Molecular Assemblies of Cholic Acid Derivatives and Use of Their Inclusion Spaces

Abstract

Cholic acid derivatives form crystalline inclusion compounds with various organic substances. More than two hundred their crystal structures have been used in the study of molecular recognition through their assemblies. Host molecules were noted to combine via intermolecular hydrogen bonds to produce diversible assemblies comprised of layers and helices. The explanation for these assemblies is that the hosts have characteristic facial structures with chirality, directionality and amphiphilicity. Multiple hydrogen bonding groups are essential to the formation of the assemblies. Slight change in the host and guest molecules may frequently lead to great change in the assemblies due to exchange of the corresponding hydrogen bonding network. Different intermolecular hydrogen bonding networks produced polymorphic crystals, depending on the particular guest components. The hosts exhibited very different inclusion ability toward aliphatic alcohols due to additional hydrogen bonding groups situated between host and guest molecules rather than among host molecules. Inclusion spaces are effective as fields for enantioselective resolution and polymerization reactions. This study has demonstrated on analogy between cholic acid derivatives and proteins, and on the basis of which, chiral and sequential carbon chains may be concluded to express their information through molecular assemblies with multiple hydrogen bonds.