Catalytic Asymmetric Desymmetrization of Cyclopentendiones via Diels–Alder Reaction of 3‑Hydroxy-2-pyrones: Construction of Multifunctional Bridged Tricyclic Lactones

An unprecedented asymmetric Diels–Alder reaction of 3-hydroxy-2-pyrones with prochiral cyclopentene-1,3-diones via desymmetrization was efficiently realized with high stereoselective control with the aid of fine-tunable cinchona alkaloid derived bifunctional amine–thiourea catalysts bearing multiple hydrogen-bonding donors. This protocol provides an expedient access to the multifunctional-bridged tricyclic lactones featuring four contiguous stereogenic centers and one remote quaternary stereogenic center with a broad substrate scope. The cycloadduct can be readily elaborated into enantioenriched cyclopentane-1,3-diones via ring opening/aromatization.