ABSTRACT
d-Galactosamine is abundant in biologically active oligosaccharides as well as in cell surfaces in bacteria. d-Galactosamine is expensive compared to d-glucosamine, which is its C-4 stereoisomer. The inversion of stereochemistry of a hydroxy group is usually conducted through its corresponding triflate in three steps; (1) triflate preparation, (2) nucleophilic attack by a carboxylate ion in the presence of base; and (3) removal of the (newly formed) acyl group. Nitrate attack reaction directly gives the hydroxy group in a single operation, so that the reaction is compatible with acyl protecting groups. 1 By using this reaction, it is possible to invert the stereochemistry of a hydroxyl group in presence of acyl protected-hydroxy groups. Here, we describe application of the method to preparation of galactosamine derivative 2, 2 which has been now obtained in the crystalline form for the first time and fully characterized.
