The rare N-unsubstituted glucosamine(GlcNH3+) residues in heparan sulfate(HS) have important biological and pathophysiological roles.Therefore,flie ability to chemically generate a series of oligosaccharides,which have a similar structure to the naturally-occurring,GlcNH3+-containing oligosaccharides from HS,would greatly contribute to investigating their natural role in HS.