Synthesis and Fungicidal Activity of (E)-5-[1-(2-Oxo-1-oxaspiro[4,5]dec/non-3-en-3-yl)ethylidene]-2-aminoimidazolin-4-one Derivatives

The novel fungicidal agents, (E)-5-[1-(2-oxo-1-oxaspiro[4,5]dec/non-3-en-3-yl)ethylidene]-2-aminoimidazolin-4-one derivatives, were designed and synthesized in moderate to excellent yields in four steps using-hydroxyketone and diketene as raw materials and characterized by HR-ESI-MS, H-1 NMR and X-ray diffraction. The preliminary bioassay showed that some of these compounds, such as 5e, 6a, 6e, and 7 h exhibit 87.8%, 91.3%, 89.9% and 87.8% inhibition rates against Sclerotinia scleotiorum, 3b, 3c, 4c and 7 h exhibit 96.4%, 92.5%, 90.3% and 76.9% inhibition rates against Phytophthora capsici at the concentration of 50 mu g/mL, respectively. These compounds exhibited significant fungicidal activities against S. scleotiorum and P. capsici with EC50 values of 2.56-11.60 mu g/mL, and compounds 6e and 7 h exhibited weak inhibition against the spore germination of S. scleotiorum, while the spore germination of P. capsici was strongly inhibited by compound 7 h solution. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observation indicated that compound 7 h had a significant impact on the structure and function of the hyphal cell wall of P. capsici mycelium.