Enantioselective Synthesis of 2′- and 3′-Substituted Natural Flavans by Domino Asymmetric Transfer Hydrogenation/Deoxygenation

A concise and highly enantioselective synthesis of the natural flavans kazinol U and (2S)-7,3'-dihydroxy-4'-methoxyflavan is reported for the first time. The key transformation is a single-step conversion of a racemic flavanone to a flavan by means of an asymmetric transfer hydrogenation/deoxygenation cascade with kinetic resolution.