Reaction Mechanism of a Nonheme Iron Enzyme Catalyzed Oxidative Cyclization via C-C Bond Formation

A complementary study including design of mechanistic probes, biochemical assays, model analysis, and liquid chromatography coupled mass spectrometry was conducted to establish the reaction mechanism for a nonheme iron enzyme catalyzed (?)-podophyllotoxin formation. Our results indicate that the originally proposed hydroxylated intermediate is unlikely to be involved in this reaction. Instead, the formation of benzylic radical/carbocation intermediate can be utilized to trigger the C-C bond formation to construct the C-ring of (?)-podophyllotoxin.