Stereoselective synthesis of β-d-GlcNAc-(1→4)-D-Glc disaccharide starting from lactose.

•The synthesis of beta-d-GlcNAc-(1→4)-d-Glc disaccharide starting from lactose is described.•The approach involves the transformation of the beta-d-galactopyranosyl unit into a N-acetyl-beta-d-glucosaminyl one.•The conversion of the β-d-talopyranosyl disaccharide into the β-d-mannopyranosyl one is achieved by stereoselective hydroboration–oxidation.•The β-d-mannopyranosyl unit is transformed into the beta-d-N-acetyl-glucosaminyl one by amination with inversion of configuration by SN2 displacement.