Directed Evolution: Bringing New Chemistry to Life

Abstract

Tailor-made: Discussed herein is the ability to adapt biology's mechanisms for innovation and optimization to solving problems in chemistry and engineering. The evolution of nature's enzymes can lead to the discovery of new reactivity, transformations not known in biology, and reactivity inaccessible by small-molecule catalysts.

Keywords: biocatalysis; enzymes; heme proteins; protein engineering; synthetic methods.

Figure 1

A B. subtilis globin variant, engineered by directed evolution, catalyzes the cyclopropanation of 3,4‐difluorostyrene to make the desired stereoisomer of a ticagrelor precursor with high selectivity and yield.7a

Figure 2

A) Chiral Si−C bond formation catalyzed by a laboratory‐evolved variant of Rhodothermus marinus cytochrome c.10 The three amino acid residues that were mutated to increase this abiological activity include the methionine axial ligand (M100). B) The enzyme catalyzes formation of different organosilane products with high enantiomeric excess from silane and diazo substrates.

Figure 3

Production of chiral organoboranes by E. coli expressing Rhodothermus marinus cytochrome c.11 The bacterial catalyst uses borane‐Lewis base complexes and diazo reagents to construct boron‐containing carbon stereocenters efficiently and selectively in cells by carbene B−H insertion. The bioconversion can be conducted readily on gram scale, and the enantio‐preference of borylation was switched to give either enantiomer of the organoborane products.

Figure 4

A cytochrome P450 anti‐Markovnikov oxygenase.12 A) Competing reaction pathways for P450‐catalyzed oxo transfer to alkenes. The concerted epoxidation pathway is favored over the stepwise anti‐Markovnikov oxidation consisting of oxo transfer followed by an (enantioselective) 1,2‐hydride migration. B) Ten rounds of directed evolution accumulated 12 amino acid mutations, many of which are distant from the active site. C) aMOx can be combined with established (bio)catalysts for various challenging anti‐Markovnikov alkene functionalization reactions.