We have been studying the preparation of new anthracyclines by fermentation, chemical synthesis or microbial glycosidation. Recently we isolated a potent new antitumor anthracycline betaclamycin A (newly named CG7) obtained by feeding β-rhodomycinone to the growing culture of an aclacinomycin-negative mutant strain KE303 derived from Streptomyces galilaeus MA144-Ml. This compound showed excellent antitumor activity against L1210 leukemia with a T/C % of over 200. In an attempt to produce derivatives with improved therapeutic properties we chemically hydrolyzed and reduced betaclamycin A. We now report four derivatives thus obtained: betaclamycins M, N, S and T.