Microbial transformation of validamycins

Alpha- or beta-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 alpha-glucoside linkage has important significance because validamycin C is considerably less active than validamycin A. Semisyntheses of validamycins including a new validamycin, beta-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.