Enantioselective synthesis of the bioactive flavanones lonchocarpol A and 6-(1,1-dimethylallyl)naringenin by catalytic asymmetric transfer hydrogenation

Practical enantioselective syntheses of the natural products lonchocarpol A and 6-(1,1-dimethylallyl)naringenin as well as their optical antipodes are reported. A rhodium-catalyzed asymmetric transfer hydrogenation of readily available racemic substrates with virtually complete kinetic resolution served as the key step. Solvent-controlled, clay-catalyzed [1,3] or [3,3] shifts of prenyl aryl ethers were used to install the C-6 prenyl or 1,1-dimethylallyl substituent of the target flavanones.