Design and Synthesis of Novel Phthalide Derivatives containing 1,3,4‐Oxadiazole/1,2,4‐Triazole Units as Potential Antifungal Agents

Abstract

Four series of novel 1,3,4‐oxadiazole/1,2,4‐triazole hybrids of phthalide derivatives were designed and synthesized to search for novel potential antifungal agents. Preliminary antifungal activity assay results showed that compounds 4a, 4b, 4m, 5b, 5f, 5h, and 7h exhibited moderate to excellent inhibitory activity against some phytopathogenic fungi. Among them, compound 5b displayed the most outstanding antifungal effects against V. mali and S. sclerotiorum, with the EC50 mean of 3.96 μg/mL and 5.60 μg/mL, respectively, which was superior to those of commercial fungicides hymexazol and chlorothalonil. Furthermore, compound 5b could completely suppress the spore germination of V. mali at a concentration of 10 μg/mL. Finally, molecular docking revealed that the potential target for the antifungal activity of compound 5b was succinate dehydrogenase (SDH). This research provides novel candidate compounds for the prevention of phytopathogenic fungi.