Syntheses and properties of chiral pentahomothiazacalix[3]arenes

Chiral calixarene analogs incorporating an aminoethanethiol unit such as L-cysteine into their rings were prepared. Conformational analysis of the macrocycles by using H-1 and C-13 nmr spectroscopy revealed that their preferred conformation was a cone, which was more stable in chloroform than in toluene. The introduction of an aminoethanethiol moiety into the macrocyclic ring caused ring fluctuation, however, the carboxylic acid derivative was a highly rigid structure in the cone form. The H-1 nmr and circular dichroism spectra of the macrocycles showed the existence of chirality of the phenol-formaldehyde unit, which was induced by the chirality of the cysteine moiety.