Stereoselective synthesis of thioxylooligosaccharides from S-glycosyl isothiourea precursors

A stereoselective synthesis of thioxylo-di-, -tri-, -tetra- and -penta-sacc harides from S-glycosyl isothiourea precursors is described. The synthesis was performed starting from 2,3,4-tri-O-acetyl-beta -D-xylopyranosyl isothi ouronium bromide using a triethylamine promoted reaction with 1,2,3-tri-O-b enzoyl-4-O-lrifluoromethanesuIphonyl-beta -L-arabinopyranose. The resulting 4-thioxylobisse was then converted into the corresponding isothiouroniurn bromide and used for the synthesis of 4,4 ' -dithioxylotriose. Higher homol ogues of the series and their alpha -methyl glycosides were also prepared. (C) 2001 Elsevier Science Ltd. All rights reserved.