Enantiospecific enzyme-catalysed resolution of novel N,N-disubstituted alpha-amino acid phenolic ester derivatives using pig liver esterase

R-Amino acid esters 1, 2 and 3 are novel compounds possessing hypnotic acti vity. On attempting an asymmetric synthesis of these molecules, racemisatio n was observed when reacting bis(2-methoxyethyl)amine with alpha -bromo int ermediate 4. In vitro plasma stability studies showed that the R enantiomer s had much greater resistance to esterase-mediated degradation than the cor responding S enantiomers. This observation led to the use of commercially a vailable pig liver esterase to prepare 1, 2 and 3 on a multigram scale. The crystal structures of 1 and 2 are reported and confirm R configuration.