title: Configuration at C-25 in 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholestan-26-oic acid by X-ray crystallography.
abstract: The two diastereoisomers at carbon-25 of 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta-cholestan-26-oic acid, a key intermediate in the biosynthetic pathway of cholic acid, were obtained in pure form by a combination of fractional crystallization and thin-layer chromatography. The configuration at C-25 of these two isomers was established by X-ray crystallography as 25S for one diastereoisomer (mp 199-201 degrees C) and 25R for the other (mp 180-182 degrees C). These findings permit us to determine, unequivocally, the configuration of this naturally occurring C27-bile acid in man and other animals and to establish the stereospecificity of the microsomal and mitochondrial omega-hydroxylation pathway for the side-chain oxidation of cholesterol to bile acids.
mesh_terms: D002777:Cholestanols / Q000302:isolation & purification; D002849:Chromatography, Gas; D002855:Chromatography, Thin Layer; D008968:Molecular Conformation; D013237:Stereoisomerism; D013329:Structure-Activity Relationship; D014961:X-Ray Diffraction
chemical_list: D002777:Cholestanols