Fortimicins A and B, new aminoglycoside antibiotics. III. Structural identification

The structures of fortimicins A and B have been determined by PMR, CMR, mass spectra and CD combined with chemical degradations. Both antibiotics are pseudodisaccha-rides and incorporate a novel aminocyclitol, fortamine. Incontrast to the diaminocyclitol moieties of known aminoglycosides, fortamine is a 1, 4-diamine, contains both N- and O-methyl groups and possesses chiro stereochemistry. Both antibiotics are glycosides of 6-epi-pur-purosamine B, but fort imicin A differs from fortimicin B by being a glycyl amide.