Remote functionalization of i-cholesterol

Abstract

i-Cholestan-6β-yl benzophenone derivatives were prepared in order to remote functionalize the unactivated carbon-hydrogen bond of i-cholesterol selectively with the benzophenone chromophore on the β-face. Decomposition was the major photoreaction, when these compounds in purified benzene solution ($10^{-3}-10^{-4}M$) were irradiated with 254 nm and 300 nm UV light. With 350 nm UV light, excited triplet benzophenone attacked the intramolecular hydrogen atoms. The major photoproducts were checked by TLC and isolated by preparative TLC or silica gel column chromatography followed by high performance liquid chromatography using μ-Bondapak CN column. The structure of photoproducts were determined by the FT-NMR, UV, IR and mass spectra. The major photoproduct of m-benzoylbenzoate of ethylene glycol i-cholesteryl ether(I) was identified to be the $C_{18}$-benzocarbonyl carbon bridged compound and other photoproducts reveal that the double bond was formed on the i-cholesterol.