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Zhao Q, Chen Z, Soler J, Chen X, Rui J, Ji NT, Yu QE, Yang Y, Garcia-Borràs M, Huang X. Engineering non-haem iron enzymes for enantioselective C(sp3)-F bond formation via radical fluorine transfer. NATURE SYNTHESIS 2024; 3:958-966. [PMID: 39364063 PMCID: PMC11446476 DOI: 10.1038/s44160-024-00507-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Accepted: 02/21/2024] [Indexed: 10/05/2024]
Abstract
In recent years there has been a surge in the development of methods for the synthesis of organofluorine compounds. However, enzymatic methods for C-F bond formation have been limited to nucleophilic fluoride substitution. Here, we report the incorporation of iron-catalysed radical fluorine transfer, a reaction mechanism that is not used in naturally occurring enzymes, into enzymatic catalysis for the development of biocatalytic enantioselective C(sp 3)-F bond formation. Using this strategy, we repurposed (S)-2-hydroxypropylphosphonate epoxidase from Streptomyces viridochromogenes (SvHppE) to catalyse an N-fluoroamide directed C(sp 3)-H fluorination. Directed evolution has enabled SvHppE to be optimized, forming diverse chiral benzylic fluoride products with turnover numbers of up to 180 and with excellent enantiocontrol (up to 94% e.e.). Mechanistic investigations showed that the N-F bond activation is the rate-determining step, and the strong preference for fluorination in the presence of excess NaN3 can be attributed to the spatial proximity of the carbon-centered radical to the iron-bound fluoride.
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Affiliation(s)
- Qun Zhao
- School of Biotechnology, Jiangnan University, Wuxi 214122, P. R. China
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Zhenhong Chen
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Jordi Soler
- Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus Montilivi, Girona E-17071, Catalonia, Spain
| | - Xiahe Chen
- State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, Key Laboratory of Green Chemistry-Synthesis Technology of Zhejiang Province, College of Chemical Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310014, China
| | - Jinyan Rui
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
| | - Nathan Tianlin Ji
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
| | | | - Yunfang Yang
- State Key Laboratory Breeding Base of Green Chemistry-Synthesis Technology, Key Laboratory of Green Chemistry-Synthesis Technology of Zhejiang Province, College of Chemical Engineering, Zhejiang University of Technology, Hangzhou, Zhejiang 310014, China
| | - Marc Garcia-Borràs
- Institut de Química Computacional i Catàlisi (IQCC) and Departament de Química, Universitat de Girona, Campus Montilivi, Girona E-17071, Catalonia, Spain
| | - Xiongyi Huang
- Department of Chemistry, Johns Hopkins University, Baltimore, MD 21218, USA
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Zou M, Waldie KM. Redox-active ligand promoted electrophile addition at cobalt. Chem Commun (Camb) 2023. [PMID: 37997162 DOI: 10.1039/d3cc04869a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2023]
Abstract
The reactivity of an electron-rich cobalt complex bearing an o-phenylenediamide ligand with electrophilic CF3+ and F+ sources is reported. These reactions lead to generation of a Co(III)-CF3 or Co(III)-F complex, promoted by redox-active ligand-to-substrate two-electron transfer. The rate of trifluoromethyl addition at cobalt correlates with the potential difference between the cobalt complex and the CF3+ source. We present initial demonstrations of radical trifluoromethylation and nucleophilic fluorination of organic substrates, setting the stage for the development of electrocatalytic pathways for these bond-forming reactions.
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Affiliation(s)
- Minzhu Zou
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 123 Bevier Road, Piscataway, New Jersey 08854, USA.
| | - Kate M Waldie
- Department of Chemistry and Chemical Biology, Rutgers, The State University of New Jersey, 123 Bevier Road, Piscataway, New Jersey 08854, USA.
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Panda C, Anny-Nzekwue O, Doyle LM, Gericke R, McDonald AR. Evidence for a High-Valent Iron-Fluoride That Mediates Oxidative C(sp 3)-H Fluorination. JACS AU 2023; 3:919-928. [PMID: 37006763 PMCID: PMC10052241 DOI: 10.1021/jacsau.3c00021] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/11/2023] [Revised: 02/14/2023] [Accepted: 02/15/2023] [Indexed: 06/19/2023]
Abstract
[FeII(NCCH3)(NTB)](OTf)2 (NTB = tris(2-benzimidazoylmethyl)amine, OTf = trifluoromethanesulfonate) was reacted with difluoro(phenyl)-λ3-iodane (PhIF2) in the presence of a variety of saturated hydrocarbons, resulting in the oxidative fluorination of the hydrocarbons in moderate-to-good yields. Kinetic and product analysis point towards a hydrogen atom transfer oxidation prior to fluorine radical rebound to form the fluorinated product. The combined evidence supports the formation of a formally FeIV(F)2 oxidant that performs hydrogen atom transfer followed by the formation of a dimeric μ-F-(FeIII)2 product that is a plausible fluorine atom transfer rebound reagent. This approach mimics the heme paradigm for hydrocarbon hydroxylation, opening up avenues for oxidative hydrocarbon halogenation.
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Chan NH, Gomez CA, Vennelakanti V, Du Q, Kulik HJ, Lewis JC. Non-Native Anionic Ligand Binding and Reactivity in Engineered Variants of the Fe(II)- and α-Ketoglutarate-Dependent Oxygenase, SadA. Inorg Chem 2022; 61:14477-14485. [PMID: 36044713 PMCID: PMC9789792 DOI: 10.1021/acs.inorgchem.2c02872] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Mononuclear non-heme Fe(II)- and α-ketoglutarate-dependent oxygenases (FeDOs) catalyze a site-selective C-H hydroxylation. Variants of these enzymes in which a conserved Asp/Glu residue in the Fe(II)-binding facial triad is replaced by Ala/Gly can, in some cases, bind various anionic ligands and catalyze non-native chlorination and bromination reactions. In this study, we explore the binding of different anions to an FeDO facial triad variant, SadX, and the effects of that binding on HO• vs X• rebound. We establish not only that chloride and bromide enable non-native halogenation reactions but also that all anions investigated, including azide, cyanate, formate, and fluoride, significantly accelerate and influence the site selectivity of SadX hydroxylation catalysis. Azide and cyanate also lead to the formation of products resulting from N3•, NCO•, and OCN• rebound. While fluoride rebound is not observed, the rate acceleration provided by this ligand leads us to calculate barriers for HO• and F• rebound from a putative Fe(III)(OH)(F) intermediate. These calculations suggest that the lack of fluorination is due to the relative barriers of the HO• and F• rebound transition states rather than an inaccessible barrier for F• rebound. Together, these results improve our understanding of the FeDO facial triad variant tolerance of different anionic ligands, their ability to promote rebound involving these ligands, and inherent rebound preferences relative to HO• that will aid efforts to develop non-native catalysis using these enzymes.
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Affiliation(s)
- Natalie H. Chan
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA
| | - Christian A. Gomez
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA
| | - Vyshnavi Vennelakanti
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Qian Du
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA
| | - Heather J. Kulik
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
| | - Jared C. Lewis
- Department of Chemistry, Indiana University, Bloomington, Indiana 47405, USA
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