Asymmetric reactions catalyzed by chiral metal complexes: XXXII. Efficient asymmetric hydrogenation of itaconic acid derivatives catalyzed by rhodium complexes of improved (2 S,4 S)- N-(t-butoxycarbonyl)-4-(diphenylphosphino)-2-[(diphenylphosphino)methyl]pyrrolidine (BPPM) analogues

We have prepared analogues of (2 S,4 S)- N-(t-butoxycarbonyl)-4-(diphenylphosphino)-2-[(diphenylphsphino)methyl]pyrrolidine (BPPM), bearing para-dimethyl-amino groups to prove the utility of our designing concept with regard to electronic effects of the phosphino groups on the enantioselectivity and the activity of the rhodium complex catalysts. Their rhodium complexes are much more effective than those of BPPM and (2 S,4 S)- N-(t-butoxycarbonyl)-4-(dicyclohexylphosphino)-2-[(diphenylphosphino)methyl]pyrrolidine (BCPM) for the asymmetric hydrogenation of dimethyl itaconate. The hydrogenation has also been used successfully in an efficient asymmetric synthesis of the key intermediate of new human renin inhibitors.