Liquid chromatographic separation of enantiomeric alkanolamines via diastereomeric tartaric acid monoesters

Abstract

A new resolution method for the analytical and preparative separation of enantiomeric alkanolamines into their antipodes is presented. It involves formation of the monoesters of the alkanolamines with optically pure and symmetrically O,O- disubstituted (R,R)- or (S,S)-tartaric acids. The derivatization reactions are carried out in aprotic media by reaction with the tartaric acid anhydrides. The amine functions are ionically blocked via ion-pair formation with strong acids, e.g. trichloro-acetic acid. The resulting diastereomeric monoesters are easily separable into their antipodes by reversed-phase liquid chromatographic technique. Relative retention factors,α, up to 4 can be obtained, depending on the structural parameters of the alkanolamines and reagents, as well as on the mobile phase conditions (pH). The monoesters are zwitterions, possibly capable of forming intramolecular ion pairs via a ring structure favoured for ethanolamines.