Anodic electrochemical oxidation of cholic acid

Regioselectivity in the anodic electrochemical oxidation of cholic acid wit h different anodes is described. The oxidation with PbO2 anode affords the dehydrocholic acid in quantitative yield after 22 h. 3 alpha ,12 alpha -Dih ydroxy-7-oxo-5 beta -cholan-24-oic acid (59%) and 3 alpha -hydroxy-7, 12-di oxo-5 beta -cholan-24-oic acid (51%) are obtained stopping the reaction at lower time. The rate of the OH-oxidation is C-7 > C-12 > C-3. The electro-o xidation with platinum foil anode gives selectively the 7-ketocholic acid i n 40% yield. On the other hand, the graphite plate anode, varying the react ion conditions, produces selectively the dehydrocholic acid in quantitative yield or the 3 alpha ,12 alpha -dihydroxy-7-oxo-5 beta -cholan-24-oic acid (96%) while the 3 alpha ,7 alpha -dihydroxy-12-oxo-5 beta -cholan-24-oic a cid (34%) is obtained together with the other oxo acids. (C) 2001 Elsevier Science Inc. All rights reserved.