ABSTRACT
Electrochemical cholesterylation of various sugars with cholesteryl diphenylphosphate was studied. The reaction afforded mono-, di-, tri-, and tetra-cholesterylated products using equivalent amounts of the reagent. The reactions turned out to be completely stereoselective with respect to both sugar and steroid but only partially regioselective - primary and anomeric hydroxyl groups in sugars were the most reactive ones while no substantial differences in reactivity was found for different secondary hydroxyl groups.
Subject(s)
Cholesterol/chemistry , Cholesterol/metabolism , Electrochemistry/methods , Glycosylation , Molecular Structure , StereoisomerismABSTRACT
3α,5α-Cyclocholestan-6ß-yl alkyl and aryl ethers were proved to be efficient cholesteryl donors in the electrochemical synthesis of glycoconjugates. 3α,5α-Cyclocholestan-6ß-ol (i-cholesterol) and its tert-butyldimethylsilyl ether can also be used for this purpose. The i-cholesterol derivatives show similar reactivities to those of previously studied 3α,5α-cyclocholestan-6ß-thioethers.
ABSTRACT
Several derivatives of cholesterol and other 3ß-hydroxy-Δ(5)-steroids were prepared and tested as sterol donors in electrochemical reactions with sugar alcohols. The reactions afforded glycoconjugates with sugar linked to a steroid moiety by an ether bond. Readily available sterol diphenylphosphates yielding up to 54% of the desired glycoconjugate were found to be the best sterol donors.
Subject(s)
Electrochemical Techniques , Glycoconjugates/chemical synthesis , Sterols/chemistry , Glycoconjugates/chemistry , Molecular ConformationABSTRACT
A new electrochemical glycosylation method is presented. According to the method cholesterol and other 3beta-hydroxy-Delta(5)-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.
Subject(s)
Electrochemistry/methods , Glycosides/chemistry , Glycosides/chemical synthesis , Steroids/chemistry , Glycosylation , Molecular StructureABSTRACT
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 3beta-chloro, 3beta-acetoxy, or 3beta-acetylamino group were obtained.
