Viriplanin A, a new anthracycline antibiotic of the nogalamycin group. II. The structure of a novel hydroxyamino sugar from reduced viriplanin A.

Methyl 2,3,6-trideoxy-3-hydroxyamino-3-C-methyl-alpha-D-ribo-hexopyranoside+ ++ (2) and the corresponding amino sugar (4) were isolated from reduced viriplanin A by acidic methanolysis and esterified to the di-p-bromobenzoates (3 and 5), respectively. The absolute configuration of crystalline 3 was determined by X-ray analysis to be alpha-D. This result could be confirmed by oxidation of 2 to methyl alpha-D-decilonitroside (6) and from the CD spectra of 3 and 5. Thus, the nitrogen-containing sugars of viriplanin A and probably those of decilorubicin and arugomycin belong to the D-series.