Biosynthesis of anthracyclinones: isolation of a new early cyclization product aklaviketone

Five metabolites were isolated from fermentations of a mutant strain S 383 of Streptomyces galilaeus. Components S 383-O and S 383-A were identified as known derivatives of anthraquinone and naphthacenequinone, respectively, previously isolated from cultures of Other blocked mutants of S. galilaeus strains. Component S 383-X was identical with 7-deoxyaklavinone. Compound S 383-Y (aklaviketone) was found to be a new metabolite. Its chemical structure has been determined by physico-chemical methods including mass spectrometry and NMR spectral studies. The compound (7-dehydro-7-deoxy-7-oxoaklavinone) is most likely the first cyclization product along the metabolic chain possessing the tetracyclic carbon skeleton of anthracyclinones. A proposed pathway is discussed.