Design, Synthesis and Antifungal Activities of 6‐Substituted 3‐Butylphthalide Derivatives against Phytopathogenic Fungi

In order to discover novel potential antifungal agents, a series of 6‐substituted 3‐butylphthalide derivatives were designed, synthesized and evaluated for their antifungal activities against nine phytopathogenic fungi. Preliminary bioassay tests showed that five 3‐butylphthalide derivatives exhibited more potent antifungal activities than hymexazol at the concentration of 50 μg/mL. Especially, 3‐butyl‐6‐nitro‐2‐benzofuran‐1(3H)‐one and 3‐butyl‐6‐hydroxy‐5‐nitro‐2‐benzofuran‐1(3H)‐one had significant fungicidal activity against some phytopathogenic fungi. The EC50 of 3‐butyl‐6‐nitro‐2‐benzofuran‐1(3H)‐one against FS, FO and FG were 6.6, 9.6 and 16.0 μg/mL, respectively. The EC50 of 3‐butyl‐6‐hydroxy‐5‐nitro‐2‐benzofuran‐1(3H)‐one against BC, PO, VM, SS and AS were 6.3, 5.9, 10.0, 4.5 and 8.4 μg/mL, respectively. The preliminary structure–activity relationships (SARs) of all target compounds were also investigated.