A Highly Efficient and Stereocontrolled Synthesis of 2-Deoxy-1,5-thioanhydro-L-hexitols from D-Glycals in a Tandem Nucleophilic Displacement Reaction

2-Deoxy-1,5-thioanhydro-L-hexitols have been synthesized in a concise sequence that includes: i) ring opening of glycals with aqueous mercury(II) acetate/sodium borohydride; ii) mesylation of the free hydroxy groups of the multifunctionalized open intermediates; and iii) S-heterocyclization by treatment with sodium sulfide. The thiosugar derivatives are obtained with a 60–80% yield. Thus, D-glucal and D-galactal can be converted into the corresponding 2-deoxy-1,5-thioanhydro-L-hexitols, while L-rhamnal gives 3,4-di-O-benzyl-2,6-dide-oxy-1,5-thioanhydro-D-xylo-hexitol. This straightforward chemistry is shown to be useful for the synthesis of glycosyl derivatives of 2-deoxy-1,5-thioanhydro-L-hexitol, starting from glycosyl glycals such as D-lactal, D-cellobial, D-maltal, D-melibial and D-gentiobial, thus avoiding the usually lengthy glycosylation procedures.