Preparation of Two New Diasteromeric Chiral Stationary Phases Based on (+)-(18-Crown-6)-2,3,11,12-tetracarboxylic Acid and (R)- or (S)-1-(1-Naphthyl)ethylamine and Chiral Tethering Group Effect on the Chiral Recognition.

Two new diastereomeric chiral stationary phases (CSPs) based on (+)-(18-crown-6)-2,3,11,12-tetracarboxylic acid as a chiral tethering group and a Π-basic chiral unit such as (R)-1-(1-naphthyl)ethylamine (CSP 1) or (S)-1-(1-naphthyl)ethylamine (CSP 2) were prepared. The two CSPs were applied to the enantiomeric separation of N-(3,5-dinitrobenzoyl)-1-phenylalkylamines and N-(3,5-dinitrobenzoyl)-α-amino acid derivatives using 20% isopropyl alcohol in hexane as a normal mobile phase. To elucidate the effect of the two chiral units on the chiral recognition, the chiral recognition abilities of the two CSPs were compared with each other and with that of a CSP (CSP 3) based on (R)-1-(1-naphthyl)ethylamine.

High-performance liquid chromatographic enantioseparation of isoxazoline-fused 2-aminocyclopentanecarboxylic acids on a chiral ligand-exchange stationary phase.

The application of a chiral ligand-exchange column for the direct high-performance liquid chromatographic enantioseparation of unusual β-amino acids with a sodium N-((R)-2-hydroxy-1-phenylethyl)-N-undecylaminoacetate-Cu(II) complex as chiral selector is reported. The investigated amino acids were isoxazoline-fused 2-aminocyclopentanecarboxylic acid analogs. The chromatographic conditions were varied to achieve optimal separation.