Synthesis and antimicrobial activity of some novel 2-[4-(substituted piperazin-/piperidin-1-ylcarbonyl)phenyl]- 1 H-benzimidazole derivatives

Article abstract of DOI:10.1002/ardp.200800084

In this study, we report the synthesis and antimicrobial evaluation of several new 4-(1H-benzimi-dazol-2-yl)benzamides (11 - 30) and 5-chloro-1-(p-fluorobenzyl)-2-{4-[(4-methylpiperazin-1-yl)carbonyl]phenyl} -1H-benzimidazole (33). Compound 20 exhibited the best antibacterial activity with MIC value of 6.25 μg/mL against Staphylococcus aureus and methicillin-resistant Staphylococcus aureus (MRSA). Significant antifungal activities were obtained with the compounds 13, 14, 18, 19, and 33 with MIC values of 3.12 μg/mL which are close to fluconazole.

Full text of DOI:10.1002/ardp.200800084

54
Arch. Pharm. Chem. Life Sci. 2009, 342, 54–60
Full Paper
Synthesis and Antimicrobial Activity of Some Novel
2-[4-(Substituted Piperazin-/Piperidin-1-ylcarbonyl)phenyl]-
1H-benzimidazole Derivatives
Canan Kus˛1, Fatma Sꢀzꢁdꢀnmez1, and Nurten Altanlar2
1 Department of Pharmaceutical Chemistry, Faculty of Pharmacy, Ankara University, Ankara, Turkey
2 Department of Pharmaceutical Microbiology, Faculty of Pharmacy, Ankara University, Ankara, Turkey
In this study, we report the synthesis and antimicrobial evaluation of several new 4-(1H-benzimi-
dazol-2-yl)benzamides (11–30) and 5-chloro-1-(p-fluorobenzyl)-2-{4-[(4-methylpiperazin-1-yl)carbo-
nyl]phenyl}-1H-benzimidazole (33). Compound 20 exhibited the best antibacterial activity with
MIC value of 6.25 lg/mL against Staphylococcus aureus and methicillin-resistant Staphylococcus aur-
eus (MRSA). Significant antifungal activities were obtained with the compounds 13, 14, 18, 19,
and 33 with MIC values of 3.12 lg/mL which are close to fluconazole.
Keywords: Antibacterial activity / Antifungal activity / Benzimidazole / Synthesis /
Received: April 27, 2008; accepted: September 8, 2008
DOI 10.1002/ardp.200800084
Introduction
Previously, a large number of benzimidazolecarboxa-
mide derivatives were prepared in our laboratory for
their antibacterial and antimycotic activities [1–6].
Among these compounds, 1-(4-chlorobenzyl)-2-(2,4-
dichlorophenyl)-N-(2-(diethylamino)ethyl-1H-benzimida-
zole-5-carboxamide [1] showed moderate activity
Figure 1. Structure
of
1-(4-chlorobenzyl)-2-(2,4-dichloro-
I
phenyl)-N-(2-(diethylamino)ethyl-1H-benzimidazole-5-carboxa-
mide I and ethyl 2-(4-((2-(ethylamino) ethyl) carbamoyl) phenyl)-
1-(2,4-dichloro- benzyl)-1H-benzimidazole-5-carboxylate II.
against Candida albicans which was very close to that of
fluconazole. By the way, ethyl 2-(4-((2-(ethylamino)ethyl)-
carbamoyl)-phenyl)-1-(2,4-dichloro-benzyl)-1H-benzimida-
zole-5-carboxylate II displayed the best antibacterial
activity against Staphylococcus sp. [2]. In connection with
these studies, we planned to modify the amide structure
on the final benzimidazole moiety in order to develop
new antimicrobial agents. In this paper, synthesis and
antimicrobial activity of a series of 2-[4-(substituted-piper-
azin-/piperidin-1-ylcarbonyl)phenyl]-1H-benzimidazole
derivatives (11-30, 33) are described.
Results and discussion
Chemistry
The desired products, namely 5(6)-substituted-2-{4-[(4-
substituted piperazine/piperidine-1-yl)carbonyl]phenyl}-
1H-benzimidazole 11–30 and 5-chloro-1-(4-fluorobenzyl)-
2-{4-[(4-methylpiperazin-1-yl)carbonyl]phenyl}-1H-benzi-
midazole 33 were prepared by the reactions outlined in
Scheme 1 and Scheme 2, respectively. The reaction of
substituted-1,2-phenylendiamines with the sodium bisul-
fite adduct of 4-carboxybenzaldehyde gave 4-(substituted-
1H-benzimidazole-2-yl) benzoic acid derivatives 1–5 [7].
Compounds 1–5 were converted to acyl chlorides 6–10
with SOCl2, and dehydrohalogenation between the corre-
Correspondence: Dr. Canan Kus, Department of Pharmaceutical Chem-
istry, Faculty of Pharmacy, Ankara University, 06100 Tandogan, Ankara,
Turkey.
E-mail: kus@pharmacy.ankara.edu.tr
Fax: + 90 312 2131081
i 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Arch. Pharm. Chem. Life Sci. 2009, 342, 54–60
Novel Substituted Benzimidazole Derivatives
55
Reagents: (a) p-fluorobenzylamine; (b) Zn / HCl; (c) Na2S2O5; (d) DMF; (e) SOCl2; (f)
N-methylpiperazine.
Reagents: (a) Na2S2O5; (b) DMF; (c) SOCl2; (d) related cyclic amines
/
CH2Cl2.Scheme 1. Synthesis of the 5(6)-substituted-2-{4-[(4-substitutedpiperazine/
piperidine-1-yl)carbonyl]phenyl}-1H-benzimidazoles 11 – 30.
Scheme 2. Synthesis of the 5-chloro-1-(4-fluorobenzyl)-2-{4-[(4-
methylpiperazin-1-yl)carbonyl]phenyl}-1H-benzimidazole 33.
Scheme 1. Synthesis of the 5(6)-substituted-2-{4-[(4-substitutd-
piperazine/piperidine-1-yl)carbonyl}-1H-benzimidazoles 11–30.
method [8, 9]. All final compounds 11–30, 33 were dis-
solved in DMSO (12.5%) at 100 lg/mL concentration as
starting dose. DMSO as a control has no effect at 12.5%
and 6.25% concentration against bacteria and fungi,
sponding acyl chlorides and amines gave the required
benzimidazole carboxamides 11–30 (Scheme 1).
A selective synthesis pathway was used for the synthe- respectively. The results obtained indicate that most of
these compounds are more active against fungi than bac-
teria. However, compounds 16–20, 29, and 33 displayed
sis of 33. The nucleophilic substitution of 2,5-dichloroni-
trobenzen with p-fluorobenzylamine gave 4-chloro-N-(4-
fluorobenzyl)-2-nitroaniline. Its reduction with Zn/HCl significant antibacterial activities against MRSA which
produced
4-chloro-N1-(4-fluorobenzyl)benzene-1,2-dia- were close to ampicillin, in the control experiments
(Table 2). Compound 20 exhibited the best antibacterial
mine. Condensation of this aromatic o-phenylenedi-
amine with sodium bisulfite adduct of 4-carboxybenzal- activity against both S. aureus and MRSA MIC value of
dehyde in DMF gave 4-[5-chloro-1-(4-fluorobenzyl)-1H-ben- 6.25 lg/mL. Compound 19 has the best antifungal activ-
ity against C. albicans similar to fluconazole (MIC =
3.12 lg/mL). Compounds 13, 14, 18, 19, 29, and 33 exhib-
zimidazole-2-yl] benzoic acid 31. Compound 33 was also
prepared in a similar manner with 1–5 starting from 31
(Scheme 2). When a 13C-NMR spectrum of compound 33 ited good antifungal activity (MIC = 3.12 lg/mL) against C.
in DMSO-d6 was recorded at 100 MHz, a highly character- krusei close to fluconazole (MIC = 6.25 lg/mL). Antifungal
activities of 16, 17, 24, 29, 30, and 16, 17, 20, 24, 30,
against C. krusei and C. glabrata are similar to fluconazole
istic spectrum was obtained showing intricacies of the
various 13C - 19F couplings. The four doublet resonances
centered at d = 116.2 and 116.4 (J = 21.2 Hz)], 128.9 and (MIC = 6.25 and 12.5 lg/mL), respectively. Compounds 13,
129.0 (J = 7.7 Hz), 133.36 and 133.38 (J = 2.6 Hz), 160.9 and 14, 18, 19, and 29 exhibited the best antifungal activity
(MIC = 6.25 lg/mL) against C. glabrata. All 5-nitro-substi-
tuted derivatives (14, 19, 24, 29) displayed better antimi-
crobial activity than the others. By the way, almost all
163.3 (J = 242.4 Hz) arising from the aromatic carbons of
p-fluorobenzyl coupled by the fluorine atom. There was
1
1
similar H – 19F couplings in the H-NMR spectra of 16–
20. Some physico-chemical properties and spectral find- piperidine derivatives didn't show any significant activ-
ities against both bacteria and fungi except 29 and 30
which have 5-nitro and 5,6-dichloro substituents, respec-
tively.
ings of final products 11–30 and 33 are given in Table 1.
Antibacterial activity
The results displayed that, in case there are nitro- or
dichloro-groups at the 5- and / or 6-position of the benzi-
All described benzimidazoles, 11–30 and 33, were eval-
uated in vitro for antibacterial activity against S. aureus
ATCC 25923, MRSA clinical isolate, and antifungal activ- midazole moiety and p-fluorophenylpiperazine or N-
ity against C. albicans ATCC 10231, Candida krusei ATCC methylpiperazine at the 4-position of phenyl, the anti-
fungal activity against Candidas is especially improved.
6258, Candida glabrata clinical isolate by tube dilution
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56
C. Kus˛ et al.
Arch. Pharm. Chem. Life Sci. 2009, 342, 54–60
1H- and13C-NMR d (ppm) DMSO-d6
Table 1. Physical and spectral data of compounds 11–30, 33.
No
Yield
(%)
M.p.
(8C)
Formula
IR (cm– 1
(C=O)
)
MS ESI (+)
M + H (100%)
(M + H + 2)
(M + H + 4)
11
30
150
C19H20N4O6HCl60.26H2O60.1 1610
AcOEt
Calc.: C,63.10; H, 6.06; N, 15.17
Found: C, 62.60; H, 6.22; N,15.64.
321
1H-NMR: 2.20 (s, 3H, N-CH3), 2.30 (s, 2H, pip.CH2),
2.37 (s, 2H, pip.CH2), 3.32 (s, 2H, pip.CH2 ), 3.63 (s,
2H, pip.CH2), 7.16-7.26 (q, 2H, H5,6), 7.55 (d, J =
8 Hz, 2H, H39,59), 7.67 (d, Jo = 7.6 Hz, 2H, H4,7), 8.22 (d,
J = 8 Hz, 2H, H29,69), 13.07 (s, 1H, NH).
13C-NMR: 42.2, 47.7, 55.1, 112.2, 119.7, 122.5,
123.5, 127.1, 128.3, 131.8, 137.7, 151.2, 169.1.
12
13
14
62
33
29
128–132 C20H22N4O60.5 HCl60.1 H2O
Calc.: C, 67.77; H, 6.46; N, 15.81
1608
1612
1605
335
1H-NMR: 2.20 (s, 3H, N-CH3 ), 2.30 (s, 2H, pip.CH2 ),
2.37 (s, 2H, pip.CH2 ), 2.44 (s, 3H, Ar- CH3), 3.37 (s,
2H, pip.CH2 ), 3.64 (s, 2H, pip.CH2 ), 7.02–7.08 (m,
1H, H4), 7.34-7.49 (m, 2H, H6,7), 7.56 (d, J = 8 Hz, 2H,
Found: C, 67.83; H, 6.25; N, 15.64.
H39,59), 8.22 (d, J = 8 Hz, 2H, H29,69), 12.91 (s, 1H, NH).
134–138 C19H19ClN4O60.5 HCl
Calc.: C, 61.17; H, 5.27; N, 15.02
Found: C, 61.28; H, 5.62; N, 14.93.
355
357 (32%)
1H-NMR: 2.24 (s, 3H, N-CH3 ), 2.34 (s, 2H, pip.CH2 ),
2.41 (s, 2H, pip.CH2 ), 3.36 (s, 2H, pip.CH2), 3.65 (s,
2H, pip.CH2 ), 7.22–7.28 (m, 1H, H6 ), 7.57 (d, J =
8.4 Hz, 2H, H39,59), 7.70 (d, Jo = 8.2 Hz, 1H, H7), 7.75
(d, Jm = 2 Hz, 1H, H4), 8.23 (d, J = 8.2 Hz, 2H, H29,69),
13.25 (s, 1H, NH).
271–274 C19H19N5O3 x 0.5 HCl
Calc.: C, 59.49; H, 5.12; N, 18.26
Found: C, 59.31; H, 5.25; N, 17.87.
366
1H-NMR: 2.20 (s, 3H, N-CH3 ), 2.30 (s, 2H, pip.CH2 ),
2.39 (s, 2H, pip.CH2 ), 3.37 (s, 2H, pip.CH2), 3.65 (s,
2H, pip.CH2), 7.62 (d, J = 8.4 Hz, 2H, H39,59), 7.80 (d, Jo
= 9.2 Hz, 1H, H7), 8.14 –8.17 (dd, Jo = 9.2 Hz, Jm
=2.4 Hz, 1H, H6), 8.28 (d, J = 8.4 Hz, 2H, H29,69), 8.51
(s, 1H, H4).
15
16
17
50
286–290 C19H18Cl2N4O60.4 H2O
Calc.: C, 57.56; H, 4.78; N, 14.13
Found: C, 57.56; H, 4.63; N, 13.86.
1604
1628
389
391 (73%)
393 (13%)
1H-NMR: 2.19 (s, 3H, N-CH3 ), 2.28 (s, 2H, pip.CH2 ),
2.36 (s, 2H, pip.CH2 ), 3.36 (s, 2H, pip.CH2), 3.63 (s,
2H, pip.CH2), 7.57 (d, J = 8 Hz, 2H, H39,59), 7.87 (s, 2H,
H4,7), 8.21 (d, J = 8 Hz, 2H, H29,69), 13.38 (s, 1H, NH ).
304
C24H21FN4O
401
415
1H-NMR: 3.12 (s, 2H, pip.CH2), 3.17 (s, 2H, pip.CH2),
3.53 (s, 2H, pip.CH2), 3.77 (s, 2H, pip.CH2), 6.97–
7.01 (m, 2H, H299,699), 7.06–7.10 (m, 2H, H399,599), 7.21–
7.26 (q, 2H, H5,6), 7.56 (d, J = 7.2 Hz, 1H), 7.63 (d, J =
8 Hz, 2H, H39,59), 7.70 (d, J = 8 Hz, 1H), 8.26 (d, J =
8 Hz, 2H, H2‘,6'), 13.07 (s, 1H, NH).
Calc.: C, 71.98; H, 5.29; N, 13.99
Found: C, 72.00; H, 4.94; N, 13.73.
17
18
19
27
35
36
301–305 C25H23FN4O
Calc.: C, 72.45; H, 5.59; N, 13.52
Found: C, 72.26; H, 5.63; N, 13.33.
1630
1613
1614
1H-NMR: 2.44 (s, 3H, Ar-CH3), 3.11 (s, 2H, pip.CH2 ),
3.16 (s, 2H, pip.CH2 ), 3.53 (s, 2H, pip.CH2 ), 3.79 (s,
2H, pip.CH2 ), 6.97–7.02 (m, 2H, H299,699), 7.05–7.10
(m, 2H, H399,599), 7.43–7.57 (m, 3H, H4,6,7 ), 7.61 (d, J =
8 Hz, 2H, H39,59), 8.23 (d, J = 8 Hz, 2H, H29,69), 12.90 (s,
1H, NH).
251–255 C24H20ClFN4O
435
437 (33%)
1H-NMR: 3.10 (s, 2H, pip.CH2 ), 3.17 (s, 2H, pip.CH2),
3.52 (s, 2H, pip.CH2), 3.79 (s, 2H, pip.CH2), 6.97–
7.01 (m, 2H, H299,699), 7.06–7.10 (m, 2H, H399,599), 7.26
(m, 1H, H6), 7.59 (m, 1H, H7), 7.64 (d, J = 8 Hz, 2H,
Calc.: C, 66.28; H, 4.64; N, 12.88
Found: C, 66.34; H, 4.29; N, 12.75.
H39,59), 7.76 (m, 1H, H4), 8.25 (d, J = 8 Hz, 2H, H29,69),
13.26 (s, 1H, NH).
315
C24H20FN5O360.1 H2O
446
1H-NMR: 3.11 (s, 2H, pip.CH2), 3.18 (s, 2H, pip.CH2),
3.52 (s, 2H, pip.CH2), 3.80 (s, 2H, pip.CH2), 6.98–
7.01 (m, 2H, H299,699), 7.06–7.10 (m, 2H, H399,599), 7.68
(d, J = 8 Hz, 2H, H39,59), 7.81 (s, 1H, H7), 8.16 (d, J =
8.8 Hz, 1H, H6), 8.30 (d, J = 8 Hz, 2H, H29,69), 8.52 (s,
1H, H4), 13.64 (s, 1H, NH).
Calc.: C, 64.45; H, 4.55; N, 15.66
Found: C, 64.46; H, 4.34; N, 15.46.
i 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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Arch. Pharm. Chem. Life Sci. 2009, 342, 54–60
Table 1. Continued.
Novel Substituted Benzimidazole Derivatives
57
No
Yield
(%)
M.p.
(8C)
Formula
IR (cm– 1
(C=O)
)
MS ESI (+)
1H- and13C-NMR d (ppm) DMSO-d6
M + H (100%)
(M + H + 2)
(M + H + 4)
20
7
345–348 C24H19Cl2FN4O
Calc.:C, 61.42; H, 4.08; N, 11.94
1612
1627
469
471 (70%),
473 (14%)
1H-NMR: 3.10 (s, 2H, pip.CH2), 3.17 (s, 2H, pip.CH2),
3.51 (s, 2H, pip.CH2), 3.79 (s, 2H, pip.CH2), 6.97–
7.01 (m, 2H, H299,699), 7.06–7.10 (m, 2H, H399,599), 7.64
(d, J = 8 Hz, 2H, H39,59), 7.90 (s, 2H, H4,7), 8.25 (d, J =
8 Hz, 2H, H29,69), 13.42 (s, 1H, NH).
Found: C, 61.18; H, 3.90; N, 11.69.
21
73
192–196 C25H24N4O2 x 0.2 C2H5OH60.4
C3H8O
413
427
1H-NMR: 2.98 (m, 4H, pip.CH2), 3.52 (s, 2H,
pip.CH2), 3.77 (s, 5H, pip.CH2 and O-CH3), 6.84 –7.0
(m, 4H, H399,499,599,699), 7.22 (m, 2H, H5,6), 7.55 (d, J =
6.8 Hz, 1H, H4), 7.62 (d, J = 8 Hz, 2H, H39,59), 7.69 (d, J
= 7.6 Hz, 1H, H7), 8.25 (d, J = 8 Hz, 2H, H29,69), 13.08
(s, 1H, NH).
Calc.: C, 71.67; H, 6.42; N, 12.57
Found: C, 71.14; H, 6.15; N, 12.25.
22
23
24
55
48
48
189–192 C26H26N4O260.5 H2O
Calc.: C, 71.70; H, 6.25; N, 12.86
Found: C, 71.69; H, 5.93; N, 12.59.
1613
1612
1609
1H-NMR: 2.43 (s, 3H, Ar-CH3 ), 2.99 (m, 4H, pip.CH2),
3.52 (s, 2H, pip.CH2), 3.78 (s, 5H, pip.CH2 and O-
CH3), 6.85–6.99 (m, 4H, H399,499,599,699), 7.04-7.54 (m, 3H,
H4,6,7), 7.60 (d, J = 8 Hz, 2H, H39,59,), 8.21 (d, J = 8 Hz,
2H, H29,69), 12.87 (s, 1H, NH).
269–272 C25H23ClN4O260.25 H2O
Calc.: C, 66.51; H, 5.25; N, 12.41
Found: C, 66.61; H, 5.11; N, 12.25.
447
449 (32%)
1H-NMR: 2.98 (m, 4H, pip.CH2), 3.52 (s, 2H, pip.
CH2), 3.77 (s, 5H, pip.CH2 and O-CH3), 6.84–7.02
(m, 4H, H399,499,599,699), 7.24 (dd, Jo = 8.8 Hz, Jm = 2.0 Hz,
1H, H6), 7.63 (d, J = 8.4 Hz, 3H, H7,39,59), 7.67 (s, 1H,
H4), 8.24 (d, J = 8.4 Hz, 2H, H2‘,6'), 13.24 (s, 1H, NH).
296–299 C25H23N5O4 x 0.1 C2H5OH
Calc.: C, 65.50; H, 5.14; N, 15.15
Found: C, 65.36; H, 4.87; N, 14.93.
458
1H-NMR: 2.99 (m, 4H, pip.CH2 ), 3.52 (s, 2H, pip.
CH2), 3.78 (s, 5H, pip.CH2 and O-CH3), 6.84–7.05
(m, 4H, H399,499,599,699), 7.65 –7.67 (d, J = 8.4 Hz, 2H,
H39,59), 7.75 (s, 1H, H7), 8.13–8.25 (d, J = 8.0 Hz, 1H,
H6), 8.28 (d, J = 8.4 Hz, 2H, H29,69), 8.54 (s, 1H, H4),
13.68 (s, 1H, NH).
25
26
19
36
294–298 C25H22Cl2N4O2
1609
1602
481
483 (69%),
485 (13%)
1H-NMR: 3.01 (m, 4H, pip.CH2 ), 3.52 (s, 2H, pip.
CH2), 3.79 (s, 5H, pip.CH2 and O-CH3), 6.86–7.01
(m, 4H, H 399,499,599,699), 7.64 (d, J = 8.0 Hz, 2H, H39,59), 7.89
(s, 2H, H4,7), 8.25 (d, J = 8.0 Hz, 2H, H2‘,6'), 13.42 (s,
1H, NH).
Calc.: C, 62.38; H, 4.61; N, 11.64
Found: C, 62.03; H, 4.42; N, 11.36.
204–208 C19H19N3O61.7 H2O
Calc.: C, 67.92; H, 6.72; N, 12.51
Found: C, 67.71; H, 6.36; N, 12.71.
306
320
1H-NMR: 1,38–1.53 (m, 6H, pip.H3,4,5), 2.93 (m, 2H,
pip.H6), 3.56 (s, 2H, pip.H2), 7.19 –7.22 (m, 2H, H5,6),
7.45 (d, J = 8.0 Hz, 2H, H39,59), 7.55–7.57 (m, 2H,
H4,7), 8.17 (d, J = 8.0 Hz, 2H, H29,69), 8.66 (br. s, 1H,
NH).
27
28
13
20
246–250 C20H21N3O60.6 H2O
Calc.: C, 72.75; H, 6.77; N, 12.73
Found: C, 72.52; H, 6.37; N, 12.80.
1603
1603
1H-NMR: 1.49–1.64 (m, 6H, pip.H3,4,5 ), 2.43 (s, 3H,
Ar-CH3), 3.05 (t, 2H, pip.H6), 3.60 (m, 2H, pip.H2),
7.02–7.47 (m, 3H, H4,5,6 ), 7.53 (d, J = 8.0 Hz, 2H,
H39,59), 8.20 (d, J = 8.0 Hz, 2H, H29,69), 12.89 (s, 1H, NH).
262–265 C19H18ClN3O60.6 H2O
Calc.: C, 65.08; H, 5.52; N, 11.98
Found: C, 64.90; H, 5.13; N, 11.97.
340
342 (29%)
1H-NMR: 1.49–1.63 (m, 6H, pip.H3,4,5), 2.99 (t, 2H,
pip.H6), 3.61 (m, 2H, pip.H2), 7.24–7.26 (dd, Jo =
8.2 Hz, Jm = 1.6 Hz, 1H, H6), 7.55 (d, J = 8.0 Hz, 2H,
H39,59), 7.61-7.64 (d, Jo = 8.2 Hz, 1H, H7), 7.68 (s, 1H,
H4), 8.23 (d, 2H, H29,69).
29
14
302–306 C19H18N4O360.1 C3H8O
Calc.: C, 65.04; H, 5.31; N, 15.72
Found: C, 64.93; H, 4.86; N, 15.57.
1603
351
1H-NMR: 1.50–1.63 (m, 6H, pip.H3,4,5), 3.31 (s, 2H,
pip.H6), 3.62 (s, 2H, pip.H2), 7.60 (d, J = 8.0 Hz, 2H,
H
39,59), 7.80 (d, Jo = 8.8 Hz, 1H, H7), 8.14–8.17 (dd, Jo =
8.8 Hz, Jm = 2.0 Hz, 1H, H6), 8.27 (d, J = 8.0 Hz, 2H,
29,69), 8.51 (s, 1H, H4), 13.71 (s, 1H, NH).
H
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58
C. Kus˛ et al.
Arch. Pharm. Chem. Life Sci. 2009, 342, 54–60
1H- and13C-NMR d (ppm) DMSO-d6
Table 1. Continued.
No
30
33
Yield
(%)
M.p.
(8C)
Formula
IR (cm– 1
(C=O)
)
MS ESI (+)
M + H (100%)
(M + H + 2)
(M + H + 4)
24
29
369–373 C19H17Cl2N3O60.1 H2O
Calc.: C, 60.68; H, 4.61; N, 11.17
Found: C, 60.56; H, 4.96; N, 11.07.
1600
1619
374
376 (78%)
378 (14%)
1H-NMR: 1.49–1.62 (m, 6H, pip.H3,4,5), 3.30 (s, 2H,
pip.H6), 3.61 (s, 2H, pip.H2), 7.56 (d, J = 8.0 Hz), 2H,
H39,59, 7.89 (s, 2H, H4,7), 8.22 (d, J = 8.0 Hz, 2H, H2‘,6'),
13.46 (br.s, 1H, NH).
125–127 C26H24ClFN4O
463
465 (30%)
1H-NMR: 2.20 (s, 3H, N-CH3), 2.28 (s, 2H, pip.CH2),
2.37 (s, 2H, pip.CH2), 3.32 (s, 2H, pip.CH2), 3.64 (s,
2H, pip.CH2), 5.63 (s, 2H, N-CH2-), 7.04 (t, J = 8.4 Hz,
2H, H399,599), 7.11 (t, J = 8.4 Hz, 2H, H299,699), 7.31(d, J =
8 Hz, 1H, H6), 7.53 (d, J = 8.0 Hz, 2H, H39,59), 7.57 (s,
1H, H7), 7.79 (d, J = 8.0 Hz, 2H, H29,69), 7.82 (s, 1H, H4).
13C-NMR: 42.1, 46.3, 47.7, 55.1, 113.3, [116.2 and
116.4 (J = 21.2 Hz)], 119.5, 123.7, 127.6, 128.0,
[128.9 and 129.0 (J = 7.7 Hz)], 129.8, 131.2, [133.36
and 133.38 (J = 2.6 Hz)], 135.4, 138.1, 144.2, 154.6,
[160.9 and 163.3 (J = 242.4 Hz)], 168.8.
Calc.: C, 67.45; H, 5.23; N, 12.10
Found: C, 66.96; H, 5.11; N, 12.07.
Table 2. In-vitro antifungal and antibacterial activities and formulas of 11–30, 33 (MIC: in lg/mL).
Compounds
R9
R
S. aureus
MRSA
C. albicans
C. krusei
C. glabrata
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
N-methylpiperazine
N-methylpiperazine
N-methylpiperazine
N-methylpiperazine
N-methylpiperazine
p-fluorophenylpiperazine
p-fluorophenylpiperazine
p-fluorophenylpiperazine
p-fluorophenylpiperazine
p-fluorophenylpiperazine
o-methoxyphenylpiperazine
o-methoxyphenylpiperazine
o-methoxyphenylpiperazine
o-methoxyphenylpiperazine
o-methoxyphenylpiperazine
piperidine
5(6)-H
5(6)-CH3
5(6)-Cl
5(6)-NO2
5,6- Cl2
5(6)-H
5(6)-CH3
5(6)-Cl
5(6)-NO2
5,6-dichloro
5(6)-H
5(6)-CH3
5(6)-Cl
5(6)-NO2
5,6-Cl2
5(6)-H
5(6)-CH3
5(6)-Cl
A100
A100
A100
A100
A100
12.5
12.5
50
50
50
A100
A100
A100
25
12.5
25
12.5
25
50
12.5
6.25
50
12.5
12.5
6.25
3.12
25
50
50
25
12.5
>100
>100
>100
50
25
25
50
25
3.12
3.12
50
6.25
6.25
3.12
3.12
12.5
25
6.25
6.25
25
12.5
12.5
6.25
6.25
12.5
50
25
25
12.5
25
50
50
50
6.25
12.5
3.12
–
25
6.25
A100
A100
25
A100
A100
A100
A100
A100
50
6.25
A100
A100
50
A100
A100
A100
A100
A100
25
25
12.5
6.25
50
50
50
27
28
29
30
piperidine
piperidine
piperidine
piperidine
50
5(6)-NO2
5,6-Cl2
5-Cl
25
6.25
6.25
3.12
–
50
25
3.12
–
50
25
25
12.5
6.25
–
33
N-methylpiperazine
Ampicillin
Fluconazole
–
3.12
6.25
12.5
Compound 33 which is the 1-(p-fluorobenzyl)-substi- crobial activity with N1-substitution was confirmed here
tuted analog of 13 has better antibacterial activity (MIC = one more time, as already previously reported.
25 lg/mL) against both S. aureus and MRSA than 13
(MIC>100 lg/mL). Similarly, 33 is more effective against This work was supported by the Research Organization of
Candida sp. (MIC = 3.12 and 6.25 lg/mL) than 13 (MIC = Ankara University (No. 2005 08 03 050). The central Laboratory
6.25 and 12.5 lg/mL); so, the importance of the antimi- of the Pharmacy Faculty of Ankara University provided sup-
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Arch. Pharm. Chem. Life Sci. 2009, 342, 54–60
Novel Substituted Benzimidazole Derivatives
59
Table 3. Formulas and melting points of compounds 1–5.
port for the acquisition of the NMR, mass spectrometer and ele-
mental analyser used in this work.
The authors have declared no conflict of interest.
Comp. No
R
Formulas
M.p. (8C)
Experimental
1 [10-12]
2 [12]
3 [11,12]
4 [11-14]
5 [6,15]
-H
5-CH3
5-Cl
5-NO2
5,6-Cl2
C14H10N2O2
C15H12N2O2
C14H9ClN2O2
C14H9N3O4
373–376
333–335
313–315
375–377
Chemistry
Melting points were determined with an Electrothermal (Elec-
trothermal Eng. Ltd., Essex, UK) and a Bꢀchi SMP-20 (Bꢀchi Labo-
ratoriumstechnik, Flawil, Switzerland) melting point apparatus
and are uncorrected. IR spectra were recorded on a Jasco FT/IR
420 spectrometer (Jasco Corp., Tokyo, Japan) as potassium bro-
mide discs.1H- and13C-NMR spectra were measured with a Varian
Mercury 400, 400 MHz instrument (Varian, Palo Alto, CA, USA)
using TMS internal standard and DMSO-d6. All chemical shifts
were reported as d (ppm) values. Mass spectra were obtained
with a Waters Micromass ZQ LC-MS spectrometer (Waters, Mil-
ford, MA, USA) with Positive Electrospray Ionization method.
Elemental analyses (C, H, and N) were determined on a Leco
CHNS 932 instrument (Leco, St.Joseph, MI, USA), and were
within 0.4% of the theoretical values. All chemical analyses were
performed at Ankara University, Faculty of Pharmacy. All chem-
icals used in synthesis purchased from E. Merck (Darmstadt,
FRG) and Aldrich (Milwaukee, USA). The purity of the com-
pounds were controlled with Merck precoated TLC plates and
spots were visualized with ultraviolet light. N-(4-Fluorobenzyl)-2-
nitro-4-chloroaniline[3] m.p.: 86-888C (m.p.lit.: 888C), N-(4-fluoro-
benzyl)-2-amino-4-chloro-aniline [3] m.p.: 958C (mplit.: 958C) were
prepared according to the literature. Compounds 11–15 were
purified by column chromatography using AcOEt / isopropanol /
NH3, (1 : 1 : 1gtt). CH2Cl2 / isopropanol (10 : 1) and CH2Cl2 / isopro-
panol (20 : 1) were used for 16–25 and for 26–30, respectively.
ATCC strains of the bacteria and fungus were obtained from the
culture collection of Refik Saydam Health Institution of Health
Ministry, Ankara, Turkey.
C14H8ClN2O2
362–365; 365 [6]
1,2-diamine 0.3 g (1.2 mmol) in DMF (10 mL) were heated at
1108C for 4 h. The reaction mixture was cooled, poured into the
water, and the formed solid was filtrated. Crystallization of the
crude product from EtOH gave 31.
Yield: 0.24 g, 52%; m.p.: 258–2628C.; IR (KBr)[cm– 1]: 1690
(C=O); 1H-NMR d [ppm] DMSO-d6: 5.64 (s, 2H, -CH2-), 7.02 (t, 2H,
H399,599, J = 8.8 Hz), 7.11 (t, 2H, H2999,6999, J = 8.8 Hz), 7.31-7.34 (dd, 1H,
H6, Jo = 8.4, Jm = 1.8 Hz), 7.60 (d, 2H, H7, Jo = 8.4 Hz), 7.83 (d, 1H, H4,
Jm = 1.8), 7.87 (d, 1H, H39,59, J = 8.4 Hz), 8.07 (d, 2H, H29,69, Jo = 8.4 Hz);
MS [ESI (+)] m/z: 381 [M + H] (100%), 383 [M + H + 2] (32%).
Synthesis of 11-30 and 5-Chloro-1-(4-fluorobenzyl)-2-{4-
[(4-methylpiperazin-1-yl) carbonyl] phenyl}-1H-
benzimidazole 33
4-[5-Chloro-1-(4-fluorobenzyl)-1H-benzimidazole-2-yl]
benzoic
acid 31 (1.5 mmol) or one of appropriate benzoic acid derivatives
1–5 was refluxed in benzene (5 mL) with SOCl2 (5 mL) for 2 h at
808C. Then solvent and excess of SOCl2 were evaporated com-
pletely and the residue was dissolved in chloroform (20 mL).
Related secondary amine was added and the mixture was stirred
and heated for 30 min at 508C. The chloroform layer was
washed with Na2CO3 (5%) and with water, and then purified by
column chromatography [AcOEt
(1 : 1 : 1gtt)]. Some physico-chemical properties and spectral
findings of 11–30 and 33 are given in Table 1.
/
isopropanol
/
NH3,
Synthesis of sodium bisulfite adduct of 4-
carboxybenzaldehyde
4-Carboxybenzaldehyde (15 mmol) was dissolved in 50 mL EtOH.
Sodium bisulfite (1.6 g) in water (10 mL) was added to a cooled
solution in portions, stirred vigorously, then EtOH was added,
and cooled again. The precipitate was filtered off and dried
(yield: 85%).
Microbiology
The minimal inhibitory concentrations (MIC) of the compounds
was determined by the dilution method.
Sample preparation
Synthesis of compounds 1–5
Each of the test compounds and standards (ampicillin, flucona-
zole) was dissolved in 12.5% DMSO, at concentrations of 200 lg/
mL. Further dilutions of the compounds and standards in the
test medium were prepared at the required quantities of 100,
50, …, …, 1.56 and 0.78 lg/mL.
The mixture of sodium bisulfite adduct of 4-carboxybenzalde-
hyde (2 mmol) and appropriate 4-substituted-1,2-phenylenedi-
amines (2 mmol) in DMF (5 mL) were heated at 1408C for 4 h. The
reaction mixture was cooled, poured into water and the solid
was filtrated. Crystallization of the crude products from EtOH
gave 1–5. Formulas and melting points of compounds 1–5 are
given in Table 3.
Culture of microorganisms
Bacteria and fungal species used were obtained from the micro-
biology department of Ankara University, Faculty of Pharmacy
and Refik Saydam Health Institution of Health Ministry, Ankara,
Turkey. Bacterial strains were maintained on MHA (Mꢀller–Hin-
ton Agar) medium for 24 h at 378C and fungi were maintained
Synthesis of 4-[5-chloro-1-(4-fluorobenzyl)-1H-
benzimidazole-2-yl] benzoic acid 31
The mixture of sodium bisulfite adduct of 4-carboxybenzalde-
hyde 0.31 g (1.2 mmol) and 4-chloro-N1-(4-fluorobenzyl) benzene-
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www.archpharm.com

60
C. Kus˛ et al.
Arch. Pharm. Chem. Life Sci. 2009, 342, 54–60
on SDA (Sabouraud Dextrose Agar) for 2–5 days at 25 l 18C. The
bacteria and fungi inocula were prepared by suspension in 9 mL
of sterile water for colonies from culture on MHA and SDA
medium.
[3] H. Gꢁker, C. Kus, U. Abbasoglu, Arch. Pharm. (Weinheim)
1995, 328, 425–430.
[4] H. Gꢁker, M. Tuncbilek, G. Ayhan, N. Altanlar, Farmaco
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Assay for in-vitro antimicrobial activity
The in-vitro antimicrobial activity of compounds was tested by
tube dilution technique [8, 9]. The tube dilution technique was
followed to determine the minimum inhibitory concentration
(MIC) of all the synthesized compounds. MHB (Mꢀller-Hinton
Broth) was used for bacteria, SDB (Sabouraud Dextrose Broth)
was used for Candida spp. The cell density of each inoculum was
adjusted in sterile water of a 0.5 McFarland standard. A final con-
centration of the test medium is approximately 103 CFU/mL and
104 CFU/mL for the bacteria and fungi, respectively. Microbial
inocula were added to the two-fold diluted samples. After incu-
bation for bacteria 18–24 h at 37 l 18C and for fungi 2–5 days
25 l 18C, the last tube with no growth of microorganism was
recorded to represent MIC expressed in lg/mL.
[6] S. ꢂzden, H. Karatas, S. Yildiz, H. Gꢁker, Arch. Pharm.
Pharm. Med. Chem. 2004, 337, 556–562.
[7] H. F. Ridley, R. G. W. Spickett, G. M. Timmis, J. Het. Chem.
1965, 2, 453–456.
[8] NCCLS, Reference Method for Broth Dilution Antifungal
Susceptibility Testing of Yeasts; Approved standard M27-A,
National Committee on Clinical Laboratory Standards
1997, 17, 9.
[9] NCCLS, Methods for Dilution Antimicrobial Susceptibility
Tests for Bacteria that Grow Aerobically M7-A5, National
Committee on Clinical Laboratory Standards 2000, 20, 2.
[10] Y. J. Xu, H. Q. Miao, W. Pan, E. C. Navarro, et al., Bioorg.
Med. Chem. Lett. 2006, 16, 404–408.
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[12] L. Edgardo, M. Yukiharu, U.S. 2001, US 6251689 B1.
[13] M. Francesco, G. Antonio, A. Roberto, M. Stefano, et al.,
Eur. Pat. Appl. 2005, EP 1571142 A1.
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www.archpharm.com