Directed evolution of nonheme iron enzymes to access abiological radical-relay C(sp ³ )−H azidation

Abstract

We report the reprogramming of nonheme iron enzymes to catalyze an abiological C(sp3)‒H azidation reaction through iron-catalyzed radical relay. This biocatalytic transformation uses amidyl radicals as hydrogen atom abstractors and Fe(III)‒N3intermediates as radical trapping agents. We established a high-throughput screening platform based on click chemistry for rapid evolution of the catalytic performance of identified enzymes. The final optimized variants deliver a range of azidation products with up to 10,600 total turnovers and 93% enantiomeric excess. Given the prevalence of radical relay reactions in organic synthesis and the diversity of nonheme iron enzymes, we envision that this discovery will stimulate future development of metalloenzyme catalysts for synthetically useful transformations unexplored by natural evolution.

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“…The future of enzymatic electrosynthesis should seek to adapt this machinery to reactions and conditions beyond the realm of biology. Directed evolution [183–184] has proven invaluable to the design of new biocatalysts for abiological reactivity, and adaptation of these methods to bioelectrosynthetic systems could open the door to a renaissance of novel synthetic reactivity. Utilizing directed evolution to design the active site, access new reactivity, or even impart redox behavior to non‐redox enzymes represents an exciting avenue for future reaction design, well outside the scope of what is presently possible.…”

Bioelectrocatalytic Synthesis: Concepts and Applications

“…The future of enzymatic electrosynthesis should seek to adapt this machinery to reactions and conditions beyond the realm of biology. Directed evolution [183][184] has proven invaluable to the design of new biocatalysts for abiological reactivity, and adaptation of these methods to bioelectrosynthetic systems could open the door to a renaissance of novel synthetic reactivity. Utilizing directed evolution to design the active site, access new reactivity, or even impart redox behavior to non-redox enzymes represents an exciting avenue for future reaction design, well outside the scope of what is presently possible.…”