Preparation of core 2 type tetrasaccharide carrying decapeptide by benzyl protection-based solid-phase synthesis strategy

β-d-Gal-(1→4)-β-d-GlcNAc-[β-d-Gal-(1→3)]-α-d-GalNAc-(1→3)-l-Ser/Thr building blocks for solid-phase synthesis of glycopeptide were stereoselectively synthesized in a benzyl-protected form. The key glycosylation reaction to form β-d-GlcNAc linkage was established by the use of protected N-trichloroacetyl-d-lactosaminyl fluoride. Usefulness of the building block was demonstrated by solid-phase synthesis of a segment of human leukosialin. Benzyl protecting group was efficiently removed by ‘low acidity TfOH’ conditions.