title: Syntheses of chiral homoazacalix[4]arenes incorporating amino acid residues: molecular recognition for racemic quaternary ammonium ions.
abstract: Chiral calixarene analogues incorporating amino acid residues into the macrocyclic rings were prepared from the cyclization reactions of bis(chloromethyl)phenol-formaldehyde tetramer with amino acid methyl ester in moderate yields. The macrocycles form a chiral concavity, which is induced by the chiral transmission from the point chirality of the amino acid residues to the phenol-formaldehyde tetramer unit. The macrocycles have the cavity pi-basic enough to include the quaternary ammonium ion due to the cation-pi interaction and can serve as a shift reagent for racemic ammonium ions during 1H NMR analysis.
authors.affiliation: Department of Chemistry and Chemical Engineering, Faculty of Engineering, Yamagata University, Yonezawa 992-8510, Japan. itokazu@yz.yamagata-u.ac.jp
authors.forename: Kazuaki
authors.initials: K
authors.lastname: Ito
authors.forename: Motoyoshi
authors.initials: M
authors.lastname: Noike
authors.forename: Atsushi
authors.initials: A
authors.lastname: Kida
authors.forename: Yoshihiro
authors.initials: Y
authors.lastname: Ohba