COPPER(II) COMPLEXES OF N-2-ALKYL-(S)-AMINO ACID-AMIDES AS CHIRAL SELECTORS FOR DYNAMICALLY COATED CHIRAL STATIONARY PHASES IN RP-HPLC

Copper(II) complexes of N-2-octyl-(S)-phenylalaninamide (Noc-Phe-NH2), N-2-dodecyl-(S)-phenylalaninamide (Ndo-Phe-NH2), and N-2-octyl-(S)-no rleucinamide (Noc-NLeu-NH2), dynamically adsorbed on a reversed-phase C-18 column, were able to perform the direct enantiomeric separation o f unmodified amino acids, amino acid amides and esters, hydroxy acids, and dipeptides by elution with aqueous or mixed aqueous-organic solut ions containing copper(II) sulphate or acetate. The role played by sev eral parameters in the separation procedure was examined with the copp er(II) complex of Noc-Phe-NH2 [concentration of the copper(II) ion in the eluent, pH and eluent polarity, amount of adsorbed selector], The separation was shown to occur entirely on the stationary phase. The me chanism of chiral discrimination is discussed in terms of the chromato graphic parameters and of the structure of the copper(II) complexes in solution and in the solid state. The chiral stationary phase maintain ed its separation ability for about 3 months. However, the column coul d be easily restored by recovering the selector with methanol and repe ating the loading procedure. (C) 1996 Wiley-Liss, Inc.