Design, Synthesis, and Bioactivity Evaluation of Novel 1,3,4-Thiadiazole Sulfone-Derived Compounds Incorporating an Amide Moiety as Active Antibacterial Agents

A series of novel 1,3,4-thiadiazole sulfone-derived compounds incorporating an amide moiety was synthesized. The in vitro antibacterial activities against Xanthomonas oryzae pv. oryzae (Xoo), Xanthomonas oryzae pv. oryzicola (Xoc), and Xanthomonas axonopodis pv. citri (Xac) demonstrated that 2-(2-methoxyphenoxy)-N-[5-(methylsulfonyl)-1,3,4-thiadiazol-2-yl]acetamide exhibited remarkable antibacterial activities against all three pathogenic bacteria with EC₅₀ values of 6 μg/mL for Xoo, 11 μg/mL for Xoc, and 16 μg/mL for Xac, which were even surpassed those of bismerthiazol and thiodiazole copper. Furthermore, under greenhouse conditions at a concentration of 200 μg/mL, this compound showed superior efficacy compared to bismerthiazol and thiodiazole copper in reducing rice bacterial leaf blight with a protection activity of 53.43% and curative activity of 47.16%. To the best of our knowledge, this study presents the inaugural report on the synthesis and bioactivity evaluation of novel 1,3,4-thiadiazole sulfone-derived compounds incorporating an amide moiety.