Stereochemistry of the antibiotic carminomycin.

The properties and the structure of a new anthracycline antibiotic carminomycin, were described recently.1) In this paper we wish to discuss the stereochemistry of carminomycin. We have studied the NMR and CD spectra of carminomycin, its aglycone (carminomycinone) and 7-deoxycarminomycinone. For comparative purposes the corresponding derivatives of daunomycin (rubomycin) were prepared and investigated. It has been shown2) that the differences between the structures of carminomycin and daunomycin lie in the aglycones of these compounds. In contrast to daunomycinone, C-4 of carminomycinone is substituted with a hydroxyl instead of methoxyl. The NMR spectra of both aglycones are very similar to each other (Table 1). There are, however, differences in the chemical shifts of the aromatic protons (not listed in the table). A pseudoequatorial orientation of the C-7 proton is apparent for both of