2,3,4,6-tetra-O-benzyl-D-galactopyranosylacetate (79.8 g) was dissolved in a mixture of toluene (160 ml) and isopropyl ether (520 ml), and the solution was cooled to −10 to 0° C. To this solution, an isopropyl ether solution (2.8 mmol/ml, about 100 ml) containing 2.0 equivalent volumes of HBr was added. After stirring for about 90 minutes at −10 to 0° C., an aqueous 5% sodium hydrogencarbonate solution was poured into the reaction solution, and excessive HBr was neutralized by stirring. The whole volume was transferred into a separation funnel for separation, then the water layer was discarded and washing was carried 2 times with an aqueous 10% sodium chloride solution. After concentration under vacuum, 2,3,4,6-tetra-O-benzyl-α-D-galactopyranosyl bromide (GalBr) was obtained as a syrup.
