(Trimethylsilyl)ethyl 2,3,4,6-tetra-O-acetyl-beta-D-glucopyranoside and (trimethylsilyl)ethyl 2,3,6-tri-O-acetyl-4-O-(2,3,6-tri-O-acetyl-4-O-[2-acetamido-4,6-di-O-ace tyl-2- deoxy-3-O-(2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl)-beta-D- galactopyranosyl]-beta-D-galactopyranosyl)-beta-D-glucopyranoside have been transformed in high yield into the corresponding 1-O-beta-acyl saccharides by treatment with various carboxylic anhydrides in the presence of boron trifluoride-diethyl ether in toluene. The carboxylic anhydrides (4-pentenoic, 2-cyclopentenylacetic, 2,4-dimethoxy-benzoic, and 2-methoxybenzoic anhydride) were synthesized from the corresponding carboxylic acids by treatment with N,N-bis[2-oxo-3-oxazolidinyl]phosphorodiamidic chloride.