The synthesis of (22R)-22-hydroxycholesterol, featuring formation of three contiguous chiral centers (C-17, 20, and 22) in a single step by the use of a 6-endo α-silyl radical-mediated cyclization is presented. Additionally, an interesting protiodesilylation used to activate a cyclic siloxane towards C–Si bond oxidation, and a modified, bulky aryl thionocaronate reagent for regioselective diol-monodeoxygenation are described.
![O-(2,6-dimethoxyphenyl) O-((3S,8S,9S,10R,13S,14S,16R,17R)-17-((2S,3R)-3-hydroxy-6-methylheptan-2-yl)-10,13-dimethyl-3-((tetrahydro-2H-pyran-2-yl)oxy)-2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthren-16-yl) carbonothioate Structure](https://image.chemsrc.com/caspic/412/128292-46-6.png)