Synthesis of oligosaccharide substrates for N-linked glycoprotein processing enzymes

The stereoselective syntheses of one pentasaccharide and one tetrasaccharide containing the Glc-α-(1 → 3)-Man-α moiety as their terminal unit, as well as one tetrasaccharide and one trisaccharide containing the Man-α-(1 → 2)-Man-α terminal unit were accomplished through the utilization of two key glycosyl donors, namely, 4-pentenyl 3-O-acetyl-2,4,6-tri-O-benzyl-α-d-mannopyranoside and ethyl 2-O-acetyl-3,4,6-tri-O-benzyl-1-thio-α-d-mannopyranoside.