Synthesis of Acrylopimaric Acid Triazole Derivatives and Their Antioomycete Activity against Phytophthora capsici

To develop new antioomycete agents against plant pathogens, two series of acrylopimaric acid triazole derivatives from rosin were synthesized. The in vitro antioomycete activity of these derivatives was evaluated and screened against Pseudoperonospora cubensisi, Plasmopara viticola, Phytophthora sojae, Phytophthora infestans, and Phytophthora capsici. Compound 5m showed the highest antioomycete activity against P. capsici, with a half-maximal effective concentration (EC₅₀) value that was lower than that of the positive control metalaxyl (1.391 and 1.815 mg/L, respectively). Compound 5m demonstrated satisfactory protective and curative efficacy against P. capsici in pepper in in vivo antioomycete activity studies. Physiological and biochemical testing showed that the action mechanism of compound 5m on P. capsici involved altering the morphology and ultrastructure of the mycelium, increasing cell membrane permeability, inducing dysfunction of the nucleus and mitochondria, and ultimately causing cell necrosis. In addition, the analysis of three-dimensional quantitative structure–activity relationship (3D-QSAR) revealed the significance of the molecular structure and charge distribution in the interaction between compound 5m and its target. Collectively, these findings indicate that compound 5m has the potential as an antioomycete candidate.