SYNTHESIS OF NOVEL 25-SUBSTITUTED MILBEMYCIN A(4) DERIVATIVES AND THEIR ACARICIDAL ACTIVITY AGAINST TETRANYCHUS-URTICAE

Novel 25-substituted milbemycin A(4) derivatives were synthesized from 25a-hydroxymilbemycin A(4) and 25b-hydroxymilbemycin A(4), which had been obtained by the microbial oxidation of milbemycin A(4). The acari cidal activity of each synthesized derivative was tested against Tetra nyclus urticae, and all of the synthesized derivatives showed higher a ctivity than parent milbemycin A(2). Some of the derivatives had highe r acaricidal activity than milbemycin D, which had higher acaricidal a ctivity than milbemycin A(4). Among them, 25b-methylmilbemycin A(4) wa s the most active derivative, with 100% mortality of the mite at a con centration of 1 ppm, and 63% mortality at 0.1 ppm.