Synthesis of eight glycosides of hexasaccharide fragments representing the terminus of the O-polysaccharide of Vibrio cholerae O:1, serotype Inaba and Ogawa, bearing aglycons suitable for linking to proteins

The title substances were prepared from intermediate, fully acetylated α-trimethylsilylethyl (SE) glycosides. The latter were assembled in a blockwise manner, using as the glycosyl donor the α-glycosyl chloride of a disaccharide bearing two 4-azido-4-deoxy functions. Next, the azido groups in the assembled hexasaccharides were converted to the corresponding amines, and these were acylated with 4-O-benzyl-3-deoxy-l-glycero-tetronic acid in the presence of a water-soluble carbodiimide. The SE glycosides were then transformed to glycosyl imidates, and these were coupled with methyl 6-hydroxyhexanoate or methyl 2-(2-hydroxyethylthio)propionate. The aglycons in the glycosides thus obtained were then converted to the corresponding carboxylic acids or acyl hydrazides. Such compounds are suitable for linking to proteins to obtain neoglycoproteins.