Enantioselective synthesis of β2-amino acids using rhodium-catalyzed hydrogenation

A series of protected beta(2)-dehydroamino acids has been prepared in three steps from commercially available starting materials in good yields. These were used as substrates in rhodium-catalyzed asymmetric hydrogenation applying a mixed ligand system of monodentate phosphoramidites and phosphines. Optimization of the catalyst structure was achieved by high throughput experimentation. High enantioselectivities were obtained ( up to 91%) with full conversion for a number of beta-amino acids.