A straightforward synthetic strategy has been developed for the synthesis of the hexasaccharide
repeating unit of the cell wall O-antigen of Escherichia coli O140 strain in good yield. Several stereoselective 1,2-cis and 1,2-trans glycosylations have been carried out exploiting the presence of the functional group
in the glycosyl donor and selection of reaction solvents. A late-stage oxidation of
the primary hydroxyl group to the carboxylic functionality has been carried out by
the TEMPO-mediated oxidation in a phase transfer condition. The synthesis of the hexasaccharide
was carried out by [2+2+1+1] glycosylations.
Keywords
Carbohydrates - Glycosylation - Glycosides - Oligosaccharides - Synthesis
