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.