Abstract: A process for the preparation of an enantiomerically enriched beta-amino acid derivative of formula (1), or the opposite enantiomer thereof, wherein R1 is an optionally substituted alkyl, aryl or heteroaryl group of up to 20 C atoms, R2 is ann alkyl group of up to 20 C atoms, and R3 is H or an alkyl or aryl group of up to 20 C atoms, which comprises asymmetric hydrogenation of the (z)-enamide precursor (2) in an alcohol solvent or cosolvent, catalysed by a cationic rhodium complex of a chiral phosphine ligand having the partial formula (3), wherein n is 0 to 6 and R represents at least one non-hydrogen organic group of up to 20 C atoms.