Study of the mechanism of enantioseparation. I.: Chiral analysis of alkylamino derivatives of aryloxypropanols by HPLC using macrocyclic antibiotics as chiral selectors

The enantiomeric separation of alkylamino derivatives of aryloxypropanols using macrocyclic bonded chiral stationary phases was studied. Teicoplanin and vancomycin chiral stationary phases were used to separate a large number of derivatives of aryloxypropanol enantiomers by HPLC in the polar-organic mode. By comparison of chromatographic parameters obtained by using both chiral stationary phases (CSPs), aspects of the enantioselective separation mechanism could be discerned. Originally, the polar organic mode was developed for chiral compounds that contained a minimum of two hydrogen bonding groups, resulting in a minimum of two hydrogen bonding interactions to the CSP. This work demonstrated that a combination of one hydrogen bonding interaction and one electrostatic interaction is equally effective. The environment (i.e., functional groups) nearest to the stereogenic center of the aryloxypropanols had the greatest effect on the enantioresolution. Teicoplanin CSPs produced the greatest Delta DeltaG(o)'s and the best enantiomeric separations of these compounds. The site of a possible electrostatic interaction of these compounds is different from that found for amino acids.