Design, synthesis, and antifungal activity studies of pyrimidinamine‐substituted 1,3,4‐oxadiazole derivatives for controlling kiwifruit soft rot

BACKGROUND Plant diseases caused by fungal pathogens not only lead to the deterioration of crop quality and a sharp decrease in yield, but also cause huge economic losses to global agricultural production, while posing a potential threat to human well‐being. Currently, chemical agents remain the mainstream method for controlling such diseases. Therefore, the development of novel and efficient antifungal agents holds significant theoretical value and application prospects. RESULTS In this study, 26 novel 5‐(((6‐(difluoromethyl)pyrimidin‐4‐yl)amino)methyl)‐1,3,4‐oxadiazole‐2‐thioether derivatives were synthesized, and the in vitro antifungal efficacy of these novel pyrimidine derivatives were evaluated. The results showed that compound 6g demonstrated the highest inhibition against Botryosphaeria dothidea , with a half‐maximal effective concentration (EC 50 ) of 7.38 μg mL −1 , surpassing the reference fungicide prothioconazole (EC 50 = 12.85 μg mL −1 ). In vivo antifungal testing demonstrated that compound 6g exhibited significant efficacy against kiwifruit soft rot at a concentration of 200 μg mL −1 , with protective and curative activities reaching 82.21% and 85.97%, respectively. Molecular docking simulations further confirmed that compound 6g forms hydrogen bonds with the CYP51 protein through residues Tyr121 and Arg444. In addition, scanning electron microscopy observations, along with measurements of dry weight, membrane permeability, cellular components, and reactive oxygen species levels, were conducted to further elucidate its mechanism of action. CONCLUSION This study reveals the potential of difluoromethyl pyrimidinamine‐substituted 1,3,4‐oxadiazole thioether derivatives as lead compounds for controlling kiwifruit soft rot, and also their low toxicity to earthworms as a soil indicator. The findings provide important insights that can aid the development of novel, efficient fungicides and contribute to the improvement of crop protection strategies in agriculture.