Structural analysis of stereoselective galactose pyruvylation toward the synthesis of bacterial capsular polysaccharides.

Pyruvate ketal is a biologically essential moiety due to its key role as an intermediate in metabolic pathways, serving as a key precursor for the synthesis of various essential biomolecules in organisms. However, the / stereochemistry of pyruvate ketal is difficult to control through chemical methods. In this study, the acid-labile pyruvate ketal linked to the 4- and 6-positions of galactose was cautiously constructed, and the X-ray analysis of the -configured product was successfully obtained. Subsequently, the compound was used for the synthesis of zwitterionic polysaccharide A1 (PS A1) precursor, and a clear structural elucidation was applied by using nuclear magnetic resonance and X-ray.