The products of Fischer's methyl glycosylation of 3-deoxy-D-glycero-D-galacto-2-nonulosonic acid (KDN) revealed existence of an the anomeric equilibrium between α, β-furanose and α, β-pyranose of KDN. In spite of the anomeric equilibrium, peracetylation of KDN and its derivatives by acetic anhydride with pyridine gave only α- and β-pyranose derivatives. The obtained methyl glycosides and hexa-O-acetyl derivatives were characterized by X-ray, nuclear magnetic resonance and cicular dichroism spectral analyses.