α‐Amino Acid Derivatives by Enantioselective Decarboxylation

Abstract

Abstract 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 °C 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‐deoxy)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‐methoxybenzamide as the chiral base to give ethyl N ‐acetyl‐ L ‐phenylalaninate in 70% ee . (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)