A concise route to the core pentasaccharide of N-linked glycoproteins

A concise preparation of the common pentasaccharide core of the N-linked glycoproteins is described. The reducing end glycal is functionalized at the level of chitobiose, which is then β-mannosylated using Crichʹs direct coupling protocol. Deprotection of the branching mannose residue, and di-α-mannosylation complete the synthesis.