Synthesis and characterization of new chiral calix[4]arenes.
The unique chiral calixarenes were successfully synthesized by the following two methods: the Williamson ether synthesis and a stepwise ether cleavage with a mild Lewis acid. The high regioselectivity is recognized by the latter stepwise method. The ionophores having oligoethylene glycol unit efficiently extracted larger alkali metal ions like K+, Rb+, and Cs+ than smaller ones like Li+ and Na+. Their ion selectivity apparently changed by the chain length of crown ether. All racemates obtained could be resolved to each enantiomer by HPLC using a chiral column. The calixarenes with planar chirality recognized the chirality of guest molecules. Thus, the (-)-receptor resolved strongly forms 1:1 complex with (R)-(+)-alpha-phenylethylammonium picrate.
Okada
Yukihiro
Y
Department of Chemistry, Gunma University, Kiryu, Japan. okada@chem.gunma-u.ac.jp
Mizutani
Manabu
M
Ishii
Fuyuhiko
F
Nishimura
Jun
J