Synthesis and antimicrobial activity of 3,5-disubstituted-1,3,4-oxadiazole derivatives

In this study, twenty two original derivatives of 5-(3,4-dichlorophenyl)-3-(4-substitutedpiperazino)methyl-1,3,4-oxadiazole-2(3H)-one have been synthesized. Their antimicrobial activity was screened compared to reference drug nystatin. 5-(3,4-Dichlorophenyl)-3-(4-substitutedpiperazino)methyl-1,3,4-oxadiazole-2(3H)-ones were synthesized by the reaction of 3,4-dichlorobenzoic acid as the starting material with hydrazine hydrate. Triethylamine, 1,1?-carbonyldiimidazole and tetrahydrofurane were added to synthesize 1,3,4-oxadiazole ring. 5-(3,4-Dichlorophenyl)-3-(4-substituted piperazino)methyl-1,3,4-oxadiazole-2(3H)-one derivatives were obtained by Mannich reaction of appropriate piperazine derivatives with 1,3,4-oxadiazole.The physical properties and Rf values on thin layer chromatography of the synthesized compounds were determined. Structure identification of the compounds was done by IR, 1H-NMR, 13C-NMR spectra, X-Ray crystallography and elemental analyses. Antimicrobial activity screening of compounds were determined by disc-diffusion methods against Aspergillus sp., Fusarium oxysporium, Botrytis cinerea, Penicillium sp., Bacillus megatarium, Escherichia coli, Staphylacoccus aureus and Pseudomonas aeruginosa strains.According to the activity studies, all compounds possess selective antifungal effect. Compound 2 and 8 show better activity against Aspergillus sp. Compound 15, 17, 18 and 20 show similar activity whereas; 1, 2 and 10 have higher activity against Fusarium oxysporium compared to nystatin. Compound 2, 3, 4 and 16 show preferable activity and also Compound 15 show efficient activity against Botrytis cinerea. Except compounds 5 and 9, all 5-(3,4-dichlorophenyl)-3-(4-substitutedpiperazino)methyl-1,3,4-oxadiazole-2(3H)-one derivatives show moderate to better activity than standard against Penicillium. Among all novel synthesized 1,3,4-oxadiazole derivatives, compound 2 and 15 possess best antimicrobial activity.