The allyl ether as a protecting group in carbohydrate chemistry. Part VII. The 2-O-allyl group as a non-participant in 1,2-cis-glycoside synthesis

Abstract

2-O-Allyl-3,4,6-tri-O-benzyl-D-galactopyranose was prepared and converted into the corresponding galactosyl chloride. The chloride was condensed with benzyl 2,3,4-tri-O-benzyl-α-D-galactopyranoside to give crystalline benzyl 6-O-(2-O-allyl-3,4,6-tri-O-benzyl-α-D-galactopyranosyl)-2,3,4-tri-O-benzyl-α-D-galactopyranoside. The allyl group was removed from this fully protected disaccharide to give a disaccharide derivative suitable for conversion into a trisaccharide or for oxidation to a ketone and subsequent conversion into a disaccharide containing an α-linked 2-amino-2-deoxy-sugar.