Structural and Stereochemical Aspects of Base-Catalyzed Double Bond Isomerization of Sterols with Unsaturated Side Chains

Article abstract of DOI:10.1021/jo00143a025

A careful analysis of the N-lithioethylenediamine-catalyzed isomerization of 22-, 23-, and 24-methylenecholesterol demonstrated the existence of subtle factors which are responsible for the kinetically and thermodynamically preferred products.In general, the results can be related to the anticipated energy preferences of the intermediate carbanions.Through the use of 1H and 13C NMR spectroscopy the configuration of the various double bond isomers could be established.Since all major products are readily separated by HPLC, such base-catalyzed isomerization offers a convenient synthetic route to a variety of stereochemically pure sterol olefins, which either have been found in the marine environment or may be detected in the future.