Chromatographic separation of putative precursors of cholestanol
This paper describes convenient syntheses for labeled and unlabeled cholest-5-en-3-one, cholest-4-en-3-one, epicholesterol, cholest-4-en-3 beta-ol, and cholest-4-en-3 alpha-ol. The thin-layer chromatography, high-performance liquid chromatography, and gas-liquid chromatography of these compounds and of cholestanol and epicholestanol are also described. The synthesized compounds are potential precursors in the biosynthesis of cholestanol in mammals.
Sterol metabolism. XLI. Cholesterol A-ring autoxidations
Abstract Chromatographic and spectral evidence is adduced for the presence of cholest-5-en-3-one, cholest-4-en-3-one, and cholest-4-ene-3,6-dione in samples of cholesterol aged naturally in air or subjected to irradiation in air by 60 Co gamma radiation. These findings establish an additional mode of air oxidation of cholesterol to A-ring 3-ketones. Moreover, the oxidation by air of cholest-5-en-3-one induced by 60 Co gamma radiation yielded cholest-4-en-3-one, cholest-4-ene-3,6-dione, and the epimeric 3-oxocholest-4-ene-6-hydroperoxides. Cholest-4-en-3-one was not altered by irradiation in air, nor was cholesterol isomerized to cholest-4-en-3β-ol upon irradiation. From these observations it is deduced that the radiation-induced A-ring dehydrogenation of cholesterol yields initially cholest-5-en-3-one which upon isomerization yields cholest-4-en-3-one not further oxidized and which by a second oxidation yields the epimeric 3-oxocholest-4-ene-6-hydroperoxides which decompose to cholest-4-ene-3,6-dione.
Autoxidation products from cholesterol
Thin-layer chromatography and gas-liquid chromatography were used to separate and identify products from the autoxidation of cholesterol. Both cholesterol-a-epoxide and 1,4-cholestadien-3-one were found. In addition, several other compounds, identified also by previous workers, were shown to be present. Autoxidation in bulk was quite slow at 82C, requiring several weeks for development of detectable quantities of decomposition products. The reaction could be accelerated by irradiation with ultraviolet light or by heating the sterol above its melting point.