Synthesis and antimicrobial activity of some novel oxadiazole derivatives

A series of 5-(3'-oxo-6'-(substituted aryl)-2',3',4',5'-tetrahydropyridazin-2'-ylmethyl )-2-substituted 1,3,4-oxadiazole has been synthesized. Appropriate aromatic hydrocarbon reacts with succinic anhydride in the presence of AICl3 to yield beta-aroyl propionic acid (1a). The corresponding acid is cyclized with hydrazine hydrate to give 6-(substituted aryl)-2,3,4,5-tetrahydro-3-pyridazinone (1b). This ntermediate after reaction with ethyl bromoacetate, was hydrazinolyzed into 3-oxo-6-(substituted aryl)-2, 3, 4, 5-tetrahydropyridazinyl acetohydrazide (1c). The resulting product was converted into 5-[3'-oxo-6'-(substituted aryl)-2',3',4',5'-tetrahydropyridazin-2'-ylmethyl]-2-substituted 1,3,4-oxadiazole (Scheme 1). All the final compounds were structurally elucidated on the basis of IR, H-NMR, MS data and elemental analysis and screened for antibacterial, antifungal and antitubercular activity. All the compounds are evaluated for their antibacterial activity against E. coli, S. aureus, Micrococcus luteus and Klebsiella pneumoniae by using cup plate technique in the nutrient agar at 100 microg/mL concentration. Antitubercular activity was determined using the BACTEC 460 system. Stock solutions of test compounds were prepared in DMSO. MIC of rifampin was calculated by established procedures. All the synthesized compounds were screened at 6.25 microg/mL against M. tuberculosis H37 Rv comparable with that of standard rifampicin and isoniazid. All the final compounds were evaluated for antifungal activity against C. albicans and C. neoformans by using cup-plate method in the Sabouraud agar media The zone of inhibition (mm) of each compound was determined and compared with standard drug fluconazole.