In our screening program for antitumor antibiotics, we isolated a novel antibiotic FR901228(1) from the culture broth of bacteria No.968. The molecular formula of 1 was established as C_<24>H_<36>N_4O_6S_2 by elemental analysis, EMAX, and FA BMS. The structure of FR901228(1) was established by using variety of NMR technique, and finaly by X ray crystal analysis to be 1. The structure of 1 is a novel cyclic depsipeptide which contains a S-S bond in the molecule. FR901228(1) prolonged the survival periods of mice bearing P388 leukemia (3.2mg/kg, T/C=200%).
