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Rogge T, Zhou Q, Porter NJ, Arnold FH, Houk KN. Iron Heme Enzyme-Catalyzed Cyclopropanations with Diazirines as Carbene Precursors: Computational Explorations of Diazirine Activation and Cyclopropanation Mechanism. J Am Chem Soc 2024; 146:2959-2966. [PMID: 38270588 DOI: 10.1021/jacs.3c06030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2024]
Abstract
The mechanism of cyclopropanations with diazirines as air-stable and user-friendly alternatives to commonly employed diazo compounds within iron heme enzyme-catalyzed carbene transfer reactions has been studied by means of density functional theory (DFT) calculations of model systems, quantum mechanics/molecular mechanics (QM/MM) calculations, and molecular dynamics (MD) simulations of the iron carbene and the cyclopropanation transition state in the enzyme active site. The reaction is initiated by a direct diazirine-diazo isomerization occurring in the active site of the enzyme. In contrast, an isomerization mechanism proceeding via the formation of a free carbene intermediate in lieu of a direct, one-step isomerization process was observed for model systems. Subsequent reaction with benzyl acrylate takes place through stepwise C-C bond formation via a diradical intermediate, delivering the cyclopropane product. The origin of the observed diastereo- and enantioselectivity in the enzyme was investigated through MD simulations, which indicate a preferred formation of the cis-cyclopropane by steric control.
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Affiliation(s)
- Torben Rogge
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Qingyang Zhou
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
| | - Nicholas J Porter
- Division of Chemistry and Chemical Engineering, Division of Biology and Bioengineering, California Institute of Technology, Pasadena, California 91125, United States
| | - Frances H Arnold
- Division of Chemistry and Chemical Engineering, Division of Biology and Bioengineering, California Institute of Technology, Pasadena, California 91125, United States
| | - K N Houk
- Department of Chemistry and Biochemistry, University of California, Los Angeles, California 90095-1569, United States
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2
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Farshadfar K, Hashemi A, Khakpour R, Laasonen K. Kinetics of N 2 Release from Diazo Compounds: A Combined Machine Learning-Density Functional Theory Study. ACS OMEGA 2024; 9:1106-1112. [PMID: 38222626 PMCID: PMC10785077 DOI: 10.1021/acsomega.3c07367] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 09/24/2023] [Revised: 11/10/2023] [Accepted: 11/28/2023] [Indexed: 01/16/2024]
Abstract
Diazo compounds are commonly employed as carbene precursors in carbene transfer reactions during a variety of functionalization procedures. Release of N2 gas from diazo compounds may lead to carbene formation, and the ease of this process is highly dependent on the characteristics of the substituents located in the vicinity of the diazo moiety. A quantum mechanical density functional theory assisted by machine learning was used to investigate the relationship between the chemical features of diazo compounds and the activation energy required for N2 elimination. Our results suggest that diazo molecules, possessing a higher positive partial charge on the carbene carbon and more negative charge on the terminal nitrogen, encounter a lower energy barrier. A more positive C charge decreases the π-donor ability of the carbene lone pair to the π* orbital of N2, while the more negative N charge is a result of a weak interaction between N2 lone pair and vacant p orbital of the carbene. The findings of this study can pave the way for molecular engineering for the purpose of carbene generation, which serves as a crucial intermediate for many chemical transformations in synthetic chemistry.
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Affiliation(s)
- Kaveh Farshadfar
- Department of Chemistry and Material
Science, School of Chemical Engineering, Aalto University, 02150 Espoo, Finland
| | - Arsalan Hashemi
- Department of Chemistry and Material
Science, School of Chemical Engineering, Aalto University, 02150 Espoo, Finland
| | - Reza Khakpour
- Department of Chemistry and Material
Science, School of Chemical Engineering, Aalto University, 02150 Espoo, Finland
| | - Kari Laasonen
- Department of Chemistry and Material
Science, School of Chemical Engineering, Aalto University, 02150 Espoo, Finland
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3
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Chatterjee R, Jindal G. Role of mutations in a chemoenzymatic enantiodivergent C(sp 3)-H insertion: exploring the mechanism and origin of stereoselectivity. Chem Sci 2023; 14:8810-8822. [PMID: 37621422 PMCID: PMC10445471 DOI: 10.1039/d3sc02788k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 07/23/2023] [Indexed: 08/26/2023] Open
Abstract
New-to-nature enzymes have emerged as powerful catalysts in recent years for streamlining various stereoselective organic transformations. While synthetic strategies employing engineered enzymes have witnessed proliferating success, there is limited clarity on the mechanistic front and more so when considering molecular-level insights into the role of selected mutations, dramatically escalating catalytic competency and selectivity. We have investigated the mechanism and correlation between mutations and exquisite stereoselectivity of a lactone carbene insertion into the C(sp3)-H bond of substituted aniline, catalyzed by two mutants of a cytochrome P450 variant, "P411" (engineered through directed evolution) in which the axial cysteine has been mutated to serine, utilizing various computational tools. The pivotal role of S264 and L/R328 mutations in the active site has been delineated computationally using two cluster models, thus rationalizing the enantiodivergence. This report provides much-needed insights into the origin of enantiodivergence, furnishing a mechanistic framework for understanding the anchoring effects of H-bond donor residues with the lactone ring. This study is expected to have important implications in the rational design of stereodivergent enzymes and toward successful in silico enzyme designing.
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Affiliation(s)
- Ritwika Chatterjee
- Department of Organic Chemistry, Chemical Sciences Division, Indian Institute of Science Bangalore 560012 India
| | - Garima Jindal
- Department of Organic Chemistry, Chemical Sciences Division, Indian Institute of Science Bangalore 560012 India
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Epping RF, Vesseur D, Zhou M, de Bruin B. Carbene Radicals in Transition-Metal-Catalyzed Reactions. ACS Catal 2023; 13:5428-5448. [PMID: 37123600 PMCID: PMC10127290 DOI: 10.1021/acscatal.3c00591] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2023] [Revised: 03/21/2023] [Indexed: 04/08/2023]
Abstract
Discovered as organometallic curiosities in the 1970s, carbene radicals have become a staple in modern-day homogeneous catalysis. Carbene radicals exhibit nucleophilic radical-type reactivity orthogonal to classical electrophilic diamagnetic Fischer carbenes. Their successful catalytic application has led to the synthesis of a myriad of carbo- and heterocycles, ranging from simple cyclopropanes to more challenging eight-membered rings. The field has matured to employ densely functionalized chiral porphyrin-based platforms that exhibit high enantio-, regio-, and stereoselectivity. Thus far the focus has largely been on cobalt-based systems, but interest has been growing for the past few years to expand the application of carbene radicals to other transition metals. This Perspective covers the advances made since 2011 and gives an overview on the coordination chemistry, reactivity, and catalytic application of carbene radical species using transition metal complexes and catalysts.
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Affiliation(s)
- Roel F.J. Epping
- Homogeneous, Supramolecular and Bio-Inspired Catalysis Group, van ‘t Hoff Institute for Molecular Sciences (HIMS), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - David Vesseur
- Homogeneous, Supramolecular and Bio-Inspired Catalysis Group, van ‘t Hoff Institute for Molecular Sciences (HIMS), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Minghui Zhou
- Homogeneous, Supramolecular and Bio-Inspired Catalysis Group, van ‘t Hoff Institute for Molecular Sciences (HIMS), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
| | - Bas de Bruin
- Homogeneous, Supramolecular and Bio-Inspired Catalysis Group, van ‘t Hoff Institute for Molecular Sciences (HIMS), University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands
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5
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Ma C, Wang S, Sheng Y, Zhao XL, Xing D, Hu W. Synthesis and Characterization of Donor-Acceptor Iron Porphyrin Carbenes and Their Reactivities in N-H Insertion and Related Three-Component Reaction. J Am Chem Soc 2023; 145:4934-4939. [PMID: 36811995 DOI: 10.1021/jacs.2c12155] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/24/2023]
Abstract
Iron porphyrin carbenes (IPCs) have been extensively recognized as the reactive intermediates in various iron porphyrin-catalyzed carbene transfer reactions. While donor-acceptor diazo compounds have been frequently used for such transformations, the structures and reactivities of donor-acceptor IPCs are less explored. To date, no crystal structures of donor-acceptor IPC complexes have been reported, and therefore, the involvement of IPC intermediacy for such transformations lacks direct evidence. Here we report the synthesis and NMR characterization of several donor-acceptor IPC complexes from iron porphyrin and corresponding donor-acceptor diazo compounds. The X-ray crystal structure of an IPC complex derived from a morpholine-substituted diazo amide was obtained. The carbene transfer reactivities of those IPCs were tested by the N-H insertion reactions with aniline or morpholine as well as the three-component reaction with aniline and γ,δ-unsaturated α-keto ester based on electrophilic trapping of an ammonium ylide intermediate. Based on these results, IPCs were identified as the real intermediates for iron porphyrin-catalyzed carbene transfer reactions from donor-acceptor diazo compounds.
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Affiliation(s)
- Chaoqun Ma
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - Shang Wang
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - Yuan Sheng
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - Xiao-Li Zhao
- Shanghai Key Laboratory of Green Chemistry and Chemical Processes, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - Dong Xing
- Shanghai Engineering Research Center of Molecular Therapeutics and New Drug Development, School of Chemistry and Molecular Engineering, East China Normal University, Shanghai 200062, China
| | - Wenhao Hu
- Guangdong Key Laboratory of Chiral Molecule and Drug Discovery, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou 510006, China
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Sosa Alfaro V, Waheed SO, Palomino H, Knorrscheidt A, Weissenborn M, Christov CZ, Lehnert N. YfeX - A New Platform for Carbene Transferase Development with High Intrinsic Reactivity. Chemistry 2022; 28:e202201474. [PMID: 35948517 PMCID: PMC9691539 DOI: 10.1002/chem.202201474] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2022] [Indexed: 01/11/2023]
Abstract
Carbene transfer biocatalysis has evolved from basic science to an area with vast potential for the development of new industrial processes. In this study, we show that YfeX, naturally a peroxidase, has great potential for the development of new carbene transferases, due to its high intrinsic reactivity, especially for the N-H insertion reaction of aromatic and aliphatic primary and secondary amines. YfeX shows high stability against organic solvents (methanol and DMSO), greatly improving turnover of hydrophobic substrates. Interestingly, in styrene cyclopropanation, WT YfeX naturally shows high enantioselectivity, generating the trans product with 87 % selectivity for the (R,R) enantiomer. WT YfeX also catalyzes the Si-H insertion efficiently. Steric effects in the active site were further explored using the R232A variant. Quantum Mechanics/Molecular Mechanics (QM/MM) calculations reveal details on the mechanism of Si-H insertion. YfeX, and potentially other peroxidases, are exciting new targets for the development of improved carbene transferases.
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Affiliation(s)
- Victor Sosa Alfaro
- Department of Chemistry and Department of BiophysicsUniversity of MichiganAnn Arbor, Michigan48109–1055United States
| | - Sodiq O. Waheed
- Department of ChemistryMichigan Technological UniversityHoughton, Michigan49931United States
| | - Hannah Palomino
- Department of Chemistry and Department of BiophysicsUniversity of MichiganAnn Arbor, Michigan48109–1055United States
| | - Anja Knorrscheidt
- Institute of ChemistryMartin-Luther-University Halle-WittenbergKurt-Mothes-Str. 206120HalleGermany
| | - Martin Weissenborn
- Institute of ChemistryMartin-Luther-University Halle-WittenbergKurt-Mothes-Str. 206120HalleGermany
| | - Christo Z. Christov
- Department of ChemistryMichigan Technological UniversityHoughton, Michigan49931United States
| | - Nicolai Lehnert
- Department of Chemistry and Department of BiophysicsUniversity of MichiganAnn Arbor, Michigan48109–1055United States
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Wei Y, Conklin M, Zhang Y. Biocatalytic Intramolecular C-H aminations via Engineered Heme Proteins: Full Reaction Pathways and Axial Ligand Effects. Chemistry 2022; 28:e202202006. [PMID: 35840505 PMCID: PMC9804930 DOI: 10.1002/chem.202202006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2022] [Indexed: 01/09/2023]
Abstract
Engineered heme protein biocatalysts provide an efficient and sustainable approach to develop amine-containing compounds through C-H amination. A quantum chemical study to reveal the complete heme catalyzed intramolecular C-H amination pathway and protein axial ligand effect was reported, using reactions of an experimentally used arylsulfonylazide with hemes containing L=none, SH- , MeO- , and MeOH to simulate no axial ligand, negatively charged Cys and Ser ligands, and a neutral ligand for comparison. Nitrene formation was found as the overall rate-determining step (RDS) and the catalyst with Ser ligand has the best reactivity, consistent with experimental reports. Both RDS and non-RDS (nitrene transfer) transition states follow the barrier trend of MeO- <SH- <MeOH<None due to the charge donation capability of the axial ligand to influence the key charge transfer process as the electronic driving forces. Results also provide new ideas for future biocatalyst design with enhanced reactivities.
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Affiliation(s)
- Yang Wei
- Department of Chemistry and Chemical BiologyStevens Institute of Technology1 Castle Point on HudsonHobokenNJ 07030USA,Department of Chemistry and BiochemistryLoyola University Chicago1032 W Sheridan RdChicagoIL 60660USA
| | - Melissa Conklin
- Department of Chemistry and Chemical BiologyStevens Institute of Technology1 Castle Point on HudsonHobokenNJ 07030USA
| | - Yong Zhang
- Department of Chemistry and Chemical BiologyStevens Institute of Technology1 Castle Point on HudsonHobokenNJ 07030USA
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Balhara R, Jindal G. Does an Enol Pathway Preclude High Stereoselectivity in Iron-Catalyzed Indole C-H Functionalization via Carbene Insertion? J Org Chem 2022; 87:7919-7933. [PMID: 35652604 DOI: 10.1021/acs.joc.2c00573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
C-H functionalization of indoles via Fe carbenoids presents an attractive strategy to obtain biologically important structural motifs. However, obtaining good stereoselectivity with Fe has been a significant challenge. It is unclear whether the low selectivity is due to a radical pathway or an ionic mechanism involving metal-free species. We therefore present a density functional theory (DFT) study of indole alkylation with diazoacetates catalyzed by Fe(ClO4)TMEDA/spirobisoxazoline and myoglobin. We explore three mechanistic pathways: nucleophilic, radical, and oxocarbenium routes. The nucleophilic pathway is the most feasible with the formation of an enol species that tautomerizes to furnish the alkylated indole. While this mechanism is routinely proposed, the stereochemical model has been conspicuously absent until now. We show that the conventionally invoked enol pathway is not responsible for the low enantiomeric excess. The enol intermediate can stay coordinated to the catalyst via different binding sites placing the enol in proximity to the chiral environment and affecting the stereoselective proton transfer. Both the binding strength and the chiral environment are crucial for obtaining high selectivity. Our study provides the much needed insights for the modest-low selectivities of Fe systems and could help in expediting the discovery of an efficient catalytic system. These mechanistic underpinnings could also be applicable to other metal (Rh, Pd, Cu, etc.)-catalyzed X-H insertion reactions.
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Affiliation(s)
- Reena Balhara
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, Karnataka 560012, India
| | - Garima Jindal
- Department of Organic Chemistry, Indian Institute of Science, Bangalore, Karnataka 560012, India
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9
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Shan ZW, Chen XY, Zhang H, Liu HY, Yuan G. Copper Porphyrin-catalyzed C(sp3)-H Activation via Cross Dehydrogenative Coupling: Facile Transformation of Aldehydes to Esters. Synlett 2022. [DOI: 10.1055/a-1813-4235] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Copper porphyrin-catalyzed alkane C−H bond functionalization with aldehydes via cross dehydrogenative coupling (CDC) using DTBP oxidant has been firstly described in non-solvents or non-additives system. Different aryl/heteroaryl-carboxilic esters were obtained in good to excellent yields depending on the aldehyde derivatives. This CDC reaction catalyzed by copper porphyrin has the advantages of shorter reaction time, lower reaction temperature and catalyst loading as well as the aerobic reaction atmosphere.
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Affiliation(s)
- Zi-Wei Shan
- Department of Chemistry, South China University of Technology, Guangzhou, China
| | - Xiao-Yan Chen
- Department of Chemistry, South China University of Technology, Guangzhou, China
| | - Hao Zhang
- Department of Chemistry, South China University of Technology, Guangzhou, China
| | - Hai-Yang Liu
- Department of Chemistry, South China University of Technology, Guangzhou, China
| | - Gaoqing Yuan
- Department of Chemistry, South China University of Technology, Guangzhou, China
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Planas F, Costantini M, Montesinos-Magraner M, Himo F, Mendoza A. Combined Experimental and Computational Study of Ruthenium N-Hydroxyphthalimidoyl Carbenes in Alkene Cyclopropanation Reactions. ACS Catal 2021; 11:10950-10963. [PMID: 34504736 PMCID: PMC8419840 DOI: 10.1021/acscatal.1c02540] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2021] [Revised: 08/05/2021] [Indexed: 01/14/2023]
Abstract
A combined experimental-computational approach has been used to study the cyclopropanation reaction of N-hydroxyphthalimide diazoacetate (NHPI-DA) with various olefins, catalyzed by a ruthenium-phenyloxazoline (Ru-Pheox) complex. Kinetic studies show that the better selectivity of the employed redox-active NHPI diazoacetate is a result of a much slower dimerization reaction compared to aliphatic diazoacetates. Density functional theory calculations reveal that several reactions can take place with similar energy barriers, namely, dimerization of the NHPI diazoacetate, cyclopropanation (inner-sphere and outer-sphere), and a previously unrecognized migratory insertion of the carbene into the phenyloxazoline ligand. The calculations show that the migratory insertion reaction yields an unconsidered ruthenium complex that is catalytically competent for both the dimerization and cyclopropanation, and its relevance is assessed experimentally. The stereoselectivity of the reaction is argued to stem from an intricate balance between the various mechanistic scenarios.
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Affiliation(s)
| | | | - Marc Montesinos-Magraner
- Department of Organic Chemistry,
Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Fahmi Himo
- Department of Organic Chemistry,
Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
| | - Abraham Mendoza
- Department of Organic Chemistry,
Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden
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12
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Balhara R, Chatterjee R, Jindal G. A computational approach to understand the role of metals and axial ligands in artificial heme enzyme catalyzed C-H insertion. Phys Chem Chem Phys 2021; 23:9500-9511. [PMID: 33885085 DOI: 10.1039/d1cp00412c] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Engineered heme enzymes such as myoglobin and cytochrome P450s metalloproteins are gaining widespread importance due to their efficiency in catalyzing non-natural reactions. In a recent strategy, the naturally occurring Fe metal in the heme unit was replaced with non-native metals such as Ir, Rh, Co, Cu, etc., and axial ligands to generate artificial metalloenzymes. Determining the best metal-ligand for a chemical transformation is not a trivial task. Here we demonstrate how computational approaches can be used in deciding the best metal-ligand combination which would be highly beneficial in designing new enzymes as well as small molecule catalysts. We have used Density Functional Theory (DFT) to shed light on the enhanced reactivity of an Ir system with varying axial ligands. We look at the insertion of a carbene group generated from diazo precursors via N2 extrusion into a C-H bond. For both Ir(Me) and Fe systems, the first step, i.e., N2 extrusion is the rate determining step. Strikingly, neither the better ligand overlap with 5d orbitals on Ir nor the electrophilicity on the carbene centre play a significant role. A comparison of Fe and Ir systems reveals that a lower distortion in the Ir(Me)-porphyrin on moving from the reactant to the transition state renders it catalytically more active. We notice that for both metal porphyrins, the free energy barriers are affected by axial ligand substitution. Further, for Fe porphyrin, the axial ligand also changes the preferred spin state. We show that for the carbene insertion into the C-H bond, Fe porphyrin systems undergo a stepwise HAT (hydrogen atom transfer) instead of a concerted hydride transfer process. Importantly, we find that the substitution of the axial Me ligand on Ir to imidazole or chloride, or without an axial substitution changes the rate determining step of the reaction. Therefore, an optimum ligand that can balance the barriers for both steps of the catalytic cycle is essential. We subsequently used the QM cluster approach to delineate the protein environment's role and mutations in improving the catalytic activity of the Ir(Me) system.
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Affiliation(s)
- Reena Balhara
- Department of Organic Chemistry, Indian Institute of Science, Bangalore 560012, India.
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