Synthesis of a core trisaccharide building block for the assembly of N-glycan neoconjugates

A short and high yielding synthesis of a core trisaccharide 1 as the key building block in the assembly of a library of N -glycan neoconjugates is presented. The β- d -Manp-(1→4)- d -GlcpNAc linkage was introduced by inversion of the C-2 position of a β-glucoside. The glucosyl donor was efficiently synthesised following a recently published one-pot strategy. 2-Naphthylmethyl and benzylidene-acetal protection in the terminal mannose permitted selective liberation of main branching sites for subsequent glycosylation. A C5 azido linker attached to the anomeric position, which is stable throughout the synthesis, will allow for the posterior immobilisation of deprotected glycans on a microarray surface.