First chemical synthesis of triglucosylated tetradecasaccharide (Glc3Man9GlcNAc2), a common precursor of asparagine-linked oligosaccharides

Triglucosylated high-mannose-type tetradecasaccharide (Glc₃Man₉GlcNAc₂), the oligosaccharide part of the donor substrate of oligosaccharyl transferase (OST) complex, and diglucosylated tridecasaccharide (Glc₂Man₉GlcNAc₂) were synthesized. These oligosaccharides were assembled in a convergent and stereoselective manner. Undecasaccharide 5 was employed as the common intermediate, and coupling with trisaccharide (4) and disaccharide (3) donor afforded fully protected tetradeca-(17) and tridecasaccharide (16), respectively. These oligosaccharides were deprotected to give Glc₃Man₉GlcNAc₂ and Glc₂Man₉GlcNAc₂, respectively.