I adopted the synthesis reported in the paper for selective sulfation of compound 2 in the synthesis of 3’O Sulfo β-methyl D-galactoside similar in structure to compound 2 save for a methyl group at the anomeric position in place of an azidoethyl. I altered the procedure a little bit to utilize the solvents and equipment available in our lab. To this end, after formation of the tin acetal intermediate, the reaction with trimethyl sulfur trioxide was carried out in dry THF instead of 1,3-dimethylimidazolidin-2-one that the authors report. Further more, the purification was "modernized" in that after the reaction was quenched with methanol, it was concentrated under vacuum and the residue taken up (adsorbed) in a slurry of silica gel/methanol and dried again. This silica gel residue was then added atop of a silica gel column and eluted with a solvent-gradient of 100 % DCM to 75 %MeOH/DCM. Avoiding the use of DEAE cellulose reported in the published protocol. To get the final product as a sodium salt, the product from the colunm was passed through a sodium-exchange resin readily prepared in lab from Amberlite H form (available in our ) by washing it with brine to neutral pH. The yield of the product was moderate (68 %) and is comparable to a yield of 77 % in the reference published protocol.
Overall, the protocol for selective sulfation of galactose at position 3 is versatile and reproducible even with slight operational alteration the chemistry still works