4
S.S. Chhajed et al.
as antibacterial potential than standard ampicillin. Good
correlation is found between in-silico molecular docking
experiments and in vitro antibacterial activity.
Table 3. Physiscal data of synthesized compounds 3a-3h
experimental
Synthesis of 2-(1H-benzimidazol-2-yl)-benzenamine (1)
In 250 ml round bottom flask, 0.01 M (1.08 g)
O-phenylenediamine was taken; to it was added 20 mL of
ethylene glycol. O.03 M (4.11 g) anthranilic acid and 2–3
drops of polyphosphoric acid ware added. e reaction
mixture was heated on sand bath at about 190–195°C for
4 h. e reaction mixture was poured into crushed ice.
Precipitate formed was filtered, washed with cold water,
dried and recrystalized from ethanol. Yield: (77%). M.p:
190–192°C, Rf: -0.62 [benzene: ethyl acetate (9:1)].
Sr compound
-R
-H
Formula
Melting point°C
276-278
154-156
202-204
109-111
92-94
1
2
3
4
5
6
7
8
3a
3b
3c
3d
3e
3f
C22H16ClN3O
C22H15Cl2N3O
C22H15Cl2N3O
C22H15ClFN3O
C22H16ClN3O2
C22H16ClN3O2
C22H15ClN4O3
C23H18ClN3O2
-2Cl
-4Cl
-4F
-2OH
-4OH
-4NO2
-4OCH3
197-199
123-125
67-69
3g
3h
General procedure for synthesis of 2-(1H-
benzimidazol-2-yl)-N-[Un/substituted- benzylidene]
benzenamine
Molecular docking against enzymes transpeptidase shows
binding energy (dock score) for compounds 3a, 3b, 3d, 3g
and ampicillin are -11.32, -10.82, -14.83 -12.18, and 10.11
kj/moles, respectively.
Equimolar quantities of unsubstituted/substituted aro-
matic aldehydes and 2-(1H-benzimidazol-2-yl)-benze-
namine were dissolved in 20 mL of warm dry ethanol. To
it was added 1–2 drops of concentrated sulfuric acid and
heated at reflux for 3 h on water bath. After standing for
approximately 1 h at room temperature (r.t), the crystal-
line product was separated by filtration, dried.
conclusion
e functionalized β-lactam compounds 3-chloro-4-
substituted-1-(2-(1H-benzimidazol-2-yl)phenyl))-azeti-
din-2-ones 3a-3h can be easily prepared in good yields.
Synthesized scaffold was screened for in vitro antibacte-
rial activity against various strains. Solvent DMSO was
incubated as control shows no antibacterial activity. All
compounds screened, has shown good activity when com-
pared with reference antibacterial ampicillin. Compounds
had shown MIC in the range 1.0–86 μM/L. Compounds
3a, 3b, 3d and 3g were found to be potent antibacteri-
als, with MICs 1.0–10 μM/L against Bacillus subtilis and
Staphylococcus aureus. Docking was performed using
Molecular Design Suite (MDS) v 3.5, into the 3D model of
thecatalyticsiteofenzymestranspeptidase,andtowellcor-
relate the obtained binding score with inhibitory activities
of compounds. Obtained results were evaluated in terms
of binding score into the catalytic site of enzymes trans-
peptidase, affinity and orientation of molecules in to the
active site of enzyme transpeptidase. Low binding scores
represent high affinity for the receptor. Compounds 3a-3h
were docked in to the active site of enzyme transpeptidase.
Binding energy (dock score) obtained for compounds 3a,
3b, 3d, 3g and ampicillin are -11.32, -10.82, -12.18, -14.83
and -10.11 kj/moles respectively against transpeptidase
enzyme. It has found from the docking experiments that,
all synthesized compounds forms hydrogen bond between
oxygen of 2-azetidinone and hydroxyl group of serine 409.
Further tested compounds show large charge interactions
with surrounding amino acid residues in to the active site
of transpeptidase. Smaller dock score (binding energy)
shows more affinity towards the receptor. Compounds
3a, 3b, 3d and 3g have more affinity for receptor as well
General procedure for synthesis of 1-(2-(1H-
benzimidazol-2-yl)phenyl)-3-chloro-4-[(Un)/
substituted phenyl)]azetidin-2-one
To 0.01 M various 2-(1H-benzimidazol-2-yl)-N-[Un/
substitutedbenzylidene]benzenamines, was added 20 ml
of 1,4 dioxane .e mixture was warmed to dissolve, the
resultant solution was allowed to cool, and to it was added
0.01 M triethyl amine and 0.01 M chloroacetyl chloride
drop wise and with stirring. Mixture was refluxed on the
boiling water bath for 4 h. Allowed to cool and filtered at
pump, air dried.
1-(2-(1H-benzimidazol-2-yl)phenyl)-3-chloro-4-
phenylazetidin-2-one (3a)
C22H16ClN3O, Yield: 76%, m.p: 276–278°C, IR ( KBr
cm−1): 3061.06 (aromatic C-H str), 1751.42(C=O str
1
amides),1248.67 600 (C-lCl str). H NMR (CDCl3): δ 4.4
(s, 1H, -NH), δ 5.4 (s, 1H, C4-H), δ 5.7 (s, 1H, C3-H), δ
6.9–8.3 (m, 13H, Ar-H). m/e: 373.
1-(2-(1H-benzimidazol-2-yl)phenyl)-3-chloro-4-(2-
chlorophenyl)azetidin-2-one (3b)
C22H15Cl2N3O, Yield: 65%, m.p: 154–156°C, IR (KBr cm−i):
3232.80 (N-H stretching sec amine), 3066.06 (Aromatic
C-H str ), 1749.49 (C=O str amides), 734.90 (C-Cl str). 1H
NMR (CDCl3): δ 5.2 (s, 1H, C4-H), δ 5.5 (s, 1H, C3-H), δ
6.7–8.6(m, 12H, Ar-H), δ 4.2 (s,1H,-N-H) m/e:408.
In vitro anti-bacterial assay
ecultureswereobtainedinMueller–HintonBroth(Difco)
for all the bacteria after 18–24h of incubation at 37 1°C.
Journal of Enzyme Inhibition and Medicinal Chemistry