Nocardicyclins A and B: new anthracycline antibiotics produced by Nocardia pseudobrasiliensis.

Nocardicyclins A (1) and B (2), new anthracycline antibiotics have been isolated from the mycelial cake of Nocardia pseudobrasiliensis IFM 0624 (JCM 9894). The molecular formulae of 1 and 2 have been determined as C30H35NO11 and C32H37NO12, respectively, and the structures were characterized by 1- and 8-methoxyl groups, a 10-carbonyl group and a novel carbon-methylated aminosugar constituent. Nocardicyclin A (1) exerts cytotoxic activity against L1210 and P388 leukemia. Nocardicyclins A (1) and B (2) are active against Gram-positive bacteria including Mycobacterium spp. and Nocardia spp., but inactive against Gram-negative bacteria.