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. 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, which has been now obtained in the crystalline form for the first time and fully characterized.
