Stereoselective Synthesis of C- and N-Ketosides by Lewis Acid-Catalyzed C- and N-Glycosidation of Alkynyl, Phenyl, and Methyl Ketoses

C‐Ketosides can be prepared conveniently, in a stereoselective manner, from alkynyl, phenyl and methyl glucopyranose hemiketals by reaction with carbon nucleophiles in the presence of Lewis acids. The reaction of the hemiketals with trimethylsilyl azide provides an efficient route to the corresponding N‐ketopyranosides. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)