Cholesterol, trityl ether

Cholestenone, labelled with C , III, 233 Cholesterol, trityl ether, III, 86 Cholic acid, phytochemical reduction of, IV, 92... 

The simple alcohols whose trityl ethers have been prepared by treatment with trityl chloride and pyridine include, in addition to primary alcohols, 2-propanol, cyclohexanol, Z-menthol, d-borneol, and cholesterol. Trityl ethers involving the secondary hydroxyl group in glycerol are also known. - There can be no doubt, therefore, that secondary as well as primary hydroxyl groups react with trityl chloride in pyridine. 

In the early 1970s, Barton et al. published the results of their woik on the oxidation of acetals and ethers by hy de transfer. o They observed that substituted benzyl ethers and benzyloxy carbonates, on brief exposure to trityl tetrafluoroborate in dichloromethane at 0 C followed by aqueous work-up, afforded go( yields of the parent alcohols together with the corresponding bennldehydes. Undw the same conditions, the tetrahydropyranyl ether of cholesterol was also efficiently deprotected. A mechanism was proposed which involved an initial hydrogen abstraction, followed by quenching of the resulting stabilized cation by water (Scheme 6). 

---