Synthesis of a functionalized hexasaccharide precursor of a glycoconjugate vaccine against cholera

A hexasaccharide fragment of the O-polysaccharide of Vibrio cholerae O:1, serotype Inaba was constructed from mono and disaccharides carrying azido groups. After the azido→amino group conversion, the requisite N-acylation was achieved using as the reagent 4-O-benzyl- -glycero-tetronic acid, prepared from the corresponding derivative of -homoserine by deamination.