STEREOSELECTIVE SYNTHESIS OF 3-BETA-BILE ACID-DERIVATIVES FROM THE 3-ALPHA-ANALOG

The stereoselective transformation from the commonly occurring 3 alpha-bile acids and derivatives to their 3 beta-analogs is important for certain applications of these amphiphilic natural compounds, especially in the preparation of polymers. We report here the stereoselective conversion of methyl cholate to its 3 beta-hydroxy epimer by the use of the Mitsunobu reaction and to a 3 beta-amino cholic acid analog via a tosylation followed by a S(n)2 displacement with sodium azide and a hydrogenation of the azide group with overall yields of 86% and 78%, respectively. The preparation of the methacrylate and methacrylamide derivatives from these compounds is also described.