Enantioselective synthesis of β-amino-diacids

An efficient route to orthogonally protected β-amino-diacids is described: chiral derivative 3 was shown to be a precursor of enantiopure substituted β-amino acids. The key step of the procedure is a diastereoselective reduction of β-enaminolactones 5 by NaBH3CN in CH2Cl2. A study concerning the regio- and diastereoselectivity of alkylation of β-enaminolactone 3 is also presented.