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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.

3α,5α-Cyclocholestan-6β-yl alkyl and aryl ethers were proved to be efficient cholesteryl donors in the electrochemical synthesis of glycoconjugates. 3α,5α-Cyclocholestan-6β-ol (i-cholesterol) and its tert-butyldimethylsilyl ether can also be used for this

The Hendrickson reagent is able to perform efficiently dehydrative glycosylation of 1-hydroxyglycosyl donors. The reaction occurs under mild conditions through an anomeric oxophosphonium intermediate detected by nuclear magnetic resonance. Further insight into the mechanism was gained by 18O labeling of anomeric OH.

A new electrochemical glycosylation method is presented. According to the method cholesterol and other 3β-hydroxy-Δ5-steroids can be selectively transformed to glycosides using non-activated sugars. The method is also useful for the synthesis of glycoconjugates with sugar linked to a steroid moiety by an ether bond.

It has been found that cholesterol undergoes direct electrochemical oxidation on platinum electrode in dichloromethane. Voltammetric measurements show that the process is controlled by the rate of electron transfer and the height of the oxidation peak is linear vs. concentration of cholesterol. Preparative electrolysis with separated cathodic and anodic compartments afforded dicholesteryl ether in a relatively high material yield. Depending on electrolysis conditions (composition of supporting electrolyte and electrolytic cell construction) various by-products with a 3β-chloro, 3β-acetoxy, or 3β-acetylamino group were obtained.

Treatment of 3β-hydroxyl-5-Δ steroids with anhydrous FeCl 3 in CH2Cl2 afforded reasonable yields of the corresponding alkyl chlorides with a retention of configurations. The structures of the chlorine-exchanging products were determined by NMR and HRMS spectra. The absolute configurations were confirmed by X-ray crystal analysis of 3β-chloro-androst-5-en-17-one. The generality and scope of the reaction were also investigated.

A series of 3β-arylcholestenes were synthesised by Friedel-Crafts reaction of cholesterol with arenes catalysed by montmorillonite K-10.

Reaction of cholesterol with silica bound FeCl3 resulted in a mixture of 3β-cholesteryl chloride and dicholesteryl ether.5-cholestene and hydroxy-and halogeno-substituted cholestane derivatives gave on heating at 100 deg C with this reagent a 1:1 mixture of 20-epimeric diacholestenes.The 20(R)-isomer gave with meta-chloroperbenzoic acid 20(R)-α-epoxide, while the 20(S)-gave a mixture of 20(S)-α- and 20(S)-β-epoxides.5α,6β-Dihydrocholestane reacted with the FeCl3/SiO2 under milder conditions (50 deg C) to give 6β-hydroxy-20(R)-diacholestene, which was converted to the 20(R)-diacholestene.

The glycosylation of cholesterol, β-sitosterol, 28-O-acetylbetulin, and betulin with acylated glycosyl halides in the presence of Hg(OAc)2, Hg(CN)2, CdCO3, Ag2O, Ag2CO3, and HgO + HgBr2 usually gives acylated αβ-glycosides accompanied by acetates, ethers, and bromo and unsaturated derivatives of the initial alcohols.The use of Hg(CN)2 gave mainly β anomers (40-87percent), whereas α anomers preponderated when Hg(OAc)2 was the catalyst.When there was a deficiency of hydrogen halide acceptor and in the presence of the acidic catalyst HgBr2*HBr, the β anomer, produced initially, underwent anomerisation.Cholesteryl α-D-glucopyranoside tetra-acetate (48percent) was obtained by anomerisation of the β anomer.