Novel Supramolecular Palladium Catalyst for the Asymmetric Reduction of Imines in Aqueous Media

A novel approach to the asymmetric reduction of dihydro-β-carboline derivatives to the corresponding tetrahydro-β-carbolines is described based on the supramolecular lyophilized complex formed from β-cyclodextrin/imines as an enzyme mimetic and palladium hydride as the reducing agent. The methodology allowed us to develop a short and efficient preparation of (R)-harmicine and (R)-deplancheine alkaloids in high overall yields and ee of 89 and 90%, respectively.