SYNTHESIS AND ANTIMICROBIAL STUDIES OF NOVEL BINOL INDUCED HETEROCYCLES

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www.wjpr.net Vol 7, Issue 01, 2018. 1174

SYNTHESIS AND ANTIMICROBIAL STUDIES OF NOVEL BINOL

INDUCED HETEROCYCLES

Shailesh S. Gurav1*, Dr. Sandeep B. Kotwal2, Shweta N. Dandekar3 and Seema R.

Jadhav4

1, 3,4

VIVA College, Virar, Maharashtra, India.

2

Smt. C.H.M. College, Ulhasnagar-3, Thane, Maharashtra, India.

ABSTRACT

Novel potential benzimidazole based heterocycles were prepared using

simpler chemical methods with good yield and screening of these

newer heterocycles for antimicrobial activity was carried out.

KEYWORDS: Benzimidazole, antimicrobial agents, binaphthol,

chloroacetyl chloride.

INTRODUCTION

Very high rates of resistance have been observed in bacteria that cause

common health-care associated and community-acquired infections (e.g. urinary tract

infection, pneumonia) in all WHO regions.[1] Mutations change the parts of the cell that are

affected by drugs, decreasing their effectiveness.[2] Development of resistance of bacteria

against multiple antibiotics[3] and multiple drug resistance against fungi[4] are threats for

treatment of diseases. Infections caused by multi-drug resistant organism (MDROs) can be

more difficult to treat, since there are fewer antibiotics that work against them.[5] Resistance

and tolerances of many bacteria as well as viruses had always triggered the search for novel

drugs. In recent years, attention has increasingly been drawn to the synthesis of

benzimidazole derivatives as a source of new antimicrobial agents. The synthesis of novel

benzimidazole derivatives remains the main focus of medicinal research. Trends observed

suggest that substituted benzimidazoles and heterocycles, which are the structural isosters of

nucleotides with fused heterocyclic nuclei in their structures that allow them to interact easily

with the biopolymers, possess potential activity with lower toxicities in the chemotherapeutic

approach in man.[6-22]

Volume 7, Issue 01, 1174-1179. Research Article ISSN 2277–7105

Article Received on 15 Nov. 2017,

Revised on 04 Dec. 2017, Accepted on 25 Dec. 2017

DOI: 10.20959/wjpr20181-10578

*Corresponding Author

Shailesh S. Gurav

VIVA College, Virar,

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www.wjpr.net Vol 7, Issue 01, 2018. 1175 MATERIALS AND METHODS

All the chemicals and reagents used were of analytical reagent (AR) grade. Double distilled

water was used. The reaction was monitored on silica gel TLC plates. All melting points are

uncorrected. IR spectra were recorded on Shimadzu FTIR-4200. TLC refers to thin layer

chromatography and silica gel used was from S.D. Fine Chemicals Ltd. Mumbai; Silica gel

(S.D. Fine Chem. Limited) used for column chromatography was 60-120 mesh.

Preparation of compound 1

In a 1 litre three -necked flask, provided with a dropping funnel, a sealed stirrer and a reflux

condenser, was placed 14.4 g (0.1 mol) of 2-naphthol and 600 mL of water and heated to the

boiling point. To the boiling liquid containing liquid 2-naphthol in suspension, a solution of

28 g (0.1 mol) of crystallized iron (III) chloride in 60 mL of water was added slowly using a

dropping funnel and stirred vigorously. The oily drops of 2-napthol completely disappeared

and the bis-2-napthol separated out in flakes. The hot suspension was filtered through a

previously warmed Buchner funnel, and washed with boiling water and dried in air to get the

product. The crude product was recrystalised from toluene.

Yield: 52% M.P. 218 oC

BINOL (1mmol) was dissolved in AR grade acetone (20 mL) in a 50 mL round bottom flask.

Anhydrous Potassium carbonate (1.5 mmol) was added. Chloroacetyl chloride (1 mmol) was

added and the mixture was stirred at room temperature overnight. After completion of

reaction as monitored by TLC, reaction mixture was poured into crushed ice. The solid which

separated out was filtered and dried. The solid obtained was then purified by column

chromatography using silica gel bed and chloroform and ethyl acetate (90:10) as eluant.

Yield: 60% M.P.: 178°C

FTIR (KBr) cm-1: 3386, 3056, 2926, 1811, 1453, 1241, 1043, 824, 756, 688.

1

H NMR : (300 MHz, CDCl3): at δ = 6.89-6.99 (m, 2H;ArH), 7.03-7.10 (m, 2H; ArH),

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7.92-7.97 (d, 1H, Ar H) 7.00-7.019 (d, 1H, Ar H ), 5.36-5.27 (dd, 2H, CH2, due to geminal

coupling of two protons.) 5.54 (s, 1H, OH).

Compound 2 (1mmol) was dissolved in AR grade dimethyl formamide (25 mL) in a 50 mL

round bottom flask. Anhydrous Potassium carbonate (1.5 mmol) was added. Benzimidazole

(1 mmol) was added and the mixture was stirred at room temperature overnight. After

completion of reaction as monitored by TLC, reaction mixture was poured into crushed ice.

The solid which separated out was filtered and dried. The solid obtained was then purified by

column chromatography using silica gel bed and chloroform and ethyl acetate (90:10) as

eluant.

Yield: 55% M.P.: 128°C

FTIR (KBr) cm-1: 3447, 3391, 2912, 1630, 1545, 1211, 1156, 1062, 822.

1

H NMR (300 MHz, CDCl3) : at δ = 6.89-6.99 (m, 2H; ArH), 7.03-7.10 (m, 2H; ArH),

7.12-7.20 (m, 2H; ArH), 7.30-7.37 (m, 2H; ArH), 7.22-7.42 (m, 2H; ArH), 7.59-7.65 (m, 2H;

ArH), 7.40-7.56 (d, 1H; ArH), 7.57-7.68 (d, 1H,ArH), 7.21-7.26 (d, 1H; ArH), 7.69-7.74 (d,

1H, Ar H), 8.00-8.019 (s, 1H, Ar H ), 5.12 -5.14 (dd, 2H, CH2, due to geminal coupling of

two protons.) 5.30. (s,1H,OH)

RESULTS AND DISCUSSION

BINOL 1 was prepared by reported procedure and was confirmed by melting point. 1 was

monoalkylated at one oxygen atom of BINOL using chloroacetyl chloride. 1 (1 mmol) was

reacted with chloroacetyl chloride (1 mmol) in acetone with potassium carbonate. Crude

product was recrystallized to obtain pure product. Melting point of purified 2 was found to be

178°C with 60% yield. Its FTIR-1 absorption spectrum shown presence of carbonyl peaks at

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Free O-H bond stretching band frequency of BINOL was present in the spectrum between

3000-3500cm-1. IR spectrum also shown sharp peak at 1241 cm-1, hence it was suggestive

that new C-O bond formation took place between 2 and chloroacetyl chloride. We attempted

to predict the possible structure of 2 with help of 1H-NMR spectra. Consequently, 2 and

benzimidazole was charged in the ratio (1:1) in dry DMF at room temperature in presence of

anhydrous potassium carbonate and the mixture was left overnight (Scheme 2). After work

up, filtered compound was purified by percolating through silica gel (60-120 mesh size) using

chloroform and ethyl acetate (90:10) as eluant. FTIR absorption spectra of compounds 3

confirmed the presence of amide bond stretching frequency in the region of 1713-1630 cm-1.

Qualitative elemental analysis of compound 3 confirmed the absence of element chlorine.

Hence the information of the new C-N bond was confirmed by FTIR spectra and qualitative

analysis for chloride. With help of 1H-NMR spectra We attempted to predict the possible

structure of 3.

Antimicrobial Activity

The antimicrobial activity of the synthesized compounds was tested by disc diffusion method.

They were dissolved in DMSO and sterilized by filtering through 0.45ìm Millipore filter.

Final inoculum of 100μL suspension containing 108 CFU/mL of each bacterium and fungus was used. Nutrient agar (antibacterial activity) and sabouraud’s dextrose agar medium

(antifungal activity) was prepared and sterilized in an autoclave (118°C and 14 Ibs for 22

min) and transferred to previously sterilized petridishes (9 cm in diameter). After

solidification, petridishes were inoculated with bacterial organisms in sterile nutrient agar

medium at 45oC, and fungal organisms in sterile sabouraud’s dextrose agar medium at 45oC

in aseptic condition. Sterile Whatmann filter paper discs (previously sterilized in U.V. lamp)

were impregnated with the synthesized compounds at a concentration of 25 mg/disc and were

placed in the organism-impregnated Petri plates under sterile condition. The plates were left

for 30 min to allow the diffusion of compounds at room temperature. Antibiotic discs of

ciprofloxacin (100μg/disc) and ketaconazole (100μg /disc) were used as positive control,

while DMSO was used as negative control. Then the plates were incubated for 24 h at

37±1°C for antibacterial activity and 48 h at 37±1°C for antifungal activity. The zone of

inhibition was calculated by measuring the minimum dimension of the zone of no microbial

growth around the each disc. Compounds 3 and 4 were evaluated for in-vitro antibacterial

activity against gram negative bacteria Proteus vulgaris (NCTC 4635) and Klesibella

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Enterococcus faecium (ATCC 29212). These are the agents that commonly causes urinary

tract infection, nosocomial infection, biliary tract infection. The gram negative organism

Klesibella pneumonia cause pneumonia, bronco pneumonia and bronchitis infection. The

gram negative organisms Bacillus cereus and Enterococcus faecium cause endocarditis,

bacteremia, meningitis and septicaemia. From Table 1, it is evident that compound 3 was

more active against Klesibella pneumonia (ATCC 29655), Bacillus cereus (NL98), and

Enterococcus faecium (ATCC 29212); whereas compound 4 was found to be more active

against Proteus vulgaris (NCTC 4635). Compound 3 was found to be more active against

Aspergillus niger and Aspergillus fumigatus. However the antimicrobial activity of the

synthesized compounds against the tested organisms was found to be less than that of

respective standard drug at the tested dose level.

Table 1: Antimicrobial activity.

Organism

Diameter of zone of inhibition in mm Compound 3

25mg

Compound 4 25mg

Compound 5 25mg

Ketoconazole 100 μg

Ciprofloxacin 100 μg

Bacillus Cerus 12 10 08 ---- 28

Proteus Vulgaris 09 12 11 ---- 29

Klesibella Pneumonia 13 10 09 ---- 25

Enterococcus Faecium 10 08 07 ---- 24

Aspergillus Niger 11 11 08 25 ----

Aspergillus Fumigatus 09 07 10 26 ----

CONCLUSIONS

In search for a novel but potential bioactive drug, compounds 3 and 4 were prepared using

simpler chemical methods of synthesis with satisfactory yield. The screening against both

gram positive and gram negative bacteria showed that compound 3 is more capable than

compound 4 but less than the standards used like ketoconazole and ciprofloxacin.

ACKNOWLEDGEMENT

The authors are thankful to University of Mumbai, Mumbai, India.

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