calculated as [A590(treated
cells) ꢀ background]/[A590(untreated cells) ꢀ background] ꢂ 100.
4. Results and discussion
We have synthesized a series of heterocycles, 2-(arylsulfonylme-
thyl)-5-aryl-1,3,4-oxadiazoles 7a–d, 2-(arylmethanesulfonylmethyl)-
5-aryl-1,3,4-oxadiazoles 8a–d, 2-(arylsulfonylmethyl)-5-aryl-1,3,
4-thiadiazoles 9a–d, 2-(arylmethanesulfonylmethyl)-5-aryl-1,3,4-
thiadiazoles 10a–d, 3-(arylsulfonylmethyl)-5-aryl-4H-1,2,4-triazol-4-
amines 11a–d and 3-(arylmethanesulfonylmethyl)-5-aryl-4H-1,2,
4-triazol-4-amines 12a–d as illustrated in Scheme 1. Structures of all
the compounds were established on the basis of elemental analyses,
IR, 1H NMR and 13C NMR spectral data.
3.2. MTT assay for cell viability
4.1. Biological results
Toxicity of compounds 8d,10d and 12d in different cell lines in the
presence of 10% and 0.2% FBS, respectively, was determined using 3-
(4,5-dimethylthiazole-2-yl)-2,5-diphenyltetrazolium bromide reduc-
tion assay [31,32]. The compounds were dissolved in DMSO at 10 mM
concentration and stored at ꢀ20 ꢁC. The dilutions were made in
culture medium before treatment.
Nearly 5000 cells/well were plated in 96 well plates. After 3–4 h,
the compounds were added to the cells at different concentrations.
After 48 h of incubation, 20 ml of MTT solution was added and the cells
The results of preliminary antibacterial testing of compounds
7a–d to 12a–d are shown in Table 1. The results revealed that 2-
(arylmethanesulfonylmethyl)-5-aryl-1,3,4-thiadiazoles 10a–d, 3-
(arylmethanesulfonylmethyl)-5-aryl-4H-1,2,4-triazol-4-amines 12
a–d exhibited high activity (22–39 mm) on both Gram (þve) and
Gram (ꢀve) bacteria. In fact, compounds 10d and 12d showed
pronounced activity (31–39 mm) towards Gram (þve) bacteria.
Compounds 2-(arylmethanesulfonylmethyl)-5-aryl-1,3,4-oxadia-
zoles 8a–d, 2-(arylsulfonylmethyl)-5-aryl-1,3,4-thiadiazoles 9a–d,

2108
V. Padmavathi et al. / European Journal of Medicinal Chemistry 44 (2009) 2106–2112
Table 1
Table 2
Antibacterial activity of 7–12.
Antifungal activity of 7–12.
Compound
Concentration Zone of inhibition (mm)
g/disc)
Compound
Concentration
(mg/ml)
Zone of inhibition (mm)
(
m
Gram-positive bacteria Gram-negative bacteria
Fusarium
solani
Curvularia
lunata
Aspergillus
niger
Staphylococcus Bacillus Klebsiella Proteus
7a
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
15
18
16
20
16
20
16
19
17
20
17
19
16
19
18
22
18
22
19
22
18
21
20
24
18
20
20
23
24
27
28
31
22
25
23
25
21
24
24
27
19
21
21
23
24
26
29
32
38
42
15
19
18
22
15
17
17
19
18
22
18
23
19
22
16
19
16
19
18
21
19
21
19
22
21
23
19
21
23
25
25
27
20
24
22
25
22
25
23
25
22
24
18
20
24
27
27
31
41
44
14
17
15
17
16
19
15
16
16
17
18
21
17
21
17
21
15
17
15
18
16
19
17
21
16
19
16
19
17
20
20
23
19
22
18
21
19
22
20
24
17
21
17
21
18
20
22
24
36
39
aureus
subtilis pneumoniae vulgaris
7a
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
100
200
12
15
14
16
15
18
15
18
16
18
17
20
18
20
20
23
19
21
20
23
20
23
21
23
24
29
26
29
28
30
29
33
16
18
17
20
19
23
19
23
22
24
29
32
27
31
32
37
35
41
11
13
16
17
15
17
16
17
14
17
15
18
18
19
19
21
15
17
15
18
18
23
19
23
22
25
25
28
24
28
27
31
14
17
19
22
17
20
16
18
23
26
30
34
28
33
37
39
38
44
16
18
12
15
14
16
14
17
15
18
14
16
16
18
17
20
16
18
17
21
15
17
16
19
17
22
19
23
19
23
20
24
15
18
17
20
17
19
18
20
18
22
24
28
27
29
33
36
37
42
14
17
14
17
12
15
16
19
12
15
15
17
15
17
15
18
18
20
16
19
16
19
19
21
16
24
18
22
17
22
20
23
16
18
16
18
18
21
19
20
17
22
26
29
26
29
31
34
42
45
7b
7b
7c
7c
7d
7d
8a
8a
8b
8b
8c
8c
8d
8d
9a
9a
9b
9b
9c
9c
9d
9d
10a
10b
10c
10d
11a
11b
11c
11d
12a
12b
12c
12d
Ketoconazole
10a
10b
10c
10d
11a
11b
11c
11d
12a
12b
12c
12d
Chloramphenicol 100
200
(Table 3). The structure–antimicrobial activity relationship of the
synthesized compounds revealed that the compounds having
oxadiazole exhibited least activity when compared with
compounds having triazole and thiadiazole moieties. Besides, the
compounds with benzylsulfonyl group were the most active.
The presence of chloro substituent enhances the activity of the
compounds. The maximum activity was observed with compounds
10d and 12d (Table 3).
and 3-(arylsulfonylmethyl)-5-aryl-4H-1,2,4-triazol-4-amines 11a–d
displayed moderate to high activity towards Gram (þve) bacteria
(17–23 mm) and moderate activity (15–21 mm) towards Gram
(ꢀve) bacteria. On the other hand, 2-(arylsulfonylmethyl)-5-aryl-
1,3,4-oxadiazoles 7a–d exhibited least activity against both
bacteria.
All the test compounds inhibited the spore germination of
tested fungi A. niger, F. solani and C. lunata. Results of the inves-
tigation presented in Table 2 revealed that all the compounds
except 7a–d possess relatively high inhibitory effect on F. solani
and C. lunata than on A. niger. Further, compounds 2-(4-chlor-
obenzylsulfonylmethyl)-5-(2-chlorophenyl)-1,3,4-thiadiazole 10d
Compounds 8d, 10d and 12d, were tested for their cytotoxic
potential using A549 (lung adenocarcinoma) cells in the pres-
ence of fetal bovine serum. As shown in Fig. 1 10d showed
maximum cytotoxicity at a concentration of 250
EC50 of 150 M approximately. The other compounds 12d and
8d showed appreciable cytotoxicity of about 50% of the vehicle
control at a concentration of 250 M. The effect of these
mM, with an
m
and
3-(4-chlorobenzylsulfonylmethyl)-5-(2-chlorophenyl)-4H-
1,2,4-triazol-4-amine 12d displayed greater activity.
m
The MIC values were determined as the lowest concentration
that completely inhibited visible growth of the microorganisms
compounds was similar in the presence of 0.2% serum (data not
shown).

V. Padmavathi et al. / European Journal of Medicinal Chemistry 44 (2009) 2106–2112
2109
Table 3
Minimum inhibitory concentration (MIC),
mg/ml of 7–12.
Compound
Minimum inhibitory concentration (MIC), mg/ml
S. aureus
B. subtilis
K. pneumoniae
P. vulgaris
F. solani
C. lunata
A. niger
7a
–
–
–
–
–
–
–
7b
–
–
–
–
–
–
–
7c
7d
8a
8b
8c
8d
9a
9b
9c
9d
10a
10b
10c
10d
11a
11b
–
–
400
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
400
400
400
400
400
200
400
400
400
200
200
200
200
100
400
400
200
200
200
100
100
100
–
–
400
–
–
–
–
–
–
200
–
400
400
200
200
200
200
100
–
400
400
400
400
200
400
400
400
200
200
100
100
50
400
400
400
400
400
100
100
25
400
400
200
400
400
400
200
200
200
200
100
400
200
200
200
200
100
200
50
400
400
400
400
200
200
200
200
100
400
200
400
400
400
200
100
25
–
–
400
200
200
200
100
–
400
400
200
200
200
–
–
–
–
–
11c
11d
12a
12b
12c
12d
400
400
200
200
200
100
12.5
–
200
400
400
100
200
50
–
400
200
200
200
50
6.25
–
Chloramphenicol
Ketoconazole
6.25
–
6.25
–
–
12.5
6.25
6.25
5. Conclusion
6.1.2. General procedure for the synthesis of arylsulfonylacetic acid
hydrazides 5a–d/arylmethanesulfonylacetic acid hydrazides 6a–d
To a solution of 3/4 (10 mmol) in methanol (6 ml), hydrazine
hydrate (11 mmol) and 3 drops of pyridine were added and refluxed
for 6–7 h. The reaction mixture was cooled and the solid separated
was collected by filtration, dried and recrystallized from methanol.
A new class of heterocycles, 1,3,4-oxadiazoles, 1,3,4-thiadia-
zoles and 1,2,4-triazoles were developed adopting simple, elegant
and well-versed methodologies. We have also evaluated prelim-
inary antimicrobial activity and cytotoxic activity of the
compounds. The maximum antimicrobial activity was observed
with 10d and 12d. Compound 10d showed maximum cytotoxic
activity.
6.1.3. General procedure for the synthesis of 2-(arylsulfonylmethyl)-
5-aryl-1,3,4-oxadiazoles 7a–d/2-(arylmethanesulfonylmethyl)-5-
aryl-1,3,4-oxadiazoles 8a–d
A mixture of 5/6 (10 mmol), substituted aromatic carboxylic acid
(10 mmol) and POCl3 (7 ml) was heated under reflux for 5–6 h. The
6. Experimental
6.1. Chemistry
Melting points were determined in open capillaries on a Mel-
Temp apparatus and are uncorrected. The purity of the
compounds 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 wave numbers
were given in cmꢀ1. The 1H NMR spectra were recorded in CDCl3/
DMSO-d6 on a Varian EM-360 spectrometer (300 MHz). The 13C
NMR spectra were recorded in CDCl3/DMSO-d6 on a Varian VXR
spectrometer operating at 75.5 MHz. All chemical shifts are
reported in
microanalyses were performed on
d
(ppm) using TMS as an internal standard. The
Perkin–Elmer 240C
a
elemental analyzer. The starting compounds arylsulfonylacetic
acid (1) and arylmethanesulfonylacetic acid (2) were prepared by
the literature procedure [33–35].
6.1.1. General procedure for the synthesis of arylsulfonylacetic acid
methyl esters 3a–d/arylmethanesulfonylacetic acid methyl esters
4a–d
A solution of 1/2 (10 mmol) in methanol (10 ml) and conc. H2SO4
(1 ml) was refluxed on steam bath for 8–10 h. The contents of the
flask were cooled and poured onto crushed ice. The solid separated
was collected by filtration, washed with cold water and dried. The
crude product was recrystallized from methanol.
Fig. 1. Cytotoxic activity of compounds 8d, 10d and 12d tested in A549 cells by MTT
assay. A549 cells are highly invasive lung carcinoma cells. Cells were cultured in
a medium containing DMEM, 10% fetal bovine serum and penicillin–streptomycin. Cells
were plated in a 96 well tissue culture plate at a density of 3 ꢂ 104 per well. After cells
attached (2–4 h), the compounds in indicated concentrations were added to the wells,
in DMSO. The bars reflect the viable cells in each treatment. Cells, cells alone without
any treatment, DMSO denotes the vehicle control. The experiment was done in
duplicate with triplicate readings of each experiment.

2110
V. Padmavathi et al. / European Journal of Medicinal Chemistry 44 (2009) 2106–2112
excess POCl3 was removed under reduced pressure and the residue
was poured onto crushed ice. The resulting precipitate was filtered,
washed with saturated sodium bicarbonate solution and then with
water, dried and recrystallized from ethanol.
(KBr): 1126, 1320 (SO2), 1630 (C]N) cmꢀ1; 1H NMR (CDCl3)
(s, 2H, CH2), 4.49 (s, 2H, Ar-CH2), 7.41–8.13 (m, 8H, Ar-H) ppm; 13
NMR (CDCl3) 46.8 (CH2SO2), 57.5 (ArCH2), 157.5 (C2), 164.7 (C5),
122.1, 125.5, 127.1, 127.2, 129.5, 131.3, 131.4, 132.4, 133.0, 133.3,
135.8 ppm (aromatic carbons). Anal. Calcd. for C16H12Cl2N2O3S: C,
50.14; H, 3.16; N, 7.31; Found: C, 50.21; H, 3.14; N, 7.35%.
d 4.47
C
d
6.1.3.1. 2-(Phenylsulfonylmethyl)-5-phenyl-1,3,4-oxadiazole 7a. White
solid (3.00 g, 74%); m.p. 75–77 ꢁC; IR (KBr): 1138, 1335 (SO2), 1632
(C]N) cmꢀ1; 1H NMR (CDCl3)
d
4.29 (s, 2H, CH2), 7.18–7.49 (m, 10H,
6.1.4. General procedure for the synthesis of 2-(arylsulfonylmethyl)-
5-aryl-1,3,4-thiadiazoles 9a–d/2-(arylmethanesulfonylmethyl)-5-
aryl-1,3,4-thiadiazoles 10a–d
In a sealed test tube, a mixture of 7/8 (5 mmol), thiourea
(20 mmol) and tertahydrofuran (5 ml) was taken and heated at
120–150 ꢁC in an oil bath for 24–30 h. After the reaction was
completed, it was extracted with dichloromethane. The organic
layer was washed with water, brine solution and dried over anhy-
drous Na2SO4. The resultant solid was recrystallized from
methanol.
Ar-H) ppm; 13C NMR (CDCl3)
d 55.1 (CH2SO2), 157.1 (C2), 164.3 (C5),
126.8, 127.6, 128.1, 128.7, 129.2, 129.6, 134.5, 136.8 ppm (aromatic
carbons). Anal. Calcd. for C15H12N2O3S: C, 59.99; H, 4.03; N, 9.33;
Found: C, 60.10; H, 4.07; N, 9.42%.
6.1.3.2. 2-(Phenylsulfonylmethyl)-5-(2-chlorophenyl)-1,3,4-oxadiazole
7b. White solid (3.34 g, 77%); m.p. 68–70 ꢁC; IR (KBr): 1125, 1332
(SO2), 1625 (C]N) cmꢀ1; 1H NMR (CDCl3)
d
4.24 (s, 2H, CH2), 7.24–
7.52 (m, 9H, Ar-H) ppm; 13C NMR (CDCl3)
d 54.4 (CH2SO2), 157.8 (C2),
164.7 (C5), 124.5, 125.2, 126.7, 127.8, 128.6, 129.2, 130.5, 133.9 ppm
(aromatic carbons). Anal. Calcd. for C15H11ClN2O3S: C, 53.82; H, 3.31;
N, 8.37; Found: C, 53.89; H, 3.33; N, 8.41%.
6.1.4.1. 2-(Phenylsulfonylmethyl)-5-phenyl-1,3,4-thiadiazole9a. White
solid (1.58 g, 64%); m.p. 174–176 ꢁC; IR (KBr): 1133, 1327 (SO2), 1632
(C]N) cmꢀ1
;
1H NMR (DMSO-d6)
d
4.45 (s, 2H, CH2), 7.14–7.42 (m,
6.1.3.3. 2-(4-Chlorophenylsulfonylmethyl)-5-phenyl-1,3,4-oxadiazole
10H, Ar-H) ppm; 13C NMR (DMSO-d6)
d
54.1 (CH2SO2), 162.4 (C2),
7c. White solid (3.34 g, 79%); m.p. 79–81 ꢁC; IR (KBr): 1128, 1334
167.5 (C5), 125.4, 126.1, 127.3, 128.7, 129.8, 131.7, 134.2, 138.1 ppm
(aromatic carbons). Anal. Calcd. for C15H12N2O2S2: C, 56.94; H, 3.82;
N, 8.85; Found: C, 56.84; H, 3.81; N, 8.93%.
(SO2), 1627 (C]N) cmꢀ1; 1H NMR (CDCl3)
d
4.32 (s, 2H, CH2), 7.16–
55.0 (CH2SO2), 157.5
7.57 (m, 9H, Ar-H) ppm; 13C NMR (CDCl3)
d
(C2), 165.8 (C5), 126.8, 127.2, 128.3, 128.6, 129.2, 130.4, 132.2,
136.6 ppm (aromatic carbons). Anal. Calcd. for C15H11ClN2O3S: C,
53.82; H, 3.31; N, 8.37; Found: C, 53.91; H, 3.35; N, 8.32%.
6.1.4.2. 2-(Phenylsulfonylmethyl)-5-(2-chlorophenyl)-1,3,4-thiadiazole
9b. White solid (1.75 g, 65%); m.p. 185–187 ꢁC; IR (KBr): 1135, 1333
(SO2), 1635 (C]N) cmꢀ1
;
1H NMR (DMSO-d6)
d
4.50 (s, 2H, CH2),
6.1.3.4. 2-(4-Chlorophenylsulfonylmethyl)-5-(2-chlorophenyl)-1,3,4-
7.26–7.83 (m, 9H, Ar-H) ppm; 13C NMR (DMSO-d6)
d
54.5 (CH2SO2),
oxadiazole 7d. Colourless crystals (3.69 g, 82%); m.p. 88–90 ꢁC; IR
163.3 (C2), 169.4 (C5), 125.5, 126.4, 126.8, 127.8, 129.5, 131.3, 134.5,
136.2 ppm (aromatic carbons). Anal. Calcd. for C15H11ClN2O2S2: C,
51.35; H, 3.16; N, 7.98; Found: C, 51.43; H, 3.18; N, 8.04%.
(KBr): 1126, 1330 (SO2), 1629 (C]N) cmꢀ1; 1H NMR (CDCl3)
d
4.25
54.8
(s, 2H, CH2), 7.18–7.90 (m, 8H, Ar-H) ppm; 13C NMR (CDCl3)
d
(CH2SO2), 157.7 (C2), 164.8 (C5), 126.3, 127.1, 127.6, 128.5, 129.2,
133.2, 135.4, 136.2, 137.4, 138.5 ppm (aromatic carbons). Anal.
Calcd. for C15H10Cl2N2O3S: C, 48.79; H, 2.73; N, 7.59; Found: C,
48.73; H, 2.75; N, 7.65%.
6.1.4.3. 2-(4-Chlorophenylsulfonylmethyl)-5-phenyl-1,3,4-thiadiazole
9c. White crystals (1.75 g, 68%); m.p. 169–171 ꢁC; IR (KBr): 1130,
1328 (SO2), 1628 (C]N) cmꢀ1
;
1H NMR (DMSO-d6)
d
4.48 (s, 2H,
CH2), 7.21–7.77 (m, 9H, Ar-H) ppm; 13C NMR (DMSO-d6)
d
54.8
6.1.3.5. 2-(Benzylsulfonylmethyl)-5-phenyl-1,3,4-oxadiazole 8a. White
(CH2SO2), 163.5 (C2), 167.5 (C5), 126.5, 128.9, 129.2, 129.6, 130.5,
130.7, 131.3, 133.5 ppm (aromatic carbons). Anal. Calcd. for
C15H11ClN2O2S2: C, 51.35; H, 3.16; N, 7.98; Found: C, 51.40; H, 3.19;
N, 8.02%.
solid (3.14 g, 79%); m.p. 85–87 ꢁC; IR (KBr): 1122, 1334 (SO2), 1620
(C]N) cmꢀ1; 1H NMR (CDCl3)
d
4.45 (s, 2H, CH2), 4.48 (s, 2H, Ar-CH2),
7.28–7.62 (m, 10H, Ar-H) ppm; 13C NMR (CDCl3)
d
46.5 (CH2SO2), 57.4
(ArCH2), 157.3 (C2), 164.1 (C5), 127.4, 128.1, 128.9, 129.5, 131.2, 131.3,
134.8, 135.7 ppm (aromatic carbons). Anal. Calcd. for C16H14N2O3S: C,
61.13; H, 4.49; N, 8.91; Found: C, 61.05; H, 4.43; N, 8.99%.
6.1.4.4. 2-(4-Chlorophenylsulfonylmethyl)-5-(2-chlorophenyl)-1,3,4-
thiadiazole 9d. White solid (1.92 g, 66%); m.p. 194–196 ꢁC; IR
(KBr): 1146, 1328 (SO2), 1639 (C]N) cmꢀ1 1H NMR (DMSO-d6)
;
6.1.3.6. 2-(Benzylsulfonylmethyl)-5-(2-chlorophenyl)-1,3,4-oxadiazole
d
4.46 (s, 2H, CH2), 7.37–8.21 (m, 8H, Ar-H) ppm; 13C NMR (DMSO-
8b. White solid (3.48 g, 74%); m.p. 99–101 ꢁC; IR (KBr): 1134, 1328
d6) d 55.1 (CH2SO2), 162.8 (C2), 168.0 (C5), 124.9, 128.8, 129.3, 130.8,
(SO2), 1632 (C]N) cmꢀ1; 1H NMR (CDCl3)
d
4.44 (s, 2H, CH2), 4.47 (s,
131.1, 132.3, 133.4, 134.6, 135.2 ppm (aromatic carbons). Anal.
Calcd. for C15H10Cl2N2O2S2: C, 46.76; H, 2.62; N, 7.27; Found: C,
46.83; H, 2.58; N, 7.32%.
2H, Ar-CH2), 7.32–7.88 (m, 9H, Ar-H) ppm; 13C NMR (CDCl3)
d
47.8
(CH2SO2), 57.6 (ArCH2), 157.9 (C2), 164.5 (C5), 125.4, 126.4, 128.1,
129.5, 130.7, 132.1, 133.7, 139.2 ppm (aromatic carbons). Anal. Calcd.
for C16H13ClN2O3S: C, 55.09; H, 3.76; N, 8.03; Found: C, 55.15; H,
3.80; N, 8.11%.
6.1.4.5. 2-(Benzylsulfonylmethyl)-5-phenyl-1,3,4-thiadiazole 10a. White
solid (1.65 g, 65%); m.p. 188–190 ꢁC; IR (KBr): 1137, 1326 (SO2), 1625
(C]N) cmꢀ1; 1H NMR (DMSO-d6)
d
4.57 (s, 2H, CH2), 4.65 (s, 2H, Ar-
6.1.3.7. 2-(4-Chlorobenzylsulfonylmethyl)-5-phenyl-1,3,4-oxadiazole
CH2), 7.25–7.62 (m, 10H, Ar-H) ppm; 13C NMR (DMSO-d6)
d
52.8
8c. White solid (3.48 g, 72%); m.p. 112–114 ꢁC; IR (KBr) 1130, 1336
(CH2SO2), 58.5 (ArCH2), 164.5 (C2), 167.9 (C5), 127.2, 128.5, 129.3, 129.9,
130.6, 131.5, 131.8, 134.3 ppm (aromatic carbons). Anal. Calcd. for
C16H14N2O2S2: C, 58.16; H, 4.27; N, 8.48; Found: C, 58.13; H, 4.31; N,
8.40%.
(SO2), 1625 (C]N) cmꢀ1; 1H NMR (CDCl3)
d
4.46 (s, 2H, CH2), 4.50
(s, 2H, Ar-CH2), 7.39–7.90 (m, 9H, Ar-H) ppm; 13C NMR (CDCl3)
47.3 (CH2SO2), 56.5 (ArCH2), 158.1 (C2), 164.2 (C5), 125.3, 125.9,
d
126.7, 127.4, 129.1, 131.3, 137.8, 138.3 ppm (aromatic carbons). Anal.
Calcd. for C16H13ClN2O3S: C, 55.09; H, 3.76; N, 8.03; Found: C,
55.03; H, 3.81; N, 8.09%.
6.1.4.6. 2-(Benzylsulfonylmethyl)-5-(2-chlorophenyl)-1,3,4-thiadiazole
10b. White solid (1.82 g, 68%); m.p. 181–183 ꢁC; IR (KBr): 1128, 1313
(SO2),1634 (C]N) cmꢀ1; 1H NMR (DMSO-d6)
d
4.52 (s, 2H, CH2), 4.60
(s, 2H, Ar-CH2), 7.29–7.68 (m, 9H, Ar-H) ppm; 13C NMR (DMSO-d6)
51.0 (CH2SO2), 57.8 (ArCH2), 163.7 (C2), 167.5 (C5), 128.6, 129.2,
6.1.3.8. 2-(4-Chlorobenzylsulfonylmethyl)-5-(2-chlorophenyl)-1,3,4-
oxadiazole 8d. White crystals (3.83 g, 79%); m.p. 118–120 ꢁC; IR
d

V. Padmavathi et al. / European Journal of Medicinal Chemistry 44 (2009) 2106–2112
2111
129.8, 130.2, 132.4, 133.1, 134.6, 134.9 ppm (aromatic carbons). Anal.
Calcd. for C16H13ClN2O2S2: C, 52.67; H, 3.59; N, 7.68; Found: C, 52.60;
H, 3.55; N, 7.73%.
C15H12Cl2N4O2S: C, 47.01; H, 3.16; N, 14.62; Found: C, 47.04; H, 3.14;
N, 14.71%.
6.1.5.5. 3-(Benzylsulfonylmethyl)-5-phenyl-4H-1,2,4-triazol-4-amine
12a. White solid (1.64 g, 63%); m.p. 189–191 ꢁC; IR (KBr): 1125,
1324 (SO2), 1639 (C]N), 3242, 3256 (NH2) cmꢀ1; 1H NMR (DMSO-
6.1.4.7. 2-(4-Chlorobenzylsulfonylmethyl)-5-phenyl-1,3,4-thiadiazole
10c. White solid (1.82 g, 67%); m.p. 195–197 ꢁC; IR (KBr): 1131, 1321
(SO2), 1630 (C]N) cmꢀ1
;
1H NMR (DMSO-d6)
d
4.48 (s, 2H, CH2),
4.57 (s, 2H, Ar-CH2), 7.30–7.75 (m, 9H, Ar-H) ppm; 13C NMR (DMSO-
d6) 51.5 (CH2SO2), 58.8 (ArCH2), 164.1 (C2), 168.8 (C5), 127.2, 128.8,
d6)
d
4.57 (s, 2H, CH2), 4.63 (s, 2H, Ar-CH2), 5.62 (bs, 2H, NH2), 7.14–
53.0 (CH2SO2), 58.4
7.65 (m, 10H, Ar-H) ppm; 13C NMR (DMSO-d6)
d
d
(ArCH2), 163.0 (C2), 168.5 (C5), 124.4, 128.3, 129.0, 130.5, 131.3, 132.2,
133.4, 135.8 ppm (aromatic carbons). Anal. Calcd. for C16H16N4O2S:
C, 58.52; H, 4.91; N, 17.06; Found: C, 58.63; H, 4.96; N, 17.16%.
129.2, 130.4, 130.8, 131.3, 132.2, 134.8 ppm (aromatic carbons). Anal.
Calcd. for C16H13ClN2O2S2: C, 52.67; H, 3.59; N, 7.68; Found: C,
52.60; H, 3.55; N, 7.64%.
6.1.5.6. 3-(Benzylsulfonylmethyl)-5-(2-chlorophenyl)-4H-1,2,4-triazol-
4-amine 12b. White solid (1.81 g, 68%); m.p. 185–187 ꢁC; IR (KBr):
6.1.4.8. 2-(4-Chlorobenzylsulfonylmethyl)-5-(2-chlorophenyl)-1,3,4-
thiadiazole 10d. White crystals (1.99 g, 68%); m.p. 206–208 ꢁC; IR
1132, 1318 (SO2), 1633 (C]N), 3239, 3246 (NH2) cmꢀ1 1H NMR
;
(KBr): 1138, 1330 (SO2), 1629 (C]N) cmꢀ1
;
1H NMR (DMSO-d6)
(DMSO-d6)
d
4.54 (s, 2H, CH2), 4.66 (s, 2H, Ar-CH2), 5.65 (bs, 2H, NH2),
53.4 (CH2SO2),
d
4.50 (s, 2H, CH2), 4.59 (s, 2H, Ar-CH2), 7.41–8.17 (m, 8H, Ar-H)
7.23–7.71 (m, 9H, Ar-H) ppm; 13C NMR (DMSO-d6)
d
ppm; 13C NMR (DMSO-d6)
d
51.7 (CH2SO2), 57.7 (ArCH2), 164.6 (C2),
58.9 (ArCH2), 164.4 (C2), 168.2 (C5), 127.6, 128.3, 128.9, 129.6, 131.5,
132.6, 133.4, 134.8 ppm (aromatic carbons). Anal. Calcd. for
C16H15ClN4O2S: C, 52.96; H, 4.17; N,15.44; Found: C, 53.04; H, 4.14; N,
15.53%.
167.6 (C5), 127.9, 128.7, 129.7, 130.4, 131.2, 131.8, 132.6, 133.1, 134.3,
135.6 ppm (aromatic carbons). Anal. Calcd. for C16H12Cl2N2O2S2: C,
48.13; H, 3.03; N, 7.02; Found: C, 48.19; H, 3.00; N, 6.93%.
6.1.5. General procedure for the synthesis of 3-(arylsulfonylmethyl)-
5-aryl-4H-1,2,4-triazol-4-amines 11a–d/3-(arylmethanesulfonylm-
ethyl)-5-aryl-4H-1,2,4-triazol-4-amines 12a–d
6.1.5.7. 3-(4-Chlorobenzylsulfonylmethyl)-5-phenyl-4H-1,2,4-triazol-
4-amine 12c. White solid (1.81 g, 67%); m.p. 198–200 ꢁC; IR (KBr):
1137, 1325 (SO2), 1636 (C]N), 3245, 3251 (NH2) cmꢀ1 1H NMR
;
To a solution of 7/8 (5 mmol) in n-butanol (25 ml), hydrazine
hydrate (15 mmol) was added and refluxed for 4 h. Then, KOH
(10 mmol) was added to the reaction media and the precipitate
formed was filtered. The solid obtained was acidified with conc. HCl
to pH z 3 and washed with water. The resultant solid was recrys-
tallized from ethanol.
(DMSO-d6)
d
4.58 (s, 2H, CH2), 4.64 (s, 2H, Ar-CH2), 5.60 (bs, 2H,
52.6
NH2), 7.16–7.74 (m, 9H, Ar-H) ppm; 13C NMR (DMSO-d6)
d
(CH2SO2), 59.1 (ArCH2), 164.7 (C2), 167.6 (C5), 126.7, 127.1, 128.1,
128.6, 129.0, 129.4, 131.7, 134.4 ppm (aromatic carbons). Anal. Calcd.
for C16H15ClN4O2S: C, 52.96; H, 4.17; N, 15.44; Found: C, 52.93; H,
4.13; N, 15.50%.
6.1.5.1. 3-(Phenylsulfonylmethyl)-5-phenyl-4H-1,2,4-triazol-4-amine
11a. White solid (1.57 g, 65%); m.p. 147–149 ꢁC; IR (KBr): 1141, 1337
6.1.5.8. 3-(4-Chlorobenzylsulfonylmethyl)-5-(2-chlorophenyl)-4H-1,
2,4-triazol-4-amine 12d. White solid (1.98 g, 65%); m.p. 202–
204 ꢁC; IR (KBr): 1134, 1337 (SO2), 1638 (C]N), 3248, 3257 (NH2)
(SO2), 1630 (C]N), 3243, 3269 (NH2) cmꢀ1 1H NMR (DMSO-d6)
;
d
4.52 (s, 2H, CH2), 5.61 (bs, 2H, NH2), 7.17–7.48 (m, 10H, Ar-H) ppm;
cmꢀ1
;
1H NMR (DMSO-d6)
d
4.61 (s, 2H, CH2), 4.69 (s, 2H, Ar-CH2),
5.58 (bs, 2H, NH2), 7.43–8.22 (m, 8H, Ar-H) ppm; 13C NMR (DMSO-
d6) 52.8 (CH2SO2), 58.2 (ArCH2), 163.5 (C2), 167.3 (C5), 127.0, 127.4,
13C NMR (DMSO-d6)
d 55.2 (CH2SO2), 162.9 (C2), 168.3 (C5), 126.5,
127.1,127.9,129.2,130.5,132.5,135.8,136.3 ppm (aromatic carbons).
Anal. Calcd. for C15H14N4O2S: C, 57.31; H, 4.49; N, 17.82; Found: C,
57.37; H, 4.54; N, 17.94%.
d
129.7, 130.4, 130.0, 132.7, 133.8, 134.2, 135.6, 137.1 ppm (aromatic
carbons). Anal. Calcd. for C16H14Cl2N4O2S: C, 48.37; H, 3.55; N,
14.10; Found: C, 48.30; H, 3.53; N, 14.16%.
6.1.5.2. 3-(Phenylsulfonylmethyl)-5-(2-chlorophenyl)-4H-1,2,4-triazol-
4-amine 11b. White solid (1.74 g, 68%); m.p. 133–135 ꢁC; IR (KBr):
6.2. Biological assays
1128, 1331 (SO2), 1626 (C]N), 3247, 3259 (NH2) cmꢀ1 1H NMR
;
(DMSO-d6)
d
4.56 (s, 2H, CH2), 5.57 (bs, 2H, NH2), 7.19–7.85 (m, 9H,
54.9 (CH2SO2), 163.4 (C2), 167.9
6.2.1. Compounds
Ar-H) ppm; 13C NMR (DMSO-d6)
d
Compounds 7a–d to 12a–d were dissolved in DMSO at different
(C5), 125.1, 125.7, 126.6, 127.4, 128.3, 131.7, 133.8, 139.9 ppm (aromatic
carbons). Anal. Calcd. for C15H13ClN4O2S: C, 51.65; H, 3.76; N, 16.06;
Found: C, 51.73; H, 3.74; N, 16.17%.
concentrations of 100, 200 and 800 mg/ml.
6.2.2. Cells
Bacterial strains S. aureus, B. subtilis, E. coli, K. pneumonie and
fungi F. solani, C. lunata and A. niger were obtained from National
Collection of Industrial Microorganisms (NCIM), National Chemical
Laboratory, Pune, India.
6.1.5.3. 3-(4-Chlorophenylsulfonylmethyl)-5-phenyl-4H-1,2,4-triazol-
4-amine 11c. White solid (1.74 g, 69%); m.p. 142–144 ꢁC; IR (KBr):
1145, 1338 (SO2), 1625 (C]N), 3240, 3252 (NH2) cmꢀ1 1H NMR
;
(DMSO-d6)
d
4.53 (s, 2H, CH2), 5.63 (bs, 2H, NH2), 7.22–7.79 (m, 9H,
54.7 (CH2SO2), 162.7 (C2), 168.8
Ar-H) ppm; 13C NMR (DMSO-d6)
d
6.2.3. Antibacterial and antifungal assays
(C5), 126.4, 126.9, 127.2, 129.3, 130.4, 131.3, 133.6, 138.7 ppm
(aromatic carbons). Anal. Calcd. for C15H13ClN4O2S: C, 51.65; H, 3.76;
N, 16.06; Found: C, 51.60; H, 3.73; N, 16.00%.
Preliminary antimicrobial activities of compounds 7a–d to 12a–
d were tested by Agar disc-diffusion method. Sterile filter paper discs
(6 mm diameter) moistened with the test compound solution in
DMSOofspecificconcentration100 mgand200 mg/discwerecarefully
6.1.5.4. 3-(4-Chlorophenylsulfonylmethyl)-5-(2-chlorophenyl)-4H-1,
2,4-triazol-4-amine 11d. White crystals (1.91 g, 66%); m.p. 179–
181 ꢁC; IR (KBr): 1142, 1334 (SO2), 1637 (C]N), 3244, 3253 (NH2)
placed on the agar culture plates that had been previously inoculated
separately with the microorganisms. The plates were incubated at
37 ꢁC and the diameterofthegrowth inhibition zonesweremeasured
after 24 h in case of bacteria and after 48 h in case of fungi.
The MICs of the compound assays were carried out using
microdilution susceptibility method. Chloramphenicol was used as
reference antibacterial agent. Ketoconazole was used as reference
cmꢀ1
;
1H NMR (DMSO-d6)
d
4.49 (s, 2H, CH2), 5.58 (bs, 2H, NH2),
7.38–8.14 (m, 8H, Ar-H) ppm; 13C NMR (DMSO-d6)
d
54.5 (CH2SO2),
163.2 (C2), 168.2 (C5), 125.3, 126.6, 127.1, 128.6, 129.5, 131.7, 133.9,
134.6, 135.2, 137.5 ppm (aromatic carbons). Anal. Calcd. for

2112
V. Padmavathi et al. / European Journal of Medicinal Chemistry 44 (2009) 2106–2112
[11] B. Tozkoparan, N. Gokhan, G. Aktay, E. Yesilada, M. Ertan, Eur. J. Med. Chem. 35
(2000) 743–750.
[12] A.A. Ikizler, E. Uzunali, A. Demirbas, Indian J. Pharm. Sci. 5 (2000) 289.
[13] N. Demirbas, R. Ugurluoglu, A. Demirbas, Bioorg. Med. Chem. 10 (2002)
3717–3723.
[14] G. Turan-Zitouni, M. Sivaci, F.S. Kilic, K. Erol, Eur. J. Med. Chem. 36 (2001)
685–689.
[15] A. Demirbas, C.B. Johansson, N. Duman, A.A. Ikizler, Acta Pol. Pharm.-Drug Res.
53 (1996) 117–121.
[16] A. Ikizler, N. Demirbas, A.A. Ikizler, J. Heterocycl. Chem. 33 (1996) 1765–1769.
[17] F. Malbec, R. Milcent, P. Vicart, A.M. Bure, J. Heterocycl. Chem. 21 (1984) 1769–
1774.
[18] V. Padmavathi, A.V. Nagendra Mohan, K. Mahesh, A. Padmaja, Chem. Pharm.
Bull. 56 (2008) 815–820.
antifungal agent. The test compounds, chloramphenicol and keto-
conazole were dissolved in DMSO at concentration of 800 g/ml
m
and two-fold serial dilution of the solution was prepared (400, 200,
100, ., 6.25 mg/ml). The microorganism suspensions were inocu-
lated to the corresponding wells. The plates were incubated at
36 ꢁC for 24 h and 48 h for bacteria and fungi, respectively. The
minimum inhibitory concentrations of the compounds were
recorded as the lowest concentration of each chemical compounds
in the tubes with no turbidity (i.e. no growth) of inoculated
bacteria/fungi.
[19] V. Padmavathi, P. Thriveni, G. Sudhakar Reddy, D. Deepti, Eur. J. Med. Chem. 43
(2008) 917–924.
Acknowledgements
[20] V. Padmavathi, D.R.C. Venkata Subbaiah, K. Mahesh, T.R. Lakshmi, Chem.
Pharm. Bull. 55 (2007) 1704–1709.
[21] F. Shih-Hua, V. Padmavathi, Y.K. Rao, D.R.C. Venkata Subbaiah, P. Thriveni,
M. Geethangili, A. Padmaja, T. Yew-Min, Int. Immunopharmacol. 6 (2006)
1699–1705.
This study was supported by financial grant under Department
of Science and Technology (DST) project (SR/S1/OC-12/2004 dated
15-09-2004) India.
[22] V. Padmavathi, B.J.M. Reddy, B.C. Obula Reddy, A. Padmaja, Tetrahedron 61
(2005) 2407–2411.
References
[23] C.A. Bordner, U.S. Patent 2,600,689, June 10, 1952. Chem. Abstr. 47 (1953) 4373.
[24] E.E. Van Tamelen, J. Am. Chem. Soc. 73 (1951) 3444–3448.
[25] C.C. Price, P.F. Kirk, J. Am. Chem. Soc. 75 (1953) 2396–2400.
[26] C.C. Culvenor, W. Davies, W.E. Savige, J. Chem. Soc. (1952) 4480–4486.
[27] N. Linganna, K.M. Lokanatha Rai, Synth. Commun. 28 (1998) 4611–4617.
[28] F. Kiyoshi, T. Senji, Chem. Pharm. Bull. 8 (1960) 908–912.
[29] National Committee for Clinical Laboratory Standards (NCCLS), Approved
Standard Document M-7A, Villanova, PA, 1985.
[1] B.S. Holla, R. Gonsalves, S. Shenoy, Eur. J. Med. Chem. 35 (2000) 267–271.
[2] B. Tinperciuc, A. Parvu, M. Palage, O. Oniga, D. Ghiran, Farmacia (Bucharest) 47
(1999) 77–84.
[3] D.H. Boschelli, D.T. Connor, D.A. Bornemeier, R.D. Dyer, J.A. Kennedy, P.J. Kuipers,
G.C. Okonkwo, D.J. Schrier, C.D. Wright, J. Med. Chem. 36 (1993) 1802–1810.
[4] P.C. Unangst, G.P. Shrum, D.T. Conner, R.D. Dyer, D.J. Schrier, J. Med. Chem. 35
(1992) 3691–3698.
[30] P.R. Murray, E.J. Baron, M.A. Pfaller, F.C. Tenover, R.H. Yolken, in: G.L. Wood,
J.A. Washington (Eds.), Manual of Clinical Microbiology, Am. Soc. Microbiol.,
Washington DC, 1995.
[5] M.D. Mullican, M.W. Wilson, D.T. Conner, C.R. Kostlan, D.J. Shrier, R.D. Dyer, J.
Med. Chem. 36 (1993) 1090–1099.
[31] T. Mosmann, J. Immunol. Methods 65 (1983) 55–63.
[32] M.B. Hansen, S.E. Nielsen, K. Berg, J. Immunol. Methods 119 (1989) 203–210.
[33] W.J. Kenney, J.A. Walsh, A. Davenport, J. Am. Chem. Soc. 83 (1961) 4019–4022.
[34] D. Bhaskar Reddy, N.S. Reddy, S. Reddy, M.V.R. Reddy, S. Balasubramanyam,
Org. Prep. Proced. Int. 20 (1988) 83.
[6] I.P. Singh,A.K. Saxena, K. Shankar, Eur. J. Med. Chem. Chim. Ther. 21(1986)267–269.
[7] L.V.G. Nargund, G.R.N. Reddy, V.J. Hariprasad, Pharm. Sci. 83 (1994) 246–248.
[8] J.P. Arrington, L.L. Wade, Method for the control of manure-breeding insects,
U.S. Patent 4215129, 1980.
[9] S.G. Kucukguzel, S. Rollas, H. Erdeniz, M. Kiraz, Eur. J. Med. Chem. 34 (1999) 153–160.
[10] H. Yuksek, A. Demirbas, A. Ikizler, C.B. Johansson, C. Celik, A.A. Ikizler, Arzn.-
Forsh Drug Res. 47 (1997) 405–409.
[35] V. Padmavathi, P. Thriveni, B. Jagan Mohan Reddy, A. Padmaja, J. Heterocycl.
Chem. 42 (2005) 113–116.