Synthesis and Fungicidal Activity of Novel Butenolide Compounds Containing Oxime Ether Moiety

A series of novel butenolide compounds containing oxime ether moiety were designed and synthesized through diversity modification of the benzene ring at 4-phenyl and the 3-oxime ether group based on the fungicidal 3-acetyl-4-phenyl-1-oxaspiro[4,5]dec-3-en-2-one oxime ether as the lead structure. Their structures were characterized by H-1 NMR, C-13 NMR, HR-ESI-MS data and X-ray diffraction. The preliminary in vitro bioassay results indicated that some compounds exhibited good fungicidal activities against Thanatephorus cucumeris, Sclerotinia sclerotiorum and Botrytis cinerea. For example, (E)-3-(1-((2-chlorobenzyloxy)imino)ethyl)-4-(pyridin-2-yl)-1-oxaspiro[4.5]dec-3-en-2-one (A(7)) had EC50 values of 6.02, 8.25 and 15.70 mg/L against T. cucumeris, S. sclerotiorum and B. cinerea. For Example (E)-3-(1-((2chlorobenzyloxy)imino)ethyl)-4-(pyridin-4-yl)-1-oxaspiro[4.5]dec-3-en-2-one (A8) had EC50 values of 1.31 and 10.62 mg/L against T. cucumeris and S. sclerotiorum, respectively. A(7) had an excellent inhibition against spore germination of B. cinerea, and the inhibition rate was 95% at the concentration of 100 mg/L. The in vivo bioassay results showed that compounds A(7) had a notable protective activity against tomato gray mould and rice sheath blight disease.