Abstract

A macrocyclic receptor shaped by two xanthone units bonded to binaphthyl is able to extract zwitterionic amino acids enantioselectively front water to chloroform in the presence of 18-crown-6 ether. Based on H-1 NMR and circular dichroism spectra. the most stable associate of receptor 1 with alanine is assigned to the (M,S) configuration while the opposite configuration in phenylglycine yields the strong associate (M,R). (C) 2004 Elsevier Ltd. All rights reserved.