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Synthesis of Antifungal 5-Anilino-1,2,4-oxadiazole and 5-Anilino-1,2,4-thiadiazoles, and Their Inhibitory Effects on Fungal Sterol Biosynthesis
Izumi KUMITA and Atsushi NIWA
J. Pestic. Sci.
26, 60-66 (2001)
In the screening process we found that two 1,2,4-oxadiazole compounds showed antifungal activity against Trychophyton mentagrophytes. Microscopic observation revealed that these compounds inhibited mycelial growth with morphological changes without inhibition of germination. When treated with the oxadiazoles, ergosterol of Candida albicans decreased strikingly and much squalene was accumulated. These results firmly suggested that the compounds were new squalene epoxidase inhibitors. We synthesized the related oxadiazoles and thiadioazoles having various substituents to investigate the structure-activity relationships. Among the synthesized compounds, 3-(2,6-dichlorophenyl)-5-(4-chloroanilino)-1,2,4-thiadiazole (51) showed the highest fungicidal activity against Botrytis cinerea, and accumulated squalene remarkably. This compound is of interest as a new lead of squalene epoxidase inhibitors.
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