Stereoselective Synthesis of 2‐Deoxyglycosides from Glycals by Visible‐Light‐Induced Photoacid Catalysis

: The direct, photoacid-catalyzed synthesis of 2-deoxyglycosides from glycals is reported. A series of phenol-conjugated acridinium-based organic photoacids were rationally designed, synthesized, and studied alongside the commercially available phenolic catalyst eosin Y. In the presence of such a photoacid catalyst and light, synthetic glycals were activated and coupled with a range of alcohols to afford 2-deoxyglycosides in good yields and with excellent α-selectivity.