Design, Synthesis, and Antifungal Evaluation of Novel α-Methylene-γ-Butyrolactone Derivatives Bearing a Diaryl Ether Moiety for Phytopathogen Control

A series of α-methylene-γ-butyrolactone derivatives (A1-A23, B1-B23, and C1-C2) bearing a diaryl ether moiety were designed and synthesized. Bioassays revealed that several target compounds demonstrated potent fungicidal and bactericidal activities, particularly against Phytophthora capsici and Pseudomonas syringae pv actinidiae (Psa). Notably, compound C2 (EC₅₀ = 0.74 mg/L) exhibited the highest antioomycete activity against P. capsici and admirable in vivo activities (protective activity of 100.0% and curative activity of 84.2%) against P. capsici. Meanwhile, compound A10 (EC₅₀ = 11.38 mg/L) showed the strongest antibacterial activity against Psa and significant protective activity (74.4%) against kiwifruit bacterial canker. Preliminary mechanistic studies of P. capsici suggested that compound C2 exerts its bioactivity primarily by binding to respiratory chain complex III, thereby inhibiting mitochondrial ATP synthesis and impairing fungal energy metabolism. This work provides valuable insights for the development of MBL derivatives incorporating a diaryl ether moiety as promising novel agricultural fungicidal and bactericidal agents.