Determination of the optical purity for serine and threonine by gas chromatography on a chiral column

In a two-step procedure, serine and threonine were converted first to N-isobutoxycarbonyl-amino acid 2,2,2-trifluoroethyl esters and subsequently also to novel N,O-bis-isobutoxycarbonyl-derivatives. As such all four isomers of threonine could easily be resolved on a commercial chiral (Chirasil-D-Val) gas chromatography column at 140 degrees C. A significant influence of the configuration at the beta-position on the retention time was thereby observed. Similarly, improved separation was demonstrated for the two enantiomers of N,O-bis-isobutoxycarbonyl-serine isobutylamide.