Separation of Enantiomeric Aminoalcohols and Amines using (2R,3R)-Di-n-butyltartrate as Chiral Selector in Reversed-Phase Partition Chromatography

Abstract

Enantiomeric amines and aminoalcohols are separated by reversed-phase ion-pair partition chromatography with hexanesulfonate or hexafluorophosphate as counterion in the aqueous mobile phase and with (2R,3R)-di-n-butyltartrate (DBT) as the liquid stationary phase. Chiral separations of underivatized α-aminoalcohols with primary and secondary amine function, as well as amines having no hydroxy function (e.g., α-(1-naphthyl)ethylamine) are demonstrated. Stereoselectivity decreases for ephedrine and analogues thereof when exchanging (2R,3R)-di-n-butyltartrate for (2R,3R)-diisopropyltartrate, and no enantiomeric separation is observed with (S)-n-butyllactate as the chiral liquid stationary phase. The amount of DBT adsorbed on the solid phase (Phenyl Hypersil) is increased by increasing content of DBT in the aqueous eluent. Optimum stereoselectivity is found at high loading of DBT on the support. Retention can be adjusted by change of type or concentration of the counterion. It has no significant effect on the stereoselectivity.