carboxylic acids in the presence of phosphorus oxychloride. Interconversion of oxadiazoles to thiadiazoles and triazoles was carried out with appropriate reagents. The antimicrobial and cytotoxic activities of compounds 7a–d to 12a–d were tested. Compounds 10d and 12d showed pronounced antimicrobialactivity. Further, compound 10d exhibited maximum cytotoxicity.