Highly diastereoselective preparation of anti-α,β-dialkyl β-amino acids containing natural α-amino acid side chains

An efficient synthesis of anti-2-alkyl β3-amino acids was developed starting from the fully protected β3-amino acids. The strategy allows the introduction of the side chain of natural α-amino acids such as Ala, Phe and Ser at the C-2 position, with high diastereoselectivity. The preparation of 2-methyliden-β3-amino acids is also reported. This methodology does not need the use of expensive chiral reagents and/or chiral auxiliaries, and leads to compounds with orthogonal protecting groups.