Abstract
Conditions are described for the preparation of cholesterol with 17O and 18O labels from i-cholesteryl methyl ether using minimal amounts of isotopically enriched water. Optimum yields employed trifluoromethanesulfonic acid as catalyst in 1,4-dioxane at room temperature with 5 equivalents of water. An isotopic enrichment >90% of that of the water used for the reaction could be attained. Tetrafluoroboric acid could also be used as catalyst, at the expense of a lower overall reaction yield. Byproducts from the reaction included dicholesteryl ether, methyl cholesteryl ether, compounds formed by ether hydrolysis, and olefins arising from elimination reactions. Reactions in tetrahydrofuran yielded significant amounts of cholesteryl ethers formed by reaction with alcohols arising from hydrolysis of the solvent.
Highlights
Cholesterol is one of the most important natural sterols because of its role in modifying the properties of cell membranes (Róg and Vattulainen, 2014) and the link between in vivo transport of cholesterol in plasma lipoprotein fractions and disease states related to dietary intake of cholesterol (Birner-Gruenberger et al, 2014)
From the data it is apparent that trifluoromethanesulfonic acid produced by some margin the greatest yield of cholesterol, at the expense of having exchangeable oxygen
Tetrafluoroboric acid, on the other hand, gave a poor yield of cholesterol but, being a hydracid, did offer the potential for preparing cholesterol with an isotopic enrichment matching that of the water used for its preparation
Summary
Cholesterol is one of the most important natural sterols because of its role in modifying the properties of cell membranes (Róg and Vattulainen, 2014) and the link between in vivo transport of cholesterol in plasma lipoprotein fractions and disease states related to dietary intake of cholesterol (Birner-Gruenberger et al, 2014). A convenient route to cholesterol analogues has been described in the literature, involving acid-catalyzed reaction of the commercially available i-cholesteryl methyl ether (1) with water (Scheme 1). This reaction has been known for some time and generally gives good yields of cholesterol (2) when water is present in large excess (Chu and Li, 2000; Riegel et al, 1946; Steele and Mosettig, 1963; Smith et al, 1993; Nicotra et al, 1981). We investigate the ability of different acids to catalyse the reaction, and establish conditions that use minimal amounts of water and catalyst
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
