Design and synthesis of novel n-butyphthalide derivatives as promising botanical fungicides

In order to obtain novel botanical fungicides, three series of novel 6-substituted n-butyphthalide derivatives have been designed and synthesized via nucleophilic addition, reduction, nitrification, amination, sulfonation, Sandmeyer and Suzuki reaction. The mycelium growth rate method was used to evaluate the inhibition activity against eight phytopathogenic fungi in vitro. Preliminary bioassay tests showed that compounds 6f, 6n, 6p, 6r and 7a exhibited better activity for some fungi at 50 μg/mL than the positive drug hymexazol and lead compound n-butyphthalide (NBP). The preliminary structure-activity relationships indicated that the antifungal activity is significantly affected by the substituents on the benzene ring.