Synthesis of 4-methyl-N'-(3-alkyl-2r,6c-diarylpiperidin-4-ylidene)-1,2,3-thiadiazole-5-carbohydrazides with antioxidant, antitumor and antimicrobial activities.

The structures of the newly synthesized 4-methyl-N'-(3-alkyl-2r,6c-diarylpiperidin-4-ylidene)-1,2,3-thiadiazole-5-carbohydrazide (5a­5l) were confirmed by spectral and elemental analysis. The difference in the potency of activity against various free radicals, human cancer cells and microbial strains has been evaluated by SAR. Compounds with electron-donating methoxy (5i and 5c) and methyl (5h and 5b) substitutions at the para position of the phenyl showed excellent free radical scavenging effects. In the tested compounds, electron withdrawing fluoro (5k and 5e), chloro (5j and 5d), and bromo (5l and 5f) substitution at the para position of the phenyl ring attached to C-2 and C-6 carbons of the piperidine moiety outperformed cytotoxic and antimicrobial activities. Our findings suggest that the antioxidant, anti-tumor and anti-microbial activities of compounds 5a­5l create promising leads for the development of potent anti-tumor and anti-microbial agents.