Flexible Synthesis of 2-Deoxy-C-Glycosides and (1→2)-, (1→3)-, and (1→4)-Linked C-Glycosides

摘要

C-Glycosides are an important class of carbohydrate mimics. In these compounds the monosaccharide units are linked by a methylene unit instead of an oxygen atom, rendering the disaccharide highly stable towards enzymatic and chemical hydrolysis. The conformational differences between C- and O-glycosides have been the subject of debate in the recent past because of the absence of exo and endo anomeric effects in C-glycosides; however, a general conclusion cannot be drawn to date. The difficulties associated with the synthesis of a C-glycosidic bond between two monosaccharide moieties are readily apparent. Several groups have addressed the synthesis of such structures in the past decade. Typically, methods have been developed only for specific linkages or have required elaborate building blocks. Thus, a modular and robust approach for the synthesis of a variety of different C-glycosidic linkages would be of high synthetic and biochemical interest. Recently, we reported a Sonogashira reaction to promote the synthesis of α- and β-linked (1 →6)-C-disaccharides. Herein we focus on the preparation of more challenging C-glycosidic bonds and present a strategy to build α- and β-linked (1 →2)-, (1 →3)-, and (1 →4)-C-disaccharides.