Deoxycholic acid structure

Also deoxycholic acid (6) crystallizes in an inclusion lattice with channel-shaped cavities 13). Figure 3 shows that they are formed by facing molecules of deoxycholic acid, 4). This characteristic structural unit is a double layer of head-to-tail linked deoxycholic acid molecules at which specific H-bridges between hydroxy and carboxy groups are the decisive fact. The channels as such (e.g. in case of the orthorhombic crystal, see Fig. 3) are lined with lipophilic groups. Thus only van der Waals contacts are kept between the included guest molecules (also for polar molecules like acetone, Fig. 3) and the molecules of the channel wall. 

Fig. 8 Preparation of amphiphilic polysaccharide. Chemical structures of deoxycholic acid-modified chitosan (a) and Phe-modified pectin (pectin-gra/t-Phe) (b). SEM image of nanoparticles prepared from pectin-gra/t-Phe (c)...

Kim YH, Gihm SH, Park CR et al (2001) Structural characteristics of size-controlled selfaggregates of deoxycholic acid-modified chitosan and their application as a DNA delivery carrier. Bioconjug Chem 12 932-938... 

Lee KY, Jo WH, Kwon IC et al (1998) Structural determination and interior polarity of selfaggregates prepared from deoxycholic acid-modified chitosan in water. Macromolecules 31 378-383... 

Adequate x-ray crystallographic studies have been made of some of the structures in Table VII. The end-view cross section of channels in urea- -paraffin complexes is shown in Figure 5 53). The urea (and thiourea) molecules are hydrogen bonded to create hollow cylindrical channels whose walls are helices of linked urea or thiourea. These helices can be right or left handed in a given crystal (but not both). In the orthorhombic structure of the deoxycholic acid complex with acetic acid having a =... 

The bile acids are produced in the liver by the metabolism of cholesterol. They are di- and trihydroxylated steroids with 24 C atoms. The structure of cholic acid was seen earlier (Sec. 6.6). Deoxycholic acid and chenodeoxycholic acid are two other bile acids. In the bile acids, all the hydroxyl groups have an a orientation, while the two methyl groups are /3. Thus, one side of the molecule is more polar than the other. However, the molecules are not planar but bent because of the cis conformation of the A and B rings. 

The anaesthetic steroid 3a-hydroxy-5a-pregnane-ll,20-dione has normal conformational features, both in the crystal and in solution. X-Ray data show that deoxycholic acid can form an inclusion complex in which alternate molecules of dimethyl sulphoxide and water are held in canals formed by helically arranged host molecules.Six different crystalline forms of 17a-ethynyloestradiol have been recognized. X-Ray structural data are reported for 3-methoxy-2-aza-oestra-l,3,5(10)-trien-17/3-yl acetate, 3/3-hydroxypregn-5-en-20-one (pregnenolone), 5a-cholest-2-ene, 3/3-bromo- and 3/3-chloro-cholest-5-enes, and cholesteryl acetate (at 123 K), benzoate, chloroformate, ° laurate, methyl carbonate, and 24-norcholesteryl acetate. ... 

Choleic acid A specific complex between deoxycholic acid, which crystallizes with channels throughout the structure, and various organic molecules, such as hydrocarbons or fatty acids, that can fit in these channels. 

The same situation can also be found in arch-shaped or concave deoxycholic acid (= DC Figure 7.17) derivatives, in which rings A and B are cw-fused. As an example, a bilayer was observed in monoclinic crystals of the rubidium salt of DC (= RbDC). Hexagonal crystals of NaDC and RbDC hydrates, on the other hand, produced interesting helical structures (Figure 7.17) with hydrophilic centres. They constitute the prototype of a well defined micellar structure,... 

Packing Properties of the Deoxycholic Acid Complexes.—The crystal structures of a variety of DCA complexes listed in Table 3 have been determined elsewhere and in... 

Structure-Reactivity Relationship in Deoxycholic Acid Complexes.—The three-channel motifs offer a variety of host-guest arrangements that may be exploited for the performance of solid-state reactions. Two kinds of reagents were occluded (a) peroxides, hydroperoxides, and peresters, which were activated thermally or by irradiation, (b) ketones, which were activated photochemically. 

Insight into the photochemical reactions between deoxycholic or apocholic acid ( choleic acids ) and guest molecules in crystalline inclusion complexes has been obtained by X-rzy studies. The choleic acids form channels with wall structures determined by the nature of the guest molecule. Guest ketones of various types react photochemically by addition to the choleic acid at a site determined by the orientation of the ketone molecule in relation to the host (e.g. deoxycholic acid reacts at C-5 or C-6 with linear aliphatic ketones, but at C-16 with cyclohexanone).12... 

The most common hosts for inclusion polymerization are urea, thiourea, perhydrotriphenylene (PHTP), deoxycholic acid (DCA), apocholic acid (ACA) and tris(o-phenylenedioxy)cyclotriphosphazene (TPP)(Fig. 2). They have the common feature of forming channel-like clathrates, but differ in many specific properties. For instance, urea and thiourea have a rigid structure in which the host molecules are connected by hydrogen bonds and possess a high selectivity towards the guests. In urea channels are rather narrow whereas in thiourea they are wider as a consequence, linear molecules include only in urea and branched or cyclic molecules in thiourea. On the contrary, chainnels existing in PHTP clathrates are very flexible and can accomodate linear, branched and cyclic molecules. 

Bile acids contain hydroxyl groups, which are usually substituted at positions, C-3, C-7, or C-12 of the steroid nucleus. The three major bile acids found in man are 3a,7a,12a-trihydroxy-5P-cholan-24-oic acid 3a,7a-dihydroxy-5p-cholan-24-oic add and 3a,12a-dihydroxy-5p-cholan-24-oic acid. Because of the complexities of steroid nomenclature, bile acids are nearly always referred to by trivial names. 11108, the three major human bile acids are named cholic acid, chenodeoxycholic acid, and deoxycholic acid, respectively, and their chemical structures are shown in Fig. 1. Human bile does, however, contain small amounts of other bile acids, such as lithocholic acid (3a-hydroxy-5P-cholan-24-oic add) and ursodeoxycholic add (3a,7p-dihydroxy-5p-cholan-24-oic acid) (see Fig. 1). 

These days chemistry students usually accept the structures of biomolecules shown in their textbooks as certain and unchangeable revelations of the unseen world of molecules. However, those who learned steroid chemistry in 1950s know that the initial structures proposed for cholesterol and deoxycholic acid by Wieland in 1928 (Figure 7.1) were challenged by the X-ray crystallographer Bernal in 1932, resulting in proposals of more plausible structures by others.1,2 These historical episodes in steroid chemistry led us to believe that the truth about such matters would finally be revealed. 

FIGURE 18-6 Chemical structures of major sterols and cholesterol derivatives. The major sterols in animals (cholesterol), fungi (ergosterol), and plants (stigmasterol) differ slightly in structure, but all serve as key components of cellular membranes. Cholesterol is stored as cholesteryl esters in which a fatty acyl chain (R = hydrocarbon portion of fatty acid) is esterified to the hydroxyl group. Excess cholesterol is converted by liver cells into bile acids (e.g., deoxycholic acid), which are secreted into the bile. Specialized endocrine cells synthesize steroid hormones (e.g., testosterone) from cholesterol, and photochemical and enzymatic reactions in the skin and kidneys produce vitamin D. 

Johns WH and Bates TR., Quantification of the binding tendencies of cholestyramine I effect of structure and added electrolytes on the binding of unconjugated and conjugated bile salt anions, /. Pharm. Sci., 58,179-183 (1969). NB These values were quoted from Ekwall P, Rosendahl T and Lofman N, Bile salt solutions. I. The dissociation constants of Bie cholic and deoxycholic acids, Acta Chem. Scand., 11,590-598 (1957). They were measured at concentrations boBi above and below Bie critical micellar concentration range. 

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