Selection of Planar Chiral Conformations between Pillar[5, 6]arenes Induced by Amino Acid Derivatives in Aqueous Media.

Chiral α-amino acids play critical roles in the metabolic process in nearly all life forms. So far, chiral recognitions of α-amino acids have mainly focused on the determination of L / D enantiomers. Herein, selection of planar chiral conformations between water-soluble pillar[5]arene WP5 and pillar[6]arene WP6 was observed due to α -side chain or ethyl ester moieties of L - α -amino acid ethyl ester hydrochlorides binding with WP5 and WP6 , respectively. Therefore, α -side chain and ethyl ester moieties of L - α -amino acid ethyl ester hydrochlorides were recognized by observing the induced CD signal and its inversion. It is the rare example that the chiral region around α -carbon of a chiral α -amino acid molecule could be detected.