Study on the synthesis of regio- and stereoisomers of the disaccharide unit of the OSW-1 saponin

A convenient method for the preparation of the OSW-1 disaccharide unit was developed and used for the synthesis of its regio- and stereoisomers. The corresponding allyl and 1-propenyl xylopyranosides and arabinopyranosides were used as starting materials. In all cases studied the groups protecting the anomeric position were easily removed under very mild conditions. The influence of the configuration at the anomeric centre on the regioselectivity of glycosylation was studied and discussed. New disaccharides were synthesized with a view to use them in the preparation of OSW-1 analogues.