A process for preparing epirubicin or acid addition salts thereof from daunorubicin

This invention relates to a novel method for the chemical preparation of epirubicin or acid addition salts thereof, in particular the HCl salt, from daunorubicin. This process avoids the disadvantages of the prior art. First daunorubicin is methanolized to obtain daunomycinone and daunosamine methyl ether in very high yields. Daunomycinone is converted to 14-acetoxy daunomycinone by bromination and acetoxylation, while daunosamine methyl ether is converted into an N-protected 4'-epi daunosamine. The choice of the protecting group of the amino group of the daunosamine methyl ether is important because it has to be removed after coupling the sugar with the aglycone without causing side reactions of the aglycone. Two protecting groups were selected: the trifluoroacetyl group and the allyloxycarbonyl group. After coupling the 14-acetoxy daunomycinone with the N-protected 4'-epi daunosamine, the obtained compound was converted to epirubicin; for the latter conversion two routes were developed, depending on the amino-protecting group.