Cholic acid hydrogen bonding

Nakano, K., Sada, K. and Miyata, M. (1996). Novel additive effect of inclusion crystals on polymorphs of cholic acid crystals having different hydrogen-bonded networks with the same organic guest. Chem. Commun., 989-90. [58]... 

Porous host substructures with parallel channels are typical of many inclusion compounds formed by bile acids and their derivatives (see Deoxycholic, Cholic, and Apocholic Acids). In this class of compounds, host molecules are always optically active, and the resulting host networks are chiral. The best known among them are inclusion compounds of deoxycholic acid (DCA) (also known as choleic acidsj. With most guests. DCA molecules assemble via hydrogen bonds into a coiTugated... 

Amide- and Urea-Based Anion Receptors, p. 51 Amino Acids Applications, p. 42 Chiral Guest Recognition, p. 236 Deoxycholic, Cholic, and Apocholic Acids, p. 441 Fluorescence Sensing of Anions, p. 566 Guanidinium-Based Anion Receptors, p. 615 Hydrogen Bonding, p. 658 lonophores, p. 760... 

Recently Bennet et al. (122) showed that the methyl ester of cholic acid forms small aggregates in relatively nonpolar organic solvents. These aggregates are made up of about four molecules of the methyl ester hydrogen bonded to one another through the hydroxyl groups and therefore might be considered as a form of reversed micelle. These derivatives do not form micelles in a more polar solvent, such as alcohol, but are present in true solution (122). 

The conformation of the core cholic acid scaffold is curved with three hydroxyl groups on the a surface (Figure 19). The equatorial Ba-OH group is the least hindered, while the lla-OH is less hindered than the la-OH because of unfavorable 1,3-diaxial interactions between the 7q -OH and CH2 groups. The hydroxyl groups can themselves act as hydrogen-bond donors to bind anions however, it is possible to convert all or individual hydroxyl functional groups to amine or amide moieties to further... 

ABSTRACT. New synthetic hosts have been designed incorporating two molecules of cholic acid linked by a rigid diamine. Proton NMR studies indicate that the compounds exist in a rigid conformation with the steroid hydroxyl groups intramolecularly hydrogen-bonded. Heat or addition of methanol leads to conformational isomerism due to insertion of methanol into the cavity. 

Abstract Selective acquisition of polymorphic inclusion crystals of cholic acid with acrylonitrile and methacrylonitrile is described. Two polymorphic inclusion crystals of 1 with methacrylonitrile have different hydrogen-bonded networks from those with acrylonitrile. 

Real polymorphic inclusion crystals, which consist of not only identical host-to-guest ratios but also different hydrogen-bonded networks, were found by two groups. The one deals with the crystals of deuterated urea (ND2COND2) with sebaconitrile [1], and the other deals with those of cholic acid(l) (Fig. 1) with acrylonitrile [2]. It is empirically known that selective acquisition of any desirable crystal from multiple polymorphic crystals on the basis of recrystallization accompanies poor reproducibility [3]. In fact, we happened to obtain the latter crystals by addition of a third component. But now, we can surely and selectively acquire the crystals in the presence of different kinds of butanols under definite temperatures and concentrations. This method led us to the finding of another polymorphic crystals of 1 with methacrylonitrile having different hydrogen-bonded networks from those of 1 with acrylonitrile. 

---