Design and Synthesis of Novel 1,3,4-Oxadiazole Thioether-Fused 1,4-Benzothiazine-3-one Derivatives as Potential Antibacterial Agents

A novel class of 4-{[5-(benzylthio)-1,3,4-oxadiazol-2-yl]methyl}-2H-benzo[b][1,4]thiazin-3(4H)-one derivatives were designed, synthesized and screened for their in vitro antibacterial activities against Pseudomonas syringae pv. Actinidiae (Psa) and Xanthomonas axonopodis pv. Citri (Xac). Preliminary bioactivity test results indicated that some compounds showed moderate to good inhibitory effects against the tested bacteria at the concentrations of 100 and 50 μg/mL. Among them, 4-({5-[(4-fluorobenzyl)thio]-1,3,4-oxadiazol-2-yl}methyl)-2H-benzo[b][1,4]thiazin-3(4H)-one and 4-[(5-{[4-(trifluoromethyl)benzyl]thio}-1,3,4-oxadiazol-2-yl)methyl]-2H-benzo[b][1,4]thiazin-3(4H)-one exhibited the best inhibitory effects against Psa and Xac than other compounds, which showed a broad range of antibacterial activities. Further bioactive applications of these molecules are in progress in our laboratories.