ENANTIOSELECTIVE ION-PAIR CHROMATOGRAPHY OF PHENOLIC 2-DIPROPYLAMINOTETRALIN DERIVATIVES ON ACHIRAL STATIONARY PHASES - AN EXPERIMENTAL ANDTHEORETICAL-STUDY OF CHIRAL DISCRIMINATION

Separation of the enantiomers of six phenolic 2-dipropylaminotetralin derivatives by liquid ion-pair chromatography has been accomplished on an achiral stationary phase by the addition of a protected peptide de rivative as a chiral selector to the mobile phase. The influence on th e stereoselectivity and retention by the structure and concentration o f the counterion and the properties of the stationary phase has been i nvestigated. Maximal stereoselectivity was observed when benzyloxycarb onylglycyl-L-proline (L-ZGP) was used as a chiral selector on a porous graphitic carbon (Hypercarb) stationary phase. The separation factors (alpha) ranged from 1.0 to 3.46. When 8-hydroxy-2-dipropylaminotetral in was chromatographed in this system, the largest separation factors were observed at high counterion concentrations, indicating that the d ifference in adsorption constants between the diastereomeric complexes is responsible for the maximal stereoselective retention. Complexes f ormed between L-ZGP and the various enantiomers were subjected to forc e-field (MMX) minimizations to determine the geometries and energies o f energetically accessible complex conformers. The results of the calc ulations were used to determine various dynamic properties of the comp lexes, such as total and partial surface areas, dipole moments, bindin g energies and relative steric energies. A correlation (r2 = 0.80) was observed between the separation factor alpha and the difference in dy namic unsaturated surface of the diastereomeric complexes.