MICROBIAL TRANSFORMATION OF VALIDAMYCINS

α- or β-Glucosidic linkage of validamycin was selectively cleaved by microbial hydrolysis, and especially the conversion of validamycin C into validamycin A by the selective hydrolysis of α-glucosidic linkage has important significance because validamycin C is considerably less active than validamycin A. Semisyntheses of validamycins including a new validamycin, β-D-galactosyl-validoxylamine A were carried out by microbial transglycosidation using validoxylamine A as a glycosyl acceptor. D-[U-14C]glucose and [14C]validoxylamine A were highly incorporated into validamycin A by validamycin-producing Streptomyces hygroscopicus var.limoneus.