Synthesis of novel 1,3,4-oxadiazole derivatives and their biological properties.

A novel series of 2-[3-(4-bromophenyl)propan-3-one]-5-(substituted phenyl)-1,3,4-oxadiazoles (4a-n) have been synthesized from 3-(4-bromobenzoyl)propionic acid (3) with the aim to get better anti-inflammatory and analgesic agents with minimum or without side effects (ulcerogenicity). Compound 3 was reacted with several aryl acid hydrazides (2a-n) in phosphorous oxychloride to obtain the title compounds. Structures of the synthesized compounds were supported by means of IR, 1H NMR and mass spectroscopy. Title compounds were evaluated for their anti-inflammatory, analgesic, ulcerogenic and antibacterial activities. Antibacterial activity was expressed as the corresponding minimum inhibitory concentration (MIC). A fair number of compounds were found to have significant anti-inflammatory and analgesic activities, while a few compounds showed appreciable antibacterial activity. The newly synthesized compounds showed very low ulcerogenic action. The findings of the present study indicate that cyclization of the carboxylic group of 3 into novel 1,3,4-oxadiazole nucleus resulted in increased anti-inflammatory and analgesic activities with a significant decrease of ulcerogenic activity.