Marmara University School of Pharmacy Department of Pharmaceutical Chemistry, Istanbul, Turkey DOI : 10.12991/201216402 Novel derivatives of substituted hydrazone (2a-e), 2-pyrazoline-5-one (3a-e, 4ae) and 2-isoxazoline-5-one (5a-e) derivatives possessing 1,3,4-thiadiazole moiety were synthesized and evaluated for their antitubercular activity. The highest inhibitions were observed with the synthesized compounds are 87% for 3-methyl-4-[4-(5-cyclohexylamino- 1,3,4-thiadiazole-2-yl)phenylhydrazono]-2-isoxazoline-5-one (5b) and 86% for ethyl 2-[4-(5-cyclohexylamino-1,3,4-thiadiazole-2-yl)phenylhydrazono]-3-oxobutirate (2b). Compounds 2b and 5b could be a good initial point to develop new lead compound. Keywords : 1,3,4-thiadiazole, 2-pyrazolin-5-one, 2-isoxazoline-5-one, hydrazone and antitubercular activity