Fatty acid steryl, stanyl, and steroid-esters by esterification and transesterification in vacuo using Candida rugosa lipase as catalyst

Sterols (sitosterol, cholesterol, stigmasterol, ergosterol, and 7-dehydroch olesterol) and sitostanol have been converted in high to near-quantitative yields to the corresponding long-chain acyl esters via esterification with fatty acids or transesterification with methyl esters of fatty acids or tri acylglycerols using lipase from Candida rugosa as biocatalyst in vacuo (20- 40 mbar) at 40 degreesC. Neither organic solvent nor water is added in thes e reactions. Under similar conditions, cholesterol has been converted to ch olesteryl butyrate and steroids (5 alpha -pregnan-3 beta -ol-20-one or 5-pr egnen-3 beta -ol-20-one) have been converted to their propionic acid esters , both in moderate to high yields, via transesterification with tributyrin and tripropionin, respectively. Reaction parameters studied in esterificati on include the temperature and the molar ratio of the substrates as well as the amount and reuse properties of the C, rugosa lipase. Lipases from porc ine pancreas, Rhizopus arrhizus, and Chromobacterium viscosum are quite ine ffective as biocatalysts for the esterification of cholesterol with oleic a cid under the above conditions.