3,4,6-Tri-O-acetyl-D-glucose-oxazoline, prepared from 2-acetamido-2-deoxy-1,3,4, 6-tetra-O-acetyl-β-D-glucopyranose with trimethylsilyl trifluoromethanesulfonate, was used for O-glycosylating resin-bound protected peptides having a serine residue with free hydroxyl group. 2-acetamido-2-deoxy-D-glucopyranosyl peptides were obtained after trifluoracetic acid (TFA) cleavage and deacetylation.