A New Receptor Molecule for Lysine and Histidine in Water � Strong Binding of Basic Amino Acids by a Macrocyclic Host

The effective and selective molecular recognition of amino acids in water is still a challenge in supramolecular chemistry. Because of the frequent use of the side chains of basic amino acids (Lys, Arg, His) for biological processes the molecular recognition of these amino acids by synthetic receptor molecules is of special interest [1]. Recently we presented a new macrocyclic receptor molecule, which binds arginine and lysine in a stereoselective fashion (Fig. 1) [2]. The mechanism of enantioselective recognition relies on two simultaneous cation-phosphonate interactions � i. e. binding of a specific cationic group of the amino acid to a specific phosphonate moiety in the receptor molecule. After docking the amino acid comes into van der Waals-contact of the chiral surface of the chiral bridging unit in 1 and one enantiomer is bound preferentially.