CARBAMATE-DIRECTED STEREOSELECTIVE HYDROGENATION AND KINETIC RESOLUTION OF N-PROTECTED ALPHA-(ALPHA-AMINOALKYL)ACRYLATES

A series of racemic methyl alpha-[alpha-(methoxycarbonylamino)alkyl]acrylates (1a-e) were hydrogenated using a variety of Rh(I) cationic complexes containing diphosphines and a chiral [Ru(OAc)2(S)-BINAP] (BINAP = 2,2'-bis(diphenylphosphino)-1,1'-dinaphthyl) as catalyst precursors to give preferentially the threo isomers (2a-d), the diastereoselectivity depending markedly on the alkyl group in 1. In addition, the relative rate ratio, k(R)/k(S), of a kinetic resolution during the Ru-catalyzed hydrogenation was found to be in a range 8-17, varying rather randomly as the alkyl group in 1 altered. The intercorrelation between the diastereoselectivity by virtue of the substrate-control and the kinetic discrimination of (+/-)-1 arising from the chiral catalyst-control was discussed in one particular case.