Stereochemical Aspects of the C-Glycosylation of Pyranosides and Furanosides

The stereoselective synthesis of α- and β-C-glycosides is one of the most challenging areas of research in the field of glycoside chemistry. In this review, we summarize the various methods available for stereocontrolled glycosylation and also discuss the predictive models available to explain the stereochemical outcome of six- and five-membered-ring oxocarbenium ions with allyltrimethylsilane nucleophile under Lewis acid conditions. 1 Introduction 2 Stereochemical Aspects during Glycoside Bond Formation in Pyranosides 2.1 Lewis Acid Mediated Nucleophilic Addition to Six-Membered-Ring Oxocarbenium Ions 2.2 Arylalane Addition to Anhydroglucose 2.3 Glucal Epoxide Method 2.4 Glycosyl Leaving Group Substitution Method 2.5 Glycosylation via Transition-Metal-Mediated Cross-Coupling 3 Stereochemical Aspects during Glycoside Bond Formation in Furanosides­ 3.1 Lewis Acid Mediated Nucleophilic Addition to Five-Membered-Ring Oxocarbenium Ions 4 Summary and Conclusion