Aliphatic hydroxylation by highly purified liver microsomal cytochrome P-450. Evidence for a carbon radical intermediate.

The oxidation of norbornane by a reconstituted liver cytochrome P-450 system affords exoand endo-2-norborneol in a ratio of 3.4:1. The ratio ofese products was found to be 0.76:l when exo!exo,exo,exo-2,3,5,6-tetradueteronorbornane --was oxidized. Analysis of the mass spectra of the products from the deuterated hydrocarbon showed that 25% of the exo-norborneol contained four deuterium atoms whereas 9% of the endo-norborneol contained three deuterium atoms. These results, wm indicate a very large isotope effect (kH/kD = 11.521) and a significant amount of epimerization for the hydroxylation of norbornane by cytochrome P-450, suggest an initial hydrogen abstraction to give a carbon radical intermediate.