Synthesis and biological property of some novel 1,3,4-oxadiazoles

Article abstract of DOI:10.1016/j.ejmech.2010.07.021

A series of biphenyl-1,3,4-oxadiazoles namely 5-[substituted-(1,1′- biphenyl)-3-yl]-1,3,4-oxadiazole-2(3H)-thiones and its S-alkyl derivatives have been synthesized by multi step organic synthesis involving Suzuki-Miyaura coupling using palladium catalyst. The synthesized compounds were characterized by ¹H NMR, ¹³C NMR, ¹⁹F NMR, IR and LCMS spectroscopic properties. They were tested for their antimicrobial and analgesic activities. Some of them showed significant activity.

Full text of DOI:10.1016/j.ejmech.2010.07.021

European Journal of Medicinal Chemistry 45 (2010) 4587e4593
Contents lists available at ScienceDirect
European Journal of Medicinal Chemistry
journal homepage: http://www.elsevier.com/locate/ejmech
Original article
Synthesis and biological property of some novel 1,3,4-oxadiazolesq
,
,
c
c
G.C. Ramaprasad a b, Balakrishna Kalluraya a , B. Sunil Kumar , Ravindra K. Hunnur
*
a Department of Studies in Chemistry, Mangalore University, Mangalagangothri 574199, Karnataka, India
b Syngene International Ltd., BIOCON Park, Plot No. 2&3 Bommasandra IV Phase, Bangalore 99, India
c Department of Pharmaceutical Chemistry, N.E.T Pharmacy College, Raichur 584103, India
a r t i c l e i n f o
a b s t r a c t
A series of biphenyl-1,3,4-oxadiazoles namely 5-[substituted-(1,10-biphenyl)-3-yl]-1,3,4-oxadiazole-2
(3H)-thiones and its S-alkyl derivatives have been synthesized by multi step organic synthesis involving
Suzuki-Miyaura coupling using palladium catalyst. The synthesized compounds were characterized by
1H NMR, 13C NMR, 19F NMR, IR and LCMS spectroscopic properties. They were tested for their antimi-
crobial and analgesic activities. Some of them showed significant activity.
Article history:
Received 2 January 2010
Received in revised form
9 July 2010
Accepted 12 July 2010
Available online 12 August 2010
Ó 2010 Elsevier Masson SAS. All rights reserved.
Keywords:
1,3,4-Oxadiazole
Suzuki coupling
Boronic acids
Antimicrobial and analgesic activity
1. Introduction
In view of these findings and as a part of our general search for
biologically active nitrogen, sulphur and oxygen containing
Palladium catalyzed cross-coupling between a formal electro-
phile C-X (X¼Br, I etc.) and an organometallic species C-M (M ¼ Mg,
Zn, Sn and B) is a versatile synthetic route for making CeC bonds
[1]. The discovery by Suzuki and Miyaura [2] that arylboronic acids
undergo palladium catalyzed cross-coupling with aryl halides in
the presence of a base has stimulated enormous interest in the
application of the Suzuki reaction and variants developed subse-
quently, to the synthesis of unsymmetrical biaryls and related
compounds.
heterocycles, we have employed the Suzuki-Miyaura reaction with
palladium catalyst and to synthesize a series of 5-[substituted-(1,10-
biphenyl)-3-yl]-1,3,4-oxadiazole-2(3H)-thione 5aed and its S-alkyl
derivative 6ae9d.
2. Results and discussion
2.1. Chemistry
It has been reported in the literature that compounds bearing
1,3,4-oxadiazole ring possess significant biological properties such
as anti-inflammatory [3,4,5], hypoglycemic [6], antifungal [7],
antibacterial [8aec], anticancer [9], antitubercular [10], analgesic
[11], antiviral [12] activities. Some of the oxadiazole derivatives act
as muscle relaxants [13], hypnotic, sedatives [14], and show anti-
mitotic activities [15]. Some material applications of oxadiazole
derivatives in the fields of photosensitizers [16] and liquid crystals
have also been reported [17].
The synthesis of hitherto unreported title compounds was per-
formed as outlined in Scheme 1. Ethyl 3-bromobenzoate (2) was
prepared from its acid derivative. This underwent palladium cata-
lyzed Suzuki reaction with various boronic acids to form the
substituted biphenyl compounds 3aed in good yield [2]. The esters
3aed on hydrazinolysis with hydrazine hydrate yielded the corre-
sponding hydrazides 4aed [19]. Intramolecular cyclization of 4aed
with carbon disulfide resulted in 5-[substituted-(1,10-biphenyl)-3-
yl]-1,3,4-oxadiazole-2(3H)-thiones 5aed [3,20]. Compounds 5aed
were regioselectively S-alkylated with alkyl halides having inter-
esting functional groups, to give compounds 6ae9d in good yield
[4,21]. The structures of the newly synthesized compounds have
been established on the basis of 1H NMR, 13C NMR, 19F NMR, IR and
mass spectral studies.
Further sulphur and fluorine containing molecules are known
for their interesting bioactivities and have attracted considerable
attention in the pesticide and medicinal formulation [18].
q
Presented at the CSIR sponsored National conference held at Osmania
In the IR spectra of compounds 5aed the CeOeC, C]S and C]N
absorption bands were observed in the region of 1167e1180,
1245e1255 and 1599e1618 cmꢀ1 respectively. For compounds
University, Hyderabad during 6e7th February, 2009.
* Corresponding author. Tel.: þ91 824 2287262; fax: þ91 8242287367.
E-mail address: bkalluraya@gmail.com (B. Kalluraya).
0223-5234/$ e see front matter Ó 2010 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2010.07.021

4588
G.C. Ramaprasad et al. / European Journal of Medicinal Chemistry 45 (2010) 4587e4593
O
HO
OH
B
O
CH
3
O
O
O
CH
3
OH
(COCl)2 / EtOH
R1
Na2CO3 / Pd(PPh3)4
DME / H2O /
Br
R1
Br
1
2
3a-d
H
N
O
N
N
N
NH
2
S
SH
NH
O
O
H2N-NH2 / EtOH
CS2 / KOH
EtOH /
R1
R1
R1
4a-d
5a-d
N
R
N
2
S
O
R2-Br / K2CO3
R1
6a-9d
R1
6a: 5'-F, 2'-OMe
6b: 2'-OMe
6c: 2'-F
R2
R1
R2
-(CH2)3COOMe
-(CH2)3COOMe
-(CH2)3COOMe
-(CH2)3COOMe
-(CH2)4F
8a:
8b:
8c:
8d:
9a:
9b:
9c:
9d:
5'-F, 2'-OMe
2'-OMe
2'-F
-(CH2)3CN
-(CH2)3CN
-(CH2)3CN
-(CH2)3CN
-C2H5
6d: 3'-Cl
3'-Cl
7a: 5'-F, 2'-OMe
7b: 2'-OMe
7c: 2'-F
5'-F, 2'-OMe
2'-OMe
2'-F
-(CH2)4F
-C2H5
-(CH2)4F
-C2H5
7d: 3'-Cl
-(CH2)4F
3'-Cl
-C2H5
Scheme 1.
6ae9d the band at 1245e1255 cmꢀ1 disappeared indicating the
S-alkylation. Further in the IR spectra of compounds 6aed the
ester carbonyl appeared as a strong band in the region of
1731e1742 cmꢀ1. In compounds 8aed the carbon-nitrogen triple
In 19F NMR of compounds 6a and 6c the signals observed at
ꢀ123.2 and ꢀ128.2 ppm were due to fluorines at the aromatic
ring. In compounds 7b and 7d having fluorine attached to an
aliphatic system the signals were seen at ꢀ218.5 and ꢀ220.9 ppm
respectively.
bond appeared around 2242e2246 cmꢀ1
.
In the 1H NMR spectra of 4aed the NH proton were seen
around 9.80e9.91 ppm, whereas in compounds 5aed the NH
signal was shifted to 14.80 ppm, indicating the thiol-thione
tautomerism. For compounds 6ae9d the formation of S-alkyl
derivative was indicated by the presence of a peak around
3.32e3.42 ppm for the SeCH2 group. Similarly in the 13C NMR of
5aed the C]S signal was observed at around 177e182 ppm.
However in compounds 6ae9d this signal was absent which is
a strong evidence for S-alkylation.
2.2. Biological activity
The antibacterial activities of compounds 5aed and 6ae9d were
evaluated against four bacterial strains namely Staphylococcus
aureus, Pseudomonas aeruginosa, Eschericia coli, Bascillus subtilis by
cup-plate method.
The results indicated that the compounds having a fluoro
substituent in the biphenyl ring showed maximum activity (5c, 6c,

G.C. Ramaprasad et al. / European Journal of Medicinal Chemistry 45 (2010) 4587e4593
4589
7c, 8c). The results are summarized in Table 1. None of the tested
compounds showed any significant antifungal activity.
The compounds were tested for their analgesic activity using
Eddy’s hot plate method. The results are summarized in Table 2.
Analgesic results showed that compounds 5aeb, 5d, 6aeb, 6d, 7b,
7d and 8b had high activity, whereas compounds 5c, 6c, 7a, 7c, 8a,
8c and 8d had moderate activity.
washed with water (200 mL), saturated sodium bicarbonate solu-
tion (100 mL), saturated sodium chloride solution (100 mL), dried
over sodium sulphate, concentrated to afford compound 2 (20.5 g,
89.51 mmol, 90%) as colorless liquid.
1H NMR (DMSO-d6)
d
: 1.21 (t, 3H, J ¼ 7.2, CH3), 4.23 (q, 2H, J ¼ 7.1,
OCH2), 7.58e7.65 (m, 1H, AreH), 7.78 (d, 1H, J ¼ 8.1, AreH), 7.90
(d, 1H, J ¼ 8.1, AreH), 8.08 (s, 1H, AreH); GCMS: (m/z) 229.
3. Conclusion
4.1.2. Procedure for synthesis of ethyl 50-fluoro-20-methoxy-(1,10-
biphenyl)-3-carboxylate: (3a)
A
series of 1,3,4-oxadiazoles, namely 5-[substituted-(1,10-
To a degassed mixture of compound 2 (20.0 g, 87.33 mmol),
5-fluoro-2-methoxy boronic acid (17.8 g, 104.8 mmol), sodium
carbonate (37.0 g, 349.32 mmol), in 1,2-dimethoxy ethane (100 mL)
and water (40 mL), palladium tetrakis (1.0 g, 0.87 mmol) was added
and resulting mixture was heated to 85 ꢁC for 10 h. The solvents
were removed and the compound was taken in ethyl acetate
(500 mL), washed with water (200 mL), saturated sodium bicar-
bonate solution (100 mL), saturated sodium chloride solution
(100 mL), dried over sodium sulphate. The contents were concen-
trated and purified by column chromatography [3e5% ethyl acetate
in petroleum ether] to afford compound 3a (14.3 g, 51.09 mmol,
58%) as colorless liquid.
biphenyl)-3-yl]-1,3,4-oxadiazole-2(3H)-thiones 5aed and its S-
alkyl derivatives 6ae9d have been synthesized in good yield and
screened for their antibacterial, antifungal and analgesic activities.
The antibacterial screening showed that among the tested
compounds, the fluoro substituted compound 7c exhibited the
highest activity against all the tested microorganisms.
Analgesic activity screening indicated that the compounds
bearing ester functional group in the S-alkylated derivatives 6aeb
and 6d gave the highest activities.
4. Experimental
Compound 3a: 1H NMR (DMSO-d6)
d
: 1.31 (t, 3H, J ¼ 7.1, CH3),
3.74 (s, 3H, OMe), 4.33 (q, 2H, J ¼ 7.1, OCH2), 7.13e7.23 (m, 3H,
AreH), 7.54e7.59 (m, 1H, AreH), 7.76 (d, 1H, J ¼ 7.9, AreH), 7.94 (d,
4.1. Chemistry
1H, J ¼ 7.8, AreH), 8.04 (s, 1H, AreH); 13C NMR (DMSO-d6)
d: 14.1,
Thin layer chromatography was used to analyse the reaction
progress and purity of the compounds synthesized. Melting points
were determined in open glass capillary methods and were
uncorrected. IR spectra were obtained in KBr discs on a Shimadzu-
8400 FTIR spectrophotometer, 1H NMR spectra were recorded on
Brucker spectrometer (400 MHz) in DMSO-d6/CDCl3 using TMS as
an internal standard, Mass spectra were recorded on Agilent 6320
Ion Trap method, 13C NMR spectra were recorded on Brucker
spectrometer (100 MHz) in DMSO-d6/CDCl3. 19F NMR spectra were
recorded on 376 MHz in CDCl3 as solvent.
55.2, 60.9, 112.0, 115.7, 115.8, 122.0, 123.0, 124.0, 127.0, 128.0, 131.0,
133.0, 151.6 (d, J ¼ 230.1), 159.0, 166.0; 19F NMR (CDCl3)
d: -123.3
(m, 1F); GCMS: (m/z) 274.
Compound 3b: yield: 10.1 g, 39.06 mmol, 55%, colorless oil; 1H
NMR (DMSO-d6)
d
: 1.41 (t, 3H, J ¼ 7.1, CH3), 3.83 (s, 3H, OMe), 4.11
(q, 2H, J ¼ 7.0, OCH2), 7.01e7.08 (m, 2H, AreH), 7.33e7.39 (m, 2H,
AreH), 7.45e7.51 (m, 1H, AreH), 7.73 (d, 1H, J ¼ 9.1, AreH), 8.01
(d, 1H, J ¼ 9.1, AreH), 8.21 (s, 1H, AreH); 13C NMR (DMSO-d6)
d:
14.0, 55.0, 60.9, 108.0, 118.0, 122.0, 124.1, 126.4, 127.0, 128.0, 129.0,
129.9, 132.0, 136.7, 157.9, 166.2; GCMS: (m/z) 256.
Compound 3c: yield: 11.2 g, 45.08 mmol, 50%, colorless oil; 1H
4.1.1. Procedure for synthesis of ethyl 3-bromobenzoate: (2)
NMR (CDCl3)
d
: 1.42 (t, 3H, J ¼ 7.1, CH3), 4.44 (q, 2H, J ¼ 7.1,
Oxalyl chloride (50.5 g, 398 mmol) and catalytic amount of N,N-
dimethylformamide were added to a solution of 3-bromobenzoic
acid (1) (20.0 g, 99.5 mmol) in ethyl alcohol (200 mL) and the
resulting mixture was heated to 95 ꢁC for 3 h. The solvent was
removed and the compound was taken in ethyl acetate (500 mL),
OCH2), 7.16e7.26 (m, 2H, AreH), 7.35e7.37 (m, 1H, AreH), 7.45
(d, 1H, J ¼ 8.0, AreH), 7.51e7.55 (m, 1H, AreH), 7.75 (d, 1H, J ¼ 9.0,
AreH), 8.07 (d, 1H, J ¼ 9.0, AreH), 8.23 (s, 1H, AreH); 13C NMR
(DMSO-d6)
d: 14.0, 60.9, 113.0, 122.2, 123.0, 126.0, 127.9, 128.0,
Table 1
Antibacterial activity data (
mg/mL) of the compounds 5aed, 6ae9d: zone of inhibition in mm.
Compound
Gram-positive bacteria
Gram-negative bacteria
S. aureus
B. subtilis
E. coli
P. aeruginosa
50 (
m
g/mL)
100 (
m
g/mL)
50 (
m
g/mL)
100 (
m
g/mL)
50 (
mg/mL)
100 (
mg/mL)
50 (m
g/mL)
100 (mg/mL)
5a
5b
5c
5d
6a
6b
6c
6d
7a
7b
7c
7d
8a
8b
8c
8d
12
11
15
10
10
09
15
10
12
15
13
05
07
12
11
10
e
17
18
20
11
16
14
17
16
15
21
20
12
13
18
16
15
e
12
10
12
13
13
11
09
11
10
15
20
15
07
17
12
08
e
19
21
19
09
18
15
16
18
17
20
22
20
18
20
18
16
e
08
12
15
11
15
07
09
18
12
12
13
12
10
10
17
10
21
e
20
18
19
16
18
16
16
19
19
16
19
15
18
20
21
17
25
e
14
11
18
09
13
18
13
06
07
06
17
15
15
09
16
12
21
e
19
18
21
14
19
21
21
18
15
15
18
20
18
20
20
16
25
e
Streptomycin
Procaine penicillin
22
27
24
28

4590
G.C. Ramaprasad et al. / European Journal of Medicinal Chemistry 45 (2010) 4587e4593
Table 2
Analgesic activities of the compounds 5aed and 6ae9d.
Reaction time (s) after drug administration
Compound
0 h ꢂ SEa
0.5 h ꢂ SEa
1 h ꢂ SEa
2nd h ꢂ SEa
4th h ꢂ SEa
5a
5b
5c
5d
6a
6b
6c
6d
7a
7b
7c
7d
8a
8b
8c
8d
4.35 ꢂ 0.10
4.43 ꢂ 0.08
4.46 ꢂ 0.09
4.15 ꢂ 0.06
4.73 ꢂ 0.11
4.91 ꢂ 0.21
4.43 ꢂ 0.14
4.71 ꢂ 0.13
4.31 ꢂ 0.08
4.59 ꢂ 0.11
4.51 ꢂ 0.19
4.48 ꢂ 0.13
4.88 ꢂ 0.11
5.05 ꢂ 0.11
4.44 ꢂ 0.13
4.24 ꢂ 0.08
4.18 ꢂ 0.04
4.24 ꢂ 0.04
5.22 ꢂ 0.24
4.94 ꢂ 0.21
4.99 ꢂ 0.15
4.71 ꢂ 0.12
4.75 ꢂ 0.09
5.01 ꢂ 0.19
4.53 ꢂ 0.14
4.96 ꢂ 0.11
4.35 ꢂ 0.09
4.9 ꢂ 0.09
5.74 ꢂ 0.21
5.84 ꢂ 0.89
5.24 ꢂ 0.21
4.84 ꢂ 0.21
5.11 ꢂ 0.02
5.21 ꢂ 0.15
4.62 ꢂ 0.15
5.36 ꢂ 0.11
4.48 ꢂ 0.11
5.01 ꢂ 0.98
4.69 ꢂ 0.19
5.79 ꢂ 0.25
4.86 ꢂ 0.04
5.40 ꢂ 0.11
4.71 ꢂ 0.19
4.77 ꢂ 0.81
4.38 ꢂ 0.12
5.93 ꢂ 0.09
8.41 ꢂ 0.31
7.61 ꢂ 0.71
5.38 ꢂ 0.15
5.01 ꢂ 0.11
6.01 ꢂ 0.18
6.58 ꢂ 0.13
4.84 ꢂ 0.11
6.58 ꢂ 0.15
4.72 ꢂ 0.15
6.17 ꢂ 0.17
4.87 ꢂ 0.25
8.35 ꢂ 0.34
4.99 ꢂ 0.08
6.57 ꢂ 0.22
4.92 ꢂ 0.23
5.12 ꢂ 0.12
4.86 ꢂ 0.18
8.06 ꢂ 0.31
6.35 ꢂ 0.77
6.28 ꢂ 0.37
5.04 ꢂ 0.02
5.08 ꢂ 0.01
6.01 ꢂ 0.22
6.21 ꢂ 0.16
4.49 ꢂ 0.11
5.59 ꢂ 0.12
4.55 ꢂ 0.14
6.01 ꢂ 0.21
4.47 ꢂ 0.16
6.44 ꢂ 0.72
4.74 ꢂ 0.13
5.59 ꢂ 0.25
4.49 ꢂ 0.09
4.71 ꢂ 0.21
4.57 ꢂ 0.11
7.85 ꢂ 0.37
4.62 ꢂ 0.19
5.56 ꢂ 0.22
4.92 ꢂ 0.11
5.25 ꢂ 0.08
4.54 ꢂ 0.15
4.51 ꢂ 0.01
4.17 ꢂ 0.04
5.58 ꢂ 0.07
Control
Standard
a
SE ¼ Standard Error.
129.3, 130.0, 133.0, 133.6, 136.2, 162.2 (d, J ¼ 256.1), 166.2; 19F NMR
4.1.4. Procedure for synthesis of 5-[50-fluoro-20-methoxy-(1,10-
biphenyl)3-yl]-1,3,4-oxadiazole-2(3H)-thione: (5a)
(CDCl3) d: -127.4 (m, 1F); GCMS: (m/z) 244.
Compound 3d [22]: yield: 13.1 g, 50.01 mmol, 51%, colorless oil;
To a solution of 4a (8.2 g, 31.53 mmol) in ethyl alcohol (140 mL),
carbon disulfide (4.79 g, 63.07 mmol), and potassium hydroxide
(1.76 g, 31.53 mmol) were added and the resulting solution was
heated to reflux for 10 h. The reaction mixture was concentrated
and the residue was dissolved in water and acidified with hydro-
chloric acid. The resulting solid was filtered, dried and recrystal-
lized from ethanol to afford compound 5a (4.3 g, 14.23 mmol, 45%)
as a white solid.
1H NMR (CDCl3)
d
: 1.43 (t, 3H, J ¼ 7.1, CH3), 4.44 (q, 2H, J ¼ 7.1,
OCH2), 7.35e7.41 (m, 2H, AreH), 7.43e7.57 (m, 2H, AreH),
7.61e7.62 (m, 1H, AreH), 7.75 (d, 1H, J ¼ 10.8, AreH), 8.05 (d, 1H,
J ¼ 10.8, AreH), 8.24 (1H, s, AreH); GCMS: (m/z) 260.
4.1.3. Procedure for synthesis of 50-fluoro-20-methoxy-(1,10-
biphenyl)-3-carbohydrazide: (4a)
To a solution of 3a (14.3 g, 51.09 mmol) in ethyl alcohol (160 mL),
hydrazine hydrate (3.8 g, 76.64 mmol) was added and resulting
mixture was heated to 100 ꢁC for 10 h. The mixture was concen-
trated and to the residue water was added and resulting solid was
filtered, washed with water and recrystalized from ethyl alcohol to
give compound 4a (8.3 g, 31.92 mmol, 62%) as a white solid.
Compound 5a: mp: 176.6e178 ꢁC; IR (KBr): 1178 (CeOeC), 1245
(C]S) 1618 (C]N), 3073 cmꢀ1 (]CeH of Ar); 1H NMR (DMSO-d6)
d
: 3.75 (s, 3H, OCH3), 7.13e7.27 (m, 3H, AreH), 7.61e7.65 (m, 1H,
AreH), 7.73 (d, 1H, J ¼ 9.0, AreH), 7.86 (d, 1H, J ¼ 9.0, AreH), 7.95
(s, 1H, AreH), 14.81 (bs, 1H, NH); 13C NMR (DMSO-d6)
: 56.2, 113.3,
d
115.5, 116.7, 122.4, 125.1, 126.6, 129.4, 129.5, 133.1, 137.9, 152.4, 156.4
Compound 4a: mp: 199e200 ꢁC; 1H NMR (DMSO-d6)
d: 3.74
(d, J ¼ 235.1), 160.4, 177.4; 19F NMR (CDCl3)
Mþ1: 303.
d: -122.1 (m, 1F) LCMS:
(s, 3H, OCH3), 4.51 (bs, 2H, NH2), 7.11e7.25 (m, 3H, AreH), 7.45e7.49
(m, 1H, AreH), 7.64 (d, 1H, J ¼ 7.7, AreH), 7.78 (d, 1H, J ¼ 7.7, AreH),
Compound 5b: yield: 3.3 g, 11.61 mmol, 50%, white solid; mp:
144e146.8 ꢁC; IR (KBr): 1180 (CeOeC), 1249 (C]S) 1599
7.90 (s, 1H, AreH), 9.81 (bs, 1H, NH); 13C NMR (DMSO-d6)
d: 55.2,
112.0, 116.5, 116.8, 124.0, 126.0, 128.1, 129.5, 130.1, 131.1, 136.5, 152.3
(C]N), 3059 cmꢀ1 (]CeH of Ar); 1H NMR (DMSO-d6)
d: 3.77
(d, J ¼ 230.3), 161.0, 171.0; 19F NMR (CDCl3)
Mþ1: 261.
d
: -124.1 (m, 1F); LCMS:
(s, 3H, OCH3), 7.03e7.08 (m, 1H, AreH), 7.13 (d, 1H, J ¼ 8.1,
AreH), 7.33e7.41 (m, 2H, AreH), 7.59e7.64 (m, 1H, AreH), 7.73
Compound 4b: yield: 5.6 g, 23.14 mmol, 60%, white solid; mp:
(d, 1H,
J
¼
7.7, AreH), 7.83 (d, 1H,
J
¼
7.6, AreH), 7.93
: 60.8, 117.1,
180e181 ꢁC; 1H NMR (DMSO-d6)
d: 3.75 (s, 3H, OCH3), 4.61 (bs, 2H,
(s, 1H, AreH), 14.7 (bs, 1H, NH); 13C NMR (DMSO-d6)
d
NH2), 7.11e7.12 (m, 2H, AreH), 7.31e7.35 (m, 2H, AreH), 7.43e7.48
(m, 1H, AreH), 7.59 (d, 1H, J ¼ 7.7, AreH), 7.73 (d, 1H, J ¼ 7.6, AreH),
126.1,127.5,129.7, 131.7, 133.3,134.5, 134.8, 135.5,138.2, 144.3,161.2,
165.7, 182.6; LCMS: M-1: 283.
7.88 (s, 1H, AreH), 9.79 (bs, 1H, NH); 13C NMR (DMSO-d6)
d: 56.0,
Compound 5c: yield: 3.6 g, 13.23 mmol, 51%, white solid; mp:
109.0, 120.1, 125.1, 126.2, 128.1, 128.6, 130.0, 131.0, 134.1, 136.1, 137.3,
159.0, 172.0; LCMS: Mþ1: 243.
155e158 ꢁC; IR (KBr): 1178 (CeOeC),1255 (C]S) 1607 (C]N), 3082
cmꢀ1 (]CeH of Ar); 1H NMR (DMSO-d6)
d: 7.33e7.36 (m, 3H,
Compound 4c: yield: 6.0 g, 26.24 mmol, 58%, white solid; mp:
AreH), 7.39e7.51 (m, 1H, AreH), 7.60e7.69 (m, 1H, AreH), 7.81 (d,
1H, J ¼ 7.6, AreH), 7.92 (d, 1H, J ¼ 8.1, AreH), 7.99 (s, 1H, AreH),
172e174 ꢁC; 1H NMR (DMSO-d6)
d: 4.91 (bs, 2H, NH2), 7.29e7.36
(m, 2H, AreH), 7.41e7.43 (m, 1H, AreH), 7.52e7.61 (m, 2H, AreH),
7.69 (d, 1H, J ¼ 7.6, AreH), 7.85 (d, 1H, J ¼ 7.7, AreH), 7.98 (s, 1H,
14.81 (bs, 1H, NH); 13C NMR (DMSO-d6)
d: 113.1, 116.1, 116.3, 121.5,
124.7, 126.7 128.5, 128.6, 129.8, 133.2, 138.3, 153.9 (d, J ¼ 259.2),
AreH), 9.86 (bs, 1H, NH); 13C NMR (DMSO-d6)
d: 113.0, 124.1, 127.1,
161.7, 179.6; 19F NMR (CDCl3)
d: -128.2 (m, 1F); LCMS: M-1: 271.
128.2, 131.0, 131.5, 133.2, 133.8, 135.2, 135.8, 136.1, 162.1
Compound 5d: yield: 3.6 g, 12.51 mmol, 45%, white solid; mp:
(d, J ¼ 253.4), 171.2; 19F NMR (CDCl3)
Mþ1: 231.
d: -128.1 (m, 1F); LCMS:
146e148 ꢁC; IR (KBr): 1167 (CeOeC), 1251 (C]S) 1618 (C]N), 3057
cmꢀ1 (]CeH of Ar); 1H NMR (DMSO-d6)
d: 7.48e7.57 (m,
Compound 4d: yield: 6.8 g, 27.6 mmol, 55%, white solid; mp:
2H, AreH), 7.63e7.77 (m, 2H, AreH), 7.82e8.26 (m, 4H, AreH),
14.81 (bs, 1H, NH); 13C NMR (DMSO-d6) 123.7, 124.7, 126.0, 126.1,
127.1, 128.4, 130.7, 131.1, 131.7, 134.3, 140.1, 141.3, 160.7, 177.9; LCMS:
M-1: 287.
160e162 ꢁC; 1H NMR (DMSO-d6)
d: 4.51 (bs, 2H, NH2), 7.42e7.56
(m, 4H, AreH), 7.58 (d, 1H, J ¼ 7.7, AreH), 7.69e7.85 (m, 2H, AreH),
8.11 (s, 1H, AreH), 9.91 (bs, 1H, NH); LCMS: Mþ1: 247.

G.C. Ramaprasad et al. / European Journal of Medicinal Chemistry 45 (2010) 4587e4593
4591
4.1.5. Procedure for synthesis of methyl 4-{[5-(50-fluoro-20-methoxy-
(1,10-biphenyl)-3-yl)-1,3,4-oxadiazol-2-yl]sulfanyl}butanoate: (6a)
To a solution of 5a (0.5 g, 1.65 mmol) in dry N,N-dime-
thylformamide (5 mL), dry potassium carbonate (0.27 g, 1.98 mmol)
and methyl 4-bromobutanoate (0.35 g, 1.98 mmol) were added and
the resulting solution was heated to 85 ꢁC for 1 h. The mixture was
concentrated and taken in ethyl acetate (50 mL), washed with
water (20 mL), saturated sodium chloride solution (20 mL) and
dried over sodium sulphate. The resulting solution was concen-
trated and purified by column chromatography [20e30% ethyl
acetate in petroleum ether] to afford compound 6a (0.36 g,
0.89 mmol, 55%) as a colorless oil.
J ¼ 5.8, FeCH), 4.57 (t, 1H, J ¼ 5.7, FeCH), 7.01e7.08 (m, 2H, AreH),
7.35e7.39 (m, 2H, AreH), 7.51e7.55 (m, 1H, AreH), 7.71 (d, 1H,
J ¼ 10.2, AreH), 7.97 (d, 1H, J ¼ 8.9, AreH), 8.17 (s, 1H, AreH); 13C
NMR (CDCl3)
d
: 25.4, 29.3, 32.1, 55.2, 83.3 (d, J ¼ 164.2), 111.2, 120.9,
123.4,125.1,127.7,128.7,129.2,129.3,130.7,132.8,139.5,156.4,164.1,
165.9; 19F NMR (CDCl3)
d
: -218.5 (m, 1F); LCMS Mþ1: 359.
Compound 7c: yield: 0.34 g, 0.98 mmol, 55%, colorless oil; IR
(KBr): 1039 (CeOeC linkage.) 1598, 1497, 1255 cmꢀ1 (oxadiazole
ring strech); 1H NMR (CDCl3)
d: 1.84e1.88 (m, 2H, CH2), 1.92e2.01
(m, 2H, CH2), 3.36 (t, 2H, J ¼ 7.2, SCH2), 4.45 (t, 1H, J ¼ 6.1, FeCH),
4.57 (t, 1H, J ¼ 6.1, FeCH), 7.16e7.25 (m, 2H, AreH), 7.36e7.51 (m,
2H, AreH), 7.55e7.59 (m, 1H, AreH), 7.72 (d, 1H, J ¼ 8.8, AreH), 8.02
Compound 6a: IR (KBr): 1742, 1080 (CeOeC linkage) 1642, 1473,
(d, 1H, J ¼ 8.8, AreH), 8.17 (s, 1H, AreH); 13C NMR (CDCl3)
d: 25.3,
1374 cmꢀ1 (oxadiazole ring stretch); 1H NMR (CDCl3)
d: 2.19e2.22
29.1, 32.0, 83.2 (d, J ¼ 164.2), 116.1, 123.8, 124.4, 125.7, 127.0, 127.7,
(m, 2H, CH2), 2.55 (t, 2H, J ¼ 7.2, CH2), 3.39 (t, 2H, J ¼ 7.2, SCH2), 3.69
(s, 3H, ester CH3), 3.81 (s, 3H, OCH3), 6.94 (d, 1H, J ¼ 13.2, AreH),
7.09e7.22 (m, 2H, AreH), 7.52e7.56 (m, 1H, AreH), 7.68 (d, 1H,
J ¼ 8.0, AreH), 7.99 (d, 1H, J ¼ 7.6, AreH), 8.15 (s, 1H, AreH); 13C
129.1, 129.7, 130.5, 132.2, 136.7, 159.6 (d, J ¼ 247.1), 164.3, 165.5; 19F
NMR (CDCl3)
d
: -127.1 (m, 1F), -218.9 (m, 1F); LCMS Mþ1: 347.
Compound 7d: yield: 0.32 g, 0.88 mmol, 51%, colorless oil; IR
(KBr): 1026 (CeOeC linkage.), 1553, 1392, 1183 cmꢀ1 (oxadiazole
NMR (CDCl3)
d: 24.5, 31.7, 32.3, 51.7, 56.2, 112.3, 114.9, 117.4,
ring strech); 1H NMR (CDCl3)
d: 1.86e1.93 (m, 2H, CH2), 2.01e2.06
123.5, 125.5, 127.6, 128.8, 130.4, 132.6, 138.4, 152.5, 157.1
(m, 2H, CH2), 3.37 (t, 2H, J ¼ 7.1, SCH2), 4.46 (t, 1H, J ¼ 5.8, FeCH),
4.58 (t, 1H, J ¼ 5.7, FeCH), 7.27e7.51 (m, 2H, AreH), 7.53e7.57
(m, 2H, AreH), 7.59e7.63 (m, 1H, AreH), 7.73 (d, 1H, J ¼ 10.7, AreH),
(d, J ¼ 237.1), 164.1, 165.1, 172.9; 19F NMR (CDCl3)
LCMS Mþ1: 403.
d: -123.2 (m, 1F);
Compound 6b: yield: 0.39 g, 1.02 mmol, 58%, pale yellow oil; IR
(KBr): 1731, 1025 (CeOeC linkage), 1598, 1434, 1366 cmꢀ1 (oxa-
8.02 (d, 1H, J ¼ 10.5, AreH), 8.21 (s, 1H, AreH); 13C NMR (CDCl3)
d:
25.4, 29.3, 32.6, 83.3 (d, J ¼ 165.1), 124.3, 125.1, 125.3, 125.9, 127.3,
diazole ring str.); 1H NMR (CDCl3)
d: 2.12e2.21 (m, 2H, CH2), 2.53
127.7, 128.1, 129.7, 130.2, 134.8, 140.7, 141.6, 164.4, 165.5; 19F NMR
(t, 2H, J ¼ 7.2, CH2), 3.34 (t, 2H, J ¼ 7.2, SCH2), 3.69 (s, 3H, ester CH3),
3.83 (s, 3H, OCH3), 7.01e7.06 (m, 2H, AreH), 7.34e7.36 (m, 2H,
AreH), 7.51e7.54 (m, 1H, AreH), 7.68 (d, 1H, J ¼ 9.6, AreH), 7.95 (d,
(CDCl3)
d
: -220.9 (m, 1F) LCMS Mþ1: 363.
Compound 8a: yield: 0.29 g, 0.79 mmol, 48%, colorless oil; IR
(KBr): 2246, 1023 (CeOeC linkage.), 1592, 1499, 1287 cmꢀ1 (oxa-
1H, J ¼ 9.2, AreH), 8.16 (s, 1H, AreH); 13C NMR (CDCl3)
d: 24.5, 31.7,
diazole ring str.); 1H NMR (CDCl3)
d: 2.25e2.32 (m, 2H, CH2), 2.59
32.4, 51.7, 55.5, 111.2, 120.9, 123.3, 125.1, 127.7, 128.6, 129.2, 129.3,
130.7, 132.8, 139.5, 156.4, 163.9, 165.9, 173.1; LCMS: Mþ1:385.
Compound 6c: yield: 0.35 g, 0.94 mmol, 52%, colorless oil; IR
(KBr): 1734.5, 1042 (CeOeC linkage), 1554, 1468, 1368 cmꢀ1 (oxa-
(t, 2H, J ¼ 14.4, CH2), 3.42 (t, 2H, J ¼ 11.2, SCH2), 3.79 (s, 3H, OCH3),
6.91e7.08 (m 3H, AreH), 7.54e7.58 (m, 1H, AreH), 7.67 (d, 1H,
J ¼ 7.6, AreH), 7.97 (d, 1H, J ¼ 1.2, AreH), 8.21 (s, 1H, AreH); 13C
NMR (CDCl3) d: 16.1, 25.1, 30.9, 56.2, 118.5, 112.4, 115.2, 117.4, 123.3,
diazole ring str.); 1H NMR (CDCl3)
d: 2.19e2.23 (m, 2H, CH2), 2.54 (t,
125.5, 127.6, 128.9, 130.4, 132.8, 138.5, 152.6, 157.1 (d, J ¼ 237.2),
2H, J ¼ 7.1, CH2), 3.38 (t, 2H, J ¼ 7.1, SCH2), 3.69 (s, 3H, ester CH3),
7.17e7.25 (m, 3H, AreH), 7.47e7.51 (m, 1H, AreH), 7.56e7.61
(m, 1H, AreH), 7.71 (d, 1H, J ¼ 9.2, AreH), 8.03 (d, 1H, J ¼ 8.9, AreH),
163.3, 166.1; 19F NMR (CDCl3)
d: -124.3 (m, 1F); LCMS: Mþ1: 370.
Compound 8b: yield: 0.32 g, 0.91 mmol, 52%, colorless oil; IR
(KBr): 2245, 1023 (CeOeC linkage.), 1597, 1423, 1255 cmꢀ1 (oxa-
8.18 (s, 1H, AreH); 13C NMR (CDCl3)
d: 24.5, 31.7, 32.4, 51.7, 116.3,
diazole ring str.); 1H NMR (CDCl3)
d: 2.28e2.33 (m, 2H, CH2), 2.62
123.9,124.5,125.8, 127.1,127.7,129.2, 129.7,129.8, 130.6, 136.8, 159.6
(t, 2H, J ¼ 7.2, CH2), 3.43 (t, 2H, J ¼ 6.8, SCH2), 3.84 (s, 3H,
OCH3), 7.01e7.08 (m 2H, AreH), 7.34e7.39 (m, 2H, AreH),
7.52e7.56 (m, 1H, AreH), 7.72 (d, 1H, J ¼ 9.2, AreH), 7.97
(d, J ¼ 246.1), 164.1, 165.6, 173.2; 19F NMR (CDCl3)
LCMS: Mþ1: 373.
d: -128.2 (m, 1F);
Compound 6d: yield: 0.33 g, 0.86 mmol, 50%, colorless oil; IR
(KBr): 1732, 1180 (CeOeC linkage), 1593, 1318, 1291 cmꢀ1 (oxa-
(d, 1H, J ¼ 10.0, AreH), 8.16 (s, 1H, AreH); 13C NMR (CDCl3)
d: 16.1,
25.1, 32.3, 55.6, 111.3, 118.4, 120.9, 123.1, 125.1, 127.7, 128.7, 129.1,
129.3, 130.7, 133.0, 139.6, 156.4, 163.1, 166.2; LCMS: Mþ1: 352.
Compound 8c: yield: 0.35 g, 1.01 mmol, 57%, colorless oil; IR
(KBr): 2245, 1068 (CeOeC linkage.), 1585, 1422, 1180 cmꢀ1 (oxa-
diazole ring str.); 1H NMR (CDCl3)
d: 2.18e2.24 (m, 2H, CH2), 2.57
(t, 2H, J ¼ 7.1, CH2), 3.38 (t, 2H, J ¼ 7.1, SCH2), 3.71 (s, 3H, ester CH3),
7.37e7.44 (m, 2H, AreH), 7.52 (d, 1H, J ¼ 7.3, AreH), 7.59 (s, 1H,
AreH), 7.61e7.63 (m, 1H, AreH), 7.72 (d, 1H, J ¼ 7.7, AreH), 8.01
diazole ring str.); 1H NMR (CDCl3)
d: 2.29e2.34 (m, 2H, CH2), 2.61
(d, 1H, J ¼ 7.8, AreH), 8.22 (s, 1H, AreH); 13C NMR (CDCl3)
d
: 24.4,
(t, 2H, J ¼ 7.1, CH2), 3.44 (t, 2H, J ¼ 6.9, SCH2), 7.17e7.28 (m 2H,
AreH), 7.38e7.57 (m, 2H, AreH), 7.59e7.61 (m, 1H, AreH), 7.73
(d, 1H, J ¼ 9.1, AreH), 8.02 (d, 1H, J ¼ 9.1, AreH), 8.19 (s, 1H, AreH);
31.7, 32.4, 51.6, 124.2, 125.1, 125.2, 125.8, 127.2, 127.9, 129.6 130.1,
130.2, 134.8, 140.7, 141.5, 164.1, 165.5, 172.8; LCMS: Mþ1:389.
Compound 7a: yield: 0.34 g, 0.91 mmol, 56%, colorless oil; IR
(KBr): 1018 (CeOeC linkage.) 1596, 1478, 1392 cmꢀ1 (oxadiazole
13C NMR (CDCl3)
d: 16.1, 25.1, 30.8, 116.1, 118.5, 123.7, 124.6, 125.8,
127.1, 127.7, 129.2, 129.8, 130.6, 132.4, 136.8, 159.6 (d, J ¼ 246.2),
ring str.); 1H NMR (CDCl3)
d: 1.86e1.95 (m, 2H, CH2), 2.01e2.05
163.4, 165.9; 19F NMR (CDCl3)
d
: -128.7 (m, 1F); LCMS Mþ1: 340.
(m, 2H, CH2), 3.39 (t, 2H, J ¼ 7.1, SCH2), 3.80 (s, 3H, OCH3), 4.46 (t,1H,
J ¼ 5.8, FeCH), 4.57 (t, 1H, J ¼ 5.7, FeCH), 6.95e7.11 (m, 3H, AreH),
7.55e7.61 (m, 1H, AreH), 7.68 (d, 1H, J ¼ 10.6, AreH), 8.01
Compound 8d: yield: 0.35 g, 0.98 mmol, 58%, colorless oil; IR
(KBr): 2242, 1087 (CeOeC linkage.), 1547, 1415, 1080 cmꢀ1 (oxa-
diazole ring str.); 1H NMR (CDCl3)
d: 2.29e2.33 (m, 2H, CH2), 2.61
(d, 1H, J ¼ 10.6, AreH), 8.15 (s, 1H, AreH); 13C NMR (CDCl3)
d
:
(t, 2H, J ¼ 7.1, CH2), 3.46 (t, 2H, J ¼ 6.9, SCH2), 7.27e7.52 (m, 2H,
AreH), 7.53e7.58 (m, 2H, AreH), 7.61e7.63 (m, 1H, AreH), 7.75
(d, 1H, J ¼ 10.7, AreH), 8.01 (d, 1H, J ¼ 10.2, AreH), 8.20 (s, 1H,
25.4, 29.3, 32.1, 56.2, 83.3 (d, J ¼ 165.1), 112.3, 115.1, 117.4, 123.5,
125.5, 127.5, 128.8, 130.4, 132.6, 138.4, 152.6, 157.1 (d, J ¼ 237.1),
164.2, 165.1; 19F NMR (CDCl3)
d: -124.2 (m, 1F), -218.3 (m, 1F); LCMS
AreH); 13C NMR (CDCl3)
d: 16.1, 25.2, 30.8, 118.5, 124.1, 125.1, 125.2,
Mþ1: 377.
125.9, 127.2, 127.9, 129.6, 130.1, 130.3, 134.8, 140.7, 141.4, 163.4,
165.7; LCMS Mþ1: 356.5.
Compound 7b: yield: 0.32 g, 0.89 mmol, 51%, colorless oil; IR
(KBr): 1023 (CeOeC linkage.) 1579, 1429, 1255 cmꢀ1 (oxadiazole
Compound 9a: yield: 0.30 g, 0.91 mmol, 55%, pale yellow oil; IR
(KBr): 1024 (CeOeC linkage.), 1593, 1499, 1398 cmꢀ1 (oxadiazole
ring strech); 1H NMR (CDCl3)
(m, 2H, CH2), 3.36 (t, 2H, J ¼ 7.1, SCH2), 3.81 (s, 3H, OCH3), 4.45 (t,1H,
d: 1.86e1.92 (m, 2H, CH2), 1.94e2.04
ring str.); 1H NMR (CDCl3)
d: 1.53 (t, 3H, J ¼ 7.4, CH3), 3.34 (q, 2H,

4592
G.C. Ramaprasad et al. / European Journal of Medicinal Chemistry 45 (2010) 4587e4593
J ¼ 7.3, CH2), 3.81 (s, 3H, OCH3), 6.92e7.10 (m, 3H, AreH), 7.53e7.56
(m,1H, AreH), 7.67 (d,1H, J ¼ 9.1, AreH), 8.01 (d,1H, J ¼ 10.1, AreH),
made in each plate. Two cups were filled with 0.1 mL of two test
dilutions and the other two cups with respective concentrations of
standard dilutions. Then, the plates were left as it is for 2e3 h for
diffusion and then they were kept for incubation at 37 ꢁC for 24 h.
8.15 (s, 1H, AreH); 13C NMR (CDCl3)
d: 14.7, 27.1, 56.2, 112.3, 115.1,
117.4, 123.6, 125.5, 128.8, 130.4, 130.7, 132.6, 138.4, 152.6, 157.1
(d, J ¼ 238.2), 164.3, 165.6; 19F NMR (CDCl3)
Mþ1: 331.
d: -124.1 (m, 1F); LCMS:
4.2.2. Analgesic activity
Compound 9b: yield: 0.30 g, 0.98 mmol, 56%, pale yellow oil;
IR (KBr): 1023 (CeOeC linkage.), 1598, 1497, 1255 cmꢀ1 (oxadiazole
All the compounds were tested for their analgesic activity using
Eddy’s hot plate method. In this method heat is used a source of
pain. Animals are placed individually on hot plate, maintained at
constant temperature (55 ꢂ 1 ꢁC). The reaction time i.e. time taken
by the animal to lick its hind paw or to leap out after placing it on
the hot plate is taken as the reaction time. Albino mice of either sex
were selected and divided into 12 groups, containing 6 animals in
each group. These animals were fasted for 24 h, prior to the
experiment. Animals of Group-I were considered as control, which
are administered with 2% acacia suspension. Where as Group-II was
treated with standard drug i.e. Pentazocin (35 mg/kg) which is
considered as standard group. (Ref-IP) Similarly Group- III, to XII
treated with compounds 5aed and 6ae9d (100 mg/kg). The reac-
tion time for each mouse was recorded at 0, 30, 60,120 and 240 min
after the administration of test compounds by using Eddy’s hot
plate.
ring str.); 1H NMR (CDCl3)
d
: 1.53 (t, 3H, J ¼ 7.3, CH3), 3.34
(q, 2H, J ¼ 7.3, SCH2), 3.83 (s, 3H, OCH3), 7.01e7.08 (m, 2H, AreH),
7.35e7.39 (m, 2H, AreH), 7.51e7.55 (m, 1H, AreH), 7.70 (d, 1H,
J ¼ 10.6, AreH), 7.98 (d, 1H, J ¼ 9.1, AreH), 8.18 (s, 1H, AreH); 13C
NMR (CDCl3) d: 14.7, 27.2, 55.5, 111.2, 120.9, 123.6, 125.1, 127.7,
128.6, 129.2, 129.3, 130.7, 132.8, 139.5, 156.4, 164.2, 165.8; LCMS:
Mþ1: 313.
Compound 9c: yield: 0.28 g, 0.93 mmol, 51%, pale yellow oil; IR
(KBr): 1025 (CeOeC linkage.), 1555, 1406, 1110 cmꢀ1 (oxadiazole
ring str.); 1H NMR (CDCl3)
d
: 1.53 (t, 3H, J ¼ 7.4, CH3), 3.32
(q, 2H, J ¼ 7.3, SCH2), 7.16e7.38 (m, 3H, AreH), 7.46e7.51 (m, 1H,
AreH), 7.56e7.61 (m, 1H, AreH), 7.71 (d, 1H, J ¼ 9.1, AreH), 8.02
(d, 1H, J ¼ 10.6, AreH), 8.18 (s, 1H, AreH); 13C NMR (CDCl3)
d: 14.7,
29.3, 116.3, 124.5, 124.6, 125.8, 127.0, 127.8, 129.1, 129.6, 130.6, 132.1,
136.8, 159.6 (d, J ¼ 247.1), 164.5, 165.5; 19F NMR (CDCl3)
(m, 1F); LCMS: Mþ1: 301.
d: -129.4
4.2.3. Determination of acute toxicity (LD50
)
Compound 9d: yield: 0.27 g, 0.85 mmol, 50%, pale yellow oil; IR
(KBr): 1025(CeOeC linkage.), 1565, 1406, 1120 cmꢀ1 (oxadiazole
The acute toxicity of compounds 5aed and 6ae9d was deter-
mined in albino mice of either sex weighing between 18 and 22 g,
maintained under standard husbandry conditions. The animals
were fasted 3 h prior to the experiment and “up and down” (OECD
guidelines NO: 425) method of CPCSEA was adopted for toxicity
studies. Animals were administered with single dose of compound
and observed for its mortality during 48 h study period (short term)
toxicity. Based on the compounds short term toxicity profile the
doses of the next animals were determined as per OECD guidelines
NO: 425. All the animals were observed for long term toxicity
(7days) and then 1/10th of the lethal dose of the individual
compound was taken as effective dose ED50 and was used
throughout the experimental studies.
ring str.); 1H NMR (CDCl3)
d
: 1.54 (t, 3H, J ¼ 7.4, CH3), 3.36 (q, 2H,
J ¼ 7.3, SCH2), 7.26e7.44 (m, 3H, AreH), 7.51e7.53 (m, 1H, AreH),
7.57e7.64 (m, 1H, AreH), 7.73 (d, 1H, J ¼ 10.8, AreH), 8.03 (d, 1H,
J ¼ 10.5, AreH), 8.21 (s, 1H, AreH); 13C NMR (CDCl3)
d: 14.1, 27.2,
124.3, 125.1, 125.3, 125.9, 127.3, 127.4, 127.9, 129.6, 130.2, 134.8,
140.7, 141.2, 164.6, 165.4; LCMS: Mþ1: 317.
4.2. Biological activity
4.2.1. Antimicrobial activity studies
4.2.1.1. Antibacterial activity. The newly synthesized compounds
were screened for their antibacterial activity against four bacterial
strains namely S. aureus, P. aeruginosa, Eschericia coli, Bascillus
subtilis by cup-plate method. The sterilized nutrient agar medium
was distributed 100 mL each in two 250 mL conical flasks and
allowed to cool to room temperature. To these media, 18e24 h
grown sub-cultures were added and shaken thoroughly to ensure
uniform distribution of organism’s throughout the medium. Then,
this agar medium was distributed in equal portions, in sterilized
petridishes, ensuring that each petridish contains about 45e50 mL
of the medium. The medium was then allowed for solidification.
Then, cups were made with the help of a sterile cork borer (6 mm
diameter) punching into the set of agar media. The cups were filled
with 0.1 mL of two test dilutions. Then, the petridishes were kept
for incubation in an inverted position for 24e48 h at 37 ꢁC, in an
incubator. When growth inhibition zones were developed
surrounding each cup, their diameter in mm was measured and
compared with that of the standard drugs Streptomycin, Procaine
penicillin.
Acknowledgements
The authors are thankful to Dr. Goutam Das C O O syngene
International Ltd. Dr. Ashis Baran Mandal, Dr. Sandipan Sarkar,
Dr. Sateesh Rai, Dr. Venkatraman Sundaraman, and Dr. Prashanth
Latte for good support and providing laboratory facilities.
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