Isolation, structure elucidation and activity of anthracycline acetates from a terrestrial Streptomyces sp.

The red coloured ethyl acetate extract of the Streptomyces sp. isolate GW37/3236 delivered the two new antibiotics 13-O-acetyl-bisanhydro-13-dihydrodaunomycinone (3c) and 4,13-O-diacetyl-bisanhydro-4-O-demethyl-13-dihydrodaunomycinone (3d) and additionally several known compounds. The quinones 3c and 3d are the first naturally occurring quinone acetates. Their structures were derived by comparison of the NMR data with those of bisanhydro-13-dihydrodaunomycinone (3b) and by interpretation of the 2D NMR data accompanied by the molecular weight and formula. 2-Acetamido-3-hydroxybenzamide (5) was also isolated from the extract and was identified by comparison of the NMR data with those of 2-acetamidobenzamide and by 2D NMR correlations. 6,9,11 Trihydroxy-4-methoxy-5,12-naphthacenedione (4) is isolated for the first time as a natural product.