Stereocontrolled Synthesis of d- and l-β-Rhamnopyranosides with 4-O-6-S-α-Cyanobenzylidene-Protected 6-Thiorhamnopyranosyl Thioglycosides

Abstract

The synthesis of both enantiomers of a 4-O-6-S-α-cyanobenzylidene-protected 6-thiorhamnopyranosyl thioglycoside is described starting from d-mannnose and l-arabinose derivatives for the d- and l-series, respectively. This donor is effective in the preparation of the corresponding β-glycosides using the 1-benzenesulfinyl piperidine/trifluoromethanesulfonic anhydride protocol. Following desulfurization and concomitant debenzylation with Raney nickel, the so-formed 6-thio-β-mannosides are converted in high yield to the β-rhamnopyranosides.