Synthesis of derivatives of N-glycolylneuraminic acid ethylthioglycoside and their use as glycosyl donors

The synthesis of a completely protected derivative of N-glycolylneuraminic acid thioglycoside from the corresponding derivative of N-acetylneuraminic acid via deprotection to the free thioglycoside followed by N-glycolylation, esterification, and acetylation was described. The reverse order of the stages of esterification and glycolylation resulted in the N-glycolylneuraminic acid derivative with two glycolylated hydroxyl groups. Both compounds obtained can be used as glycosyl, donors in the reactions of sialylation promoted with thiophilic agents.