Site-selective enzymatic C‒H amidation for synthesis of diverse lactams

Science ◽  
2019 ◽  
Vol 364 (6440) ◽  
pp. 575-578 ◽  
Author(s):  
Inha Cho ◽  
Zhi-Jun Jia ◽  
Frances H. Arnold
Keyword(s):  
Bond Formation ◽  
Enantiomeric Excess ◽  
Cytochrome P450 Enzymes ◽  
Preparative Scale ◽  
Bond Functionalization ◽  
Reactive Iron ◽  
Site Selectivity ◽  
Site Selective ◽  
And Control ◽  
Nitrogen Bond

A major challenge in carbon‒hydrogen (C‒H) bond functionalization is to have the catalyst control precisely where a reaction takes place. In this study, we report engineered cytochrome P450 enzymes that perform unprecedented enantioselective C‒H amidation reactions and control the site selectivity to divergently construct β-, γ-, and δ-lactams, completely overruling the inherent reactivities of the C‒H bonds. The enzymes, expressed in Escherichia coli cells, accomplish this abiological carbon‒nitrogen bond formation via reactive iron-bound carbonyl nitrenes generated from nature-inspired acyl-protected hydroxamate precursors. This transformation is exceptionally efficient (up to 1,020,000 total turnovers) and selective (up to 25:1 regioselectivity and 97%, please refer to compound 2v enantiomeric excess), and can be performed easily on preparative scale.

Theoretical and experimental studies of palladium-catalyzed site-selective C(sp3)−H bond functionalization enabled by transient ligands

2017 ◽  
Author(s):  
Haibo Ge ◽  
Lei Pan ◽  
Piaoping Tang ◽  
Ke Yang ◽  
Mian Wang ◽  
...  
Keyword(s):  
Bond Activation ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Bond Functionalization ◽  
Aliphatic Ketones ◽  
Site Selectivity ◽  
Mechanistic Investigation ◽  
Palladium Catalyzed ◽  
Metal Catalyzed ◽  
Site Selective

Transition metal-catalyzed selective C–H bond functionalization enabled by transient ligands has become an extremely attractive topic due to its economical and greener characteristics. However, catalytic pathways of this reaction process on unactivated sp<sup>3</sup> carbons of reactants have not been well studied yet. Herein, detailed mechanistic investigation on Pd-catalyzed C(sp<sup>3</sup>)–H bond activation with amino acids as transient ligands has been systematically conducted. The theoretical calculations showed that higher angle distortion of C(sp2)-H bond over C(sp3)-H bond and stronger nucleophilicity of benzylic anion over its aromatic counterpart, leading to higher reactivity of corresponding C(sp<sup>3</sup>)–H bonds; the angle strain of the directing rings of key intermediates determines the site-selectivity of aliphatic ketone substrates; replacement of glycine with β-alanine as the transient ligand can decrease the angle tension of the directing rings. Synthetic experiments have confirmed that β-alanine is indeed a more efficient transient ligand for arylation of β-secondary carbons of linear aliphatic ketones than its glycine counterpart.<br><br>

scholarly journals Site-Selective A-C-H Functionalization of Trialkylamines via Reversible Hydrogen Atom Transfer Catalysis

2021 ◽  
Author(s):  
Yangyang Shen ◽  
Franziska Schoenebeck ◽  
Ignacio Funes-Ardoiz ◽  
Tomislav Rovis
Keyword(s):  
Drug Discovery ◽  
Hydrogen Atom ◽  
Late Stage ◽  
Hydrogen Atom Transfer ◽  
Atom Transfer ◽  
Bond Functionalization ◽  
Carbon Centers ◽  
Radical Trapping ◽  
Site Selectivity ◽  
Site Selective

Trialkylamines are widely found in naturally-occurring alkaloids, synthetic agrochemicals, biological probes, and especially pharmaceuticals agents and pre-clinical candidates. Despite the recent breakthrough of catalytic alkylation of dialkylamines, the selective a-C(sp3 )–H bond functionalization of widely available trialkylamine scaffolds holds promise to streamline complex trialkylamine synthesis, accelerate drug discovery and execute late-stage pharmaceutical modification with complementary reactivity. However, the canonical methods always result in functionalization at the less-crowded site. Herein, we describe a solution to switch the reaction site through fundamentally overcoming the steric control that dominates such processes. By rapidly establishing an equilibrium between a-amino C(sp3 )-H bonds and a highly electrophilic thiol radical via reversible hydrogen atom transfer, we leverage a slower radical-trapping step with electron-deficient olefins to selectively forge a C(sp3 )-C(sp3 ) bond with the more-crowded a-amino radical, with the overall selectivity guided by Curtin-Hammett principle. This subtle reaction profile has unlocked a new strategic concept in direct C-H functionalization arena for forging C– C bonds from a diverse set of trialkylamines with high levels of site-selectivity and preparative utility. Simple correlation of site-selectivity and 13C NMR shift serves as a qualitative predictive guide. The broad consequences of this dynamic system, together with the ability to forge N-substituted quaternary carbon centers and implement late-stage functionalization techniques, holds tremendous potential to streamline complex trialkylamine synthesis and accelerate drug discovery

scholarly journals Site-Selective Alkoxylation of Benzylic C–H Bonds via Photoredox Catalysis

2019 ◽  
Author(s):  
Byung Joo Lee ◽  
kimberly deglopper ◽  
Tehshik Yoon
Keyword(s):  
Late Stage ◽  
Functional Group ◽  
Bond Formation ◽  
Bioactive Molecules ◽  
Site Selectivity ◽  
Wide Range ◽  
High Site ◽  
Alkoxy Groups ◽  
Site Selective ◽  
Mediated Oxidation

<div> <div> <div> <p>There are relatively few methods that accom- plish the selective alkoxylation of sp3-hybridized C–H bonds, particularly in comparison to the numerous analogous strate- gies for C–N and C–C bond formation. We report a photo- catalytic protocol for the functionalization of benzylic C–H bonds with a wide range of readily available oxygen nucleo- philes. Our strategy merges the photoredox activation of arenes with copper(II)-mediated oxidation of the resulting benzylic radicals, which enables the introduction of benzylic C–O bonds with high site selectivity, chemoselectivity, and functional group tolerance. This method enables the late- stage introduction of complex alkoxy groups into bioactive molecules, providing a practical new tool with potential appli- cations in synthesis and medicinal chemistry. </p> </div> </div> </div>

scholarly journals Biocatalytic oxidative cross-coupling reactions for biaryl bond formation

2021 ◽  
Author(s):  
Lara Zetzsche ◽  
Jessica Yazarians ◽  
Suman Chakrabarty ◽  
Meagan Hinze ◽  
April Lukowski ◽  
...  
Keyword(s):  
Asymmetric Catalysis ◽  
Bond Formation ◽  
Cross Coupling ◽  
Building Blocks ◽  
Coupling Reactions ◽  
Cytochrome P450 Enzymes ◽  
Cross Coupling Reactions ◽  
Site Selectivity ◽  
Valuable Compounds ◽  
Selective Process

Despite their varied purposes, many indispensable molecules in medicine, materials, and asymmetric catalysis share a biaryl core. The necessity of joining arene building blocks to access these valuable compounds has inspired multiple approaches for biaryl bond formation and challenged chemists to develop increasingly concise and robust methods for this task. Oxidative coupling of two C–H bonds offers an efficient strategy for the formation of a biaryl C–C bond, however, fundamental challenges remain in controlling the reactivity and selectivity for uniting a given pair of substrates. Biocatalytic oxidative cross-coupling reactions have the potential to overcome limitations inherent to small molecule- mediated methods by providing a paradigm with catalyst-controlled selectivity. In this article, we disclose a strategy for biocatalytic cross-coupling through oxidative C–C bond formation using cytochrome P450 enzymes. We demonstrate the ability to catalyze cross-coupling reactions on a panel of phenolic substrates using natural P450 catalysts. Moreover, we engineer a P450 to possess the desired reactivity, site- selectivity, and atroposelectivity by transforming a low-yielding, unselective reaction into a highly efficient and selective process. This streamlined method for constructing sterically hindered biaryl bonds provides a programmable platform for assembling molecules with catalyst-controlled reactivity and selectivity.

scholarly journals Design principles for site-selective hydroxylation by a Rieske oxygenase

2022 ◽  
Vol 13 (1) ◽  
Author(s):  
Jianxin Liu ◽  
Jiayi Tian ◽  
Christopher Perry ◽  
April L. Lukowski ◽  
Tzanko I. Doukov ◽  
...  
Keyword(s):  
Structural Information ◽  
Diverse Range ◽  
Bond Functionalization ◽  
Site Selectivity ◽  
Site Selective ◽  
Common Architecture ◽  
Rieske Oxygenase ◽  
Rieske Oxygenases ◽  
Native Site ◽  
Selective Hydroxylation

AbstractRieske oxygenases exploit the reactivity of iron to perform chemically challenging C–H bond functionalization reactions. Thus far, only a handful of Rieske oxygenases have been structurally characterized and remarkably little information exists regarding how these enzymes use a common architecture and set of metallocenters to facilitate a diverse range of reactions. Herein, we detail how two Rieske oxygenases SxtT and GxtA use different protein regions to influence the site-selectivity of their catalyzed monohydroxylation reactions. We present high resolution crystal structures of SxtT and GxtA with the native β-saxitoxinol and saxitoxin substrates bound in addition to a Xenon-pressurized structure of GxtA that reveals the location of a substrate access tunnel to the active site. Ultimately, this structural information allowed for the identification of six residues distributed between three regions of SxtT that together control the selectivity of the C–H hydroxylation event. Substitution of these residues produces a SxtT variant that is fully adapted to exhibit the non-native site-selectivity and substrate scope of GxtA. Importantly, we also found that these selectivity regions are conserved in other structurally characterized Rieske oxygenases, providing a framework for predictively repurposing and manipulating Rieske oxygenases as biocatalysts.

scholarly journals Site-Selective Alkoxylation of Benzylic C–H Bonds via Photoredox Catalysis

2019 ◽  
Author(s):  
Byung Joo Lee ◽  
kimberly deglopper ◽  
Tehshik Yoon
Keyword(s):  
Late Stage ◽  
Functional Group ◽  
Bond Formation ◽  
Bioactive Molecules ◽  
Site Selectivity ◽  
Wide Range ◽  
High Site ◽  
Alkoxy Groups ◽  
Site Selective ◽  
Mediated Oxidation

<div> <div> <div> <p>There are relatively few methods that accom- plish the selective alkoxylation of sp3-hybridized C–H bonds, particularly in comparison to the numerous analogous strate- gies for C–N and C–C bond formation. We report a photo- catalytic protocol for the functionalization of benzylic C–H bonds with a wide range of readily available oxygen nucleo- philes. Our strategy merges the photoredox activation of arenes with copper(II)-mediated oxidation of the resulting benzylic radicals, which enables the introduction of benzylic C–O bonds with high site selectivity, chemoselectivity, and functional group tolerance. This method enables the late- stage introduction of complex alkoxy groups into bioactive molecules, providing a practical new tool with potential appli- cations in synthesis and medicinal chemistry. </p> </div> </div> </div>

Theoretical and experimental studies of palladium-catalyzed site-selective C(sp3)−H bond functionalization enabled by transient ligands

2017 ◽  
Author(s):  
Haibo Ge ◽  
Lei Pan ◽  
Piaoping Tang ◽  
Ke Yang ◽  
Mian Wang ◽  
...  
Keyword(s):  
Bond Activation ◽  
Theoretical Calculations ◽  
Experimental Studies ◽  
Bond Functionalization ◽  
Aliphatic Ketones ◽  
Site Selectivity ◽  
Mechanistic Investigation ◽  
Palladium Catalyzed ◽  
Metal Catalyzed ◽  
Site Selective

Transition metal-catalyzed selective C–H bond functionalization enabled by transient ligands has become an extremely attractive topic due to its economical and greener characteristics. However, catalytic pathways of this reaction process on unactivated sp<sup>3</sup> carbons of reactants have not been well studied yet. Herein, detailed mechanistic investigation on Pd-catalyzed C(sp<sup>3</sup>)–H bond activation with amino acids as transient ligands has been systematically conducted. The theoretical calculations showed that higher angle distortion of C(sp2)-H bond over C(sp3)-H bond and stronger nucleophilicity of benzylic anion over its aromatic counterpart, leading to higher reactivity of corresponding C(sp<sup>3</sup>)–H bonds; the angle strain of the directing rings of key intermediates determines the site-selectivity of aliphatic ketone substrates; replacement of glycine with β-alanine as the transient ligand can decrease the angle tension of the directing rings. Synthetic experiments have confirmed that β-alanine is indeed a more efficient transient ligand for arylation of β-secondary carbons of linear aliphatic ketones than its glycine counterpart.<br><br>

Asymmetric remote C–H borylation of aliphatic amides and esters with a modular iridium catalyst

Science ◽  
2020 ◽  
Vol 369 (6506) ◽  
pp. 970-974 ◽  
Author(s):  
Ronald L. Reyes ◽  
Miyu Sato ◽  
Tomohiro Iwai ◽  
Kimichi Suzuki ◽  
Satoshi Maeda ◽  
...  
Keyword(s):  
Quantum Chemical ◽  
Noncovalent Interactions ◽  
Saturated Hydrocarbon ◽  
Receptor Ligand ◽  
Bond Functionalization ◽  
Iridium Catalyst ◽  
Site Selectivity ◽  
Synthetic Utility ◽  
Tertiary Amides ◽  
Site Selective

Site selectivity and stereocontrol remain major challenges in C–H bond functionalization chemistry, especially in linear aliphatic saturated hydrocarbon scaffolds. We report the highly enantioselective and site-selective catalytic borylation of remote C(sp3)–H bonds γ to the carbonyl group in aliphatic secondary and tertiary amides and esters. A chiral C–H activation catalyst was modularly assembled from an iridium center, a chiral monophosphite ligand, an achiral urea-pyridine receptor ligand, and pinacolatoboryl groups. Quantum chemical calculations support an enzyme-like structural cavity formed by the catalyst components, which bind the substrate through multiple noncovalent interactions. Versatile synthetic utility of the enantioenriched γ-borylcarboxylic acid derivatives was demonstrated.

scholarly journals Site-selective enzymatic C‒H amidation for synthesis of diverse lactams

2020 ◽  
Author(s):  
Inha Cho ◽  
Zhijun Jia ◽  
Frances H. Arnold
Keyword(s):  
Cytochrome P450 ◽  
Directed Evolution ◽  
Chemical Engineering ◽  
Careful Examination ◽  
California Institute ◽  
Cytochrome P450 Enzymes ◽  
California Institute Of Technology ◽  
Site Selectivity ◽  
Institute Of Technology ◽  
Site Selective

<p>Please note that this work has been retracted by the authors.</p><p><br></p><p>After publication of the Report “Site-selective enzymatic C‒H amidation for synthesis of diverse lactams” in <i>Science </i>(<i>1, also linked in metadata</i>), efforts to reproduce the work showed that the enzymes do not catalyze the reactions with the activities and selectivities claimed. Careful examination of the first author’s lab notebook then revealed missing contemporaneous entries and raw data for key experiments. The authors therefore have retracted the article from <i>Science</i> and are now retracting the preprint from ChemRxiv. The original paper can be accessed by selecting “Version 1” of the preprint below, or by accessing <a href="https://doi.org/10.26434/chemrxiv.7711418.v1">https://doi.org/10.26434/chemrxiv.7711418.v1</a>. </p><p><br></p><p><b><i> Inha Cho, Zhi-Jun Jia, Frances H. Arnold*</i></b></p><p><b><i><br></i></b></p><p>Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 91125, USA.</p><p><br></p><p>*Corresponding author. Email: [email protected]</p><p><b><br></b></p><p><b>References</b></p><p>1. I. Cho, Z.-J. Jia, F. H. Arnold, <i>Science</i> <b>364</b>, 575 (2019). DOI: 10.1126/science.aaw9068<br></p><p><br></p><p><br></p><p>*******************************************************************************************</p><p><br></p><p>Directed evolution of cytochrome P450 enzymes fine-tunes site selectivity of new-to-nature C‒H amidation for modular, sustainable and scalable preparation of enantio-enriched β-, γ- and δ-lactams.<br></p><p></p>

scholarly journals Site-Selective Alkoxylation of Benzylic C–H Bonds via Photoredox Catalysis

2019 ◽  
Author(s):  
Byung Joo Lee ◽  
kimberly deglopper ◽  
Tehshik Yoon
Keyword(s):  
Late Stage ◽  
Functional Group ◽  
Bond Formation ◽  
Bioactive Molecules ◽  
Site Selectivity ◽  
Wide Range ◽  
High Site ◽  
Alkoxy Groups ◽  
Site Selective ◽  
Mediated Oxidation

<div> <div> <div> <p>There are relatively few methods that accom- plish the selective alkoxylation of sp3-hybridized C–H bonds, particularly in comparison to the numerous analogous strate- gies for C–N and C–C bond formation. We report a photo- catalytic protocol for the functionalization of benzylic C–H bonds with a wide range of readily available oxygen nucleo- philes. Our strategy merges the photoredox activation of arenes with copper(II)-mediated oxidation of the resulting benzylic radicals, which enables the introduction of benzylic C–O bonds with high site selectivity, chemoselectivity, and functional group tolerance. This method enables the late- stage introduction of complex alkoxy groups into bioactive molecules, providing a practical new tool with potential appli- cations in synthesis and medicinal chemistry. </p> </div> </div> </div>

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