Highly enantioselective synthesis of non-natural aliphatic α-amino acids via asymmetric hydrogenation.

By employing a rhodium-Duanphos complex as the catalyst, β-alkyl (Z)-N-acetyldehydroamino esters were smoothly hydrogenated in a highly efficient and enantioselective way. Excellent enantioselectivities together with excellent yields were achieved for a series of substrates. An efficient approach for the synthesis of the intermediate of the orally administered anti-diabetic drugs Alogliptin and Linagliptin in the DPP-4 inhibitor class was also developed.