α-amino acid derivatives by enantioselective decarboxylation

The methodology of enantioselective decarboxylation was applied to 2-aminomalonic acid derivatives in order to obtain enantio-enriched amino acid derivatives. Full conversion was achieved stirring racemic N-acetylated 2-aminomalonic hemiesters in THF at 70 degreesC with 10 mol % of a chiral base for 24 h. The catalyst may be recycled. Whereas the commercially available cinchona alkaloids gave poor results, benzamide and benzenesulfonamide derivatives of 9-amino(9-de-oxy)epicinchonine turned out to be effective catalysts. The best result was obtained with 2-N-acetylamino-2-ethoxycarbonyl-3-phenylpropionic acid as the starting material and N-(9-deoxyepicinchonine-9-yl)-4-methoxybenzdmide as the chiral base to give ethyl N-acetyl-L-phenylalaninate in 70% ee. (C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003.