Syntheses of chiral homoazacalix[4]arenes incorporating amino acid residues: molecular recognition for racemic quaternary ammonium ions.
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.
Ito
Kazuaki
K
Department of Chemistry and Chemical Engineering, Faculty of Engineering, Yamagata University, Yonezawa 992-8510, Japan. itokazu@yz.yamagata-u.ac.jp
Noike
Motoyoshi
M
Kida
Atsushi
A
Ohba
Yoshihiro
Y