β‐Mannosides from β‐Glucosides by Intramolecular Nucleophilic Substitution with Inversion of Configuration

The β‐mannoside bond in the core region of N ‐glycoproteins is difficult to form. The epimerization at C‐2 of β‐glucosides, which is normally difficult to achieve, has now been accomplished by intramolecular nucleophilic attack of a carbamate substituent in the sense of neighboring‐group assistance. It was possible in this way to prepare directly isomerically pure (protected) β‐mannosides like 1 from menthol and cholesterol as well as β‐mannosidic disaccharides.