Synthesis of selected 5-thio-substituted tetrazole derivatives and evaluation of their antibacterial and antifungal activities

Article abstract of DOI:10.2298/JSC090421001D

Several 5-thio-substituted tetrazole derivatives were efficiently synthesized by a three-step process. The substituted tetrazol-5-thiol, namely, 1-benzyl-1H-tetrazole-5-thiol (2) was prepared by refluxing commercially available benzyl isothiocyanate (1) w

Full text of DOI:10.2298/JSC090421001D

J. Serb. Chem. Soc. 76 (2) 165–175 (2011)
UDC 542.913+547.367+547.79:615.281/.282
JSCS–4109
Original scientific paper
Synthesis of selected 5-thio-substituted tetrazole derivatives and
evaluation of their antibacterial and antifungal activities
VARADARAJI DHAYANITHI1, SUBAN SHAFI SYED1, KUBARAN KUMARAN1,
KASI REGURAMAN JAI SANKAR1, RAMASWAMY VENKAT RAGAVAN2,
PALUSA SANATH KUMAR GOUD3, NALILU SUCHETHA KUMARI4
5
*
and HARI NARAYAN PATI
1P.G. and Research Department of Chemistry, Islamiah College, Vaniyambadi 632 752,
2Chemistry Division, School of Science and Humanities, VIT University, Vellore 632 014
3N. E. T. College of Pharmacy, Raichur 584 102, 4Department of Biochemistry, K. S. Hegde
Medical Academy, Mangalore 574 162 and 5Department of Chemistry,
Sambalpur University, Jyoti Vihar 768 019, India
(Received 21 April 2009, revised 13 September 2010)
Abstract: Several 5-thio-substituted tetrazole derivatives were efficiently syn-
thesized by a three-step process. The substituted tetrazol-5-thiol, namely, 1-ben-
zyl-1H-tetrazole-5-thiol (2) was prepared by refluxing commercially available
benzyl isothiocyanate (1) with sodium azide in water. The second step was the
synthesis of 1-benzyl-5-[(3-bromopropyl)thio]-1H-tetrazole (3) by thioalkyla-
tion of tetrazole-5-thiol 2 with 1,3-dibromopropane in tetrahydrofuran. Finally,
the 5-thio-substituted tetrazole derivatives 4a–i were prepared by condensation
of 3 with the corresponding amine or thiol. The structures of the newly synthe-
sized compounds were characterized by NMR, LC/MS/MS, IR spectral data
and elemental analysis. All the synthesized compounds were screened for their
antibacterial and antifungal activities.
Keywords: substituted thiol; tetrazole; 1,3-dibromopropane; antibacterial; anti-
fungal.
INTRODUCTION
Tetrazole and its derivatives have attracted interest because of their unique
structure and their applications as antihypertensive, anti-allergic, antibiotic and
1–5
anticonvulsant agents.
Number of publications and patents on the preparation,
properties and applications of tetrazole derivatives is increasing every year with
respect to other heterocyclic systems. Development of the tetrazole chemistry has
been largely associated with the wide-scale application of these compounds in
1–9
medicine, biochemistry, agriculture, etc.
The tetrazole functionality plays an
*Corresponding author. E-mail: hnpati@gmail.com
doi: 10.2298/JSC090421001D
165
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166
DHAYANITHI et al.
important role in medicinal chemistry, primarily due to its ability to serve as the
10
bioequivalent (bioisostere) of the carboxylic acid group, and also the class of
1–5
tetrazole compounds has been used both as anticancer and antimicrobial agents.
In particular, 1-substituted tetrazole and 5-thio-substituted tetrazoles have been
11–19
used in the synthesis of pharmacologically active drugs.
Tetrazoles are quite suitable ligands and can serve as replacement for car-
boxylic acids not only in medicinal chemistry, but also in supramolecular che-
mistry. Most importantly, tetrazoles are highly flexible ligands and can adapt
20–23
easily to different binding modes.
As there is also a need for new and ef-
fective broad-spectrum antifungal and antibacterial agents, it was decided to ex-
ploit this interest by ascertaining the molecular features essential for activity and
utilizing them to develop a new class of drugs. Prompted by the various bio-
logical activities of tetrazole and its 5-thio substituted derivatives, the synthesis
of a novel series of 5-thio substituted tetrazole derivatives and a study of their
biological activities was envisioned. Thus, the synthesis of the new 5-thio substi-
tuted tetrazole derivatives 3 and 4a–i (Scheme 1 and Table I) and an evaluation
of their antibacterial and antifungal properties were the objectives of this study.
Scheme 1. Synthesis scheme for the compounds.
RESULTS AND DISCUSSION
Synthesis
In order to prepare a variety of derivatives of 1-benzyl-5-(propylthio)-1H-
-tetrazole, 1-benzyl-5-[(3-bromopropyl)thio]tetrazole (3) was prepared as a pre-
cursor. Preparation of 1-benzyl-5-[(3-bromopropyl)thio]tetrazole was accom-
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5-THIO-SUBSTITUTED TETRAZOLE DERIVATIVES
167
plished as given in Scheme 1. As depicted in Scheme 1, reaction between com-
mercially available benzyl isothiocyanate (1) and sodium azide in water provided
24
1-benzyl-1H-tetrazole-5-thiol (2) in good yield. The isolated compound 2 was
treated with 1,3-dibromopropane in tetrahydrofuran to give an intermediate,
1-benzyl-5-[(3-bromopropyl)thio]-1H-tetrazole (3). The synthon 3 is a new com-
pound and reported here for the first time. Compound 3 was treated with cor-
responding amines or thiols to afford the 5-thio-substituted tetrazole derivatives
4a–i.
TABLE I. Structure of the substituent (R) in the compounds 4a–i
Compound
(R2)N
Br
Compound
R
3
4e
N
N
N
N
4a
4b
4f
N
N
N
N
N
4g
N
N
N
N
N
4c
4h
4i
N
O
N
HN
N
4d
Cl
N
Cl
O
Br
N
HN
N
Characterization
1
The structures of the synthesized compounds were elucidated by H-NMR,
C-NMR, LC–MS and IR spectroscopy, and elemental analysis, the results of
13
which are given below.
1-Benzyl-5-[(3-bromopropyl)thio]-1H-tetrazole (3). Anal. Calcd. for
C H BrN S: C, 42.14; H, 4.47; N, 17.88 %. Found: C, 42.08; H, 4.46; N,
11 14
4
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DHAYANITHI et al.
–1
17.85 %. IR (KBr, cm ): 2964 (C–H), 1496 (N=N), 1453 (C=C), 1389 (C=N).
1
H-NMR (400 MHz, CDCl , δ / ppm): 2.29–2.36 (2H, qn), 3.42–3.49 (4H, m),
3
13
5.42 (2H, s), 7.27–7.44 (5H, m). C-NMR (100 MHz, CDCl , δ / ppm): 31.2,
3
31.5, 153.4, 51.0, 128.1, 129.0, 129.1, 132.7. MS Calcd. for C H BrN S:
11 14
4
+
313.22; Found: M +1, 312.9, 314. 9. MS/MS (m/z): 262.2, 233.6, 178.2, 102.0,
90.7.
3-(1-Benzyl-1H-tetrazol-5-ylthio)-N,N-dipropylpropan-1-amine (4a). Yield:
62 %; Anal. Calcd. for C H N S: C, 61.17; H, 8.10; N, 20.99 %. Found: C,
17 27
5
–1
61.08; H, 8.08; N, 21.03 %. IR (KBr, cm ): 2957 (C–H), 1497 (N=N), 1455
(C=C), 1388 (C=N). H-NMR (400 MHz, CDCl , δ / ppm): 0.84–0.88 (6H, t),
1
3
1.36–1.46 (4H, m), 1.85–1.91 (2H, qn), 2.30–2.34 (4H, t), 2.46–2.50 (2H, t), 3.33–
13
–3.37 (2H, t), 5.41 (2H, s), 7.27–7.39 (5H, m). C-NMR (100 MHz, CDCl , δ /
3
/ ppm): 11.9, 20.2, 26.9, 31.5, 56.0, 52.3, 128.0, 128.8, 129.0, 133.0, 154.3. MS
+
calculated for C H N S: 333.49; Found: M +1, 334.0. MS/MS (m/z): 233.4,
17 27
5
174.2, 132.3, 104.2, 90.1.
3-(1-Benzyl-1H-tetrazol-5-ylthio)-N-methyl-N-phenethylpropan-1-amine
(4b). Yield: 78 %. Anal. Calcd. for C H N S: C, 65.30; H, 6.80; N, 19.05 %.
20 25
5
–1
Found: C, 65.37; H, 6.79; N, 19.09 %. IR (KBr, cm ): 2947 (C–H), 1496
(N=N), 1453 (C=C), 1389 (C=N). H-NMR (400 MHz, CDCl , δ / ppm): 1.89–
1
3
–1.94 (2H, qn), 2.26 (3H, s), 2.45–2.49 (2H, t), 2.56–2.60 (2H, t), 2.71–2.76 (2H,
13
t), 3.26–3.30 (2H, t), 5.39 (2H, s), 7.17–7.36 (10H, m). C-NMR (100 MHz,
CDCl , δ / ppm): 26.8, 31.2, 33.7, 41.9, 50.8, 55.5, 59.4, 125.9, 128.1, 128.3,
3
128.7, 128.9, 129.0, 132.9, 140.4, 154.2. MS calculated for C H N S: 367.51;
20 25
5
+
Found: M +1, 368.1. MS/MS (m/z): 368.1, 339.8, 233.2, 208.0, 176.1, 105.2,
90.9.
2-[3-(1-Benzyl-1H-tetrazol-5-ylthio)propyl]-1,2,3,4-tetrahydroisoquinoline
(4c). Yield: 78 %; Anal. Calcd. for C H N S: C, 65.66; H, 6.29; N, 19.15 %.
20 23
5
–1
Found: C, 65.60; H, 6.30; N, 19.16 %. IR (KBr, cm ): 2922 (C–H), 1497
(N=N), 1453 (C=C), 1388 (C=N). H-NMR (400 MHz, CDCl , δ / ppm): 2.0–
1
3
–2.08 (2H, qn), 2.57–2.60 (2H, t), 2.67–2.70 (2H, t), 2.86–2.88 (2H, t), 3.36–3.39
13
(2H, t), 3.59 (2H, s), 5.37 (2H, s), 6.99–7.33 (9H, m). C-NMR (100 MHz,
CDCl , δ / ppm): 26.7, 50.9, 31.5, 29.1, 50.8, 56.0, 56.3, 128.1, 129.0, 125.6,
3
126.1, 126.5, 128.6, 128.8, 133.0, 134.2, 134.6, 154.2. MS calculated for
+
+
C H N S: 365.50; Found: M +1, 366.1; M +K adduct: 404.2. MS/MS (m/z):
20 23
5
338.0, 233.1, 206.1, 101.9, 91.0.
2-[3-(1-Benzyl-1H-tetrazol-5-ylthio)propyl]-6-bromo-1,2,3,4-tetrahydroiso-
quinoline (4d). Yield: 72 %; Anal. Calcd. for C H BrN S: C, 54.01; H, 4.95;
20 22
5
–1
N, 15.75 %. Found: C, 54.10; H, 4.95; N, 15.72 %. IR (KBr, cm ) 2924 (C–H),
1482 (N=N), 1453 (C=C), 1388 (C=N). H-NMR (400 MHz, CDCl , δ / ppm):
1
3
2.00–2.06 (2H, qn), 2.55–2.58 (2H, t), 2.65–2.68 (2H, t), 2.77–2.80 (2H, t), 3.35–
13
–3.38 (2H, t), 3.53 (2H, s), 5.37 (2H, s), 6.93–7.33 (8H, m). C-NMR (100
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5-THIO-SUBSTITUTED TETRAZOLE DERIVATIVES
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MHz, CDCl , δ / ppm): 26.6, 50.1, 28.5, 45.9, 31.4, 55.4, 56.0, 119.0, 128.1,
3
129.0, 128.8, 129.1, 129.3, 132.9, 133.3, 136.9, 154.2. MS calculated for
+
C H BrN S: 444.39; Found: M +1, 444.1. MS/MS (m/z): 415.9, 284.0, 102.2,
20 22
5
91.0.
1-Benzyl-5-[3-(1-ethyl-1H-tetrazol-5-ylthio)propylthio]-1H-tetrazole (4e).
Yield: 68 %; Anal. Calcd. for C H N S : C, 46.35; H, 4.97; N, 30.90 %.
14 18 8 2
–1
Found: C, 46.26; H, 4.96; N, 30.82 %. IR (KBr, cm ): 2983 (C–H), 1496
1
(N=N), 1433 (C=C), 1390 (C=N). H-NMR (400 MHz, CDCl , δ / ppm): 1.48–
3
–1.52 (3H, t), 2.27–2.34 (2H, qn), 3.40–3.44 (4H, q), 4.24–4.29 (2H, q), 5.44
13
(2H, s), 7.26–7.38 (5H, m). C-NMR (100 MHz, CDCl , δ / ppm): 14.2, 28.8,
3
31.3, 31.6, 42.6, 51.0, 128.0, 128.9, 129.0, 132.8, 152.8, 153.5. MS calculated for
+
+
+
C H N S : 362.48; Found: M +1, 363.1; M +Na adduct: 385.2; M +K
14 18 8 2
adduct: 401.0. MS/MS (m/z): 335.0, 306.2, 265.0, 233.0, 105.9, 91.0.
1-Benzyl-5-[3-(1-cyclopropyl-1H-tetrazol-5-ylthio)propylthio]-1H-tetrazole
(4f). Yield: 70 %; Anal. Calcd. for C H N S : C, 48.07; H, 4.81; N, 29.91 %.
15 18 8 2
–1
Found: C, 48.13; H, 4.80; N, 29.89 %. IR (KBr, cm ): 2938 (C–H), 1496
(N=N), 1454 (C=C), 1392 (C=N). H-NMR (400 MHz, CDCl , δ / ppm): 1.22–
1
3
–1.29 (4H, m), 2.29–2.36 (2H, qn), 3.35–3.37 (1H, m), 3.41–3.45 (4H, q), 5.44
13
(2H, s), 7.26–7.39 (5H, m). C-NMR (100 MHz, CDCl , δ / ppm): 6.8, 28.8,
3
27.8, 30.8, 31.7, 51.0, 128.1, 128.9, 129.0, 132.8, 153.5, 155.5. MS calculated for
+
+
+
C H N S : 374.49; Found: M +1, 375.3; M +Na adduct: 397.0; M +K
15 18 8 2
adduct: 413.1. MS/MS (m/z): 265.4, 233.4, 183.3, 102.0, 91.2.
5,5’-[1,3-Propanediylbis(thio)]bis(1-benzyl-1H-tetrazole) (4g). Yield: 41 %;
Anal. Calcd. for C H N S : C, 53.70; H, 4.71; N, 26.38 %. Found: C, 53.78;
19 20 8 2
–1
H, 4.72; N, 26.43 %. IR (KBr, cm ): 2942 (C–H), 1496 (N=N), 1453 (C=C),
1389 (C=N). H-NMR (400 MHz, CDCl , δ / ppm): 2.21–2.28 (2H, qn), 3.33–
–3.37 (4H, t), 5.41 (4H, s), 7.25–7.37 (10H, m). C-NMR (100 MHz, CDCl , δ /
1
3
13
3
ppm): 28.7, 31.5, 50.8, 128.0, 128.8, 128.9, 133.0, 153.5. MS calculated for
+
+
C H N S : 424.55; Found: M +1, 425.4; M +Na adduct: 447.1. MS/MS (m/z):
19 20 8 2
282.9, 265.2, 233.0, 130.9, 102.0, 90.9.
5-[3-(1-Benzyl-1H-tetrazol-5-ylthio)propylthio]-4-ethyl-2,4-dihydro-3H-
1,2,4-triazol-3-one (4h). Yield: 48 %; Anal. Calcd. for C H N OS : C, 47.68;
15 19
7
2
–1
H, 5.03; N, 25.96 %. Found: C, 47.78; H, 5.02; N, 25.99 %. IR (KBr, cm ):
1751 (C=O), 2936 (C–H), 3100 (N–H), 1523 (N=N), 1451 (C=C), 1389 (C=N).
1
H-NMR (400 MHz, CDCl , δ / ppm): 1.27–1.30 (3H, t), 2.21–2.28 (2H, qn),
3
3.15–3.19 (2H, t), 3.42–3.45 (2H, t), 3.66–3.72 (2H, q), 5.45 (2H, s), 7.29–7.37
13
(5H, m), 11.34 (1H, bs). C-NMR (100 MHz, CDCl , δ / ppm): 14.2, 28.7, 29.8,
3
31.7, 36.6, 51.0, 128.0, 128.9, 129.0, 132.8, 143.4, 153.5, 155.9. MS calculated for
+
C H N OS : 377.49; Found: M +1, 378.4. MS/MS (m/z): 308.0, 233.3, 218.1,
15 19
7
2
186.0, 101.9, 91.0.
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DHAYANITHI et al.
5-[3-(1-Benzyl-1H-tetrazol-5-ylthio)propylthio]-4-(2,5-dichlorophenyl)-2,4-
-dihydro-3H-1,2,4-triazol-3-one (4i). Yield: 39 %. Anal. Calcd. for C H Cl N OS :
19 17
2
7
2
C, 46.11; H, 3.44; N, 19.82 %. Found: C, 46.16; H, 3.43; N, 19.76 %. IR (KBr,
–1
1
cm ): 1718 (C=O), 2900 (C–H), 1519 (N=N), 1478 (C=C), 1425 (C=N). H-
NMR (400 MHz, CDCl , δ / ppm): 2.15–2.20 (2H, qn), 3.05–3.08 (2H, t), 3.33–
3
13
–3.38 (2H, t), 5.40 (2H, s), 7.24–7.51 (7H, m), 10.94 (1H, s). C-NMR (100
MHz, CDCl , δ / ppm): 28.5, 29.8, 31.6, 51.0, 128.1, 128.9, 129.0, 130.4, 130.7,
3
131.5, 131.6, 131.8, 132.8, 133.5, 143.7, 153.5, 154.6. MS calculated for
+
C H Cl N OS : 494.42; Found: M +1, 493.8. MS/MS (m/z): 334.1, 309.1,
19 17
2
7
2
302.0, 288.0, 265.6, 233.4, 165.3, 102.2, 91.2.
In the IR spectra, the bands due to –N=N– and C=N group, present in all
–1
compounds, were observed at about 1500 and 1388 cm , respectively. The bands
–1
25
at about 1244 and 985 cm are characteristic for the tetrazole ring system. In
1
the H-NMR spectra, the 1-substituted benzylic protons appeared as singlet at
about δ 5.4 ppm in all the derivatives. The other methylene protons appeared as
quintets and triplets at about δ 2.2 to 2.3 ppm and 3.3 to 3.5 ppm, respectively.
13
The aromatic protons were observed at about δ 6.9 to 7.4 ppm. In the C-NMR
spectra of all the synthesized compounds, tetrazole carbon and aromatic carbon
peaks were observed at δ 153.5 and 128.0 to 129.5 ppm, respectively. In the mass
+
spectra, an appropriate molecular ion peak (M +1) was obtained for all the deri-
vatives from ESI–MS.
Antibacterial activity
The results of the antibacterial studies against Staphylococcus aureus,
Escherichia coli, Pseudomonas aeruginosa and Klebsiella pneumoniae bacterial
strains are given in Table II and compared with the standard ampicillin drug.
Interestingly, out of eleven compounds, nine compounds were found to have
TABLE II. Antibacterial activities of the compounds 2, 3 and 4a–i (zone of inhibition in mm;
minimum inhibitory concentration (MIC), in mg mL-1, is given in parenthesis)
Compound
S. aureus
E. coli
P. aeruginosa
K. pneumoniae
2
3
4a
4b
4c
4d
4e
4f
15 (6.25)
20 (6.25)
17 (6.25)
18 (6.25)
17 (6.25)
19 (6.25)
20 (6.25)
17 (6.25)
20 (6.25)
<10 (50)
19 (6.25)
22 (6.25)
<10 (50)
18 (6.25)
18 (6.25)
17 (6.25)
18 (6.25)
19 (6.25)
19 (6.25)
17 (6.25)
19 (6.25)
<10 (50)
17 (6.25)
23 (6.25)
<10 (50)
19 (6.25)
<10 (50)
<10 (50)
<10 (50)
<10 (50)
<10 (50)
<10 (50)
19 (6.25)
<10 (50)
<10 (50)
20 (6.25)
<10 (50)
19 (6.25)
<10 (50)
<10 (50)
<10 (50)
<10 (50)
<10 (50)
<10 (50)
20 (6.25)
<10 (50)
<10 (50)
22 (6.25)
4g
4h
4i
Ampicillin
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good antibacterial activity. Among these compounds 3 and 4g were most active
against the four bacterial organisms. Compounds 4a–f and 4i showed good
growth inhibition towards S. aureus and E. coli, and pronounced growth inhi-
bition for P. aeruginosa and K. pneumoniae. The remaining compounds, 2 and
4h, were found to be less active against the four bacterial organisms.
Antifungal activity
The results of the antifungal studies against Aspergillus flavus, Aspergillus
fumigatus, Penicillium marneffei and Trichophyton mentagrophytes are given in
Table III and compared with the standard itraconazole drug. It was observed that
most of the compounds exhibited good antifungal activity. Compounds 2 and 4h
were less active against all the tested organisms. Compounds 4a–f and 4i showed
good antifungal activity against P. marneffei and T. mentagrophytes, and pro-
nounced antifungal activity towards the other two fungal organisms. On the other
hand, compounds 3 and 4g showed the highest antifungal activity against all four
fungal strains, namely A. flavus, A. fumigatus, P. marneffei and T. menta-gro-
phytes.
TABLE III. Antifungal activities of the compounds 2, 3 and 4a–i (zone of inhibition in mm,
MIC, in mg mL–1, is given in parenthesis)
Compound
T. mentagrophytes
P. marneffei
A. flavus
A. fumigatus
2
3
4a
4b
4c
4d
4e
4f
13 (6.25)
19 (6.25)
19 (6.25)
18 (6.25)
18 (6.25)
19 (6.25)
19(6.25)
18 (6.25)
20 (6.25)
<10 (50)
19 (6.25)
21(6.25)
<10 (50)
17 (6.25)
18 (6.25)
19 (6.25)
17 (6.25)
18 (6.25)
18 (6.25)
19 (6.25)
18 (6.25)
<10 (50)
17 (6.25)
20 (6.25)
<10 (50)
20 (6.25)
<10 (50)
<10 (50)
<10 (50)
<10 (50)
<10 (50)
<10 (50)
19 (6.25)
<10 (50)
<10 (50)
21 (6.25)
<10 (50)
19 (6.25)
<10 (50)
<10 (50)
<10 (50)
<10 (50)
<10 (50)
<10 (50)
20 (6.25)
<10 (50)
<10 (50)
19 (6.25)
4g
4h
4i
Itraconazole
EXPERIMENTAL
1
The H-NMR, 13C-NMR and DEPT experiments were performed on an Oxford AS 400
1
NMR instrument (Varian, City, USA) with a dual broad band. The H-NMR chemical shift
values are reported on the δ scale in ppm relative to TMS (δ = 0 ppm) and the 13C-NMR
chemical shifts values are reported relative to CDCl3 (δ = 72.5 ppm). The IR spectra were
recorded on a Perkin Elmer spectrum 100 FT-IR model. Column chromatography was per-
formed with silica gel 60–120 mesh (Merck, Mumbai, India.). All the compounds were routi-
nely checked for completion of the reaction on silica gel 60 F254 TLC plates and their spots
were visualized by exposure to a UV lamp, iodine vapor or KMnO4 reagents. The liquid chro-
matography part of the LC–MS system consisted of an Agilent-1100 series quaternary gra-
dient pump with a degasser, an auto sampler and a column oven. The MS/MS part of the sys-
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172
DHAYANITHI et al.
tem contained an API-2000 system (Sciex, Applied Bio-Systems, Canada). The yields are
reported as isolated yield after purification of the compounds.
Procedure for the preparation of 1-benzyl-5-[(3-bromopropyl)thio]-1H-tetrazole (3)
To a solution of 1,3-dibromopropane (10 g, 50 mmol) in tetrahydrofuran (200 mL), 1-
-benzyl-1H-tetrazole-5-thiol (2) (1.92 g, 10 mM) was added portionwise at 25–30 °C and then
stirred for 3 h at the same temperature. The reaction was monitored by TLC. After completion
of reaction, the reaction mixture was concentrated to dryness and the crude product was pu-
rified by column chromatography (eluent 35 % ethyl acetate–hexane). Product 3 was obtained
as light brown colored gummy mass (52 % yield).
General procedure for the preparation of derivatives 4a–i
To a mixture of 1-benzyl-5-[(3-bromopropyl)thio]-1H-tetrazole (3) (10 mmol) and an-
hydrous powdered K2CO3 (20 mmol) in ethanol (10 mL), the corresponding amine or thiol
(1.2 equivalent) was added at 25 °C and stirred at this temperature for 2–3 h. The reaction was
monitored by TLC. After completion of the reaction; the reaction mixture was concentrated to
dryness. The residue was dissolved in dichloromethane (20 mL) and washed with water. The
organic layer was concentrated under reduced pressure to give the crude product. The final
product was isolated by column purification. The column was started at 10 % ethyl acetate
with petroleum ether and slowly increased to 60 % ethyl acetate. Finally, the compound was
isolated at 25 to 30 % ethyl acetate in petroleum ether.
Antibacterial activity
The tetrazole derivatives (2, 3 and 4a–i) were investigated for their inhibition of growth
against Staphylococcus aureus (ATCC-25923), Escherichia coli (ATCC-25922), Pseudomo-
nas aeruginosa (ATCC-27853) and Klebsiella pneumoniae (recultured) bacterial strains by
the disc diffusion method.26-31 Batches of 100 discs (Whatman filter paper No. 1, 6 mm dia-
meter) were each dispensed to a screw capped bottle and sterilized by dry heat at 140 °C for 1 h.
Solutions of the test compounds were prepared at different concentrations in dimethylform-
amide (DMF). 1mL containing 100 times the amount of prepared solution in each disc was ad-
ded to each bottle, which contained 100 discs. The disc of each concentration was placed in
triplicate in a nutrient agar medium separately seeded with fresh bacteria. The incubation was
realized at 37 °C for 24 h. Solvent and growth controls were kept separate; the zones of inhi-
bition and minimum inhibitory concentration (MIC) were measured.
Antifungal activity
The newly synthesized compounds were also investigated for their antifungal activity
against four fungal strains, namely, Aspergillus flavus (NCIM No.524), Aspergillus fumigatus
(NCIM No.902), Penicillium marneffei (recultured) and Trichophyton mentagrophytes (recul-
tured). Sabouraud agar media was prepared by dissolving peptone (1 g), D-glucose (4 g) and
agar (2 g) in sterile water (100 mL) and the pH was adjusted to 5.7. Normal saline was used to
make a suspension of the spores of the fungal strain for seeding. A loopful of particular fungal
strain was transferred to 3 mL of saline to obtain a suspension of the corresponding species.
Agar media (20 mL) was poured into each petri dish. Excess of the suspension was decanted and
the plates were dried by placing them in an incubator at 37 °C for 1 h. Using an agar punch,
wells (8 mm diameter) were made on these seeded agar plates and from 6.25 to 50 µg mL-1 of
the test compounds in DMSO was added into each well labeled disc. Controls were run using
DMSO at the same concentration as used with the test compounds. The petri dishes were pre-
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5-THIO-SUBSTITUTED TETRAZOLE DERIVATIVES
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pared in triplicate and maintained at 37 °C for 3 to 4 days. The antifungal activity was deter-
mined by measuring the diameter of the inhibition zone.32,33
CONCLUSIONS
In conclusion, a series of new 5-thio-substituted tetrazole derivatives were
successfully synthesized. The antimicrobial screening suggests that all the
synthesized compounds showed moderate to good activity against the tested
organisms. Among the newly synthesized compounds, 4g and 3 showed the most
promising antibacterial and antifungal activities. Hence, the fact that the com-
pounds prepared in this study are chemically unrelated to the current medication,
suggests that further work with similar types of analogues is clearly warranted.
Acknowledgements. The authors thank the Department of Chemistry, Islamiah College
and Sambalpur University for support of their research.
И З В О Д
СИНТЕЗА ОДАБРАНИХ 5-ТИО СУПСТИТУИСАНИХ ДЕРИВАТА ТЕТРАЗОЛА И
ОДРЕЂИВАЊЕ ЊИХОВЕ АНТИБАКТЕРИЈСКЕ И АНТИФУНГАЛНЕ АКТИВНОСТИ
VARADARAJI DHAYANITHI1, SUBAN SHAFI SYED1, KUBARAN KUMARAN1, KASI REGURAMAN JAI SANKAR1,
RAMASWAMY VENKAT RAGAVAN2, PALUSA SANATH KUMAR GOUD3, NALILU SUCHETHA KUMARI4
и HARI NARAYAN PATI5
1P.G. and Research Department of Chemistry, Islamiah College, Vaniyambadi 632 752, India, 2Chemistry
Division, School of Science and Humanities, VIT University, Vellore 632 014, 3N. E. T. College of Pharmacy,
Raichur 584 102, 4Department of Biochemistry, K. S. Hegde Medical Academy, Mangalore 574 162 и
5Department of Chemistry, Sambalpur University, Jyoti Vihar 768 019, India
Извршена је синтеза нових деривата 5-тио-тетразола. Супституисани тетразол-5-тиол,
1-бензил-1H-тетразол-5-тиол (2) добијен је загревањем на температури кључања комерци-
јално доступног бензил-изотиоцијаната (1) са натријум-азидом у води. У другом реакционом
кораку добијен је 1-бензил-5-[(3-бромпропил)тио]-1Н-тетразол (3) тиоалкиловањем тетра-
зол-5-тиола (2) са 1,3-дибромпропаном у тетрахидрофурану. Коначно, деривати 5-тио-тетра-
зола 4a–i добијени су кондензациојом (3) са одговарајућим аминима или тиолима. Структуре
добијених једињења одређене су NMR, LC/MS/MS и IC спектроскопијом и микроанализом.
Свим синтетисаним једињењима испитана је антибактеријска и антифунгална активност.
(Примљено 21. априла 2009, ревидирано 13. септембра 2010)
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