Preparation of radiolabelled 3α‐hydroxy‐7‐keto‐5β‐cholanic acid and its glycine and taurine conjugates

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Abstract
3α‐Hydroxy‐7‐keto‐5β‐cholanic acid has been prepared from cholic acid by a route which allowed introduction of 3H into positions 11 and 12 of the steroid C ring. Labelling with 14C was done by halodecarboxylation and resynthesis of the carboxyl function with 14C cyanide. The conjugates of both 3H‐ and 14C‐labelled compounds with glycine and taurine were prepared. 14C‐labelled compounds were prepared by degradation of the carboxyl‐containing side chain to the norchloride, which was used to prepare the homologous 14C‐containing nitrile. Hydrolysis afforded the acid in good yield. 3H was introduced into the C ring of the steroid nucleus by dehydration of 3α,12α‐dihydroxy‐7‐keto‐5β‐cholanic acid to the Δ11‐alkene which was catalytically tritiated. Physical and spectral data are presented to characterize the new compounds and TLC methods for purification are reported.