Synthesis of Tofogliflozin as an SGLT2 Inhibitor via Construction of Dihydroisobenzofuran by Intramolecular [4 + 2] Cycloaddition

The synthesis of tofogliflozin (1), a sodium glucose cotransporter 2 (SGLT2) inhibitor, was achieved through the key steps of intramolecular [4 + 2] cycloaddition of dienone-yne intermediate, aerobic aromatization, and anomeric equilibration, thus enabling the construction of a dihydroisobenzofuran moiety of 1. Subsequent hydrogenolysis followed by global deprotection afforded the desired compound 1. The divergent synthesis of the anomer of 1 (15) is also described.