Differentiation between the 25R- and 25S-isomers of 5 beta-cholestane-3 alpha, 7 alpha, 26-triol by 13C NMR spectroscopy.

Abstract

This study was designed to examine whether 13C nuclear magnetic resonance (NMR) spectroscopy can be used to differentiate between the 25R and 25S diastereoisomers of 5 beta-cholestane-3 alpha, 7 alpha, 26-triol, a key intermiediate in the biosynthetic pathway of chenodeoxycholic acid. Chemical shift values were assigned to the individual carbon atoms with the help of model compounds and multiplicity in the single-frequency off-resonance decoupled spectra. It was found that the corresponding carbons 1-20 afforded identical chemical shifts for both compounds, whereas five of the remaining side-chain carbons gave observed shift differences of 0.05-0.20 ppm. Thus 13C NMR can be used as an additional tool to distinguish between the two 5 beta-cholestanetriols isomeric at C-25.