CHIRAL RECOGNITION IN COMPLEXATION OF GUESTS BY DESIGNED HOST MOLECULES

Abstract

Host molecules have been designed and synthesized to selectively complex and lipophilize guest molecules. Examples of the use of the following binding interactions are given: hydrogen bonding, ion pairing, cation to n-electrons, carbonyl to n-electrons and pi-pi bonding. Multiheteromacrocycles have been prepared whose association constants with tert-butylammonium salts in chloroform range from < 50 to 106 M-1. Host molecules with built-in counterions have been prepared that selectively complex and lipophilize metal and alkylammonium cations. Locations of complementary binding sites and non-complementary steric barriers provide for selective binding by host molecules of candidate guest molecules. Locations of appropriate chiral barriers and multiple complexing sites in guest compounds have led to the complete optical resolution of host compounds by optically active amino acids, and of amino acid esters by optically active host compounds. Ratios of association constants for diastereomeric complexes in excess of ten have been obtained. A molecular basis for designing an amino acid resolving machine has been developed.