Highly enantioselective hydrogenation of alpha-dehydroamino acids by rhodium complexes with new unsymmetric P-chirogenic bisphosphine ligands

[GRAPHICS] New rhodium catalysts with unsymmetric P-chirogenic bis(phosphino)ethanes, BisP*-Rh, exhibited very high enantioselectivity (98-99%) in the hydrogenat ion of alpha -dehydroamino acid derivatives. Such high enantioselectivity s hould result from the asymmetric environment around the Rh atom, as was sho wn in the molecular structure of the catalyst analyzed by X-rays, The asymm etry can be controlled by the combination of the alkyl groups on the two ph osphorus atoms.