Cholestanol esters, remote

The remote photochemical oxidation by means of a rigid benzophenone reagent attached to a hydroxy-group" has been further investigated with the cholestanol ester (314) as well as other steroid molecules (see Chapter 1, ref. 360). " ... 

Remote chlorination (6, 298-300). Breslow has extended his remote functionalization of steroids to a double functionalization at C, and Cn of cholestanol. Thus the ester (2) of cholestanol, prepared from a p-iodophenylnicotinic acid, when treated with 1 (1.2 equiv.) is chlorinated selectively at C9 chlorination of the same ester with 3 equiv. of C6H5IC12 results in chlorination at C9 and at C17 in quantitative yield. The para-iodo group of the ester plays an important role in this remote chlorination. 

Breriow et air have since extended this remote halogenation to the conversion of /3-cholestanol into androsterone (11) by selective halogenation at C17. In order to place the internal chlorinating reagent in proximity to the Civposition, 30-cholestanol is converted, with inversion, into the ester (7). Irradiation of (7) and iodobenzene dichloride gives an intermediate Cn-chloro compound that is... 

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