Design, synthesis and antifungal activity of novel 1,4-benzoxazin-3-one derivatives containing an acylhydrazone moiety

A series of 1,4-benzoxazin-3-one derivatives containing an acylhydrazone moiety were designed, synthesized and evaluated for their in vitro antifungal activities against Gibberella zeae , Pellicularia sasakii , Phytophthora infestans , Capsicum wilt , and Phytophthora capsica . The structures of target compounds were characterized by 1 H NMR, 13 H NMR, 19 F NMR and HRMS. The preliminary antifungal evaluation of all target compounds showed that some target compounds possessed moderate to good activities against G. zeae , P. sasakii , P. infestans and C. wilt . Among them, compounds 5L and 5o exhibited noticeable inhibition effects against G. zeae with the EC 50 values (effective concentration for 50% activity) of 20.06 and 23.17 μ g/ml, respectively, which were even nearly double effective than that of hymexazol (40.51 μ g/ml). Meanwhile, compound 5q displayed a notable inhibitory effect toward P. sasakii , with the EC 50 value of 26.66 μg/ml, which was better than that of hymexazol (32.77 μ g/ml). In addition, compound 5r yielded the EC 50 value of 15.37 μ g/ml against P. infestans , which was less than those of hymexazol (18.35 μ g/ml) and carbendazim (34.41 μ g/ml). Eventually, compound 5p showed higher inhibitory effect against C. wilt , with EC 50 value of 26.76 μ g/ml, which was better than that of hymexazol (>50 μ g/ml).