Natural Product-Based Pesticide Discovery: Design, Synthesis and Bioactivity Studies of N-Amino-Maleimide Derivatives

Natural products are an important source of pesticide discovery. A series of N-amino-maleimide derivatives containing hydrazone group were designed and synthesized based on the structure of linderone and methyllinderone which were isolated from Lindera erythrocarpa Makino. According to the bioassay results, compounds 2 and 3 showed 60% inhibition against mosquito (Culex pipiens pallens) at 0.25 µg·mL(−1). Furthermore, the results of antifungal tests indicated that most compounds exhibited much better antifungal activities against fourteen phytopathogenic fungi than linderone and methyllinderone and some compounds exhibited better antifungal activities than commercial fungicides (carbendazim and chlorothalonil) at 50 µg·mL(−1). In particular, compound 12 exhibited broad-spectrum fungicidal activity (>50% inhibitory activities against 11 phytopathogenic fungi) and compounds 12 and 14 displayed 60.6% and 47.9% inhibitory activity against Rhizoctonia cerealis at 12.5 µg·mL(−1) respectively. Furthermore, compound 17 was synthesized, which lacks N-substituent at maleimide and its poor antifungal activity against Sclerotinia sclerotiorum and Rhizoctonia cerealis at 50 µg·mL(−1) showed that the backbone structure of N-amino-maleimide derivatives containing hydrazone group was important to the antifungal activity.