Functionalization of Inclusion Cavities of Bile Acid Hosts. Channel-Type Inclusion Compounds of Cholamide

摘要

Clathrate formation and crystal structures of 3α, 7α, 12α-trihydroxy-5β-cholan-24-amide (cholamide) have been investigated. Cholamide forms inclusion compounds with various organic compounds having hydrogen-bond (H-bond) donors. X-Ray crystallographic studies showed that cholamide has bilayer structures with molecular channels. The crystal structures are quite similar to those of channel-type inclusion crystals of cholic acid. Steric dimensions of the host cavities are identical, but cholamide has an H-bond 'book' on the wall of the channels, while cholic acid does not. This difference is correlated with not only the inclusion abilities but also the molecular structures. Two H-bond donors of the amide group yield a hydrophilic inclusion cavity that includes H-bond acceptors, and one H-bond donor of the carboxylic acid gives a lipophilic inclusion cavity that includes non-polar or less polar compounds.