Chiral calix[4]azacrowns for enantiomeric recognition of amino acid derivatives

in this study the synthesis of novel chiral calix[4]azacrown derivatives has been reported. The enantioselectivity of Chiral receptors was investigated by using UV-vis spectroscopy. All the chiral calix[4]arene derivative,; exhibited certain chiral recognition toward the enantiomers of phenylalanine (Phe-OMe.HCl) and alanine methyl ester hydrochlorides (Ala-OME.HCl). As a chiral receptor, the furfuryl-armed calix[4]azacrown ether 7 has the best enantiomeric discriminating ability for alpha-amino acid ester hydrochlorides (up to K-L/K-D 2.08, Delta Delta G(0) 1.82 KJ mol (1)) in CHCl3. The enantiomeric recognition abilities for 1,guests are also discussed from a thermodynamic point of view. (C) 2009 Elsevier Ltd. All rights reserved.