As previously reported, an aclacinomycin-negative mutant strain KE303, which was isolated from Streptomyces galilaeus MA 144-M1, is capable of producing new potent antitumor anthracycline antibiotics by the microbial conversion of biologically inactive anthracyclinones. In this communication, we describe the microbial glycosidation of carminomycinone and 13-dihydrocarminomycinone using strain KE303, and the characterization of 13-dihydrocarminomycinone trisaccharide, trisarubicinol (Fig. 1).