All possible chiral isomers that can be derived from calixarene by modification of the OH groups were systematically classified. Molecular asymmetry can be generated not only by different substituents but also by conformational isomerism. The numbers of chiral isomers are 24 for tetra-O-substituted calixarenes, 10 for tri-O-substituted calixarenes, 3 for di-O-substituted calixarenes, and 0 for mono-O-substituted calixarenes. This implies that calixarene is a useful building block for the design of novel asymmetric ring structures. In order to demonstrate asymmetry in these chiral calixarenes, we synthesized several tetra-, tri-, and di-O-substituted calix-arenes by using the metal template method, the stepwise synthesis method, the protection-deprotection method, etc., which were developed in efforts directed toward regioselective O-alkylation and control of conformational isomerism in calixarenes. Finally, we succeeded in complete optical resolution of chiral calixarenes by an HPLC method using a chiral-packed column or by the formation of diastereomers with the (−)-menthoxyacetyl group. This article thus contains all of the molecular design concepts, syntheses, and optical resolutions of chiral calixarenes.
All Science Journal Classification (ASJC) codes
- Colloid and Surface Chemistry