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

Abstract

Abstract2‐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‐dideoxy‐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. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2006)