Journal of Lipid Research, Vol 20, 935-940, Copyright © 1979 by Lipid Research, Inc.
Configuration at C-25 in 3 alpha, 7 alpha, 12 alpha-trihydroxy-5 beta- cholestan-26-oic acid by X-ray crystallography
AK Batta, G Salen, JF Blount and S Shefer
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.