Abstract
Producing enantioenriched molecules from racemic mixtures is essential for manufacturing. Traditional methods such as resolution, deracemization and enantioconvergent catalysis primarily involve separating or converting enantiomers without altering their structures, or functionalization of stereocentres at or proximal to functional groups. However, there are challenges in enantioselectively forging C–H bonds that are remote from functional groups via hydrogen atom transfer (HAT) with these methods. Here we introduce a strategy for the photoenzymatic stereoablative enantioconvergence of γ-chiral oximes using repurposed flavin-dependent ene-reductases. A photoinduced single-electron reduction of the γ-chiral oxime by an ene-reductase generates an iminyl radical, which then undergoes stereoablative 1,5-HAT at the γ-stereocentre. Subsequent chiral reconstruction through enzymatic HAT and spontaneous imine hydrolysis yields the γ-chiral ketone with high enantioselectivity. This work provides a robust method for remote stereoablative enantioconvergent HAT and broadens the synthetic utility of photobiocatalysis.
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Data availability
All data are available in the main text or the Supplementary Information. The initial structure for our study was obtained from the crystallographic data of OYE1 (PDB: 3tx9). The atomic coordinates from DFT calculations are provided in the Supplementary Data. Data are available from the corresponding authors upon request. Source data are provided with this paper.
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Acknowledgements
We thank the Core Facilities at the Carl R. Woese Institute for Genomic Biology where most of the experiments in this project were performed. We thank G. Jiang and H. Li for helpful discussions. This work was funded by the DOE Center for Advanced Bioenergy and Bioproducts Innovation (US Department of Energy, Office of Science, Office of Biological and Environmental Research under award number DE-SC0018420 to H.Z.). NMR data were collected at the Carl R. Woese Institute for Genomic Biology Core, on a 600-MHz NMR funded by the National Institute of Health (number S10-RR028833 to H.Z.). We thank the School of Chemical Sciences NMR Laboratory. We acknowledge the Computational Chemistry Commune (http://bbs.keinsci.com/) for their support with the calculations. Our research benefited from the computing resources at Delta, the National Center for Supercomputing Applications, enabled by allocation BIO230215 from the Advanced Cyberinfrastructure Coordination Ecosystem: Services and Support (ACCESS) programme, funded by National Science Foundation grant numbers 2138259, 2138286, 2138307, 2137603 and 2138296. Any opinions, findings, and conclusions or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the US Department of Energy.
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H.Z. coordinated the project. Z. Zhang and H.Z. conceived the project and designed the experiments. Z. Zhang performed most of the experiments. M.L. performed computational studies. W.H. and Z. Zhao contributed to synthesis. J.L., Y.Y. and W.H. contributed to the site-directed mutagenesis. Z. Zhang, M.L. and H.Z. wrote the paper with input from all authors.
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Extended data
Extended Data Fig. 1 Schematic representation of the photoenzymatic enantioconvergent process detailing multiple pathways for the synthesis of chiral ketones with a remote stereocenter.
The diagram illustrates three primary pathways: (1) Direct background hydrolysis of R- and S-2a, leading to non-enzymatic formation of the chiral ketones. (2) Enzyme and light-mediated formation of an iminyl radical from R-2a and S-2a, followed by a HAT to the iminyl radical and subsequent hydrolysis, producing the chiral products. (3) A more complex pathway involving stereoablative 1,5-HAT, chiral HAT, and hydrolysis, further demonstrating the enzymatic control over the stereoselectivity of the product.
Extended Data Fig. 2 Computational and experimental exploration of the generation of the iminyl radical.
a, The photochemical process that results in the formation of an iminyl radical and FMNsq. Calculations were performed at the um062x-D3/def2tzvpp (SMD, ε = 4.0) // um062x-D3/def2svp (gas) level. Quantitative electron transfer dynamics were calculated using the interfragment charge transfer (IFCT) method, facilitated by Multiwfn43 software. Note that the atoms were held constant during geometry optimization, highlighted by green. For the dominant molecular orbital transitions contributing to CT excitation, the colours coding with green and blue represent positive and negative orbital phases, respectively. b, In-depth experimental assessment of hydrogen bond in tyrosine residues. Reactions were performed under the standard conditions.
Extended Data Fig. 3 Optimal structures for transition states and key intermediates.
Calculations were performed at the um062x-D3/def2tzvpp (SMD, ε = 4.0) // um062x-D3/def2svp (gas) level. Note that the atoms were held constant during geometry optimization, highlighted by green.
Extended Data Fig. 4 Comprehensive spin density analysis covering intermediates and HAT transition states.
Utilizing Multiwfn 3.8 software, we conducted an in-depth spin density analysis. Visual representations were constructed with VMD (Version 1.9.3). The green and blue areas depict α and β spin respectively, with all amino acid residues being omitted to ensure clarity in presentation.
Supplementary information
Supplementary Information (download PDF )
Supplementary Figs. 1–16, Tables 1–21, Methods and References.
Supplementary Data 1 (download PDF )
Atomic coordinates for DFT calculation
Source data
Fig. 2 (download XLSX )
Statistical Source Data
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Zhang, Z., Li, M., Harrison, W. et al. Photoenzymatic stereoablative enantioconvergence of γ-chiral oximes via hydrogen atom transfer. Nat Catal 8, 548–555 (2025). https://doi.org/10.1038/s41929-025-01347-0
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DOI: https://doi.org/10.1038/s41929-025-01347-0
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