An improved method for the synthesis of protected glycosyl fluorides from thioglycosides using N,N-diethylaminosulfur trifluoride (DAST)

The direct conversion of thioglycosides to glycosyl fluorides frequently used in oligosaccharide synthesis was examined using N,N-diethylaminosulfur trifluoride (DAST). Although the reaction proceeded without N-bromosuccinimide (NBS), in some cases it was found that the electrophilicity of the Vilsmeier-type electrophilic sulfinium cation species was not sufficient for the activation of certain less-reactive thioglycosides. Here, we report the results of fluorination reactions of a series of monosaccharides using DAST in the absence of NBS, and also discuss the acceleration of the reaction in the presence of dimethyl(methylthio)sulfonium trifluoromethanesulfonate (DMTST) resulting in excellent product yields.

Figure optionsDownload as PowerPoint slideHighlights
► A wide variety of glycosyl fluorides were synthesized in the absence of NBS.
► The reaction was applicable to conversion of compounds carrying alkene functionality.
► The reaction was effectively accelerated in the presence of DMTST.
► These reactions were much cleaner than the conventional reaction using NBS.