Olefin Cyclopropanation via Carbene Transfer Catalyzed by Engineered Cytochrome P450 Enzymes

Putting a C in Cytochrome Cytochrome P450 enzymes oxidize hydrocarbons using a highly reactive iron oxo intermediate. Much research has focused on tuning the protein structure to broaden the range of hydrocarbons that can be functionalized. Coelho et al. (p. 307 , published online 20 December; see the Perspective by Narayan and Sherman ) substituted a carbene source for the oxygen to make a P450 mutant a cyclopropanation catalyst whereby a carbon fragment is transferred in place of oxygen. Though carbene activation by iron is chemically analogous to the native oxygen activation pathway, the overall reaction is completely different from any known enzymatic transformation.