Enantioconvergent benzylic C(sp 3 )‒N coupling with a copper-substituted nonheme enzyme

Copper-catalyzed radical C(sp 3 )‒N coupling has become a major focus in synthetic catalysis over the past decade. However, achieving this reaction manifold by using enzymes has remained elusive. In this study, we introduce a photobiocatalytic approach for radical benzylic C(sp 3 )‒N coupling using a copper-substituted nonheme enzyme. Using rhodamine B as a photoredox catalyst, we identified a copper-substituted phenylalanine hydroxylase that facilitates enantioconvergent decarboxylative amination between N -hydroxyphthalimide esters and anilines. Directed evolution remodeled the active site, resulting in high enantioselectivities for most substrates. On the basis of molecular modeling and mechanistic studies, we propose that the enzyme accommodates a copper-anilide complex that reacts with a benzylic radical. This study expands the scope of non-natural biocatalytic transition metal catalysis to copper-catalyzed radical coupling.