Design, Synthesis and Fungicidal Activity of Novel Thiosemicarbazide Compounds

In order to find novel candidates for fungicides with high activity, the natural product cinnamaldehyde derivative N-alpha-amyl-(4-bromophenyl)-propenyl-N'-2',3'-O-isopropyl-5'-O-uridine formyl hydrazone (A16) was selected as the lead compound, a series of new thiosemicarbazone compounds were designed and synthesized by replacing the ester uridine with thiourea group. The structures of the target compounds were confirmed by (HNMR)-H-1, C-13 NMR, IR, elemental analysis or HRMS. The bioassay results showed that some compounds had obvious in vitro fungicidal activity at the concentration of 100 mu g/mL. Among them, the inhibition rates of compound 2a against B. cinerea, C. orbiculare and A. solani were more than 80%. Compound 2p showed good activity against R. solani, F. graminearum, C. orbiculare and A. solani. Furthermore, compound 2a had better inhibitory activity against B. cinerea (EC50=1.77 mu g/mL) than polyoxin B, and compound 2p had stronger inhibitory activity against R. solani (EC50=2.07 mu g/mL) than Polyoxin B (EC50=15.33 mu g/mL). Meanwhile, compound 2p showed better chitin synthase inhibition activity (69%) than Nikkomycin Z (52%) at the concentration of 40 mu g/mL.