A protecting group-free approach to C-glycosides using the Ramberg-Bäcklund reaction

The one-pot conversion of unprotected monosaccharides directly into benzylsulfonylmethylene C-glycosides via a Horner-Wadsworth-Emmons/ring closure process is reported. Similar reactions giving sulfone-linked disaccharides are also discussed. One-pot transformations of unprotected monosaccharides to give styrenyl C-glycosides, by a tandem Horner-Wadsworth-Emmons/ring closure-halogenation/Ramberg-Bäcklund sequence, is then described.