Green route for the heterocyclization of 2-mercaptobenzimidazole into β-lactum segment derivatives containing -CONH- bridge with benzimidazole: Screening in vitro antimicrobial activity with various microorganisms

Article abstract of DOI:10.1016/j.bmc.2006.09.017

The efficient and rapid synthesis of novel azetidin-2-ones 4a-j has been established. Thus, both microwave and conventional condensation 2-{(1H-benzimidazol)-ylthio}-N′-2-(substituted phenyl) hydrazide with chloroacetylchloride were carried out in DMF-ben

Full text of DOI:10.1016/j.bmc.2006.09.017

Bioorganic & Medicinal Chemistry 14 (2006) 8271–8279
Green route for the heterocyclization of 2-mercaptobenzimidazole
into b-lactum segment derivatives containing –CONH– bridge with
benzimidazole: Screening in vitro antimicrobial activity with various
microorganisms
Krunal G. Desai* and Kishor R. Desai
Department of Chemistry, Faculty of Science, Synthetic Organic Chemistry Research Laboratory,
Veer Narmad South Gujarat University, Udhna-Magdalla Road, Surat (west)-395 007, Gujarat State, India
Received 31 July 2006; revised 5 September 2006; accepted 8 September 2006
Available online 10 October 2006
Abstract—The efficient and rapid synthesis of novel azetidin-2-ones 4a–j has been established. Thus, both microwave and conven-
tional condensation 2-{(1H-benzimidazol)-ylthio}-N0-2-(substituted phenyl) hydrazide with chloroacetylchloride were carried out in
DMF-benzene solvent in the presence of Et3N catalyst. The microwave synthesis route afforded better yield with short time. The
novel heterocycles were characterized by elemental analysis and spectral features. Some of the produced compounds were screened
for their antimicrobial activity.
ꢀ 2006 Elsevier Ltd. All rights reserved.
1. Introduction
toward achieving green chemistry objectives. Within
the framework of ‘Green Chemistry’ we have now devel-
oped an environmentally benign and novel approach for
the synthesis of azetidine-2-ones. In view of the above,
and in continuation to our earlier work on the applica-
tion of MORE17–19 chemistry to organic synthesis and
the biological importance of 2-azetidinones, we now
report a simple, novel and environmentally benign ap-
proach using facile, microwave synthesis of 2-azetidi-
nones 4a–j from precursors 3a–j and ClCH2COCl
using triethylamine (TEA) as a catalyst (Fig. 1).
2-Mercaptobenzimidazole derivatives are known to pos-
sess varied biological activities.1 2-Azetidinone deriva-
tives have been reported to possess anti-inflammatory,2
anticonvulsant,3 fungicidal,4 antibiotic,5 anticancer,6
antielastase,7 antiviral,8 antimicrobial,9 antitumor,10
anti-HCMV,11 antibacterial12 activities and pharmalog-
ical interest.13 The incorporation of a 2-oxoazetidine
moiety in to 2-mercaptobenzimidazole scaffold enhances
its activity.
In the last few years, microwave-induced organic reac-
tion enhancement (MORE) has gained popularity as a
non-conventional technique for rapid organic synthe-
sis14 and many researchers have described accelerated
organic reactions, with a large number of papers that
have appeared proving the synthesis utility of MORE
chemistry in routine organic synthesis.15,16 It can be
termed as ‘e-chemistry’ because it is easy, effective, eco-
nomical, and eco-friendly, and is believed to be a step
4"
7"
H
N
3
2
3"
O
H
5"
6"
1'
N
4'
C
1
2"
R
SCH2C
NH
O
4
N
1"
6
5
2' 3'
Cl
4
a
b
c
R
4-NO2
4
f
g
h
i
R
2-OCH3
4-OCH3
2-Cl
3, 4, 5-(OCH3)3
2-OH
3-OH
Keywords: 2-Azetidinones; Heterocyclization; Microwave effect; Anti-
microbial interest.
d
3-Cl
e
4-OH
j
4-Cl
*
Corresponding author. Tel.:/fax: +91 0261 2258384; e-mail:
kgdapril@yahoo.co.in
Figure 1. General structure of synthesized 2-azetidinones 4a–j.
0968-0896/$ - see front matter ꢀ 2006 Elsevier Ltd. All rights reserved.
doi:10.1016/j.bmc.2006.09.017

8272
K. G. Desai, K. R. Desai / Bioorg. Med. Chem. 14 (2006) 8271–8279
2. Results and discussion
4.13 ppm due to CH3 and CH2, respectively (J = 7 Hz),
in –COOCH2CH3 of compound 1 in the 1H NMR spec-
tra and IR spectral bands at 1723 cmꢀ1 due to the ester
(>C@O) and 2915, 2871, 1423, 713 cmꢀ1 (CH2 and
CH3) also confirmed the formation of compound 1.
Compound 1 on ammonolysis with hydrazinehydrate
in ethanol as a reaction media afforded [2-(benzimidaz-
Conventional methodology sometimes has lower yields
than microwave protocols. Microwave irradiation facil-
itates the polarization of the molecule under irradiation
causing rapid reaction to occur. A comparative study in
terms of yield and reaction period is shown in Table 1.
The MS spectral fragmentation pattern is presented
(Scheme 2) as an additional evidence for the proposed
structure 4a. The synthetic route of abovementioned
compounds is shown in Scheme 1) . All the compounds
synthesised were adequately characterized by their ele-
1
olylthio)-acetyl]-hydrazine20,21 2. In the H NMR spec-
tra of compound 2, the peak at d 7.88 ppm were
observed due to –CONH– and a peak at d 4.40 ppm
was due to the –NH2 group of compound 2.
Furthermore, in the IR spectra, the bands at
1665 cmꢀ1 (>C@O of amide) and 3352, 3378 cmꢀ1
(–NHNH2) also confirm the formation of compound
2. Compound 2, an aromatic aldehyde and 2–3 drops
of glacial acetic acid in ethanol as a reaction mediator
afforded 2-{(1H-benzimidazol)-ylthio}-N0-2-(substituted
phenyl)hydrazide20,21 3. The formation of compound 3
was evidenced by appearance of signal at d 4.40 ppm
due to the –N@CH– of in 1H NMR spectra, the appear-
ance of a signal at d 60 ppm due to the >CH–N< of in
13C NMR spectra and IR spectra bands, due to
1
mental analysis and IR, H NMR, 13C NMR spectros-
copies and by mass spectrometry.
2.1. Chemistry
Condensation of 2-mercaptobenzimidazole and ethyl
chloroacetate in presence of anhydrous K2CO3 in dry
acetone as a reaction mediator afforded ethyl-2-(benzim-
idazolylthio)-acetate20,21 1. The formation of compound
1 was evidenced by appearance of a signal at d 1.23 and
Table 1. Comparative study in terms of yield and reaction period in presence of different power watts and constant temperature for microwave and
conventional techniques 4a–j
Products
MMicrowave irradiation technique (MWI)
CConventional method
Irradiation condition
AYield (%)
BYield (%)
Constant temperature (ꢁC)
Time (h)
CYield (%)
A,MPower P1
(W)/Time T1 (min)
B,MPower P2
(W)/Time T2 (min)
4a
4b
4c
4d
4e
4f
250/5.0
300/4.0
200/5.5
250/5.0
200/5.0
300/4.0
250/5.0
200/5.5
250/5.0
300/4.0
400/3.0
400/3.0
450/2.5
350/3.5
350/3.0
400/3.0
450/2.5
450/3.0
400/2.5
450/2.5
78
79
75
78
75
80
76
75
78
80
89
88
90
85
84
86
90
88
87
90
145
149
150
148
148
146
147
146
144
145
5.0
6.0
6.5
6.5
6.0
5.0
6.5
5.0
5.5
5.0
70
69
65
75
70
58
61
72
73
69
4g
4h
4i
4j
A,MYield of isolated products (P1-200-3-0 W, T1-4.0-5.5 min); B,MYield of isolated products (P2-350-450 W, T2-2.5-3.5 min);C Yield of isolated
products.
H
N
H
N
O
ClCH2COOC2H5
Anhydrous K2CO3, dry acetone
NH2NH2 , ethanol
SH
SCH2C
OC2H5
MWI and Conventional method
N
N
MWI and Conventional method
1
H
N
H
N
O
O
Ethanol
2-3 drops glacial AcOH
R
SCH2C
NHNH2
SCH2C
NH
N
C
H
N
N
2
CHO
3a-j
R
ClCH2COCl, N(C2H5)3 (triethylamine)
Conventional method
MWI and Conventional method
MWI method
DMF
Benzene
H
N
O
H
R
SCH2C
NH
O
N
C
N
Cl
4a-j
Scheme 1.

K. G. Desai, K. R. Desai / Bioorg. Med. Chem. 14 (2006) 8271–8279
8273
H
N
O
H
C
SCH2 C
NH
O
N
NO2
Fragment loss
Fragment ion
C9H7ON2
N
C18H14O4N5SCl
[ M ] 396
S
CO
C9H7N3O3Cl
C8H7N2S
C7H5N2S
C6H5NS
Cl
NH
4a
Homolytic cleavage
C6H5NO2
CH2
H
N
H
C
CNS
CS
S
C6H5N2
HN
O
N
NO2
SCH2C
O
C7H5N2
N
C9H7N3O3Cl
m/z 240
C9H6N2O3Cl
Cl
-
C9H7ON2
m/z 191
S
-
CO
C8H7N3O2Cl
C3H3N2OCl
C8H6N2O2Cl
(- 28)
-
C
6H5NO2
(- 123)
CO
-
NH
H
N
(- 28)
(- 15)
H
C
SCH2
H
H
C
N
HN
N
HN
N
C
NO2
N
NO2
-
CH2
(- 14)
C8H7N2S
m/z 163
O
Cl
H
N
O
C8H7N3O2Cl
m/z 212
Cl
Cl
C3H3N2OCl
m/z 117
C9H6N2O3Cl
m/z 225
-
CO
S
-
NH
N
C7H5N2S
m/z 149
(- 28)
(- 15)
-
S
-
CNS
-
CS
(- 32)
(- 58)
H
(- 44)
C6H5N2
m/z 105
C6H5NS
m/z 91
C7H5N2
m/z 117
N
C
NO2
C8H6N2O2Cl
m/z 197
Cl
Scheme 2. Mass spectral fragmentation pattern of 10-[(benzimidazol-2-yl)thioacetamidyl]- 30-chloro-40-(4-nitrophenyl-azetidin- 20-one) 4a.
(–N@CH–) at 1626 cmꢀ1, also confirmed the formation
of compound 3. This compound 3 on cycloaddition with
chloroacetylchloride in presence of triethylamine [Et3N]
in DMF/benzene as a reaction mediator afforded 10-
[(benzimidazol-2-yl)thioacetamidyl]-30-chloro-40-(substi-
tuted phenyl-azetidin-20-one) 4. In the 1H NMR spectra
of compound 4, the peak was observed at d 4.0 ppm due
to the >CH–Cl in the b-lactam ring; in the 13C NMR
spectra of compound 4, peaks at d 50 ppm was ob-
served, due to >CH–Cl, at 172.5 ppm (cyclic, >C@O)
and 157.5 ppm (heteroaromatics) in the b-lactam moie-
ty. In the IR spectra of compound 4, the bands at
1717 cmꢀ1 (>C@O, cyclic) also confirmed the formation
of azetidinones 4. In the mass spectra of compound 4a,
the molecular ion peak 396 [M+] (24%) also confirmed
the formation of the azetidinone. The fragment ion
(m+) peak was observed at 240 m/z (78%), 225 m/z
(37%), 212 m/z (31%), 197 m/z (29%), 191 m/z (34%),
163 m/z (24%), 149 m/z (35%), 117 m/z (30%), 105 m/z
(38%) and 91 m/z (29%) by the loss of fragment radicals
and neutrals ÆCO (ꢀ28), ÆNH (ꢀ15), ÆC6H5NO2 (ꢀ123),
ÆCH2 (ꢀ14), ÆCNS (ꢀ58), ÆS (ꢀ32) and ÆCS (ꢀ44).
tion state.22 The effectiveness of microwave irradiation
and conventional heating for the synthesis of com-
pounds 4a–j has been compared (Table 1). Under micro-
wave irradiation conditions, the yields of 4a–j are high
(90–84%). Whereas using conventional heating the
yields are only 58–75%. The effects of irradiation power
and time on the reaction were also studied and the re-
sults summarized in Tables 2 and 3. High yields of com-
pounds 4a–j can be obtained in 450 W for 2.5 min under
microwave irradiation.
2.3. Antibacterial activity
The antibacterial screening results (the zone of inhibi-
tion), presented in Table 4, the results revealed that all
newly synthesized compounds were exhibited potent
antibacterial activity. In general, compounds 4a, 4i
and 4j exhibited more pronounced antibacterial activi-
ties than the compounds 4b–h, with better activity
against both Gram positive and Gram negative bacteria.
Among all the compounds tested, 4i and 4j exhibited
remarkable antibacterial activity against the Gram neg-
2.2. Microwave irradiation technique
Table 2. The effect of microwave irradiation powerK
Irradiation power (W)
200
250
78
300
80
350
85
400
88
450
90
All the reactions that used microwave irradiation
(MWI) were completed with in 2–5.5 min, whereas sim-
ilar reactions under conventional heating (steam bath)
at similar temperatures (80–100 ꢁC) gave poor yields
with comparatively longer reaction time period (Table
1), demonstrating that the effect of microwave irradia-
tion is not purely thermal. Microwave irradiation facili-
tates the polarization of the molecules under irradiation
causing rapid reaction to occur. This is consistent with
the reaction mechanism, which involves a polar transi-
Yield (%)
75
K Irradiation time is 2.5 min.
Table 3. The effect of microwave irradiation timeG
Irradiation time (min)
5.5
5.0
75
4.0
79
3.5
81
3.0
87
2.5
90
Yield (%)
73
G Irradiation power is 450 W.

8274
K. G. Desai, K. R. Desai / Bioorg. Med. Chem. 14 (2006) 8271–8279
Table 5. The MIC values (lg/mL) of compounds 4a–j
Table 4. The zone of inhibition values (mm) of compounds 4a–j
Compounds
Antibacterial activity (mm)
Compounds
Antifungal activity (lg/mL)
Gram positive
(+ve)
Gram negative
(ꢀve)
E.c [u]
C.a [n]
(ATCC 64550)
C.k [a]
(ATCC 14243)
A.n [l]
B.s [k] S.a [r]
(ATCC 6633) (ATCC 6538) (ATCC 6538)
4a
4b
4c
4d
4e
4f
ꢀ
ꢀ
ꢀ
+ +
+ +
+ +
+
+ +
+ + +
+ +
+ +
+ +
+ +
+ +
ꢀ
+ +
+ +
+ +
+ +
+ + +
+ +
+ +
ꢀ
4a
4b
4c
4d
4e
4f
+ + +
+ +
ꢀ
+ +
+ +
ꢀ
+ +
+ +
ꢀ
+ +
+ +
+ +
ꢀ
+ +
+ +
ꢀ
+ +
+ +
ꢀ
+ +
+ +
ꢀ
4g
4h
4i
4g
4h
4i
+ +
+ +
+ +
+
+ +
+ +
+ + +
+
+ +
+ +
+ + +
+ + +
4j
+ +
+ +
+
Minimum inhibitory concentration of standard drugs (lg/mL)
Flucanozole + + + + + + + + + + + +
4j
Zone of inhibition of standard drugs (mm)
50 lg/mL = + + + +, 100 lg/mL = + + +, 150 lg/mL = + +,
200 lg/mL = +, Not active upto 200 lg/m = Flucanozole23 is
(+ + + +) at 650 lg/mL.
Streptomycin + + + +
+ + + +
+ + + +
Diameter of the zone of inhibition: (ꢀ) 6 mm; (+) 6–15 mm; (+ +)
15–20 mm; (+ + +) 20–25 mm; (+ + + +) 25–30 mm.
Diameter of the MIC: (ꢀ) 6 lg/mL; (+) 6–15 lg/mL; (+ +)
15–20 lg/mL; (+ + +) 20–25 lg/mL; (+ + + +) 25-30 lg/mL.
[k] B.s, Bacills substilis; [r] S.a, Staphylococcus aureus; [u] E.c,
Escherchia coli.
[n] C.a, Candida albicans; [a] C.k, Candida krusei; [l] A.n, Aspergillus
niger.
ative Escherichia coli (ATCC 6538) as compared with
antibiotic streptomycin.
Candida krusei with a MIC of 150 lg/mL and com-
pounds 4c and 4e showed moderate antifungal activity
against Aspergillus niger with a MIC of 150 lg/mL. By
visualizing the antifungal data it could be observed that
some of the compounds possess significant activity.
However, none of compounds were was superior to
standards used against any fungi. Generally, the com-
pounds 4e and 4j (both have R = –OH and –Cl, respec-
tively) were less active their methoxy counterparts, with
exception of compound 4c against Candida krusei. The
rest of the tested compounds 4a and 4i were not active
against all organisms with MIC values upto P200 lg/
mL.
On the other hand, compounds 4a and 4i exhibited po-
tent activity against the Gram positive Bacills substilis
(ATCC 6633) and Staphylococcus aureus (ATCC 6538)
as compared with Streptomycin. The antibacterial activ-
ities of compounds 4c, 4f and 4j were 70% lower than,
the standard against the Gram positive bacteria species
and 4c and 4f against Gram negative bacteria species.
Moreover, compounds 4b, 4d, 4e, 4g and 4h were mod-
erately active against the same organisms.
2.4. Antifungal activity
For all drugs, the minimum inhibitory concentration
(MIC) of the compounds was defined as the lowest con-
centration at which there was 100% inhibition of growth
compared with the growth for a drug free control.23 Sen-
sitivity of the selected fungal pathogens to some synthe-
sized compounds 4a–j was determined in vitro at four
concentrations (50, 100, 150 and 200 lg/mL). Standard
minimum inhibitory concentration for Flucanozole
(FLU)23 is (+ + + +) at 650 lg/mL against all microbes.
3. Experimental
3.1. General
Regents, instrumentation and measurements: all re-
agents, 2-mercaptobenzimidazole, solvents and catalyst
were of analytical grade and used directly. All the melt-
ing points were determined in PMP–DM scientific melt-
ing point apparatus and are uncorrected. The
completion of reaction was monitored by thin-layer
chromatography (TLC) using silica gel-G coated Al-
plates (0.5 mm thickness, Merck) and spots were visual-
ized by exposing the dry plates to iodine vapour. The
product was purified by silica gel column chromatogra-
phy (60–120 mesh) eluted by benzene and ethyl acetate
(8:2 v/v) mixture.24 IR spectra (tmax in cmꢀ1) were
recorded on a Shimadzu FT-IR 8300 spectrophotometer
The antifungal screening results (MIC), presented in
Table 5, it is evident from the screening data compounds
4c and 4f were more effective against Candida krusei
(100 lg/mL) and Aspergillus niger (100 lg/mL), respec-
tively, compared with the other derivatives. Compounds
4e and 4j showed weak antifungal activity against Can-
dida albicans and Aspergillus niger, respectively, with a
MIC of 200 lg/mL, but compounds 4b, 4d, 4g and 4h
showed moderate antifungal activity against all fungal
species with a MIC of 150 lg/mL, compounds 4c, 4f
and 4j showed moderate antifungal activity against Can-
dida albicans with a MIC of 150 lg/mL, compounds 4e,
4f and 4j showed moderate antifungal activity against
1
using KBr or the Nujol technique; H NMR spectra
were acquired on a Bruker WM 400FT 400 MHz
NMR instrument using CDCl3 or DMSO-d6 as the sol-
vent and TMS as the internal reference (chemical shifts
in d, ppm); 13C NMR was performed on a Varian AMX

K. G. Desai, K. R. Desai / Bioorg. Med. Chem. 14 (2006) 8271–8279
8275
400 (100 MHz) spectrometer using solutions in CDCl3
and mass spectra were acquired on a Jeol JMS D-300
spectrometer operating at 75 eV. The elemental analysis
(C, H, N) of compounds was performed on Carlo Erba-
1108 elemental analyzer. Their results were found to be
in good agreement with the calculated values. The
microwave assisted reactions are carried out using
QPro-M Microwave Sample Preparation System (Que-
stron Technologies Corporation, Mississauga, Ontario
L4Z 2E9, Canada), wherein this unit, microwaves are
generated by magnetron at a frequency of 2450 MHz
having an output energy range of 100–500 W and a fibre
optic sensor for temperature control with an attached
reflux condenser with constant stirring (to avoid the risk
of high pressure development) and permitting synthesis
on preparative scales.
resulting solid was filtered, dried, and recrystallized
from ethanol to give compound 2, yield 80%, as a pink-
ish white powder. Mp 195 ꢁC. Anal. Calcd for
C9H10N4OS: C, 48.64; H, 4.5; N, 25.22. Found: C,
48.66; H, 4.8; N, 25.25%; IR (KBr): t (cmꢀ1) 3352,
3378 (–NHNH2), 1665 (>C@O of amide); 1H NMR
(CDCl3-DMSO-d6): d (ppm) 6.80–7.90 (m, 4H, Ar–H),
4.40 (s, 2H, –NH2), 4.81 (s, 2H, S–CH2–), 7.88 (s, 1H,
–CONH–), 8.4 (s, 1H, –NH–benzimidazole).
3.2.4. Conventional synthesis of 2. Compound
1
(0.01 mol, 2.36 g) and hydrazine hydrate (0.01 mol,
0.9 mL) in ethanol (20 mL) were refluxed for about 5 h
on a steam bath. After cooling the resulting solid was fil-
tered, dried, and recrystallized from ethanol to obtain
compound 2, yield 63%, as a pinkish white solid. Mp
195 ꢁC.
The QPro-M apparatus used was especially well suited
for stringent reaction conditions, including anhydrous
atmosphere.
3.2.5. Microwave assisted synthesis of 2-{(1H-ben-
zimidazol)-ylthio}-N0-2-(4-nitrophenyl) hydrazide (3a). A
mixture of compound 2 (0.01 mol, 2.22 g), 4-nitrobenz-
aldehyde (0.01 mol, 1.51 g) and 2–3 drops glacial acetic
acid in ethanol (20 mL) were placed in a round-bot-
tomed flask inside a microwave oven and irradiated
(450 W, 76–78 ꢁC) for 2–3 min.20,21 After completion
of reaction (monitored by TLC). The solvent was re-
moved and residue recrystallized from chloroform–
methanol mixture to afford compound 3, yield 87%, as
a dark yellow solid. Mp 161 ꢁC. Anal. Calcd for
C16H13N5O3S: C, 54.08; H, 3.66; N, 19.71. Found: C,
54.05; H, 3.65; N, 19.73%; IR (KBr): t (cmꢀ1) 3340,
1335 (–NH–), 1668 (>C@O), 1626 (–N@CH–); 1H
3.2. Synthesis
3.2.1. Microwave assisted synthesis of ethyl-2-(benzimi-
dazolylthio)-acetate
(1).
2-Mercaptobenzimidazol
(0.01 mol, 1.50 g) and ethyl chloroacetate (0.01 mol,
1.22 mL) in dry acetone (4 mL) in the presence of anhy-
drous K2CO3 (1 g) were placed in a round-bottomed
flask inside a microwave oven and irradiated (350 W,
61–62 ꢁC) for 3.5 min.20,21 Upon completion of the reac-
tion (monitored by TLC), the reaction mixture was al-
lowed to attain room temperature and treated with
cold water. The separated solid was filtered, washed
with water and recrystallized from chloroform to furnish
compound 1, yield 84%, as a white crystal. Mp 60 ꢁC,
Anal. Calcd for C11H12N2O2S: C, 55.93; H, 5.08; N,
11.86. Found: C, 55.95; H, 5.10; N, 11.90%; IR (KBr):
t (cmꢀ1) 3023 (aromatic ring), 1070 (aliphatic ether),
638 (C–S), 1723 (>C@O of ester), 1614 (–C@N–), 1223
and 1041 (C–O–C), 721 (C–S–C) and 2915, 2871,
1423, 713 (–CH2 and –CH3); 1H NMR (CDCl3-
NMR (CDCl3-DMSO-d6):
d (ppm) 4.40 (s, 1H,
–N@CH–), 8.13 (s, 1H, –CONH–), 6.93–7.73 (m, 4H,
Ar–H), 8.8 (s, 1H, –NH–benzimidazole).
3.2.6. Conventional synthesis of 3a. A mixture of com-
pound 2 (0.01 mol, 2.22 g) and 4-nitrobenzaldehyde
(0.01 mol, 1.51 g) and 2–3 drops of glacial acetic acid
in ethanol (20 mL) was refluxed on a water bath for
about 6 h. The solvent was removed and residue recrys-
tallized from chloroform methanol mixture to yield
compound 3a, (61%) as a pale yellow powder. Mp
161 ꢁC. Compounds 3b–j were prepared similarly by
treating 2 with various aromatic aldehydes.
DMSO-d6):
d
(ppm) 1.23 (t, 3H, J = 7 Hz,
–COOCH2CH3), 4.13 (q, 2H, J = Hz, –COOCH2CH3),
4.46 (s, 2H, S–CH2–), 6.73–7.87 (m, 4H, Ar–H), 8.6 (s,
1H, –NH–benzimidazole).
3.2.2. Conventional synthesis of ethyl 2-(benzimidazolyl-
thio)acetate (1). An equimolar solution of 2-merca-
3.2.7. Microwave assisted synthesis of 10-[(benzimidazol-
2-yl)thioacetamidyl]-30-chloro-40-(4-nitrophenyl- azetidin-
20-one) (4a). A mixture of 3a (0.01 mol, 3.55 g) in DMF
and chloroacetyl chloride (0.01 mol, 1.12 mL) with a
catalytic amount of triethylamine (1 mL) was placed in
a round-bottomed flask inside a microwave oven and
irradiated (400 W, 143–145 ꢁC) for 3 min.20,21 After
completion of the reaction (monitored by TLC), it was
then diluted with ice cold water. The solid product
formed was filtered, dried, and recrystallized from etha-
nol, yield 89%, as a brown solid. Mp 221 ꢁC. Anal.
Calcd for C18H14N4O5S: C, 54.54%; H, 3.53%; N,
17.67%. Found: C, 54.52%; H, 3.55%; N, 17.70%; IR
(KBr): t (cmꢀ1) 3340 and 1330 (–NH–), 1665 (>C@O,
amidyl), 1717 (>C@O, cyclic), 1340 (Ar–NO2). 1H
ptobenzimidazol
(0.01 mol,
1.50 g)
and
ethyl
chloroacetate (0.01 mol, 1.22 mL) in dry acetone
(4 mL) in the presence of anhydrous K2CO3 (1 g) was re-
fluxed on a water bath for 6 h. The solvent was removed
by vacuum distillation and the residue was recrystallized
from chloroform to furnish compound 1, yield 67%, as a
white solid. Mp 60 ꢁC.
3.2.3. Microwave assisted synthesis of [(2-benzimidazol-
ylthio)-acetyl]-hydrazine (2). Compound 1 (0.01 mol,
2.36 g) and hydrazine hydrate (0.01 mol, 0.9 mL) in eth-
anol (20 mL) was placed in a round-bottomed flask in-
side a microwave oven and irradiated (300 W, 76–
78 ꢁC) for 4.0 min.20,21 After completion of reaction
(monitored by TLC), the mixture was cooled and the
NMR (CDCl3-DMSO-d6):
d (ppm) 8.53 (s, 1H,
–CONH–), 7.00–7.95 (m, 8H, Ar–H), 3.15 (d, 1H,

8276
K. G. Desai, K. R. Desai / Bioorg. Med. Chem. 14 (2006) 8271–8279
>CH–Ar), 4.48 (s, 2H, S–CH2–), 4.0 (s, 1H, >CH–Cl),
8.2 (s, 1H, –NH–benzimidazole). 13C NMR (CDCl3-
DMSO-d6): d (ppm) 127 (C1), 128.9 (C2, C6),126.2 (C3,
(47%), 149 (40%), 148 (25%), 133 (17%), 117 (15%),
105 (33%), 91 (23%), 82 (57%).
4.3. 10-[(Benzimidazol-2-yl)thioacetamidyl]-30-chloro-40-
(3-hydroxyphenyl-azetidin-20-one) (4d)
0
C5), 150 (C4), 60 (> C4 H–N <), 30 (–S–CH2–), 172.5
0
(cyclic, > C2 @O), 169.2 (amide, >C@O), 51
00
00
00
00
00
00
(> C30H–Cl), 157.5 (C1 , C2 , C4 , C5 , C6 , C7 , hetero-
aromatics); MS (m/z): 396 [M+] (24%), 240 (78%), 240
(78%), 225 (37%), 212 (31%), 197 (29%), 191 (34%),
163 (24%), 149 (35%), 117 (30%), 105 (38%), 91 (29%).
Mp 153 ꢁC; Anal. Calcd for C18H16N4O3S: C, 58.71; H,
4.10; N, 15.23. Found: C, 58.69; H, 4.07; N, 15.21%; IR
(KBr): t (cmꢀ1) 3333, 1341 (–NH–), 1680 (>C@O, ami-
dyl), 1734 (>C@O, cyclic), 3571 (Ar–OH), 810 (C–Cl);
1H NMR (CDCl3-DMSO-d6): d (ppm) 8.55 (s, 1H,
–CONH–), 6.85–7.65 (m, 8H, Ar–H), 3.11 (d, 1H,
>CH–Ar), 4.36 (s, 2H, S–CH2–), 4.3 (s, 1H, >CH–Cl),
8.5 (s, 1H, –NH–benzimidazole), 3.64 (s, 1H, –OH);
13C NMR (CDCl3-DMSO-d6): d (ppm) 127.1 (C1),
129.3 (C2, C6), 126.8 (C3, C5), 153.5 (C4), 52.5
3.2.8. Conventional synthesis of 10-[(benzimidazol-2-
yl)thioacetamidyl]-30-chloro-40-(4-nitrophenyl-azetidin-20-
one) (4a). A mixture of 3a (0.01 mol, 3.55 g) in benzene
and chloroacetyl chloride (0.01 mol, 1.12 mL) with a
catalytic amount of triethylamine (1 mL) was placed in
a round-bottomed flask. It was refluxed for 5 h on a
steam bath. After completion of the reaction (monitored
by TLC), the benzene was distilled off to obtain product
4a. The solid product was filtered, dried, and recrystal-
lized from ethanol, yield 70%, as a brownish crystal.
Mp 221 ꢁC. Other compounds 4b–j were prepared in
the similar way using 3b–j, respectively.
0
0
(> C4 H–N <), 54.3 (> C3 H–Cl), 32.5 (–S–CH2–),
0
175.2 (cyclic, > C2 –O), 166.7 (amide, >C@O), 153.8
00
00
00
00
00
00
(C1 , C2 , C4 , C5 , C6 , C7 , heteroaromatics); MS (m/
z): 366[M+] (75%), 191 (40%), 175 (85%), 163 (48%),
160 (35%), 149 (50%), 147 (28%), 133 (42%), 117
(39%), 105 (22%), 91 (20%), 82 (52%).
4.4. 10-[(Benzimidazol-2-yl)thioacetamidyl]-30-chloro-40-
(4-hydroxyphenyl-azetidin-20-one) (4e)
4. Spectroscopic data of compounds 4b–j
4.1. 10-[(Benzimidazol-2-yl)thioacetamidyl]-30-chloro-40-
(3,4,5-trimethoxyphenyl-azetidin-20-one) (4b)
Mp 169 ꢁC; Anal. Calcd for C18H16N4O3S: C, 59.80; H,
4.48; N, 14.71. Found: C, 59.84; H, 4.46; N, 14.69%; IR
(KBr): t (cmꢀ1) 3390, 1337 (-NH-), 1679 (>C@O, ami-
dyl), 1730 (>C@O, cyclic), 3583 (Ar–OH), 818 (C–Cl);
1H NMR (CDCl3-DMSO-d6): d (ppm) 8.46 (s, 1H,
–CONH–), 6.88–7.90 (m, 8H, Ar–H), 3.12 (d, 1H,
>CH–Ar), 4.45 (s, 2H, S–CH2–), 4.6 (s, 1H, >CH–Cl),
8.7 (s, 1H, –NH–benzimidazole), 3.58(s, 1H, –OH);
13C NMR (CDCl3-DMSO-d6): d (ppm) 126.8 (C1),
128.5 (C2, C6), 127.1 (C3, C5), 154 (C4), 52.1
Mp 250 ꢁC; Anal. Calcd for C21H21N4O5S: C, 57.16; H,
4.05; N, 15.27. Found: C, 57.14; H, 4.08; N, 15.25%; IR
(KBr): t (cmꢀ1) 3335, 1335 (–NH–), 1660 (>C@O, ami-
dyl), 1720 (>C@O, cyclic), 2825 (Ar–OCH3), 779 (C–
Cl); 1H NMR (CDCl3-DMSO-d6): d (ppm) 8.50 (s,
1H, –CONH–), 6.98–7.93 (m, 8H, Ar–H), 3.18 (d, 1H,
>CH–Ar), 4.46 (s, 2H, S–CH2–), 4.1 (s, 1H, >CH–Cl),
8.4 (s, 1H, –NH–benzimidazole), 3.91(s, 3H, –OCH3);
13C NMR (CDCl3-DMSO-d6): d (ppm) 127.1 (C1),
129.1 (C2, C6),126.4 (C3, C5), 153 (C4), 52.3
0
(> C4 H–N <), 56 (> C3 H–Cl), 32 (–S–CH2–), 176.2
0
0
00
(cyclic, > C2 @O), 168.7 (amide, >C@O), 155.8 (C1 ,
00
00
00
00
00
C2 , C4 , C5 , C6 , C7 , heteroaromatics); MS (m/z):
368[M+] (78%), 191 (80%), 177 (43%), 163 (51%), 162
(20%), 149 (54%), 134 (48%), 117 (15%), 105 (24%), 91
(28%), 82 (57%).
0
0
(> C4 H–N <), 30.1 (–S–CH2–), 172 (cyclic, > C2 @O),
0
00
00
168.2 (amide, >C@O), 58 (> C3 H–Cl), 156.5 (C1 , C2 ,
00
00
00
00
C4 , C5 , C6 , C7 , heteroaromatics), 35.4 (CH3OC6H4–);
MS (m/z): 441[M+] (69%), 250 (33%), 235 (17%), 222
(70%), 207 (83%), 191 (47%), 163 (27%), 149 (40%),
117 (32%), 105 (19%), 91 (49%), 82 (55%).
4.5. 10-[(Benzimidazol-2-yl)thioacetamidyl]-30-chloro-40-
(2-methoxyphenyl-azetidin-20-one) (4f)
4.2. 10-[(Benzimidazol-2-yl)thioacetamidyl]-30-chloro-40-
(2-hydroxyphenyl-azetidin-20-one) (4c)
Mp 198 ꢁC; Anal. Calcd for C19H17N4O3S: C, 59.99; H,
4.49; N, 14.71. Found: C, 60.00; H, 4.46; N, 14.69%; IR
(KBr): t (cmꢀ1) 3375, 1337 (–NH–), 1671 (>C@O, ami-
dyl), 1726 (>C@O, cyclic), 2828 (Ar–OCH3), 820 (C–
Cl); 1H NMR (CDCl3-DMSO-d6): d (ppm) 8.47 (s,
1H, –CONH–), 6.88–7.95 (m, 8H, Ar–H), 3.13 (d, 1H,
>CH–Ar), 4.49 (s, 2H, S–CH2–), 4.3 (s, 1H, >CH–Cl),
8.5 (s, 1H, –NH–benzimidazole), 3.96 (s, 3H, –OCH3);
13C NMR (CDCl3-DMSO-d6): d (ppm) 126.8 (C1),
128.7 (C2, C6),125.9 (C3, C5), 153.2 (C4), 52.0
Mp 141 ꢁC; Anal. Calcd for C18H16N4O3S: C, 58.81; H,
4.09; N, 15.38. Found: C, 58.85; H, 4.07; N, 15.36%; IR
(KBr): t (cmꢀ1) 3290, 1338 (–NH–), 1670 (>C@O, ami-
dyl), 1725 (>C@O, cyclic), 3590 (Ar–OH), 811 (C–Cl);
1H NMR (CDCl3-DMSO-d6): d (ppm) 8.49 (s, 1H,
–CONH–), 7.20–7.90 (m, 8H, Ar–H), 3.17 (d, 1H,
>CH–Ar), 4.31 (s, 2H, S–CH2–), 3.9 (s, 1H, >CH–Cl),
8.1 (s, 1H, –NH–benzimidazole), 3.65(s, 1H, –OH);
13C NMR (CDCl3-DMSO-d6): d (ppm) 126.9 (C1),
128.8 (C2, C6), 127 (C3, C5), 155 (C4), 51.9
0
(> C4 H–N <), 53.1 (> C3 H–Cl), 32 (–S–CH2–), 172.5
0
0
00
(cyclic, > C2 @O), 168 (amide, >C@O), 157.5 (C1 ,
00
00
00
00
00
C2 , C4 , C5 , C6 , C7 , heteroaromatics), 35.7
(CH3OC6H4-); MS (m/z): 381[M+] (72%), 191 (44%),
190 (88%), 175 (43%), 163 (50%), 162 (54%), 149
(36%), 147 (29%), 117 (13%), 105 (27%), 91 (24%), 82
(52%).
0
0
(> C4 H–N <), 53.3 (> C3 H–Cl), 31.5 (–S–CH2–), 175
0
00
(cyclic, > C2 @O), 167.2 (amide, >C@O), 154.5 (C1 ,
00
00
00
00
00
C2 , C4 , C5 , C6 , C7 , heteroaromatics); MS (m/z):
367[M+] (70%), 191 (32%), 176 (45%), 163 (25%), 161

K. G. Desai, K. R. Desai / Bioorg. Med. Chem. 14 (2006) 8271–8279
8277
4.6. 10-[(Benzimidazol-2-yl)thioacetamidyl]-30-chloro-40-
(4-methoxyphenyl-azetidin-20-one) (4g)
IR (KBr): t (cmꢀ1) 3383, 1342 (–NH–), 1668 (>C@O,
1
amidyl), 1718 (>C@O, cyclic), 831 (Ar–Cl); H NMR
(CDCl3-DMSO-d6): d (ppm) 8.51 (s, 1H, –CONH–),
6.96–7.86 (m, 8H, Ar–H), 3.11 (d, 1H, >CH–Ar), 4.40
(s, 2H, S–CH2–), 4.5 (s, 1H, >CH–Cl), 8.1 (s, 1H,
–NH–benzimidazole); 13C NMR (CDCl3-DMSO-d6): d
(ppm) 126.8 (C1), 128.9 (C2, C6), 123.9 (C3, C5), 151.4
Mp 218 ꢁC; Anal. Calcd for C19H17N4O3S: C, 56.05; H,
3.65; N, 14.55. Found: C, 56.03; H, 3.63; N, 14.53%; IR
(KBr): t (cmꢀ1) 3378, 1339 (–NH–), 1675 (>C@O, ami-
dyl), 1721 (>C@O, cyclic), 2830 (Ar–OCH3), 816 (C–
1
0
(C4), 52.9 (> C4 H–N <), 52.3 (> C3 H–Cl), 33.4 (–S–
0
Cl); H NMR (CDCl3-DMSO-d6): d (ppm) 8.53 (s, 1H,
0
–CONH–), 6.65–7.77 (m, 8H, Ar–H), 3.16 (d, 1H,
>CH–Ar), 4.29 (s, 2H, S–CH2–), 4.2 (s, 1H, >CH–Cl),
8.2 (s, 1H, –NH–benzimidazole), 3.89 (s, 3H, –OCH3);
13C NMR (CDCl3-DMSO-d6): d (ppm) 127.8 (C1),
129.7 (C2, C6),124.9 (C3, C5), 152.2 (C4), 52.3
CH2–), 169.7 (cyclic, > C2 @O), 167.4 (amide, >C@O),
00
00
00
00
00
00
156.7 (C1 , C2 , C4 , C5 , C6 , C7 , heteroaromatics);
MS (m/z): 384[M+] (79%), 193 (49%), 191 (83%), 178
(42%), 165 (49%), 163 (52%), 150 (31%), 149 (38%),
117 (20%), 105 (29%), 91 (23%), 82 (59%).
0
(> C4 H–N <), 54.1 (> C3 H–Cl), 33 (–S–CH2–), 171.5
0
0
00
00
(cyclic, > C2 @O), 167 (amide, >C@O), 156.5 (C1 , C2 ,
00
00
00
00
C4 , C5 , C6 , C7 , heteroaromatics), 34.7 (CH3OC6H4-);
MS (m/z): 380 [M+] (69%), 191 (47%), 189 (83%), 174
(40%), 163 (48%), 161 (50%), 149 (31%), 146 (30%),
117 (10%), 105 (30%), 91 (22%), 82 (50%).
5. Antibacterial activity (the zone of inhibition)
The antimicrobial susceptibility testing (AST) was
accomplished by the Kirby Bauer method of disc diffusion
method. The sample solution was prepared by dissolving
10 lg of each of the compound in 1.0 mL of Dimethyl-
formamide (DMF). The sterilized Whatman filter paper
(No. 1) discs of approximately 6 mm were dipped in sam-
ple solution and dried in oven. These discs were placed on
the medium previously seeded with the organisms in petri
dishes at suitable distances. The petri dishes were stored in
an incubator at 30 2 ꢁC for 24 h. The zone of inhibition
thus formed around each disc containing the test com-
pound was measured accurately in mm.
4.7. 10-[(Benzimidazol-2-yl)thioacetamidyl]-30-chloro-40-
(2-chlorophenyl-azetidin-20-one) (4h)
Mp 201 ꢁC; Anal. Calcd for 18H14N4O2SCl: C, 55.98; H,
3.63; N, 14.58. Found: C, 55.95; H, 3.62; N, 14.56%; IR
(KBr): t (cmꢀ1) 3385, 1340 (–NH–), 1678 (>C@O, ami-
dyl), 1722 (>C@O, cyclic), 835 (Ar–Cl); 1H NMR
(CDCl3-DMSO-d6): d (ppm) 8.50 (s, 1H, –CONH–),
6.72–7.82 (m, 8H, Ar–H), 3.17 (d, 1H, >CH–Ar), 4.38
(s, 2H, S–CH2–), 4.1 (s, 1H, >CH–Cl), 8.1 (s, 1H,
–NH–benzimidazole); 13C NMR (CDCl3-DMSO-d6): d
(ppm) 128.8 (C1), 128.7 (C2, C6),125.9 (C3, C5), 151.2
The synthesized derivatives 4a–j were screened for their
in vitro antibacterial activity against Staphylococcus aure-
us (ATCC-6538), Bacillus substilis (ATCC-6633) and
Escherichia coli (ATCC-6538) using disc diffusion meth-
od.25 Mueller–Hinton agar (Hi Media, Difco, Detroit,
USA) was used for bacterial strains. Streptomycin was
also screened under similar conditions for comparison.
0
(C4), 54.3 (> C4 H–N <), 33.2 (–S–CH2–), 171.7 (cyclic,
0
0
> C2 @O), 167.2 (amide, >C@O), 57.4 (> C3 H–Cl),
00
00
00
00
00
00
156.7 (C1 , C2 , C4 , C5 , C6 , C7 , heteroaromatics);
MS (m/z): 385.5[M+] (77%), 194 (51%), 191 (80%), 179
(45%), 166 (47%), 163 (51%), 151 (30%), 149 (29%),
117 (13%), 105 (29%), 91 (21%), 82 (54%).
4.8. 10-[(Benzimidazol-2-yl)thioacetamidyl]-30-chloro-40-
(3-chlorophenyl-azetidin-20-one) (4i)
6. Antifungal activity (the minimum inhibitory concen-
tration)
Mp 216 ꢁC; Anal. Calcd for C18H14N4O2SCl: C, 56.24;
H, 3.64; N, 14.60. Found: C, 56.25; H, 3.62; N,
14.58%; IR (KBr): t (cmꢀ1) 3380, 1341 (–NH–), 1673
Study design. Microdilution is used according to a stan-
dard protocol described by the NCCLS.26,27 Three
stains were tested each of the following species: Candida
albicans (ATCC-64550), Candida krusei (ATCC-14243)
and Aspergillus niger.
1
(>C@O, amidyl), 1719 (>C@O, cyclic), 825 (C–Cl); H
NMR (CDCl3-DMSO-d6):
d (ppm) 8.48 (s, 1H,
–CONH–), 7.15–7.92 (m, 8H, Ar–H), 3.18 (d, 1H,
>CH–Ar), 4.41 (s, 2H, S–CH2–), 4.4 (s, 1H, >CH–Cl),
8.3 (s, 1H, –NH–benzimidazole); 13C NMR (CDCl3-
DMSO-d6): d (ppm) 127.7 (C1), 129.8 (C2, C6),124.8
Medium. RPMI 1640 broth with L-glutamine without
sodium bicarbonate and 0.165 l MOPS buffer (34.54 g/
L) was used. The medium was adjusted to pH 7.0 at
25 ꢁC. Sterility of each bottle was performed before it
was used.
0
(C3, C5), 152.3 (C4), 53.2 (> C4 H–N <), 34.3 (–S–
0
CH2–), 170.6 (cyclic, > C2 @O), 168.3 (amide, >C@O),
0
00
00
00
00
00
00
58.3 (> C3 H–Cl), 157.8 (C1 , C2 , C4 , C5 , C6 , C7 , het-
eroaromatics); MS (m/z): 386[M+] (76%), 195 (50%), 191
(79%), 180 (43%), 167 (46%), 163 (49%), 152 (28%), 149
(32%), 117 (17%), 105 (31%), 91 (24%), 82 (56%).
Antifungal agents. Terbinafine was provided by the man-
ufacturer as a standard powder. All drugs dissolved
100% dimethylsulfoxide according to the NCCLS meth-
ods.26,27 The final drug concentrations were 50–0.01 lg/
mL for all drugs.
4.9. 10-[(Benzimidazol-2-yl)thioacetamidyl]-30-chloro-40-
(4-chlorophenyl-azetidin-20-one) (4j)
Preparation of inoculum. The preparation of inoculum
suspensions was based mainly on the NCCLS guide-
line27 and as described previously.28–30 For dermato-
Mp 209 ꢁC; Anal. Calcd for C18H14N4O2SCl: C, 49.63;
H, 3.26; N, 9.68. Found: C, 49.61; H, 3.23; N, 9.66%;

8278
K. G. Desai, K. R. Desai / Bioorg. Med. Chem. 14 (2006) 8271–8279
phytes the final inoculum size was adjusted from
1.2 · 104 to 6 · 104 CFU/mL and for C. albicans it was
approximately 1 · 103 and 5 · 103 CFU/mL.26,31,32
against A. niger indicated in vitro antifungal activity com-
parable to or slightly lower than that of flucanozole. The
different substituents on the aromatic ring exert a signifi-
cant influence on the biological activity. The presence of
electron-withdrawing group on the aromatic ring in gen-
eral decreases the antimicrobial activities of test com-
pounds compared to compounds having electron-
donating groups. Based upon the results it will also be
necessary to optimize the lead compound by substituting
series of electron-donating groups on aromatic ring and
selectively modifying the b-lactum nucleus. The substitu-
tion in the C40 position in of the phenyl ring by methoxy,
chloro and polar group (phenolic or nitro moiety) seems
to be very important for antifungal effect, as well as the
presence and the position of the –CONH– group in the
connecting linker between the benzimidazole and phenyl
ring and b-lactam derivatives seems to be very important
for antibacterial effect.
Test procedure. The test procedure was applied accord-
ing to the NCCLS protocols.26,27 Microdilution plates
(96 U-shaped) were prepared and frozen at ꢀ70 ꢁC until
needed. Each microdilution well containing 100 lL of
the 2-fold drug concentration was inoculated 100 lL
of the final inoculum suspension. Two drug-free growth
controls were included for each test plate, one without
any drug (growth control) and the other with media con-
taining an equivalent amount of solvent used to dis-
solved the drug (solvent control).
The fungal pathogens were maintained in RPMI 1640
Broth after incubation for 48 h at 25 1 ꢁC. Testing
was performed in RPMI 1640 Broth at pH 7.0 and 2-
fold dilution was applied. A set of tubes containing only
inoculated broth were kept as controls. After incubation
for 48 h at 25 1 ꢁC, the last tube with no fungal growth
was recorded to represent minimum inhibitory concen-
tration (MIC), expressed in lg/mL.
Acknowledgment
One of the authors (Krunal Desai) is thankful to the
Head of the Chemistry and Bioscience Department of
Veer Narmad South Gujarat University, Surat. We
gratefully acknowledge the Gujarat Council on Science
and Technology, Gandhinagar, for financial assistance
(Grant no. GUJCOST/200389/MRP/2003-04/10689),
and the Central Drug Research Institute at Lucknow
for spectral analysis.
All of the compounds 4a–j were tested for their in vitro
growth inhibitory antifungal activity against Candida
albicans (ATCC-64550), Candida krusei (ATCC-14243)
and Aspergillus niger. Flucanozole (FLU) was also
screened under similar conditions for comparison.
7. Conclusion
References and notes
In conclusion, this new method for the synthesis of 2-
azetidinones using catalytic amount of Et3N in DMF
under microwave irradiation offers significant improve-
ments over existing procedures an thus, helps facile en-
try into a variety of 2-azetidinones of potentially high
synthetic utility. Also, this simple and reproducible tech-
nique affords various 2-azetidinones with short reaction
times, excellent yields and without formation of undesir-
able by-products.
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Banik, B. K. J. Med. Chem 2003, 46(1), 12.
7. Anaya, Josefa; Gero, D. S.; Grande, Manuel; Hernando,
A series of 2-azetidinone (b-lactam) derivatives were pre-
pared and tested for their in vitro antibacterial activity
against the three strains of bacteria (gram +ve, gram
ꢀve) and antifungal activities against the three strains
of human pathogenic fungi. Five compounds of the ob-
tained series showed high in vitro antimicrobial activity.
10-[(benzimidazol-2-yl)thioacetamidyl]-30-chloro-40-(4-
nitrophenyl- azetidin-20-one) (4a) showed excellent
activity against B. substilis, 10-[(benzimidazol-2-yl)thio-
acetamidyl]-30-chloro-40-(3-chlorophenyl-azetidin-20-
one) (4i) showed excellent activity against S. aureus, (4i)
and 10-[(benzimidazol-2-yl)thioacetamidyl]-30-chloro-
40-(4-chlorophenyl-azetidin-20-one) (4j) showed excellent
activity against E. coli indicated in vitro antibacterial
activity comparable to or slightly lower than that of strep-
tomycin. 10-[(benzimidazol-2-yl)thioacetamidyl]-30-chlo-
ro-40-(2-hydroxyphenyl-azetidin-20-one) (4c) showed
excellent activity against C. krusei and 10-[(ben-
zimidazol-2-yl)thioacetamidyl]-30-chloro-40-(2-methoxy-
phenyl-azetidin-20-one) (4f) showed excellent activity
´
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