Analysis of mixtures of stigmasterol, stigmastanol and sitosterol

Isolation of brassicasterol from steam deodorizer distillate of rapeseed oil: Some properties of its acetate tetrabromide and its reduction to 22,23-dihydrobrassicasterol

Brassicasterol (5,22-ergostadien-3β-ol) was isolated from the steam deodorizer distillate of rapeseed oil and purified by acetylation, bromination, chromatography on 20% AgNO3/SiO2 columns and hydrolysis. Brassicasteryl and stigmasteryl (5,22-stigmastadien-3β-ol) acetates were brominated, and the yields of products and solubilities of the tetrabromides from the two steryl acetates were compared. Stigmasteryl acetate tetrabromide is less soluble than the corresponding brassicasteryl derivative; yet the latter precipitates selectively during bromination of a mixture of the two steryl acetates. This is explained on the basis of the stereochemistry of the bromine atoms in the side chains of the two steryl acetate tetrabromides. Hydrogenation of brassicasteryl acetate over Raney nickel gave the 22,23-dihydro derivative in excellent yield. The latter was separated from small amounts of ergostanyl acetate on a 20% AgNO3/SiO2 column.

Titration of sterol double bonds with dibromopyridine sulfate

Cis and trans-22-dehydrocholesteryl acetates and cis and trans-22-cholesten-3beta-yl acetates were prepared and compared to delta22-phytosterylacetates by titration with dibromopyridine sulfate. The cholesterol derivatives absorbed close to the theoretical quantity of bromine (1 Br2 per double bond), whereas the delta22-C24-alkylated sterols consumed 0.14 to 0.23 Br2 in excess of the calculated values. This excess is attributed to the formation of additional unsaturation during bromination. delta7 and delta8(14)-sterols consume more than 2 and 3 moles Br2, respectively, which indicates that at least one or two new double bonds are formed in these molecules during the bromination step.

Purification of campesterol and preparation of 7-dehydrocampesterol, 7-campestenol and campestanol

Campesterol ([24R]‐24‐methyl‐5‐cholesten‐3β‐ol) was isolated from a soybean sterol mixture and purified on a small scale by column chromatography and on a large scale by crystallization from acetone to 97% purity. From this, 7‐dehydrocampesterol ([24R]‐24‐methyl‐5,7‐cholestadien‐3β‐ol) and campestanol ([24R]‐24‐methyl‐cholestan‐3β‐ol) were prepared. The acetates and benzoates of all four compounds also were obtained and compared to the corresponding members of the ergostane series.