Photochemical Functionalizations by Tethered Benzophenones

In a full paper describing this and other functionalizations of steroids tethered to benzophenones [34], it was revealed that the 3a-cholestanol ester 8 of benzophenone-4-acetic acid afforded, after hydrolytic removal of the tether, A -3a-cholestenol 4 as the product along with the diphenylcarbinol from reduction of the benzophenone. The short tether did not permit insertion into the C-14-H bond, so after the oxygen atom of excit- 

The products found in these studies indicated attack on the steroid at a predictable distance from the attachment point, except with highly flexible tethers, but the tether still permitted attack along an arc pivoting around the attachment point. This is a problem that was addressed in later work, to be described. 

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