Biomimetic iron porphyrin-catalysed oxidation of cyclopentaphenanthrenones
Peracid oxidation of two cyclopentaphenanthrenes occurs at the chemically active K-region to yield the cis-6,7-epoxides.Biomimetic oxidation of these compounds as substrates in an iron porphyrin-iodosylbenzene system produces similary high yields of these oxidation products.The steric hidrance around the periphery of the porphyrin has been increased to the extent that access of the K-region to the active iron centre is impossible.However, these steric constrains do not encourage stereoselective substrate oxidation at the more accessible terminal rings, the site of attack with the natural enzymatic system.Methoxy substitution around the porphyrin periphery produces a highly effective catalyst for these substrates.Cyclohexene oxidation is not so encouraged, suggesting a 'pocket' attractive to the cyclopentaphenanthrenones.