Synthesis and antimicrobial activity of 1,4-diaryl-2-azetidinones

Article abstract of DOI:10.1016/S0014-827X(99)00126-3

Cycloaddition of substituted 4,4-benzylidene-anilines to in situ prepared dichloroketenes in the presence of dichloroacetyl chloride and triethylamine affords a variety of 2-azetidinones. All the compounds were characterized by IR and ¹H NMR. Their antimicrobial activity, against Gram(+) and Gram(-) bacteria and fungi, was tested. Copyright (C) 2000 Elsevier Science S.A.

Full text of DOI:10.1016/S0014-827X(99)00126-3

www.elsevier.nl/locate/farmac
Il Farmaco 55 (2000) 147–150
Short Communication
Synthesis and antimicrobial activity of 1,4-diaryl-2-azetidinones
a,
a
b
b
8
Vıldan Gu¨ner *, Su¨leyman Yıldırır , Berrın Ozc¸elık , Ufuk Abbasog˘lu
a Department of Chemistry, Faculty of Science, Hacettepe Uni6ersity, 06532, Beytepe, Ankara, Turkey
b Department of Microbiology, Faculty of Pharmacy, Gazi Uni6ersity, Etiler, Ankara, Turkey
Received 22 April 1999; accepted 8 November 1999
Abstract
Cycloaddition of substituted 4,4-benzylidene–anilines to in situ prepared dichloroketenes in the presence of dichloroacetyl
1
chloride and triethylamine affords a variety of 2-azetidinones. All the compounds were characterized by IR and H NMR. Their
antimicrobial activity, against Gram(+) and Gram(−) bacteria and fungi, was tested. © 2000 Elsevier Science S.A. All rights
reserved.
Keywords: Cycloaddition; b-Lactam; Penicillin
prepared by the reaction of acid chloride and imine in
the presence of a tertiary amine [14–17].
1. Introduction
In the present paper, we report the synthesis and
Many compounds containing the b-lactam ring pos-
characterization of a number of substituted 1,4-diaryl-
sess various interesting biological properties [1]. The
2-azetidinones. 1,4-Diaryl-2-azetidinones were prepared
synthesis of 2-azetidinone continues to be a very active
by the method of Scheme 1. Imines with various sub-
research area because of the importance of this struc-
stituents in the benzene rings were prepared and used in
tural unit in penicillin and related antibiotics [2–8].
this study as illustrated in Table 1.
Selectivity (activity) can be influenced decisively by
substituents, which are attached to the p-position of the
rings [9,10].
In this paper, we report the synthesis and characteri-
zation of a number of substituted 1,4-diarylazetidinones
and their antimicrobial activity.
2. Chemistry
The ketene–imine cycloaddition reaction is one of
the most widely used methods, constructing the b-lac-
tam skeleton present in the different families of b-lac-
tam antibiotics [11,12]. The Staudinger reaction is now
widely employed in the preparation of b-lactams be-
cause it provides direct access to these compounds from
simple precursors [13]. Numerous b-lactams have been
Scheme 1.
* Corresponding author. Fax: +90-312-299 2163.
0014-827X/00/$ - see front matter © 2000 Elsevier Science S.A. All rights reserved.
PII: S0014-827X(99)00126-3

148
V. Gu¨ner et al. / Il Farmaco 55 (2000) 147–150
Table 1
Physical and spectral data of compounds 1–10
Compound
R1
R2
Formula
m.p (°C)
wCꢀO (cm−1
)
lH (ppm)
1
2
3
4
5
6
7
8
9
H
H
H
H
OCH3
CH3
Cl
NO2
NO2
OCH3
H
C15H11NOCl2
C16H13NO2Cl2
C16H13NOCl2
C15H10NOCl3
C16H13NO2Cl2
C16H13NOCl2
C15H10NOCl3
C15H10N2O3Cl2
C16H12N2O4Cl2
C16HH12NO2Cl3
164
106
142
135
128
136
154
136
126
126
1771
1780
1778
1790
1778
1780
1771
1775
1773
1771
5.55
5.49
5.51
5.53
5.49
5.51
5.52
5.65
5.61
5.47
OCH3
CH3
Cl
H
H
H
H
OCH3
Cl
10
Cycloaddition reaction between imines and
dichloroketene has been studied at room temperature
(r.t.). The structures of b-lactams were determined by
IR, 1H NMR and X-ray spectra. In the IR spectra,
stretching frequencies of carbonyl groups are changed
between 1770 and 1788 cm−1 due to the effect of the
substituents in the rings. According to X-ray results,
the CꢁN bond lengths of the compounds 4a, 4b, 4d and
4g are 1.362(6), 1.357(4), 1.367(4) and 1.374(1), respec-
tively [18–21]. The phenyl rings are nearly perpendicu-
lar to one another [66.3 (4a), 66.6 (4b), 79.4 (4d), 62.15
(4g)].
3.1.2. General procedure for the preparation of
i-lactams (4a–1)
A solution of an imine (3a–l) (0.001 mol) and tri-
ethylamine (0.002 mol) in 50 ml benzene was stirred for
15 min. Dichloroacetyl chloride (1) (0.002 mol) was
added dropwise to the solution and the mixture was
stirred at r.t. for 1 h. The triethylamine salts were
filtered. The mixture was washed with 5% HCl and
water and dried over sodium sulfate. The products were
fractionally crystallized from ethanol or petroleum
ether. Some physical properties and spectral findings of
1–10 are given in Table 1.
3. Experimental
3.2. Microbiological studies
3.1. Chemistry
3.2.1. Microorganisms
1H NMR spectra have been recorded on a Bruker
DPX-400 MHz spectrometer employing CDCl3 as the
solvent with TMS as the internal standard. The IR
spectra were obtained on a Hitachi 270-30 spectrometer
as KBr pellets. Melting points were determined on an
electrothermal melting point apparatus and are uncor-
rected. Benzene and triethylamine were dried over
sodium and freshly distilled before use.
Compounds (4a–l) were subjected to an antimicro-
bial screening procedure against Gram(+) and
Gram(−) strains of Staphylococcus aureus ATCC
25923 (S.a), Bacillus subtilis ATCC 6633 (B.s), Es-
cherichia coli ATCC 35218 (E.c), Pseudomonas aerugi-
nosa ATCC 10145 (P.a) and towards Candida albicans
ATCC 10231 (C.a), Candida glabrata ATCC 66032
(C.g). The microorganism used in this study was ob-
tained from Karadeniz Technical University.
3.1.1. General procedure for the synthesis of
4-4%-disubstituted benzylidene–anilines
The 4,4%-disubstituted benzylidene–anilines, neces-
sary to the present work, were prepared by refluxing
equimolecular amounts of 4-substituted benzaldehydes
and 4%-substitute anilines in dry benzene. The reaction
was over in about 2 h. The solvent was removed by
evaporation in vacuo and the residue was crystallized
from ethanol or petroleum ether [22].
3.2.2. Medium
Mueller Hinton Broth (Oxoid) medium was used for
diluting the microorganism suspension and two fold-di-
lution of the compounds. Sabouraud liquid medium
(Oxoid) was used for yeast-like fungi for the same
purpose.

V. Gu¨ner et al. / Il Farmaco 55 (2000) 147–150
149
Table 2
Antibacterial and antifungal activity of compounds 1–10 and the standard drugs (MIC in mg/ml) a
Compound
R1
R2
S.a
B.s
E.a
P.a
C.a
C.g
1
2
3
4
5
6
7
8
H
H
H
H
OCH3
CH3
Cl
NO2
NO2
OCH3
–
H
\250
\250
\250
\250
\250
\250
\250
\250
\250
\250
0.1
\250
\250
\250
\250
\250
\250
\250
\250
\250
\250
0.1
250
250
250
250
250
250
250
250
250
250
62.5
–
125
125
125
125
125
125
125
125
125
125
62.5
–
125
125
125
125
125
125
125
125
125
125
–
125
125
125
125
125
125
125
125
125
125
–
OCH3
CH3
Cl
H
H
H
H
OCH3
Cl
–
9
10
Ampicillin
Griseofulvin
–
–
–
–
62.5
62.5
a Microorganisms selected are as follows: S.a, Staphylococcus aureus; B.s, Bacillus subtilis; E.c, Escherichia coli; P.a, Pseudomonas aeruginosa;
C.a, Candida albicans; C.g, Candida glabrata.
3.2.3. Equipment
in Table 2, showed that, in contrast with the well-
known activity of b-lactam antibiotics, the inhibitory
effect is significant against fungi and Gram(−) bacte-
ria. The activity of compounds 1–10 was particularly
interesting against Pseudomonas aeruginosa. The unex-
pected activity of all compounds against fungi is not
affected by substituents.
Falcon® 96-well microplates were used for the mi-
crodilution method. A Brinkmann transferpette® was
used for two fold-dilution of the compounds in the
wells.
3.2.4. Method
The microdilution method was employed for antibac-
terial and antifungal activity tests [23,24]. For the anti-
fungal activity test, 0.1 ml Sabouraud liquid medium
and for the antibacterial activity test 0.1 ml Mueller
Hinton medium were placed into each well of the
microplates. 0.1 ml of the compound solution in
DMSO at 1000 mg/ml concentration was added into the
first raws of microplates; ampicillin anhydrate and
griseofulvin were used as control agents under the same
conditions. Double dilutions of the compounds and
standard 250, 125, 0.1 mg/ml were made by dispensing
the solutions to the remaining wells. 0.1 ml microorgan-
ism suspensions, at 106 cfu/ml (colony forming unit/ml)
concentration, were inoculated into all the wells. The
sealed microplates were incubated at 36°C for 24 and
36 h in the humid chamber. The lowest concentration
of the compound that completely inhibits macroscopic
growth was controlled and MIC (minimum inhibitory
concentration) reported. MIC values of the two deriva-
tives, ampicillin anhydride and griseofulvin as stan-
dards and ten compounds have been shown as mg/ml in
Table 2.
Acknowledgements
We would like to thank the Turkish Scientific and
Technical Research Association (TUBITAK) for the
financial support (Grant no: TBAG-1690) in this
research.
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