Abstract
We studied the acid moieties of the following imidoyl imidazole derivatives; alkyl, alkoxyl, alkoxyalkyl, substituted phenyl and aryl compounds with hetero atoms of sulfur or nitrogen in order to determine their fungicidal activities. Phenyl compounds that have ortho-substituents such as 2-trifluoromethyl were highly fungicidal. Moreover, N-substituted-2-pyridyl compounds, such as N-5-chloro-3-methyl-2-pyridyl, with amine moieties showed higher antifungal activity than N-phenyl compounds. Some of these compounds have excellent preventive, curative and systemic effects on various crop diseases. Certain N-2-pyridyl benzimidoyl imidazoles showed excellent fungicidal activity against powdery mildew and gray mold on cucumber and against blast on rice plants. 1-[N-(5-Chloro-3-methyl-2-pyridyl)-2-trifluoromethylbenzimidoyl] imidazole (48), a representative compound, had the following effects at the concentrations shown; preventive of powdery mildew at 0.54ppm and gray mold at 7.7ppm, and curative of rice blast at 16.8ppm (EC50). In addition, its antifungal spectrum was very broad, and it was especially efficacious against Basidiomycetes and Ascomycetes. At 1ppm in the nutrient medium, it strongly inhibited sporidial multiplication and ergosterol biosynthesis on Ustilago maydis. These results indicate that the mode of action of N-2-pyridyl benzimidoyl imidazoles is the inhibition of ergosterol biosynthesis.
