Synthesis of All Eight L ‐Glycopyranosyl Donors Using CH Activation

The synthesis of all eight rare, but biologically important L ‐hexoses as the according thioglycosyl donors was achieved through a procedure involving the CH activation of their corresponding 6‐deoxy‐ L ‐hexoses. The key steps of the procedure were the silylation of the OH group at C4 followed by an intramolecular CH activation of the methyl group in γ‐position; both steps were catalyzed by iridium. The following Fleming–Tamao oxidation and acetylation gave the suitably protected L ‐hexoses. This is the first general method for the preparation of all eight L ‐hexoses as their thioglycosyl donors ready for glycosylation and the first example of an iridium‐catalyzed C(sp 3 )H activation on sulfide‐containing compounds.