IDENTIFICATION OF -3-ALPHA,7-ALPHA-DIHYDROXY-5-BETA-CHOLEST-24-ENOIC ACID AND -3-ALPHA,7-ALPHA,24-TRIHYDROXY-5-BETA-CHOLESTANOIC ACID AS INTERMEDIATES IN THE CONVERSION OF 3-ALPHA,7-ALPHA-DIHYDROXY-5-BETA-CHOLESTANOIC ACID TO CHENODEOXYCHOLIC ACID IN RAT-LIVER HOMOGENATES

Studies of chemical structure of the intermediates in the biosynthetic sequence between 3 alpha,7 alpha-dihydroxy-5 beta-cholestanoic acid ( DHCA) and chenodeoxycholic acid have been undertaken. Radiolabeled DHC A was incubated with a rat liver preparation. The reaction products we re converted to the p-bromophenacyl esters, and analyzed by reversed-p hase high performance liquid chromatography. Under the conditions used , the radioactivity was found in (24E)-3 alpha, 7 alpha-dihydroxy-5 be ta-cholest-24-enoic acid (31%) and (24R, 25S)-3 alpha,(7 alpha,(24-tri hydroxy-5 beta-cholestanoic acid (7%) along with the starting material (62%). Neither the 24Z isomer of the alpha,beta-unsaturated bile acid nor the other three isomers of the beta-hydroxy bile acid were detect ed. The findings support the proposed pathway for the side chain cleav age in chenodeoxycholic acid biosynthesis, which is thought to be iden tical to that of cholic acid biosynthesis.