From Ground-State to Excited-State Activation Modes: Flavin-Dependent “Ene”-Reductases Catalyzed Non-natural Radical Reactions

Accounts of Chemical Research, Год журнала: 2024, Номер 57(9), С. 1446 - 1457

Опубликована: Апрель 11, 2024

ConspectusEnzymes are desired catalysts for chemical synthesis, because they can be engineered to provide unparalleled levels of efficiency and selectivity. Yet, despite the astonishing array reactions catalyzed by natural enzymes, many reactivity patterns found in small molecule have no counterpart living world. With a detailed understanding mechanisms utilized catalysts, we identify existing enzymes with potential catalyze that currently unknown nature. Over past eight years, our group has demonstrated flavin-dependent "ene"-reductases (EREDs) various radical-mediated selectivity, solving long-standing challenges asymmetric synthesis.This Account presents development EREDs as general radical reactions. While developed multiple generating radicals within protein active sites, this account will focus on examples where flavin mononucleotide hydroquinone (FMNhq) serves an electron transfer initiator. initial mechanistic hypotheses were rooted electron-transfer-based initiation commonly used synthetic organic chemists, ultimately uncovered emergent unique site. We begin covering intramolecular discussing how activates substrate reduction altering redox-potential alkyl halides templating charge complex between flavin-cofactor. Protein engineering been modify fundamental photophysics these reactions, highlighting opportunity tune systems further using directed evolution. This section highlights range coupling partners termination available reactions.The next intermolecular role enzyme-templated ternary complexes among cofactor, halide, partner gating ensure it only occurs when both substrates bound highlight applications activation mode, including olefin hydroalkylation, carbohydroxylation, arene functionalization, nitronate alkylation. also discusses favor steps elusive solution reductive nitroalkanes. aware several recent EREDs-catalyzed photoenzymatic transformations from other groups. discuss results papers context nuances substrates.These biocatalytic often complement state-of-the-art small-molecule-catalyzed making valuable addition chemist's toolbox. Moreover, underlying principles studied potentially operative cofactor-dependent proteins, opening door different types enzyme-catalyzed anticipate serve guide inspire broad interest repurposing access new transformations.

Язык: Английский

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Asymmetric Synthesis of α-Chloroamides via Photoenzymatic Hydroalkylation of Olefins

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(11), С. 7191 - 7197

Опубликована: Март 5, 2024

Photoenzymatic intermolecular hydroalkylations of olefins are highly enantioselective for chiral centers formed during radical termination but poorly selective set in the C–C bond-forming event. Here, we report evolution a flavin-dependent "ene"-reductase to catalyze coupling α,α-dichloroamides with alkenes afford α-chloroamides good yield excellent chemo- and stereoselectivity. These products can serve as linchpins synthesis pharmaceutically valuable motifs. Mechanistic studies indicate that formation occurs by exciting charge-transfer complex templated protein. Precise control over orientation molecules within potentially accounts observed The work expands types motifs be prepared using photoenzymatic catalysis.

Язык: Английский

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Enzyme engineering for biocatalysis

Molecular Catalysis, Год журнала: 2024, Номер 555, С. 113874 - 113874

Опубликована: Янв. 31, 2024

Contemporary Biocatalysis heavily relies on enzyme engineering as natural enzymes frequently lack the requisite attributes for effective organic synthesis. The inherent limitations in stability, catalytic activity, and selectivity of wild-type often hinder their suitability chemical Over past 25 years, there has been an unprecedented advancement protein tools, empowering enzymologists to customise precisely meet demands In this discussion, we delineate some most crucial techniques significance facilitating

Язык: Английский

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Novel applications of photobiocatalysts in chemical transformations

RSC Advances, Год журнала: 2024, Номер 14(4), С. 2590 - 2601

Опубликована: Янв. 1, 2024

Photocatalysis has proven to be an effective approach for the production of reactive intermediates under moderate reaction conditions.

Язык: Английский

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Unnatural Thiamine Radical Enzymes for Photobiocatalytic Asymmetric Alkylation of Benzaldehydes and α-Ketoacids

ACS Catalysis, Год журнала: 2024, Номер 14(12), С. 9144 - 9150

Опубликована: Май 30, 2024

Despite substantial progress made toward elucidating the natural radical enzymology with thiamine pyrophosphate (TPP)-dependent pyruvate:ferredoxin oxidoreductases (PFORs) and pyruvate oxidases (POXs), repurposing naturally occurring two-electron TPP-dependent enzymes to catalyze single-electron transformations significant synthetic value remains a daunting task. Enabled by synergistic use of visible-light photocatalyst fluorescein set engineered derived from benzoylformate decarboxylase (BFD) benzaldehyde lyase (BAL), we developed an asymmetric photobiocatalytic decarboxylative alkylation benzaldehydes α-keto acids produce highly enantioenriched α-branched ketones. Mechanistically, propose that this dual catalytic involves oxidation enzyme-bound Breslow intermediate subsequent interception photoredox-generated transient alkyl radical. In conjunction visible light photoredox catalysis, biocatalysis represents emerging platform discover optimize are unknown biological systems not amenable small-molecule catalysis.

Язык: Английский

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A New Age of Biocatalysis Enabled by Generic Activation Modes

JACS Au, Год журнала: 2024, Номер 4(6), С. 2068 - 2080

Опубликована: Май 31, 2024

Biocatalysis is currently undergoing a profound transformation. The field moves from relying on nature's chemical logic to discipline that exploits generic activation modes, allowing for novel biocatalytic reactions and, in many instances, entirely new chemistry. Generic modes enable wide range of reaction types and played pivotal role advancing the fields organo- photocatalysis. This perspective aims summarize principal harnessed enzymes develop biocatalysts. Although extensively researched past, highlighted when applied within enzyme active sites, facilitate transformations have largely eluded efficient selective catalysis. advance attributed multiple tunable interactions substrate binding pocket precisely control competing pathways transition states. We will highlight cases synthetic methodologies achieved by engineered provide insights into potential future developments this rapidly evolving field.

Язык: Английский

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Emergence of a distinct mechanism of C–N bond formation in photoenzymes

Nature, Год журнала: 2024, Номер unknown

Опубликована: Окт. 8, 2024

Язык: Английский

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Directed Evolution and Unusual Protonation Mechanism of Pyridoxal Radical C–C Coupling Enzymes for the Enantiodivergent Photobiocatalytic Synthesis of Noncanonical Amino Acids

Journal of the American Chemical Society, Год журнала: 2025, Номер unknown

Опубликована: Янв. 23, 2025

Visible light-driven pyridoxal radical biocatalysis has emerged as a new strategy for the stereoselective synthesis of valuable noncanonical amino acids in protecting-group-free fashion. In our previously developed dehydroxylative C–C coupling using engineered PLP-dependent tryptophan synthases, an enzyme-controlled unusual α-stereochemistry reversal and pH-controlled enantiopreference were observed. Herein, through high-throughput photobiocatalysis, we evolved set stereochemically complementary PLP enzymes, allowing both l- d-amino with enhanced enantiocontrol across broad pH window. These newly acid synthases permitted use range organoboron substrates, including boronates, trifluoroborates, boronic acids, excellent efficiency. Mechanistic studies unveiled unexpected racemase activity earlier enzyme variants. This promiscuous was abolished shedding light on origin enantiocontrol. Further mechanistic investigations suggest switch proton donor to account stereoinvertive formation highlighting stereoinversion mechanism that is rare conventional two-electron enzymology.

Язык: Английский

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Pyridylmethyl Radicals for Enantioselective Alkene Hydroalkylation Using “Ene”-Reductases

ACS Catalysis, Год журнала: 2023, Номер 13(22), С. 14680 - 14684

Опубликована: Окт. 31, 2023

Aromatic electron-deficient heterocycles, such as pyridines, are found in many biologically relevant structures, including those with medicinal applications. Methods for their substitution can streamline the synthesis of valuable molecules and allow access to unexplored chemical space. However, enantioselective methods these derivatizations remain lacking, especially at remote stereocenters. Here, we present a photoenzymatic reaction reductive coupling heterocycles alkenes using flavin-dependent "ene"-reductases. This transformation results generation γ-stereocenter high enantioselectivity. We propose that this light-driven proceeds via excitation transient enzyme–substrate complex, enabling enzyme potential needed radical initiation when substrates bound active site. work represents stereoselective method synthesizing derivatives pyridine similar an expansion substrate capabilities "ene"-reductases synthesis.

Язык: Английский

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Threonine Aldolase-Catalyzed Enantioselective α-Alkylation of Amino Acids through Unconventional Photoinduced Radical Initiation

Journal of the American Chemical Society, Год журнала: 2024, Номер 146(32), С. 22476 - 22484

Опубликована: Июль 4, 2024

Visible light-driven pyridoxal radical biocatalysis has emerged as a promising strategy for the stereoselective synthesis of valuable noncanonical amino acids (ncAAs). Previously, use well-tailored photoredox catalysts represented key to enable efficient phosphate (PLP) enzyme-catalyzed reactions. Here, we report PLP-dependent threonine aldolase-catalyzed asymmetric α-C–H alkylation abundant using Katritzky pyridinium salts alkylating agents. The engineered aldolases allowed this redox-neutral proceed efficiently, giving rise challenging α-trisubstituted and -tetrasubstituted ncAA products in protecting-group-free fashion with excellent enantiocontrol. Mechanistically, enantioselective α-alkylation capitalizes on unique reactivity persistent enzymatic quinonoid intermediate derived from PLP cofactor acid substrate allow novel C–C coupling. Surprisingly, photobiocatalytic process does not require well-established operates through an unconventional photoinduced generation involving PLP-derived aldimine. ability develop reactions without relying classic photocatalysts or photoenzymes opens up new avenues advancing intermolecular that are known either organic chemistry enzymology.

Язык: Английский

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