Next, we were interested in understanding the denitration step of the reaction. While we propose a mechanism where the alkyl radical reacts with the nitronate to form the unstable radical anion, which rapidly undergoes mesolytic cleavage, we recognized the possibility of a two-step mechanism where the coupled nitroalkane is included in a redox-neutral process. The coupled nitroalkane intermediate is a substrate for reductive denitration in this scenario. To probe this possibility, we considered the reaction using nitromethylbenzene (2l), which under standard photoenzymatic conditions forms a 1:1 mixture of cross-coupling product 18 (28% yield) and compound 40 retaining a NO2 group (29% yield) (Fig. ). When the nitroalkane product 40 is resubjected to the reaction conditions, no cross-coupling product 18 was observed, indicating that the nitroalkane is not an intermediate in the denitrative coupling reaction. As nitro radical anions are proposed intermediates in non-enzymatic radical reactions but are not reported to undergo mesolytic cleavage, we postulate the protein facilitates the mesolytic cleavage event.