BBM-928, A NEW ANTITUMOR ANTIBIOTIC COMPLEX

III. STRUCTURE DETERMINATION OF BBM-928 A, B AND C

Abstract

Structures of antitumor antibiotics BBM-928 A, B and C have been determined. They are cyclic decadepsipeptides containing 3-hydroxy-6-methoxyquinaldic acid as a chromophore. Two amino acids, not found in nature, L-β-hydroxy-N-methylvaline and trans-(3S, 4S)-4-hydroxy-2, 3, 4, 5-tetrahydropyridazine-3-carboxylic acid, were identified as structural constituents of the antibiotic. In gross structure, BBM-928 resembles the echinomycin group of antibiotics which are cyclic octadepsipeptides having a quinoxaline chromophore, but BBM-928 differs from the latter group by virtue of the lack of a sulfur-containing cross linkage.