Syntheses of 8, 9-Epoxy-and5-O-Acyl-8, 9-epoxymilbemycin A₄ and Their Activity against Tetranychus urticae

Abstract

To improve the acaricidal activity of milbemycins, 8, 9-epoxymilbemycin A₄ (3) and 5-O-acyl-8, 9-epoxymilbemycin A₄ (7) were synthesized by using selective epoxidation of the 8, 9-double bond. The acaricidal activity against the two-spotted spider mite (Tetranychus urticae) was slightly improved by 8, 9-epoxidation of milbemycin A₄ (1b). while acylation of 8, 9-epoxymilbemycin A₄ (3) markedly enhanced its activities. Some 5-O-acylated 8, 9-epoxides totally controlled the mites at a concentration of 3ppm.