Synthesis of 5 beta-cholestane-3 alpha,6 beta,7 alpha,25,26-pentol and identification of a novel bile alcohol, alpha-trichechol, present in the West Indian manatee bile

In order to confirm the structure of alpha-trichechol, the major bile alcohol of the West Indian manatee, chemical synthesis of 5 beta-cholestane-3 alpha,6 beta,7 alpha,25,26-pentol was carried out. The chain of 3 alpha-hydroxy-5 beta-chol-6-en-24-oic acid was elongated by an Arndt-Eistert reaction to form 3 alpha-hydroxy-26,27-dinor-5 beta-cholest-6-en-25-oic acid. The unsaturated C25 bile acid was converted into 3 alpha,6 beta,7 alpha-trihydroxy-25-homo-5 beta-cholan-25-oic acid by 1,2-glycol formation of the delta 6-double bond. The acetylated derivative of the trihydroxy C25 bile acid was then converted into 3 alpha,6 beta,7 alpha,26-tetraacetoxy-27-nor-5 beta-cholestan-25-one by successive treatment with thionyl chloride, diazomethane, and acetic acid. A Grignard reaction of the 25-oxo compound with methylmagnesium iodide afforded the desired bile alcohol, 5 beta-cholestane-3 alpha,6 beta,7 alpha,25,26-pentol. By direct comparison with the synthetic pentahydroxy bile alcohol, the structure of the naturally occurring alpha-trichechol was determined to be 5 beta-cholestane-3 alpha,6 beta,7 alpha,25,26-pentol.