Diphenylethanediamine derivatives as chiral selectors .5. Efficient normal-phase high-performance liquid chromatographic enantioseparation of underivatized chiral arylalcohols on four differently linked 3,5-dinitrobenzoyldiphenylethanediamine-derived chiral stationary phases

Four brush-type chiral stationary phases (CSPs) have been prepared, via immobilization of (R,R)-3,5-dinitrobenzoyl-1,2-diphenylethane-1,2-diamine (DNB-DPEDA) with structurally different anchoring groups. These phases separate at normal-phase HPLC conditions the enantiomers of numerous underivatized chiral aromatic alcohols, including ArCH(OH)R, ArCH2CH(OH)R, Ar(CH)(2)CH(OH)R, simple tertiary arylalkylcarbinols and trans-2 arylcyclohexanols. In mobile phases of low polarity separations are characterized by considerate levels of enantioselectivity (alpha = 1.1-2.7), excellent band shapes and short elution times. The hydroxyl group of the analytes is shown to be essential for stereodiscrimination, while pi-basicity and steric bulkiness determine the magnitude of enantioselectivity. For simple structured arylalkylcarbinols a correlation is found between elution order and absolute configuration of the analyte. A rationale for molecular recognition of carbinol type analytes on DNB-DPEDA-derived CSPs is advanced. Their general applicability is demonstrated for a number of chiral auxiliaries, solvating agents and drug intermediates of carbinol structure.