Synthesis of an octamannosyled glycan chain, the key oligosaccharide structure in ER-associated degradation.

The high-mannose type decasaccharide (Man(8)GlcNAc(2)), the proposed ligand of ER residing mannosidase-like proteins (MLP), and its monoglycosylated homologue (alpha-Glc(1)Man(8)GlcNAc(2)) were synthesized. The oligosaccharide assembly was performed in a convergent and stereoselective manner, using three oligosaccharide components, a core trisaccharide having a beta-mannoside bond, a liner mannotriose, and a branched mannotetraose.