Stereoselective reduction of ketones by various vegetables

Reduction of (+)-and (−)-camphorquinones (1a, 1b) by various vegetables (carrot, potato, sweet potato, apple, Japanese radish, cucumber, burdock and onion) gave α-hydroxycamphor selectively. Using burdock, (+)-camphorquinone was reduced to give (−)-3S-exo-hydroxycamphor (4a) as major product in high stereoselectivity with high yield. Moreover, 1,2-cyclohexanedione (1c) and 2-methylcyclohexanone (1d) with various vegetables afford enantiomerically pure trans- and/or cis-alcohol, respectively. Various vegetable reduction gave a new idea of a biotechnological process.