Synthesis of N-linked pentasaccharides with isomeric glycosidic linkage

As part of a program to explore the structural requirement of N-glycans in the carbohydrate-mediated biological interactions, N-linked pentasaccharide core structure was stereochemically modified in terms of glycosidic linkag e. Three isomers, alpha -D-Man-(1 -->3)-[alpha -D-Man-(1 -->6)]-alpha -D-Ma n-(1 -->4)-beta -D-GlcNAc-(1 -->4)-beta -D-GlcNAc-L-Asn, alpha -D-Man-(1 -- >3)-[alpha -D-Man-(1 -->6)]-beta -D-Man-(1 -->4)-alpha -D-GlcNAc-(1 -->4)-b eta -D-GlcNAc-L-Asn, and alpha -D-Man-(1 -->3)-[alpha -D-man-(1 -->6)]-alph a -D-Man-(1 -->4)-alpha -D-GlcNAc-(1 -->4)-beta -D-GlcNAc-L-Asn, were synth esized. Synthesis of the pentasaccharide with natural linkage is also descr ibed.