Stereoselective Synthesis of Glycosides via Tsuji-Trost Type Glycosylation Using 3,4-Carbonate Galactals.

Pd-catalyzed stereoselective glycosylations using unsaturated sugar derivatives, glycals, have been successfully achieved in recent years. This review focuses on approaches to control the stereoselectivities of glycosides via π-allyl intermediates that mimic the Tsuji-Trost asymmetric allylic alkylation reactions, enabling stereoselectivity control through rational design. In the reaction process, zwitterionic Pd-π-allyl complexes, formed after the oxidative addition and decarboxylation, play a crucial role in increasing reactivities and enhancing the stereoselectivities of α- and β-glycosides. We summarized recently developed Tsuji-Trost type glycosylations using 3,4-carbonate galactals, featuring high efficiency, exclusive stereoselectivities, and a broad reaction scope including O-, N-, S-, and C-glycosylations.