Enzymes are powerful tools for synthetic chemistry not only because they can catalyze reactions with exceptional levels of reactivity, but also because they can be tuned using directed evolution to achieve high selectivity in situations that would be intractable for small-molecule catalysts. Enzyme engineering has also enabled the heme-dependent monooxygenase cytochrome P450BM3, to catalyze carbene transfer reactions between diazoesters and mild nucleophiles, a reaction type that is completely absent in nature. The focus of this proposal is to expand the synthetic utility of this methodology by using directed evolution of P450BM3 to develop carbene transfer catalysts that can synthesize biologically important molecular scaffolds that are difficult to access with existing methods.
The specific aims are: (1) to evolve P450BM3 variants to synthesize enantioenriched di- and triarylmethanes via asymmetric carbene insertion into N-H and O-H bonds; and (2) to extend the substrate scope to include electron-rich arenes and apply this methodology to the asymmetric synthesis of 3,3-disubstituted indole and ?,?-disubstituted glycine derivatives. The di- and triarylmethane motif is prevalent in numerous synthetic drug candidates, but is difficult t synthesize asymmetrically, partly because the area surrounding the chiral center has local symmetry that makes enantioselection difficult for small-molecule catalysts. The use of enzymes is advantageous, however, because an enzyme's active site creates a chiral environment that interacts with the entire structure of the substrate. In the second aim, the application of carbene transfer to electron-rich arenes constitutes a novel approach to enzyme-catalyzed C-C bond formation, which is usually accomplished with aldolases. The indole and glycine derivatives that we propose to make with this method are found in numerous bioactive natural and synthetic compounds, and thus there is continued demand for new methods to synthesize these structures asymmetrically. We will characterize the enzymes that result from this project with a variety of techniques, such as X-ray crystallography, in order to elucidate the mechanisms of selectivity and assist in the future development of enzyme catalysts for other reaction types.

Public Health Relevance

Di- and triarylmethanes, 3,3-disubstituted indoles, and ?,?-disubstituted glycines are all motifs that are present in biologically active molecules. If such compounds are to be applied as drugs, however, then there must be methods that can synthesize these structures efficiently and in high enantiopurity. The proposed research will develop enzymes that can synthesize drug-like compounds containing these structural motifs, thus enabling the synthesis of new compounds for the treatment of disease.

Agency
National Institute of Health (NIH)
Institute
National Institute of General Medical Sciences (NIGMS)
Type
Postdoctoral Individual National Research Service Award (F32)
Project #
5F32GM117635-02
Application #
9258319
Study Section
Special Emphasis Panel (ZRG1-F04A-W (20)L)
Program Officer
Lees, Robert G
Project Start
2016-03-01
Project End
2018-02-28
Budget Start
2017-03-01
Budget End
2018-02-28
Support Year
2
Fiscal Year
2017
Total Cost
$57,066
Indirect Cost
Name
California Institute of Technology
Department
Engineering (All Types)
Type
Schools of Arts and Sciences
DUNS #
009584210
City
Pasadena
State
CA
Country
United States
Zip Code
91125
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Loskot, Steven A; Romney, David K; Arnold, Frances H et al. (2017) Enantioselective Total Synthesis of Nigelladine A via Late-Stage C-H Oxidation Enabled by an Engineered P450 Enzyme. J Am Chem Soc 139:10196-10199
Romney, David K; Murciano-Calles, Javier; Wehrmüller, Jöri E et al. (2017) Unlocking Reactivity of TrpB: A General Biocatalytic Platform for Synthesis of Tryptophan Analogues. J Am Chem Soc 139:10769-10776
Murciano-Calles, Javier; Romney, David K; Brinkmann-Chen, Sabine et al. (2016) A Panel of TrpB Biocatalysts Derived from Tryptophan Synthase through the Transfer of Mutations that Mimic Allosteric Activation. Angew Chem Int Ed Engl 55:11577-81
Herger, Michael; van Roye, Paul; Romney, David K et al. (2016) Synthesis of ?-Branched Tryptophan Analogues Using an Engineered Subunit of Tryptophan Synthase. J Am Chem Soc 138:8388-91