Tether-directed Radical Cyclization Approaches to the Synthesis of C-Glycosides

6 Tether-directed Radical Cyclization Approaches to the Synthesis of C-Glycosides 

The introduction of an olefin at the anomeric position is synthetically interesting as it permits, via ozonolytic cleavage, access to the anomeric aldehyde, useful for further manipulations. Furthermore, the cleavage of the tether after cyclization releases one hydroxyl group selectively, which may be used chemoselectively in subsequent reactions. This reaction was also shown to be applicable to furanose sugar derivatives [2]. 

Although phenylseleno sugars have been most frequently used as radical precursors, their preparation requires the use of odorous phenylselenol. Furthermore, formation of the anomeric radical usually requires BujSnH, which is also unpleasant to work with. An 

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