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A new antitumor antibiotic, 13-deoxycarminomycin, has been isolated from the anthracycline complex produced by Streptomyces peucetius var. carminatus (ATCC 31502), a biochemical mutant of Streptomyces peucetius var. caesius, the doxorubicin-producing microorganism. The new anthracycline, showing antibacterial and cytotoxic activity in vitro, was found active against P-388 murine leukemia.

The new anthracyclines 4-O-demethyl-11-deoxydoxorubicin, 4-O-demethyl-11-deoxydaunorubicin along with its 13-dihydro and 13-deoxo analogues are the main components of the anthracycline complex produced by cultures of Streptomyces peucetius var. aureus. They were isolated by solvent partition, separated by column chromatography and characterized by chemical and physical methods. Among these new anthracyclines, displaying antibacterial and cytotoxic activity "in vitro", 4-O-demethyl-11-deoxydoxorubicin and the corresponding daunorubicin analogue were also active against experimental tumors.

During the course of successive mutagenic treatments of Streptomyces peucetius var. caesius, producer of anthracyclines, a novel mutant was isolated from a plate of the surviving population. This mutant showed remarkable morphological, cultural and biochemical differences when compared to the original strain. The new culture produced four new glycosides of a novel class within the group of the daunorubicin related anthracyclines, two of which were also present in the original strain. To our surprise the taxonomical study carried out on this mutant allowed its assignment to the genus Micromonospora ORSKOVA (1923). The possibilities of whether this new strain has originated from a contamination or from a mutation are discussed. The type strain is Micromonospora sp. strain B211 F.I. (identical to ATCC 31366; DSM 1190; FRI 4363).

A mutant strain of Streptomyces peucetius produced an anthracycline antibiotic whose structure has been established to be 4-O-demethyl-13-dihydrodaunorubicin (4), by application of spectroscopic methods and chemical degradation. A new synthesis of 4-O-demethyl-daunorubicin (carminomycin I, 2) starting from daunomycinone, together with the comparison of the antitumor activity of the anthracycline glycosides 2 and 4 are also reported.