Studies on Sialic Acids. IX. : Formation of a 1, 7-Lactone Derivative by Direct Acetylation of N-Acetylneuraminic Acid

Abstract

A new lactone compound was isolated as a minor by-product from the reaction mixture of N-acetylneuraminic acid with acetic anhydride in pyridine, in addition to the major product, 2, 4, 7, 8, 9-penta-O-acetyl-N-acetylneuraminic acid. The structure of the new compound was elucidated to be 5-acetamido-2, 4, 8, 9-tetra-O-acetyl-3, 5-dideoxy-β-D-glycero-D-galacto-2-nonulopyranosono-1, 7-lactone by nuclear magnetic resonance, mass spectroscopy and X-ray crystal analysis. It was revealed that the absolute configurations of the asymmetric centers of the new compound were consistent with those for the original N-acetylneuraminic acid with the conversion of the pyranose ring conformation from ²C₅(D) to ⁵C₂(D).