Access to l- and d-Iminosugar C-Glycosides from a d-<i>gluco</i>-Derived 6-Azidolactol Exploiting a Ring Isomerization/Alkylation Strategy

A flexible synthetic access to six-membered l- and d-iminosugar C-glycosides is reported starting from the easily available 6-azido-6-deoxy-2,3,4-tri-<i>O</i>-benzyl-d-glucopyranose precursor. This methodology involves a highly diastereoselective tandem ring enlargement/alkylation and a stereocontrolled ring contraction. It allows an efficient synthesis of iminosugar C-glycosides displaying structural diversity at both C-1 and C-6