11 beta,20-dihydroxy-3-oxopregna-4,17(20)-dien-21-al: an intermediate in the biological 17-dehydroxylation of...

The role of 11 beta,20-dihydroxy-3-oxopregna-4,17(20)-dien-21-al (F enol aldehyde) as an intermediate in the biological conversion of cortisol to a 17-deoxy-21-oic acid was studied in vitro with mouse liver as the source of enzyme. The substrate, [1,2-3H]F enol aldehyde, was synthesized and found to contain cis and trans isomeric forms in a ratio of approximately 3:1. Tritium labeled F enol aldehyde was incubated with mouse liver homogenates. The metabolic products were analyzed by TLC and HPLC. 11 beta,20-Dihydroxy-3-oxopregna-4-en-21-oic acid, a 17-deoxy-21-oic acid, was identified as a quantitatively significant metabolite of the cis isomer. Metabolic conversion of the trans isomer to acid metabolites did not occur. The results are consistent with our hypothesis that the metabolic 17-dehydroxylation of cortisol requires an enol aldehyde intermediate and indicate that the conversion of the enol aldehyde to hydroxy acid is stereospecific.