Cholic acid structure

Decahn ring systems appear as structural units m a large number of naturally occur ring substances particularly the steroids Cholic acid for example a steroid present m bile that promotes digestion incorporates as decahn and trans decahn units into a rather complex tetracyclic structure... 

Steroids are another class of natural products with multiple chirality centers One such compound is cholic acid which can be obtained from bile Its structural formula IS given m Figure 7 12 Cholic acid has 11 chirality centers and so a total (including cholic acid) of 2" or 2048 stereoisomers have this constitution Of these 2048 stereoiso mers how many are diastereomers of cholic acid s Remember Diastereomers are stereoisomers that are not enantiomers and any object can have only one mirror image Therefore of the 2048 stereoisomers one is cholic acid one is its enantiomer and the other 2046 are diastereomers of cholic acid Only a small fraction of these compounds are known and (+) cholic acid is the only one ever isolated from natural sources... 

The structure of cholic acid helps us understand how bile salts such as sodium tauro cholate promote the transport of lipids through a water rich environment The bot tom face of the molecule bears all of the polar groups and the top face is exclusively hydrocarbon like Bile salts emulsify fats by forming micelles m which the fats are on the inside and the bile salts are on the outside The hydrophobic face of the bile salt associates with the fat that is inside the micelle the hydrophilic face is m contact with water on the outside... 

FIGURE 7.12 Cholic acid. Its 11 chirality centers are those carbons at which stereochemistry is indicated in the structural drawing at the left. The molecular model at the right more clearly shows the overall shape of the molecule. 

Cholanic acid C24H40O2, a monobasic saturated acid containing four hydroaromatic rings, is the parent substance of the two natural acids, which are its trihydroxy- and dihydroxy-derivatives. It is very highly probable that the following structural formula for cholic acid is correct ... 

Cholesterol exists in large amounts in aminal plasma membranes and reinforces the membrane structure cholic acids on the other hand destroy the membrane structure (Van Dijck et al, 1976). Synthetic bilayers can incorporate cholesterol molecules in appreciable amounts ( 50%) and the bound cholesterol appears to be aligned perpendicular to the plane of the... 

The aggregation behavior of C21-DA salt in dilute electrolyte medium appears to resemble that of certain polyhydroxy bile salts (25,16). That C21-DA, with a structure quite different from bile acids, should possess solution properties similar to, e.g., cholic acid is not entirely surprising in light of recent conductivity and surface tension measurements on purified (i.e., essentially monocarboxylate free) disodium salt aqueous solutions, and of film balance studies on acidic substrates (IX) The data in Figure 3 suggest that C21-DA salt micelles Incorporate detergents - up to an approximate weight fraction of 0.5 -much like cholate Incorporates lecithin or soluble... 

In order to increase structural diversity and to create a polar domain in the cage-like interior of these steroid/peptide macrocycles, dihydroxylated diacid 127 was synthesized in two steps from cholic acid (126) and reacted with diisonitrile 110, paraformaldehyde, and isopropylamine to form macrocycle 128 and its head-head isomer (Scheme 26). 

In a first set of experiments [52], the methyl ester of cholic acid 66a (Structures 8) was reacted with diphenylketene (59a) in the presence and in the absence of catalysts [pyridine (50), concave pyridine 3r]. But in all experiments, only the equatorial group in 3-position could be acylated (66b). No functionalization of the axial OH-groups in 7- and 12-position was found (66c, 66d). 

Fig. 5.4.1 Chemical structures of bile acids (BAs) (reprinted from [2]). CA Cholic acid, CDCA chenodeoxycholic acid,...

Exercise 30-11 Assuming cholesterol has the following stereochemical configuration, draw a similar configurational structure for cholic acid (including the hydroxyl groups). 

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. 

K. Miki, A. Masui, N. Kasai, M. Miyata, M. Shibakami, K. Takemoto, New Channel-Type Inclusion Compound of Steroidal Bile Acid Structure of a 1 1 Complex between Cholic Acid and Acetophenone , J. Am. Chem. Soc., 110, 6594 (1988)... 

Miki, K., Masui, A., Kasai, N., Miyata, M., Shibakami, M., and Takemoto, K., New channel-type inclusion compound of steroidal bile acid. Structure of a 1 1 complex between cholic acid and acetophenone, J.Am. Chem. Soc. 110, 6594-6596 (1988). 

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