Steroids Part 22. Photochemistry of 5,6-epoxy-4,4-dimethylcholestan-3-ones and 5,6-epoxy-17-hydroxy-4,4-dimethylestran-3-ones

Abstract

The β,γ-epoxy ketones (5), (6), (7), and (8) photolyse essentially as the equivalent ketones, e.g. (9), in methanol in that little evidence of epoxide cleavage is detected and the major products are the methyl 5-isopropyl-4-nor-3,5-secoesters. In ether, the 3-keto 5β,6β-epoxide (8) photodecarbonylates via a double hydrogen shift (C-2 → C-4 and C-1 → C-2) and it issuggested that epoxide photocleavage in β,γ-epoxy ketones may be subject to stereoelectronic control.