Synthesis of potassium (2R)-2-O-alpha-D-glucopyranosyl-(1 -> 6)-alpha-D-glucopyranosyl-2,3-dihydroxypropanoate a natural compatible solute

Ethyl 6-O-acetyl-2,3,4-tribenzyl-1-thio-D-glucopyranoside, as a mixture of anomers, was employed for the stereoselective synthesis of the potassium salt of (2R)-2-O-alpha-D-glucopyranosyl-(1 -> 6)-alpha-D-glucopyranosyl-2,3-dihydroxypropanoic acid (alpha-D-glucosyl-(1 -> 6)-alpha-D-glucosyl-(1 -> 2)-D-glyceric acid, GGG), a recently isolated compatible solute. The alpha-anomer was by far the major product of both glycosylation reactions using NIS/TfOH as activator.