Clubbed triazoles: A novel approach to antitubercular drugs

Article abstract of DOI:10.1016/j.ejmech.2006.12.001

In last few decades, though significant progress has been made in the treatment and control strategies of tubercular infections by introducing new diagnostic and monitoring tools and combination therapy, it still continues to be a severe problem. Thus wit

Full text of DOI:10.1016/j.ejmech.2006.12.001

European Journal of Medicinal Chemistry 42 (2007) 807e816
http://www.elsevier.com/locate/ejmech
Original article
Clubbed triazoles: A novel approach to antitubercular drugs
b
c
Mahendra Shiradkar a, , Gorentla Venkata Suresh Kumar , Varaprasad Dasari ,
*
Suresh Tatikonda d, Kalyan Chakravarthy Akula a, Rachit Shah e
a Dr. Reddys Laboratories, Research and Development, 7-1-27, Ameerpet, Hyderabad-500016, Andhra Pradesh, India
b St. Johns College of Pharmacy, Vijayanagar, Bangalore-40, Karnataka, India
c Sai Life Sciences, L.B.Nagar, Hyderabad, Andhra Pradesh, India
d University College of Pharmaceutical Sciences, Kakatiya University, Warangal, Andhra Pradesh, India
e AISSMS College of Pharmacy, Kennedy Road, Pune, India
Received 5 October 2006; received in revised form 16 November 2006; accepted 1 December 2006
Available online 15 December 2006
Abstract
In last few decades, though significant progress has been made in the treatment and control strategies of tubercular infections by introducing
new diagnostic and monitoring tools and combination therapy, it still continues to be a severe problem. Thus with the aim of developing novel
molecules with improved potency for treating Mycobacterium tuberculosis H37Rv strain infections and with decreased probability of developing
drug resistance, herein we report the synthesis of thiazolyl triazole derivatives, starting from ethyl acetoacetate, by microwave organic reaction
enhancement method (MORE) and results of investigations of their antimycobacterial and antimicrobial activities. Many compounds have shown
promising activity while others were inactive.
Ó 2006 Elsevier Masson SAS. All rights reserved.
Keywords: Thiazole; Triazole; Antimicrobial; Antimycobacterial
1. Introduction
and/or by additional mechanisms [4,5]. Novel emerging major
chemical groups as antimicrobials are triazole and thiazole de-
rivatives [6e11]. Triazoles, in particular, substituted-1,2,4-tri-
azoles and the open-chain thiosemicarbazide counterparts of
1,2,4-triazole, are among the various heterocycles that have re-
ceived the most attention during the last two decades as poten-
tial antimicrobial agents [12e22]. Substitutions including thio
[23,24], alkylthio and alkenylthio [25,26] derivatives have
been carried out primarily at the 3-position of the 1,2,4-tria-
zole ring, as potential antimicrobial and antimycobacterial
agents those will overcome the above mentioned resistance
problems. Thiazole moiety has already been reported for its
antimicrobial activity [27e30]. Thus in continuation of our
earlier work [31e33], we herein report the synthesis of new
1,2,4-triazole derivatives clubbed with thiazole moiety as
novel antimycobacterials. The synthesized compounds were
tested for their antimicrobial activity.
The development of resistance to current antimycobacterial
therapy endorses the search for more effective agents. In addi-
tion, primary and opportunistic microbial infections continue
to increase rapidly because of the increased number of immu-
nocompromised patients (AIDS, cancer and transplants). Sev-
eral reviews have appeared illustrating the problems
encountered by today’s infectious disease clinicians [1e3].
As known, the easily gained resistance is the main problem en-
countered in developing safe and efficient antitubercular
agents. Therefore, there is an urgent demand for a new class
of antitubercular agent with a different mode of action.
The azole antituberculars may be regarded as a new class
providing truly effective drugs which are reported to inhibit
bacteria by blocking the biosynthesis of certain bacterial lipids
Microwave assisted reactions [34] using dry media [35]
have attracted much interest because of the simplicity in
* Corresponding author. Tel.: þ91 9989263660; fax: þ91 4023731955.
E-mail address: rrshiradkar@rediffmail.com (M. Shiradkar).
0223-5234/$ - see front matter Ó 2006 Elsevier Masson SAS. All rights reserved.
doi:10.1016/j.ejmech.2006.12.001

808
M. Shiradkar et al. / European Journal of Medicinal Chemistry 42 (2007) 807e816
operation, greater selectivity and rapid synthesis of variety of
heterocyclic compounds [36]. Thus it was thought worthwhile
to synthesize titled compounds using the green route.
treatment with carbon disulphide and potassium hydroxide,
which on treatment with hydrazine hydrate gave 9aed
(Scheme 1). The NMR spectra confirmed formation of triazole
derivative from hydrazide, which shows the presence of sulf-
hydryl proton at d value 12.5. It was observed that there is re-
markable loss of product (44% yield) in the second step for the
conversion of 6 to 9 when performed in conventional method,
while reaction involving MORE method gave good yield (71e
80%).
2. Results and discussion
2.1. Chemistry
Compounds 1aed were synthesized as per the literature
[37]. Compounds 1aed, adsorbed on acidic alumina [38],
were treated with benzoyl chloride at 0 ꢀC to yield 2aed.
The transformed compounds 2aed on treatment with diiodo-
methane in the presence of strong alkali i.e. sodium hydroxide
gave 3aed. Title compounds 2aed were treated with chloroa-
cetonitrile, which on neutralization with sodium carbonate
gave a precipitates of compounds 4aed. Compounds 2aed,
when treated with methyl bromoacetate under basic conditions
produced 5aed. Chemical transformation of 5aed to 6ae
d was achieved by treating with hydrazine hydrate. While
compounds 6aed, on treatment with appropriate acid chlo-
rides, furnished 7ael. Schiff bases, the condensation products
of 8aed, were synthesized by treating 6aed with benzalde-
hyde and confirmed by absence of triplet of NH of hydrazide.
Compounds 6aed were converted to thiocarbazate salts by
2.2. Antitubercular activity
The results of the in vitro evaluation of antituberculosis ac-
tivity are reported in Tables 1 and 2. During the preliminary
screening four compounds 1aed were tested (Table 1) for
their antimycobacterial activity, one of the compounds 1b
have exhibited 100% inhibition at this concentration while
other compounds exhibited less than 90% inhibition at the
same concentration.
Thus we have considered 1b as a lead molecule and subse-
quent structural modifications were carried out. As a first step
towards lead optimization amino group was protected in the
corresponding compounds 2aed, however, all of these modi-
fications resulted in a substantial decrease in activity. The
N
N
R
R
N
NHCOC6H5
R
S
S
NHCOC6H5
N
NH2
N
N
N
N
N
CH2I2
S
C6H5COCl
N
N
SH
N
SH
2a-d
S
CH2
1a-d
3a-d
ClCH2CN
BrCH2COOCH3
N
S
R
N
S
R
NHCOC6H5
N
N
N
NHCOC6H5
N
N
N
SCH2CN
SCH2COOCH3
NH2NH2H2O
5a-d
4a-d
N
R
S
NHCOC6H5
N
N
N
C6H5CHO
SCH2CONHNH2
6a-d
CS2/KOH, N2H4.H2O
N
R
R'COCl
N
R
S
NHCOC6H5
N
N
N
S
NHCOC6H5
N
N
N
SCH2CONHN=CHC6H5
N
N
N
S
R
S
CH2
SH
N
8a-d
NHCOC6H5
N
NH2
N
N
9a-d
SCH2CONHNHCOR'
7a-l
Scheme 1.

M. Shiradkar et al. / European Journal of Medicinal Chemistry 42 (2007) 807e816
809
Table 1
Result of first antituberculosis screening
Compound
R
R0
MIC (mg mlꢁ1 a
)
GI (%)b
Compound
R
R0
MIC (mg mlꢁ1 a
)
GI (%)b
1a
1b
1c
1d
2a
2b
2c
2d
3a
3b
3c
3d
4a
4b
4c
4d
5a
5b
5c
5d
6a
6b
a
NHCOCH2Cl
NHCOCH3
NHCOC6H5
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
e
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
e
6c
6d
7a
7b
7c
7d
7e
7f
NHCOC6H5
e
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
<6.25
100
96
e
100
e
e
NHCH2CH2COOH
NHCOCH2Cl
NHCOCH3
e
CH3
CH3
CH3
CH3
C6H5
C6H5
C6H5
C6H5
CH2Cl
CH2Cl
CH2Cl
CH2Cl
e
NHCH2CH2COOH
NHCOCH2Cl
NHCOCH3
e
e
NHCOC6H5
e
e
NHCH2CH2COOH
NHCOCH2Cl
NHCOCH3
e
NHCOC6H5
e
e
e
e
NHCH2CH2COOH
NHCOCH2Cl
NHCOCH3
e
7g
7h
7i
NHCOC6H5
e
e
e
NHCH2CH2COOH
NHCOCH2Cl
NHCOCH3
e
e
NHCOC6H5
NHCH2CH2COOH
NHCOCH2Cl
NHCOCH3
e
7j
e
e
7k
7l
NHCOC6H5
e
97
100
e
NHCH2CH2COOH
NHCOCH2Cl
NHCOCH3
e
NHCOC6H5
8a
8b
8c
8d
9a
9b
9c
9d
98
96
98
98
e
NHCH2CH2COOH
NHCOCH2Cl
NHCOCH3
e
e
NHCOC6H5
e
e
e
NHCH2CH2COOH
NHCOCH2Cl
NHCOCH3
e
e
NHCOC6H5
NHCH2CH2COOH
NHCOCH2Cl
NHCOCH3
e
e
e
98
100
NHCOC6H5
NHCH2CH2COOH
e
e
e
e
MIC of rifampin: 0.015e0.125 mg mlꢁ1 versus M. tuberculosis H37Rv (97% inhibition).
Growth inhibition of virulent H37Rv strain of M. tuberculosis.
b
next structural modification made was a dimeric product of
3aed but these changes also resulted in a substantial loss of
biological activity.
good activity in secondary screening. Compounds 9aed
were found to be inactive.
All the compounds that were active in the first level screen-
ing were then tested to determine the actual minimum inhibi-
tory concentration (MIC). Therefore, compounds 8aec have
been proven to be the most active, with MIC values ranging
from 0.39 to 1.56 mM.
Compounds 4b and 4c have shown 97% and 100% inhi-
bition which was obtained by S-alkylation with acetonitrile.
Thus looking at the activity, it was decided to modify the
structure at SH group. In order to optimize the sulfhydryl
component, four compounds 5aed were synthesized and in-
vestigated, which revealed loss of activity. A further modi-
fication of compounds 5aed produced compounds 6aed.
The results of the antimycobacterial activity are quite inter-
esting because all of these compounds have shown inhibi-
tion above 90%. Compounds 6aed were selected for
further studies as it has a protected and free amino group,
which opened an area for further modification at this point.
Compounds 7ael were obtained by treatment with acid
chlorides which ultimately showed decreased antimycobacte-
rial activity. Furthermore, compounds 6aed were converted
to Schiff bases with benzaldehyde, and on investigation all
8aed have shown more than 95% inhibition. More interest-
ingly, compounds 8aec were the only which have shown
2.3. Antimicrobial activity
From the antibacterial screening it was observed that all the
compounds exhibited activity against all the organisms em-
ployed (Table 3). Looking at the structureeactivity relationship,
marked inhibition in bacteria was observed in the compounds
6b, 6c, and 8aec, whereas 1d, 3a, and 4bed have shown mod-
erate activity and others showed least activity.
3. Conclusion
Screening of the in vitro antimycobacterial activity of this
novel series has evidenced that derivatives with highly electro-
negative part at sulfhydryl group have emerged as new com-
pounds endowed with antitubercular activity. Specifically
compounds 8aec, i.e. Schiff bases probably due to their abil-
ity to increase the penetration in the bacterial cell have shown
the best of all. Due to the better activity against the mycobac-
teria, compounds 8aec were the best choice for the prepara-
tions of new derivatives in order to improve its effectiveness
on intracellular mycobacteria (macrophage) or in infected
animal. Also, improvements are required to obtain new
derivatives of these compounds which able to achieve more
Table 2
Result of second level antituberculosis assays
SN
MIC (mM)a
SN
MIC (mM)a
1b
4b
4c
6a
6b
6c
a
6.25
6.25
3.13
3.13
3.13
6.25
6d
8a
8b
8c
8d
6.25
0.78
1.56
0.39
3.13
Actual minimum inhibitory concentration (MABA assay).

810
M. Shiradkar et al. / European Journal of Medicinal Chemistry 42 (2007) 807e816
Table 3
Antibacterial activity of the synthesized compounds
Compound
Organisms
Compound
Organisms
Compound
Organisms
Sa
Pa
Ec
St
Sa
Pa
Ec
St
Sa
Pa
Ec
St
1a
1b
1c
1d
2a
2b
2c
2d
3a
3b
3c
18
18
22
25
20
16
16
11
22
16
11
17
16
20
22
20
16
10
17
22
16
24
14
15
18
20
18
20
10
15
20
12
16
12
14
14
16
14
16
18
22
16
12
12
3d
4a
4b
4c
4d
5a
5b
5c
5d
6a
6b
18
20
22
26
26
24
22
22
16
16
32
16
16
22
24
24
22
11
22
18
16
32
10
10
20
22
20
20
24
20
12
12
26
12
10
16
18
20
18
24
20
12
14
24
6c
6d
7a
33
20
24
21
32
18
12
14
12
14
34
34
18
10
18
30
12
10
16
18
11
35
30
14
14
10
30
14
10
12
18
18
31
29
12
14
18
27
12
14
18
14
12
30
7b
8c
8d
9a
9b
9c
9d
Gent
Sa: Staphylococcus aureus, Ec: Escherichia coli, Pa: Pseudomonas aeruginosa, St: Salmonella typhosa, Gent: Gentamycin.
effective antimycobacterial activity with lower toxicity to the
mammalian cells.
The precipitate was then filtered, washed thoroughly with wa-
ter and crystallized.
4. Experimental protocols
4.1.2.1. N-[3-({2-[(2-Chloroacetyl)amino]-1,3-thiazol-4-yl}-
methyl)-5-sulfanyl-4H-1,2,4-triazol-4-yl]benzamide (2a).
Yield 71%; brown; mp 241e243 ꢀC; 1H NMR (300 MHz,
CDCl3): d 3.74 (s, 2H, CH2), 4.13 (s, 2H, CH2), 6.21
(s, 1H, Thiazole CH), 7.12e7.36 (m, 5H, ArH), 8.06 (s, 2H,
NH), 12.31 (s, 1H, SH); MS (%) 408 (Mþ, 100), 323
(33.8), 309 (17.4), 248 (14.7), 247 (29.8), 233 (9.8), 220
(10.8), 180 (10.1), 095 (15.1), 86 (9.3); Anal.
C15H13N6O2S2Cl (C, H, N, O).
4.1. Chemistry
The melting points were recorded on electrothermal appa-
ratus and are uncorrected. 1H NMR spectra on a Bruker
Avance 300 MHz instrument using CDCl3 as solvent using
TMS as internal standard; the chemical shifts (d) are reported
in parts per million and coupling constants (J ) are given in
hertz. Signal multiplicities are represented by s (singlet),
d (doublet), t (triplet), ds (double singlet), dd (double doublet),
m (multiplet) and bs (broad singlet). Mass spectra were re-
corded on a Finnigan LCQ mass spectrometer. Microwave
irradiation was carried out in Raga Scientific Microwave
Systems, Model RG31L at 2450 MHz. Elemental analysis
was performed on a Heracus CHN-rapid analyser. Analysis
indicated by the symbols of the elements of functions was
within ꢂ0.4% of the theoretical values.
4.1.2.2. N-[3-({2-[Acetyl-amino]-1,3-thiazol-4-yl}methyl)-5-
sulfanyl-4H-1,2,4-triazol-4-yl]benzamide (2b). Yield 77%;
1
buff white; mp 250e252 ꢀC; H NMR (300 MHz, CDCl3):
d 2.12 (s, 3H, CH3), 3.48 (s, 2H, CH2), 4.27 (s, 4H, CH2),
6.11 (s, 1H, Thiazole CH), 7.26e7.41 (m, 5H, ArH), 8.12
(s, 2H, NH), 12.53 (s, 1H, SH); MS (%) 374 (Mþ, 100), 312
(29.6), 251 (9.8), 223 (15.1), 211 (10.8), 107 (14.7), 087
(10.1), 82 (7.6); Anal. C15H14N6O2S2 (C, H, N, O).
The purity of the compounds was checked on silica gel
coated Al plates (Merck).
4.1.2.3. N-[3-({2-[Benzoylamino]-1,3-thiazol-4-yl}methyl)-5-
sulfanyl-4H-1,2,4-triazol-4-yl]benzamide (2c). Yield 76%;
brown; mp 280e282 ꢀC; 1H NMR (300 MHz, CDCl3):
d 3.32 (s, 2H, CH2), 4.18 (s, 2H, CH2), 6.17 (s, 1H, Thiazole
CH), 7.21e7.86 (m, 10H, ArH), 8.13 (s, 2H, NH), 12.13 (s,
1H, SH); MS (%) 436 (Mþ, 80), 306 (28), 292 (8.4), 251
(20), 214 (100), 195 (15), 154 (7), 106 (65); Anal. C20H16
N6O2S2 (C, H, N, O).
4.1.1. Preparation of N-{4-[(4-amino-5-sulfanyl-4H-1,2,4-
triazol-3-yl)methyl]-1,3-thiazol-2-yl}-2-chloroacetamide (1a),
N-{4-[(4-amino-5-sulfanyl-4H-1,2,4-triazol-3-yl)methyl]-
1,3-thiazol-2-yl}-acetamide (1b), N-{4-[(4-amino-5-sulfanyl-
4H-1,2,4-triazol-3-yl)methyl]-1,3-thiazol-2-yl}-benzamide
(1c), 3-{N-(4-[(4-amino-5-sulfanyl-4H-1,2,4-triazol-3-yl)-
methyl]-1,3-thiazol-2-yl)-amino}propanoic acid (1d)
Above titled compounds were prepared as per the literature
[37].
4.1.2.4. 3-{N-[(4-[(4-(Benzoylamino)-5-sulfanyl-4H-1,2,4-tria-
zol-3-yl)methyl]-1,3-thiazol-2-yl}-aminopropanoic acid (2d).
Yield 69%; brown; mp 271e273 ꢀC; 1H NMR (300 MHz,
CDCl3): d 2.46e2.51 (t, 2H, CH2, J ¼ 4.3 Hz), 3.33e3.39
(q, 2H, CH2, J ¼ 7.6 Hz), 4.01e4.11 (t, 1H, NH, J ¼ 8.1),
4.32 (s, 2H, CH2), 6.27 (s, 1H, Thiazole CH), 7.43e7.62
(m, 5H, ArH), 8.16 (s, 1H, NH), 10.43 (bs, 1H, OH),
12.43 (s, 1H, SH); MS (%) 404 (Mþ, 100), 323 (14), 309
(17.1), 280 (6), 134 (35.9); Anal. C16H16N6O3S2 (C, H,
N, O).
4.1.2. General preparation of N-[3-({2-[(substituted)-
amino]-1,3-thiazol-4-yl}methyl)-5-sulfanyl-4H-1,2,4-
triazol-4-yl]benzamide
The triazoles 1aed (0.01 mol) in 20 ml of 10% NaOH was
treated dropwise with an equimolar amount of the benzoyl
chloride at 0 ꢀC, which was stirred for 30e45 min. At the
end of stirring a buff colored precipitate was obtained.

M. Shiradkar et al. / European Journal of Medicinal Chemistry 42 (2007) 807e816
811
4.1.3. General preparationofN,N0-(methylenebis{sulfanedial-
[5-({2-[(substituted)amino]-1,3-thiazol-4-yl}methyl)-4H-
1,2,4-triazole-3,4-dial]})dibenzamide
4.1.4. General preparation of N-{3-({2-[(substituted)-
amino]-1,3-thiazol-4-yl}methyl)-5-[(cyanomethyl)sulfanyl]-
4H-1,2,4-triazol-4-yl}benzamide
The triazoles 2aed (0.01 mol), diiodomethane (0.01 mol)
and 5.6 g (0.01 mol) potassium hydroxide were dissolved in
20 ml of dichloromethane. To the said mixture acidic alumina
(20 g) was added. Dichloromethane was evaporated in vacuo,
and the mixture was kept inside the alumina bath and irradi-
ated for 5e6 min at the power level of 300 W. The mixture
was cooled. The solid thus separated was dissolved in hot eth-
anol and filtered. After cooling, the filtrate gave the product as
white crystals.
The triazoles 2aed (0.01 mol) were mixed with 1.2 ml
(0.02 mol) of chloroacetonitrile and dissolved in 25 ml of
water. Neutralization with sodium carbonate gave a precipitate,
which was filtered, washed with cold water (2 ꢃ 20 ml), and
crystallized.
4.1.4.1. N-{3-({2-[(chloroacetyl)amino]-1,3-thiazol-4-yl}methyl)-
5-[(cyanomethyl)sulfanyl]-4H-1,2,4-triazol-4-yl}benzamide (4a).
Yield 86%; yellow; mp 241e243 ꢀC; 1H NMR (300 MHz,
CDCl3): d 3.74 (s, 2H, CH2), 4.17 (s, 2H, CH2), 4.32 (s, 2H,
CH2), 6.26 (s, 2H, Thiazole CH), 7.11e7.32 (m, 5H, ArH),
8.24 (s, 2H, NH); MS (%) 448 (Mþ, 100), 384 (21.9), 369
(20.6), 272 (34.2), 270 (40.8), 256 (17.9), 83 (28.9), 69 (16.1),
55 (11.3); Anal. C17H14N7O2S2Cl (C, H, N, O).
4.1.3.1. N,N0-(Methylenebis{sulfanedial-[5-({2-[(chloroacetyl)-
amino]-1,3-thiazol-4-yl}methyl)-4H-1,2,4-triazole-3,4-dial]})-
dibenzamide (3a). Yield 84%; brown; mp 278e280 ꢀC; 1H
NMR (300 MHz, CDCl3): d 3.34 (s, 4H, CH2), 4.19 (s, 4H,
CH2), 4.58 (s, 2H, CH2), 6.27 (s, 2H, Thiazole CH), 7.13e
7.62 (m, 10H, ArH), 7.84 (s, 4H, NH); MS (%) 829 (7.1),
679 (27.5), 622 (5.5), 607 (100), 516 (3.4), 484 (4.7), 453
(8.2), 347 (9.6), 234 (10.3), 185 (13.8), 146 (8.7), 123
(13.2), 104 (10.5), 87 (26.8), 78 (40); Anal.
C31H26N12O4S4Cl2 (C, H, N, O).
4.1.4.2. N-{3-({2-[(Acetyl)amino]-1,3-thiazol-4-yl}methyl)-5-
[(cyanomethyl)sulfanyl]-4H-1,2,4-triazol-4-yl}benzamide (4b).
Yield 82%; yellow; mp 264e266 ꢀC; 1H NMR (300 MHz,
CDCl3): d 2.31 (s, 3H, COCH3), 3.62 (s, 2H, CH2), 4.04 (s,
2H, CH2), 6.18 (s, 1H, Thiazole CH), 7.17e7.39 (m, 5H,
ArH), 7.91 (s, 2H, NH); MS (%) 413 (Mþ, 100), 384 (21.9),
369 (20.6), 272 (34.2), 270 (40.8), 256 (17.9), 83 (28.9), 69
(16.1), 55 (11.3); Anal. C17H15N7O2S2 (C, H, N, O).
4.1.3.2. N,N0-(Methylenebis{sulfanedial-[5-({2-[(acetyl)amino]-
1,3-thiazol-4-yl}methyl)-4H-1,2,4-triazole-3,4-dial]})dibenza-
mide (3b). Yield 77%; brown; mp 262e264 ꢀC; 1H NMR
(300 MHz, CDCl3): d 2.70 (s, 6H, CH3), 4.34 (s, 4H, CH2),
4.64 (s, 2H, CH2), 5.93 (s, 2H, Thiazole CH), 7.21e7.55 (m,
10H, ArH), 8.15 (s, 4H, NH); MS (%) 761 (35.9), 709
(11.1), 659 (13.2), 667 (23.6), 619 (100), 541 (3.6), 454
(3.7), 419 (9.8), 307 (8.2), 277 (8.1), 254 (11.9), 241 (15.4),
223 (35.8), 216 (24.9), 91 (23.8), 83 (54.2), 69 (25.7); Anal.
C31H28N12O4S4 (C, H, N, O).
4.1.4.3. N-{3-({2-[(Benzoyl)amino]-1,3-thiazol-4-yl}methyl)-
5-[(cyanomethyl)sulfanyl]-4H-1,2,4-triazol-4-yl}benzamide
(4c). Yield 81%; yellow; mp 267e269 ꢀC; 1H NMR
(300 MHz, CDCl3): d 3.73 (s, 2H, CH2), 4.14 (s, 2H, CH2),
6.24 (s, 1H, Thiazole CH), 7.41e7.83 (m, 10H, ArH), 8.24
(s, 2H, NH); MS (%) 475 (Mþ, 93.3), 430 (10.9), 419 (4.1),
356 (31), 273 (46), 272 (100), 271 (14.3), 256 (9.3), 228
(4.4), 217 (3.2), 189 (3.6), 124 (8.9), 109 (5.8), 81 (4.5), 53
(3); Anal. C22H17N7O2S2 (C, H, N, O).
4.1.3.3. N,N0-(Methylenebis{sulfanedial-[5-({2-[(benzoyl)amino]-
1,3-thiazol-4-yl}methyl)-4H-1,2,4-triazole-3,4-dial]})dibenzamide
(3c). Yield 79%; brown; mp 274e276 ꢀC; 1H NMR (300 MHz,
CDCl3): d 3.73 (s, 4H, CH2), 4.43 (s, 2H, CH2), 6.27 (s, 2H, Thi-
azole CH), 7.13e7.80 (m, 20H, ArH), 8.16 (s, 4H, NH); MS (%)
885 (14.1), 724 (15.7), 616 (14.3), 601 (100), 542 (23.5), 465
(3.9), 421 (13.2), 312 (5.8), 279 (7.2), 263 (11.0), 257 (11.7),
256 (35.8), 216 (32.8), 91 (22), 83 (27.1), 69 (29.6); Anal.
C41H32N12O4S4 (C, H, N, O).
4.1.4.4. 3-{N-[4-(4-(Benzoylamino)-5-[(cyanomethyl)sulfanyl]-
4H-1,2,4-triazol-3-ylmethyl)-1,3-thiazol-2-yl]amino}propanoic
acid (4d). Yield 78%; yellow; mp 275e277 ꢀC; 1H NMR
(300 MHz, CDCl3): d 2.43e2.48 (t, 2H, CH2, J ¼ 4.1 Hz),
3.31e3.37 (q, 2H, CH2, J ¼ 7.3 Hz), 3.84 (s, 2H, CH2), 4.11e
4.18 (t, 1H, NH, J ¼ 7.8 Hz), 4.34 (s, 2H, CH2), 6.26 (s, 1H, Thi-
azole CH), 7.22e7.43 (m, 5H, ArH), 8.25 (s, 1H, NH), 10.84 (bs,
1H, OH); MS (%) 443 (Mþ, 56.8), 362 (100), 351 (6.9), 349 (16),
348 (12.8), 347 (26.8), 337 (9.7), 331 (12.4), 323 (9.7), 256
(8.8); Anal. C18H17N7O3S2 (C, H, N, O).
4.1.3.4. 3-[4-(4-(Benzoylamino)-5-[([4-(benzoylamino)-5-(2-[(2-
carboxyethyl)amino]-1,3-thiazol-4-ylmethyl)-4H-1,2,4-triazol-
3-yl]sulfanylmethyl)sulfanyl]-4H-1,2,4-triazol-3-ylmethyl)-1,
3-thiazol-2-yl]aminopropanoic acid (3d). Yield 89%; yellow;
4.1.5. General preparation of methyl{[4-(benzoylamino)-5-
({2-[(chloroacetyl)amino]-1,3-thiazol-4-yl}methyl)-4H-
1,2,4-triazol-3-yl]sulfanyl}acetate
A solution of triazoles 2aed (0.01 mol), 0.4 g (0.01 mol)
of sodium hydroxide and methyl bromoacetate 1.53 g
(0.01 mol) was prepared. To this, acidic alumina was added
in 1:5 equivalent of triazole. The reaction mixture was mixed,
and the mixture was kept inside the alumina bath and irradi-
ated for 4e5 min at the power level of 300 W. The mixture
1
mp 255e257 ꢀC; H NMR (300 MHz, CDCl3): d 2.21e2.30
(t, 4H, CH2, J ¼ 4.5 Hz), 3.28e3.35 (q, 4H, CH2, J ¼ 7.4 Hz),
3.76 (s, 4H, CH2), 4.01e4.12 (t, 2H, NH, J ¼ 7.9 Hz), 4.63 (s,
2H, CH2), 6.26 (s, 2H, Thiazole CH), 7.32e7.76 (m, 10H,
ArH), 8.21 (s, 4H, NH), 10.65 (bs, 2H, OH); MS (%) 821
(Mþ, 13.6), 791 (100), 725 (40.9), 693 (6), 578 (7.3), 512
(4.1), 472 (13.6), 371 (5), 356 (3.4), 283 (13.7), 269 (6.4), 155
(14.4); Anal. C33H32N12O6S4 (C, H, N, O).

812
M. Shiradkar et al. / European Journal of Medicinal Chemistry 42 (2007) 807e816
was cooled and poured on ice. The solid thus separated was
extracted with hot ethanol and filtered. After cooling, the fil-
trate gave almost pure product.
thus obtained was crystallized from n-hexaneecarbon
tetrachloride mixture.
4.1.6.1.
N-{3-({2-[(Chloroacetyl)amino]-1,3-thiazol-4-yl}-
methyl)-5-[(2-hydrazino-2-oxoethyl)sulfanyl]-4H-1,2,4-triazol-
4-yl}benzamide (6a). Yield 83%; brown; mp 245e247 ꢀC; 1H
NMR (300 MHz, CDCl3): d 2.13 (d, 2H, NH2, J ¼ 6.5 Hz),
3.64 (s, 2H, CH2Cl), 3.94 (s, 2H, SCH2), 4.07e4.15 (t, 1H,
NH, J ¼ 4.3 Hz), 6.65 (s, 1H, Thiazole CH), 7.22e7.48 (m,
5H, ArH), 8.21 (broad, 2H, NH); MS (%) 481 (Mþ, 65),
419 (69), 386 (145), 356 (61), 328 (78), 311 (8.4), 269 (24),
235 (100), 201 (13), 184 (18), 156 (53), 124 (25), 89 (49);
Anal. C17H17N8O3S2Cl (C, H, N, O).
4.1.5.1. Methyl{[4-(benzoylamino)-5-({2-[(chloroacetyl)amino]-
1,3-thiazol-4-yl}methyl)-4H-1,2,4-triazol-3-yl]sulfanyl}acetate
(5a). Yield 82%; yellow; mp 259e251 ꢀC; 1H NMR
(300 MHz, CDCl3): d 2.11 (s, 3H, OCH3), 3.81 (s, 2H,
CH2), 3.89 (s, 2H, SCH2), 4.28 (s, 2H, CH2Cl), 6.32 (s, 1H,
Thiazole CH), 7.20e7.46 (m, 5H, ArH), 8.32 (broad, 2H,
NH); MS (%) 481 (Mþ, 100), 417 (14), 386 (12.3), 385
(11.3), 373 (7.2), 316 (7.7), 279 (79), 278 (10), 363 (8.2),
262 (19.5), 248 (7.7), 234 (7.9), 222 (10.5), 220 (5.7), 250
(31.6); Anal. C18H17N6O4S2Cl (C, H, N, O).
4.1.6.2. N-{3-({2-[(Acetyl)amino]-1,3-thiazol-4-yl}methyl)-5-
[(2-hydrazino-2-oxoethyl)sulfanyl]-4H-1,2,4-triazol-4-yl}ben-
4.1.5.2. Methyl{[4-(benzoylamino)-5-({2-[(acetyl)amino]-1,3-
thiazol-4-yl}methyl)-4H-1,2,4-triazol-3-yl]sulfanyl}acetate
(5b). Yield 78%; yellow; mp 261e263 ꢀC; 1H NMR
(300 MHz, CDCl3): d 2.17 (s, 3H, OCH3), 3.52 (s, 3H,
COCH3), 3.74 (s, 2H, CH2), 3.92 (s, 2H, SCH2), 6.46 (s,
1H, Thiazole CH), 7.17e7.38 (m, 5H, ArH), 8.13 (broad,
2H, NH); MS (%) 447 (Mþ, 9), 387 (31), 337 (1), 323
(2), 309 (1), 273 (100), 272 (8); Anal C18H18N6O4S2 (C,
H, N, O).
1
zamide (6b). Yield 82%; brown; mp 250e252 ꢀC; H NMR
(300 MHz, CDCl3): d 2.16 (d, 2H, NH2, J ¼ 6.5 Hz), 2.32 (s,
3H, CH3), 3.67 (s, 2H, CH2), 3.81 (s, 2H, SCH2), 4.15e4.31
(t, 1H, NH, J ¼ 4.5 Hz), 6.69 (s, 1H, Thiazole CH), 7.45e
7.71 (m, 5H, ArH), 8.12 (broad, 2H, NH); MS (%) 447
(Mþ, 78), 390 (72), 321 (26.3), 247 (6.3), 215 (18.3), 174
(65.3), 136 (25), 88 (100), 69 (14.3); Anal. C17H18N8O3S2
(C, H, N, O).
4.1.5.3. Methyl{[4-(benzoylamino)-5-({2-[(benzoyl)amino]-1,3-
thiazol-4-yl}methyl)-4H-1,2,4-triazol-3-yl]sulfanyl}acetate (5c).
Yield 75%; brown; mp 226e228 ꢀC; 1H NMR (300 MHz,
CDCl3): d 3.32 (s, 3H, OCH3), 3.62 (s, 2H, CH2), 3.83 (s,
2H, SCH2), 6.25 (s, 1H, Thiazole CH), 6.93e7.51 (m, 10H,
ArH), 8.22 (broad, 2H, NH); MS (%) 508 (Mþ, 69.9), 356
(54), 354 (43), 248 (100), 233 (39), 232 (15); Anal.
C23H20N6O4S2 (C, H, N, O).
4.1.6.3. N-{3-({2-[(Benzoyl)amino]-1,3-thiazol-4-yl}methyl)-
5-[(2-hydrazino-2-oxoethyl)sulfanyl]-4H-1,2,4-triazol-4-yl}-
benzamide (6c). Yield 71%; brown; mp 222e224 ꢀC; 1H
NMR (300 MHz, CDCl3): d 2.11 (d, 2H, NH2, J ¼ 6.5 Hz),
3.38 (s, 2H, CH2), 3.76 (s, 2H, SCH2), 4.12e4.39 (t, 1H,
NH, J ¼ 4.1 Hz), 6.11 (s, 1H, Thiazole CH), 7.13e7.68 (m,
10H, ArH), 8.10 (broad, 2H, NH); MS (%) 508 (Mþ, 89),
486 (31), 421 (60), 378 (14.3), 352 (45), 305 (24), 241 (73),
208 (56), 174 (66), 146 (100), 109 (18), 88 (15); Anal. C22H20
N8O3S2 (C, H, N, O).
4.1.5.4. 3-{N-[4-(4-(Benzoylamino)-5-[(2-methoxy-2-oxoethyl)-
sulfanyl]-4H-1,2,4-triazol-3-ylmethyl)-1,3-thiazol-2-yl]amino}-
propanoic acid (5d). Yield 79%; pale green; mp above
4.1.6.4. 3-{N-[4-(4-(Benzoylamino)-5-[(2-hydrazino-2-oxoethyl)-
sulfanyl]-4H-1,2,4-triazol-3-ylmethyl)-1,3-thiazol-2-yl]amino}-
1
300 ꢀC; H NMR (300 MHz, CDCl3): d 2.30e2.41 (q, 2H,
1
propanoic acid (6d). Yield 84%; brown; mp 243e245 ꢀC; H
CH2, J ¼ 4.0 Hz), 3.18e3.23 (t, 2H, CH2, J ¼ 7.3 Hz), 3.46
(s, 3H, OCH3), 3.61 (s, 2H, CH2), 3.93 (s, 2H, SCH2),
4.11e4.18 (t, 1H, NH, J ¼ 7.9 Hz), 6.26 (s, 1H, Thiazole
CH), 7.25e7.61 (m, 5H, ArH), 8.29 (broad, 1H, NH), 11.13
(broad, 1H, OH); MS (%) 476 (Mþ, 100), 379 (67), 309
(41), 272 (58), 131 (16), 120 (60), 117 (44), 94 (27), 91
(48), 84 (81); Anal. C19H20N6O5S2 (C, H, N, O).
NMR (300 MHz, CDCl3): d 2.13 (d, 2H, NH2, J ¼ 6.1 Hz),
2.27e2.31 (q, 2H, CH2, J ¼ 4.2 Hz), 3.16e3.27 (t, 2H, CH2,
J ¼ 7.1 Hz), 3.46 (s, 2H, CH2), 3.84 (s, 2H, SCH2), 4.23e
4.45 (t, 2H, NH, J ¼ 4.1 Hz, J ¼ 8.1 Hz), 6.14 (s, 1H, Thiazole
CH), 7.34e7.61 (m, 5H, ArH), 8.03 (broad, 1H, NH), 11.09
(broad, 1H, OH); MS (%) 476 (Mþ, 93.3), 435 (32), 389
(22), 334 (56.4), 306 (28), 247 (64), 217 (100), 147 (83),
108 (71), 79 (10.2); Anal. C18H20N8O4S2 (C, H, N, O).
4.1.6. General preparation of N-{3-({2-[(substituted)-
amino]-1,3-thiazol-4-yl}methyl)-5-[(2-hydrazino-2-
oxoethyl)sulfanyl]-4H-1,2,4-triazol-4-yl}benzamide
4.1.7. GeneralpreparationofN-[3-{[2-(substituted-hydrazino)-
2-oxoethyl]sulfanyl}-5-({2-[(substituted)amino]-1,3-thiazol-
4-yl}methyl)-4H-1,2,4-triazol-4-yl]benzamide
To a solution of 6aed (0.01 mol) in dichloromethane (excess
amount), appropriate acid chloride (0.01 mol) was added drop-
wise with constant vigorous stirring. After 25 min of stirring,
acidic alumina (10 g) was added. Dichloromethane was then
evaporated in vacuo, and the mixture was kept inside the
A solution of 5aed (0.01 mol) with 5 ml (0.01 mol)
hydrazine hydrate (98%) was prepared in 10 ml ethanol.
To this acidic alumina (10 g) was added. Ethanol was
then evaporated in vacuo, and the mixture was kept inside
the alumina bath and irradiated for 5e6 min at the power
level of 300 W. The mixture was cooled and the product
was extracted with ether. Ether was distilled off and product

M. Shiradkar et al. / European Journal of Medicinal Chemistry 42 (2007) 807e816
813
alumina bath and irradiated for 5e6 min at the power level of
300 W. The mixture was cooled and the product was extracted
with ether. Ether was distilled off and product thus obtained
was crystallized from n-hexaneecarbon tetrachloride mixture.
(14), 242 (13), 223 (100), 194 (29), 136 (21); Anal.
C19H20N8O4S2 (C, H, N, O).
4.1.7.6. N-[3-{[2-(2-Benzoylhydrazino)-2-oxoethyl]sulfanyl}-
5-({2-[(acetyl) amino]-1,3-thiazol-4-yl}methyl)-4H-1,2,4-tria-
zol-4-yl]benzamide (7f). Yield 74%; yellow; mp 286e
4.1.7.1.
N-[3-{[2-(2-Acetylhydrazino)-2-oxoethyl]sulfanyl}-
1
5-({2-[(chloroacetyl)amino]-1,3-thiazol-4-yl}methyl)-4H-1,2,4-
288 ꢀC; H NMR (300 MHz, CDCl3): d 2.38 (s, 3H, CH3),
triazol-4-yl]benzamide (7a). Yield 86%; yellow; mp 241e
3.68 (s, 2H, CH2), 3.71 (s, 2H, SCH2), 4.13e4.21 (dd, 2H,
JNHeNH ¼ 4.23, JNHeNH ¼ 4.54), 6.12 (s, 1H, Thiazole CH),
6.94e7.21 (m, 10H, ArH), 8.09 (s, 2H, NH); MS (%) 550
(Mþ, 86), 496 (71), 431 (14), 357 (78), 329 (38), 305 (41),
287 (17), 241 (35), 167 (100), 109 (37), 98 (19); Anal.
C24H22N8O4S2 (C, H, N, O).
1
244 ꢀC; H NMR (300 MHz, CDCl3): d 2.12 (s, 3H, CH3),
3.43 (s, 2H, CH2), 3.74 (s, 2H, SCH2), 4.11e4.20 (dd, 2H,
JNHeNH ¼ 4.21, JNHeNH ¼ 4.48), 4.54 (s, 2H, CH2Cl), 6.63
(s, 1H, Thiazole CH), 7.23e7.53 (m, 5H, ArH), 8.32 (s, 2H,
NH); MS (%) 523 (Mþ, 56), 489 (29), 462 (45), 408 (27),
389 (71), 318 (41), 274 (16), 223 (100), 188 (29), 179 (22);
Anal. C19H20N8O4S2 (C, H, N, O).
4.1.7.7. N-[3-{[2-(2-Benzoylhydrazino)-2-oxoethyl]sulfanyl}-
5-({2-[(benzoyl)amino]-1,3-thiazol-4-yl}methyl)-4H-1,2,4-tria-
zol-4-yl]benzamide (7g). Yield 79%; yellow; mp 229e233 ꢀC;
1H NMR (300 MHz, CDCl3): d 3.16 (s, 2H, CH2), 3.31 (s, 2H,
SCH2), 4.32e4.39 (dd, 2H, JNHeNH ¼ 4.37, JNHeNH ¼ 4.74),
6.47 (s, 1H, Thiazole CH), 7.11e7.82 (m, 15H, ArH), 8.26
(s, 2H, NH); MS (%) 613 (Mþ, 91), 587 (66), 526 (19), 471
(16), 436 (68), 376 (34), 316 (61), 223 (100), 111 (37), 119
(54); Anal. C19H20N8O4S2 (C, H, N, O).
4.1.7.2.
N-[3-{[2-(2-Acetylhydrazino)-2-oxoethyl]sulfanyl}-
5-({2-[(acetyl)amino]-1,3-thiazol-4-yl}methyl)-4H-1,2,4-tria-
zol-4-yl]benzamide (7b). Yield 71%; yellow; mp 227e229 ꢀC;
1H NMR (300 MHz, CDCl3): d 2.42 (s, 6H, CH3), 3.74 (s, 2H,
CH2), 3.87 (s, 2H, SCH2), 4.20e4.28 (dd, 2H, JNHeNH ¼ 4.35,
JNHeNH ¼ 4.76), 6.27 (s, 1H, Thiazole CH), 7.11e7.32 (m,
5H, ArH), 8.18 (s, 2H, NH); MS (%) 488 (Mþ, 97), 408
(62), 398 (17.2), 359 (9.1), 327 (74), 297 (54), 241 (8.3),
223 (100), 174 (24), 146 (27); Anal. C19H20N8O4S2 (C, H,
N, O).
4.1.7.8. 3-{N-(4-[(4-(Benzoylamino)-5-[2-(2-benzoylhydrazino)-
2-oxoethyl]sulfanyl-4H-1,2,4-triazol-3-yl)methyl]-1,3-thiazol-
2-yl)amino}propionic acid (7h). Yield 83%; yellow; mp 230e
1
235 ꢀC; H NMR (300 MHz, CDCl3): d 2.21e2.29 (q, 2H,
4.1.7.3.
N-[3-{[2-(2-Acetylhydrazino)-2-oxoethyl]sulfanyl}-
CH2, J ¼ 4.5 Hz), 3.14e3.21 (t, 2H, CH2, J ¼ 7.7 Hz), 3.62
5-({2-[(benzoyl)amino]-1,3-thiazol-4-yl}methyl)-4H-1,2,4-tria-
zol-4-yl]benzamide (7c). Yield 82%; yellow; mp 226e231 ꢀC;
1H NMR (300 MHz, CDCl3): d 2.03 (s, 3H, CH3), 3.21 (s, 2H,
CH2), 3.45 (s, 2H, SCH2), 4.24e4.31 (dd, 2H, JNHeNH ¼ 4.30,
JNHeNH ¼ 4.70), 6.76 (s, 1H, Thiazole CH), 7.31e7.87 (m,
10H, ArH), 8.42 (s, 2H, NH); MS (%) 550 (Mþ, 11), 507
(56), 467 (35), 423 (16), 374 (52), 329 (47), 276 (74), 223
(100), 164 (35), 151 (08); Anal. C19H20N8O4S2 (C, H, N, O).
(s, 2H, CH2), 3.85 (s, 2H, SCH2), 4.25e4.37 (dd, 2H, JNHe
¼ 4.7, JNHeNH ¼ 4.9), 6.61 (s, 1H, Thiazole CH), 7.26e
NH
7.35 (m, 10H, ArH), 8.32 (s, 2H, NH), 10.87 (broad, 1H,
OH); MS (%) 580 (Mþ, 97), 542 (17), 505 (47), 486 (53),
451 (68), 364 (24), 307 (37), 223 (100), 197 (41), 164 (46);
Anal. C19H20N8O4S2 (C, H, N, O).
4.1.7.9. N-[3-{[2-(2-Chloroacetylhydrazino)-2-oxoethyl]sul-
fanyl}-5-({2-[(chloroacetyl)amino]-1,3-thiazol-4-yl}methyl)-
4H-1,2,4-triazol-4-yl]benzamide (7i). Yield 77%; yellow; mp
233e237 ꢀC; 1H NMR (300 MHz, CDCl3): d 3.12 (s, 2H,
CH2), 3.38 (s, 2H, SCH2), 4.21e4.33 (dd, 2H, JNHe
4.1.7.4. 3-[N-(4-[5-[2-(2-Acetylhydrazino)-2-oxoethyl]sulfanyl-
4-(benzoylamino)-4H-1,2,4-triazol-3-yl]methyl-1,3-thiazol-2-yl)-
amino]propanoic acid (7d). Yield 87%; yellow; mp 239e
1
242 ꢀC; H NMR (300 MHz, CDCl3): d 2.11 (s, 3H, CH3),
2.31e2.37 (q, 2H, CH2, J ¼ 4.7 Hz), 3.20e3.26 (t, 2H, CH2,
J ¼ 7.3 Hz), 3.53 (s, 2H, CH2), 3.79 (s, 2H, SCH2), 4.12e
4.20 (dd, 2H, JNHeNH ¼ 4.4, JNHeNH ¼ 4.6), 6.39 (s, 1H, Thi-
azole CH), 7.11e7.42 (m, 5H, ArH), 8.27 (s, 2H, NH), 11.13
(broad, 1H, OH); MS (%) 518 (Mþ, 64), 476 (33), 438 (19),
387 (43), 341 (51), 317 (21), 264 (36), 224 (100), 151 (16),
138 (67); Anal. C19H20N8O4S2 (C, H, N, O).
¼ 4.10, JNHeNH ¼ 4.52), 4.47 (s, 4H, CH2Cl), 6.67 (s,
NH
1H, Thiazole CH), 7.25e7.56 (m, 5H, ArH), 8.24 (s, 2H,
NH); MS (%) 557 (Mþ, 84), 513 (46), 474 (13), 431 (68),
417 (49), 328 (42), 274 (12), 223 (100), 184 (18), 161 (34);
Anal. C19H20N8O4S2 (C, H, N, O).
4.1.7.10. N-[3-{[2-(2-Chloroacetylhydrazino)-2-oxoethyl]sul-
fanyl}-5-({2-[(acetyl)amino]-1,3-thiazol-4-yl}methyl)-4H-1,2,4-
triazol-4-yl]benzamide (7j). Yield 57%; dark brown; mp 166e
168 ꢀC; 1H NMR (300 MHz, CDCl3): d 2.53 (s, 3H, CH3), 3.81
(s, 2H, CH2), 3.92 (s, 2H, SCH2), 4.17 (s, 2H, CH2Cl), 4.28e
4.34 (dd, 2H, JNHeNH ¼ 4.52, JNHeNH ¼ 4.92), 6.41 (s, 1H,
Thiazole CH), 7.26e7.46 (m, 5H, ArH), 8.32 (s, 2H, NH);
MS (%) 523 (Mþ, 54), 487 (36), 437 (84), 369 (54.2), 284
(9.3), 238 (100), 158 (12), 128 (37), 77 (32); Anal.
C19H19N8O4S2Cl (C, H, N, O).
4.1.7.5. N-[3-{[2-(2-Benzoylhydrazino)-2-oxoethyl]sulfanyl}-
5-({2-[(chloroacetyl)amino]-1,3-thiazol-4-yl}methyl)-4H-1,2,4-
triazol-4-yl]benzamide (7e). Yield 82%; yellow; mp 241e
1
244 ꢀC; H NMR (300 MHz, CDCl3): d 3.34 (s, 2H, CH2),
3.67 (s, 2H, SCH2), 4.15e4.23 (dd, 2H, JNHeNH
¼ 4.23, JNHeNH ¼ 4.46), 4.36 (s, 2H, CH2Cl), 6.52 (s, 1H, Thi-
azole CH), 7.17e7.72 (m, 10H, ArH), 8.45 (s, 2H, NH); MS
(%) 585 (Mþ, 84), 548 (17), 389 (26), 374 (46), 331 (58), 247

814
M. Shiradkar et al. / European Journal of Medicinal Chemistry 42 (2007) 807e816
4.1.7.11. N-[3-{[2-(2-Chloroacetylhydrazino)-2-oxoethyl]sul-
fanyl}-5-({2-[(benzoyl)amino]-1,3-thiazol-4-yl}methyl)-4H-
1,2,4-triazol-4-yl]benzamide (7k). Yield 78%; yellow; mp
232e235 ꢀC; 1H NMR (300 MHz, CDCl3): d 3.27 (s, 2H,
CH2), 3.46 (s, 2H, SCH2), 4.13e4.22 (dd, 2H, JNHeNH
¼ 4.11, JNHeNH ¼ 4.57), 4.41 (s, 2H, CH2Cl), 6.39 (s, 1H, Thi-
azole CH), 7.29e7.63 (m, 10H, ArH), 8.41 (s, 2H, NH); MS
(%) 585 (Mþ, 79), 576 (16), 513 (27), 415 (42), 384 (67),
306 (41), 264 (34), 223 (100), 167 (26), 144 (18); Anal.
C19H20N8O4S2 (C, H, N, O).
4.1.8.3. N-[3-({2-[(2E )-2-Benzylidenehydrazino]-2-oxoethyl}-
sulfanyl)-5-({2-[(benzoyl)amino]-1,3-thiazol-4-yl}methyl)-4H-
1,2,4-triazol-4-yl]benzamide (8c). Yield 81%; pale brown;
mp 217e219 ꢀC; 1H NMR (300 MHz, CDCl3): d 3.63 (s,
2H, CH2), 4.17 (s, 2H, SCH2), 6.23 (s, 1H, Thiazole CH),
7.21e7.64 (m, 15H, ArH), 8.16 (s, 3H, NH), 8.41 (s, 1H,
N]CH); MS (%) 597 (Mþ, 79), 521 (25), 455 (52), 413
(63), 368 (9.2), 308 (41), 284 (31), 242 (37), 178 (100), 128
(15.2), 97 (28), 87 (7.4); Anal. C29H24N8O3S2 (C, H, N, O).
4.1.8.4. 3-{N-[4-(4-(Benzoylamino)-5-[(2-oxo-2-2-[(Z)-1-phe-
nylmethylidene]hydrazinoethyl)sulfanyl]-4H-1,2,4-triazol-3-yl-
methyl)-1,3-thiazol-2-yl]amino}propanoic acid (8d). Yield
4.1.7.12. 3-[N-(4-[4-(Benzoylamino)-5-(2-[2-(2-chloroacetyl)-
hydrazino]-2-oxo-ethylsulfanyl)-4H-1,2,4-triazol-3-yl]methyl-
1,3-thiazol-2-yl)amino]propanoic acid (7l). Yield 80%;
yellow; mp 237e239 ꢀC; 1H NMR (300 MHz, CDCl3):
d 2.11e2.18 (q, 2H, CH2, J ¼ 4.68 Hz), 3.23e3.29 (t, 2H,
CH2, J ¼ 7.3 Hz), 3.53 (s, 2H, CH2), 3.71 (s, 2H, SCH2),
4.07e4.16 (dd, 2H, JNHeNH ¼ 4.4, JNHeNH ¼ 4.7), 4.23 (s,
2H, CH2Cl), 6.49 (s, 1H, Thiazole CH), 7.12e7.19 (m, 5H,
ArH), 8.54 (s, 2H, NH), 11.17 (broad, 1H, OH); MS (%)
553 (Mþ, 91), 512 (69), 482 (12), 438 (89), 376 (73), 264
(58), 234 (76), 223 (100), 166 (28), 123 (21); Anal.
C19H20N8O4S2 (C, H, N, O).
1
78%; brown; mp 120e122 ꢀC; H NMR (300 MHz, CDCl3):
d 2.65e2.71 (t, 2H, CH2, J ¼ 4.7 Hz), 3.23e3.31 (q, 2H,
CH2, J ¼ 7.5 Hz), 3.92 (s, 2H, CH2), 4.17 (s, 2H, SCH2),
4.32 (t, 1H, NH, J ¼ 8.3 Hz), 6.23 (s, 1H, Thiazole CH),
7.17e7.63 (m, 10H, ArH), 8.15 (s, 2H, NH), 8.32 (s, 1H,
N]CH), 10.87 (bs, 1H, OH); MS (%) 564 (Mþ, 74), 497
(45), 426 (13), 364 (63), 326 (32), 248 (65), 185 (12), 146
(100), 109 (37), 87 (42); Anal. C25H24N8O4S2 (C, H, N, O).
4.1.9. General preparation of N-[3-{[(4-amino-5-thioxo-
4,5-dihydro-1H-1,2,4-triazol-3-yl)methyl]sulfanyl}-5-({2-
[(substituted)amino]-1,3-thiazol-4-yl}methyl)-4H-1,2,4-
triazol-4-yl]benzamide
4.1.8. General procedure for N-[3-({2-[(2E )-2-benzy-
lidenehydrazino]-2-oxoethyl}sulfanyl)-5-({2-[(substituted)-
amino]-1,3-thiazol-4-yl}methyl)-4H-1,2,4-triazol-4-yl]benzamide
Compounds 6aed (0.01 mol) were dissolved in alcoholic po-
tassium hydroxide (0.01 mol) and kept for stirring. Carbon disul-
phide (0.015 mol) was added dropwise to the solution with
stirring. Thicksolidmasswasobtainedtowhich50 mlofabsolute
alcohol was added. Stirring was continued for 16 h. At the end of
16th hour dry ether was added to the mixture. The precipitate (thi-
ocarbazate) obtained was taken immediately for the next step.
A solution of thiocarbazate (0.01 mol) with hydrazine hy-
drate (0.01 mol) was prepared in 10 ml ethanol. To this acidic
alumina (10 g) was added. Ethanol was then evaporated in va-
cuo, and the mixture was kept inside the alumina bath and ir-
radiated for 5e6 min at the power level of 300 W. The mixture
was cooled and poured on ice. The solid thus separated was
filtered and extracted with ether. Ether was distilled off and
product thus obtained was crystallized from hot ethanol.
A
solution of 6aed (0.01 mol) with benzaldehyde
(0.01 mol) was prepared in 10 ml ethanol. To this acidic
alumina (10 g) was added. Ethanol was then evaporated in
vacuo, and the mixture was kept inside the alumina bath
and irradiated for 1 min at the power level of 300 W. The
mixture was cooled and poured on ice. The solid thus sep-
arated was filtered and extracted with ether. Ether was dis-
tilled off and product thus obtained was crystallized from
hot ethanol.
4.1.8.1. N-[3-({2-[(2E )-2-Benzylidenehydrazino]-2-oxoethyl}sul-
fanyl)-5-({2-[(chloroacetyl)amino]-1,3-thiazol-4-yl}methyl)-
4H-1,2,4-triazol-4-yl]benzamide (8a). Yield 81%; brown; mp
222e224 ꢀC; 1H NMR (300 MHz, CDCl3): d 3.77 (s, 2H,
CH2), 4.16 (s, 2H, SCH2), 4.13 (s, 2H, CH2Cl), 6.22 (s, 1H,
Thiazole CH), 7.30e7.62 (m, 10H, ArH), 8.16 (s, 3H, NH),
8.27 (s, 1H, N]CH); MS (%) 569 (Mþ, 69), 502 (19), 457
(37), 379 (21), 315 (58), 246 (24), 195 (35), 134 (100), 107
(11.4), 88 (12.3); Anal. C24H21N8O3S2Cl (C, H, N, O).
4.1.9.1. N-[3-{[(4-Amino-5-thioxo-4,5-dihydro-1H-1,2,4-tria-
zol-3-yl)methyl]sulfanyl}-5-({2-[(chloroacetyl)amino]-1,3-
thiazol-4-yl}methyl)-4H-1,2,4-triazol-4-yl]benzamide
(9a).
Yield 72%; brown; mp 228e230 ꢀC; 1H NMR (300 MHz,
CDCl3): d 2.16 (s, 2H, NH2), 3.76 (s, 2H, CH2), 4.07 (s, 2H,
CH2), 4.25 (s, 2H, CH2Cl), 6.20 (s, 1H, Thiazole CH),
7.23e7.67 (m, 5H, ArH), 8.11 (s, 2H, NH), 12.49 (s, 1H,
SH); MS (%) 537 (Mþ, 82), 467 (31), 431 (26), 384 (31),
326 (13.2), 247 (15), 226 (17), 125 (100); Anal.
C18H17N10O2S3Cl (C, H, N, O).
4.1.8.2. N-[3-({2-[(2E )-2-Benzylidenehydrazino]-2-oxoethyl}-
sulfanyl)-5-({2-[(acetyl)amino]-1,3-thiazol-4-yl}methyl)-4H-
1,2,4-triazol-4-yl]benzamide (8b). Yield 83%; pale brown; mp
178e180 ꢀC; 1H NMR (300 MHz, CDCl3): d 2.32 (s, 3H,
CH3), 3.97 (s, 2H, CH2), 4.21 (s, 2H, SCH2), 6.25 (s, 1H, Thi-
azole CH), 7.31e7.65 (m, 10H, ArH), 8.26 (s, 3H, NH), 8.36
(s, 1H, N]CH); MS (%) 535 (Mþ, 94), 519 (41), 487 (9.6),
431 (26), 413 (8.4), 389 (100), 365 (20); Anal. C24H22N8
O3S2 (C, H, N, O).
4.1.9.2. N-[3-{[(4-Amino-5-thioxo-4,5-dihydro-1H-1,2,4-triazol-
3-yl)methyl]sulfanyl}-5-({2-[(acetyl)amino]-1,3-thiazol-4-yl}-
methyl)-4H-1,2,4-triazol-4-yl]benzamide (9b). Yield 71%;
brown; mp 252e254 ꢀC; 1H NMR (300 MHz, CDCl3):

M. Shiradkar et al. / European Journal of Medicinal Chemistry 42 (2007) 807e816
815
d 2.13 (s, 2H, NH2), 2.35 (s, 3H, CH3), 3.79 (s, 2H, CH2), 4.14
Method: Well diffusion method [41];
Solvent: Chloroform;
(s, 2H, CH2), 6.19 (s, 1H, Thiazole CH), 7.11e7.35 (m, 5H,
ArH), 8.08 (s, 2H, NH), 12.43 (s, 1H, SH); MS (%) 503
(Mþ, 76), 454 (32), 350 (30), 335 (100), 323 (2.93), 222
(12.26), 220 (3.73), 207 (5.86), 192 (7.07); Anal.
C18H18N10O2S3 (C, H, N, O).
Condition: 24 h at 24e28 ꢀC;
Medium: The nutrient agar medium;
Concentrations: 50 mM and 100 mM;
Standard: The antibiotic gentamycin.
4.1.9.3. N-[3-{[(4-Amino-5-thioxo-4,5-dihydro-1H-1,2,4-tria-
zol-3-yl)methyl]sulfanyl}-5-({2-[(benzoyl)amino]-1,3-thiazol-
The nutrient agar medium, 20 ml was poured into the sterile
Petri dishes. To the solidified plates, wells were made using
a sterile cork borer 10 mm in diameter. The 24-h subcultured
bacteria was inoculated in the Petri plates, with a sterile cotton
swab dipped in the nutrient broth medium. After inoculating,
the compounds were dissolved separately with the chloroform
solvent and poured into the wells with varying concentrations
ranging from 50 to 100 mM using a micropipette. The plates
were left over for 24 h at 24e28 ꢀC. The antibiotic gentamy-
cin was used as a standard for comparative study.
4-yl}methyl)-4H-1,2,4-triazol-4-yl]benzamide
(9c). Yield
1
80%; brown; mp 264e266 ꢀC; H NMR (300 MHz, CDCl3):
d 2.41 (s, 2H, NH2), 3.75 (s, 2H, CH2), 4.34 (s, 2H, CH2),
6.23 (s, 1H, Thiazole CH), 7.14e7.74 (m, 10H, ArH), 8.17
(s, 2H, NH), 12.63 (s, 1H, SH); MS (%) 565 (Mþ, 93.3),
513 (24), 476 (21), 432 (16), 421 (12), 323 (65), 308 (41),
289 (27), 230 (38), 207 (100), 142 (35.7), 109 (23); Anal.
C23H20N10O2S3 (C, H, N, O).
The percentage of inhibition was calculated by the formula:
% Inhibition ¼ Diameter of the inhibition zone ꢃ 100.
4.1.9.4. 3-[(4-[5-[(4-Amino-5-sulfanyl-4H-1,2,4-triazol-3-yl)-
methyl]sulfanyl-4-(benzoylamino)-4H-1,2,4-triazol-3-yl]methyl-
1,3-thiazol-2-yl)amino]propanoic acid (9d). Yield 77%;
brown; mp 237e239 ꢀC; 1H NMR (300 MHz, CDCl3):
d 2.13 (s, 2H, NH2), 2.46e2.49 (t, 2H, CH2, J ¼ 4.3 Hz),
3.14e3.20 (q, 2H, CH2, J ¼ 6.7 Hz), 3.98 (s, 2H, CH2),
4.23e4.29 (t, 1H, NH, J ¼ 7.3 Hz), 4.36 (s, 2H, CH2), 6.26
(s, 1H, Thiazole CH), 7.27e7.56 (m, 5H, ArH), 8.17 (s, 1H,
NH), 10.64 (bs, 1H, OH), 12.35 (s, 1H, SH); MS (%) 533
(Mþ, 84), 497 (23), 450 (47), 438 (38), 371 (25), 370 (75),
354 (10), 235 (100), 220 (22), 207 (68), 192 (70); Anal.
C19H20N10O3S3 (C, H, N, O).
Acknowledgements
Authors are thankful to Dr. K.G. Bothara, Principal,
AISSMS College of Pharmacy, Pune, India for providing the
facilities and to Tuberculosis Antimicrobial Acquisition and
Coordinating Facility (TAACF) for the antitubercular activity.
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