FUNCTIONALIZATION OF INCLUSION CAVITIES OF BILE-ACID HOSTS - CHANNEL-TYPE INCLUSION-COMPOUNDS OF CHOLAMIDE

Clathrate formation and crystal structures of 3 alpha, 7 alpha, 12 alp ha-trihydroxy-5 beta-cholan-24-amide (cholamide) have been investigate d. Cholamide forms inclusion compounds with various organic compounds having hydrogen-bond (H-bond) donors. X-Ray crystallographic studies s howed that cholamide has bilayer structures with molecular channels. T he crystal structures are quite similar to those of channel-type inclu sion crystals of cholic acid. Steric dimensions of the host cavities a re identical, but cholamide has an H-bond 'hook' on the wall of the ch annels, while cholic acid does not. This difference is correlated with not only the inclusion abilities but also the molecular structures. T wo H-bond donors of the amide group yield a hydrophilic inclusion cavi ty that includes H-bond accepters, and one H-bond donor of the carboxy lic acid gives a lipophilic inclusion cavity that includes non-polar o r less polar compounds.