ENANTIOMER RECOGNITION OF ORGANIC AMMONIUM-SALTS BY PODAND-TYPE AND CROWN-TYPE MONENSIN AMIDES - NEW SYNTHETIC STRATEGY FOR CHIRAL RECEPTORS

Podand- and crown-types of new chiral receptors, characterized by a chiral polyether skeleton and an amide junction, were derived from naturally occurring monensin ionophore. Their chiral recognition ability was investigated by ion-selective electrode and H-1-NMR spectroscopic methods. Several podand-type monensin amides formed 1:1 complexes with chiral amine salts and exhibited excellent enantiomer selectivity. Since biological monensin and its macrocyclic derivatives were less effective for chiral recognition, a molecular combination of pseudo-cyclic monensin cavity, chiral polyether skeleton and neutral amide moiety offered high enantiomer selectivity. Chemical modification of biological monensin allowed remarkable development of new ionophoric functions and provided an effective synthetic strategy for chiral receptors.