Synthesis of rigid and C-2-symmetric pyridino-15-crown-5 type macrocycles bearing diamide-diester functions: enantiomeric recognition for chiral primary organoammonium perchlorate salts

Four novel C-2-symmetric macrocyclic compounds with a pyridine function and possessing amide and ester lingeages were prepared. The enantiomeric discrimination abilities of these macrocycles against alpha-phenylethylammonium and alpha-(1-naphthyl)ethylammonium perchlorate salts were measured by standard H-1 NMR titration techniques in DMSO-d(6). A binding constant ratio of 31 (Kbind(S)/Kbind(R)) for two enantiomers of alpha-(1-naphthyl)ethylammonium salt with the macrocyclic host (S,S)-4 bearing phenyl arms was observed, which corresponds to an enantiomeric discrimination of approximately 94%. Molecular dynamic calculations were performed for some of the supramolecular complexes to in order to gain insight into the mode of molecular recognition between the macrocyclic compounds and ammonium salts; these results were consistent with experimental observations, which may be relevant to those in biochemical processes occurring in organisms. (C) 2014 Elsevier Ltd. All rights reserved.