Synthesis of 5-Deoxy-5-oxomilbemycin A₄ 5-Hydrazone Derivatives and Their Activity against Tetranychus urticae

Abstract

5-Deoxy-5-oxomilbemycin A₄ 5-hydrazone derivatives were synthesized by a condensation reaction of 5-deoxy-5-oxomilbemycin A₄ (2) with hydrazines. Acetic acid played an important role to give each hydrazone in a good yield by regulating the reactivity of ketone 2 and the hydrazines. The acaricidal activity of each synthesized compound was studied on the primary leaves of plants of the Vigna sinensis Savi species infected with organic phosphate-sensitive mites (Tetranychus urticae). Some of the synthesized derivatives exhibited higher miticidal activity than that of milbemycin A₄. Among them, 5-deoxy-5-oxomilbemycin A₄ 5-N-(N', N'-dimethylcarbamoyl)hydiazone (18) totally controlled the mites at a concentration of 3 ppm.