Kazusamycin B, a novel antitumor antibiotic

A novel antibiotic, kazusamycin B (C32H46O7, MW 542), was isolated from the fermentation broth of Streptomyces sp. No. 81-484 and the structure was established mainly on the basis of its physico-chemical properties. Unambiguous 13C NMR spectral analysis of kazusamycin B has been also accomplished. Kazusamycin B possesses potent cytocidal activities against L1210 (IC50 0.0018 micrograms/ml) and P388 (IC100 0.0016 micrograms/ml) leukemia cells in vitro.