Steroid esters of benzophenonecarboxylic acids, benzophenoneacetic acids, and homologs are prepared. Circular dichroism studies indicate that in some of these compounds the benzophenone chromophore can pack on the steroid; these data and phosphorescence lifetime data are interpretable in terms of conformation predicted from molecular models. On irradiation, various of these esters undergo intramolecular attack by the attached benzophenone on the steroid hydrogens. The products can be predicted from molecular models, and considerable control of steroid functionalization can be achieved by appropriate choice of reagent. Controls establish that this photochemistry is directed mainly by the geometry of the ester. Starting with 3a-cholestanol, appropriate esters can direct a photochemical dehydrogenation exclusively into ring D, at the opposite end of the molecule, leading to useful remote functionalization.

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