Stereoselective synthesis of thioxylooligosaccharides from S-glycosyl isothiourea precursors

A stereoselective synthesis of thioxylo-di-, -tri-, -tetra- and -penta-saccharides from S-glycosyl isothiourea precursors is described. The synthesis was performed starting from 2,3,4-tri-O-acetyl-β-d-xylopyranosyl isothiouronium bromide using a triethylamine promoted reaction with 1,2,3-tri-O-benzoyl-4-O-trifluoromethanesulphonyl-β-l-arabinopyranose. The resulting 4-thioxylobiose was then converted into the corresponding isothiouronium bromide and used for the synthesis of 4,4′-dithioxylotriose. Higher homologues of the series and their α-methyl glycosides were also prepared.