Side-chain functional groups, bile acid

Studies with endogenous bile acids have led to a physiological understanding of the function of bile acid and the enterohepatic circulation. The search for a deeper understanding of the molecular mechanism behind the affinity and for recognition of molecules by the bile acid carriers in both ileum and liver motivated groups to modify bile acids and to study the carrier affinity of these compounds. These modifications typically entail either the substitution of the hydroxyl groups at the 3, 7, or 12 positions by other functionalities, or the addition to or alterations at the C-17 side chain. 

Bile acids can be modified to many derivatives due to their unique molecular structures, as listed in Table 1. First, we can convert the functional groups at the side-chains from carboxylic acid to amide, alcohol, ester, and so on. Second, we can change the length of the side-chains by decreasing or increasing their methylene number. Third, we can regulate the direction of the hydroxyl groups of the skeletons at the axial or equatorial positions. 

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