Photo-oxygenation of lanosteryl acetate

3β-Acetoxylanost-8-ene has been photo-oxygenated in the presence of a dye and p-nitrobenzenesulphonyl chloride to yield, among other products, the Criegee rearrangement product 3β-acetoxy-8,9-epoxy-8,9-secolanosta-7,9(11)-diene (XV; R = Ac) and 3β-acetoxy-7α-bydroperoxylanost-8-ene (VII; R = Ac). These ARE Thought to arise from 3β-acetoxy-9α-hydroperoxylanost-7-ene (II; R = Ac); their transformations are reported. The bridged cyclodeca-1,6-diene system in (XV) takes part in transannular reactions.