S. Kohmoto et al., Novel channel structure formed with methyl 3-(9-anthrylcarbonyloxy)cholateusing orthogonally stacked building blocks, CHEM LETT, (7), 1999, pp. 621-622
The new type channel structure in the chemistry of cholic acid was created
by the protection of both end (the hydroxy group at the 3-position and the
carboxy group at the 23-position) of cholic acid. The inhibition of the int
ermolecular hydrogen bonding existing in cholic acid at these positions alt
ered the crystal structure completely.