Design, Synthesis, and Fungicidal Activity of Novel α-Methylene-γ-Butyrolactone Derivatives Bearing Benzofuran-2-yl Moiety.

A series of 30 novel α-methylene-γ-butyrolactone (MBL) derivatives were designed and synthesized. Bioassays revealed that several compounds exhibited potent fungicidal activities against Valsa mali, Rhizoctonia solani, and Phytophthora capsici. A25 showed the highest activity against V. mali (EC50 = 0.70 mg/L). Against R. solani, A5 (EC50 = 0.94 mg/L) and A21 (EC50 = 0.69 mg/L) were highly active. Against P. capsici, A14 (EC50 = 0.69 mg/L), A21 (EC50 = 0.59 mg/L), and A24 (EC50 = 0.71 mg/L) displayed potent antioomycete activity. At 200 mg/L, A21 provided protective (88.9%) and curative (67.0%) effects in potted rice against R. solani as well as protective (91.0%) and curative (85.4%) effects on pepper plants against P. capsici. Mechanistic studies indicated that A21 blocks ATP synthesis and impairs energy metabolism. Toxicity assessment showed that A21 was nontoxic to earthworms and silkworms at the tested concentrations. This work provides insights for developing MBL derivatives as potential fungicides.