Use of Constrained G-Quadruplexes for Enantioselective Sulfoxidation Site Mapping

Catalysis using G-quadruplexes (G-4) has shown promise as a way to perform asymmetric sulfoxidation of thioanisole derivatives. However, despite the relative simplicity of G-4, the mechanism of chiral control of sulfoxidation is still unknown, mainly because G-4 can adopt different topologies. To better understand the mechanism of G-4-catalyzed sulfoxidation, G-4 was chemically constrained into a unique topology. It was shown that either sulfoxidation can occur at the outer tetrads or at the grooves of G-4 and that different enantiomers can be generated depending on the region where catalysis occurs. By means of these G-4 mimics, the enantioselective control of the sulfoxidation reaction was unraveled

A Selective Sulfide Oxidation Catalyzed by Heterogeneous Artificial Metalloenzymes Iron@NikA

International audiencePerforming a heterogeneous catalysis with proteins is still a challenge. Herein, we demonstrate the importance of cross‐linked crystals for sulfoxide oxidation by an artificial enzyme. The biohybrid consists of the insertion of an iron complex into a NikA protein crystal. The heterogeneous catalysts displays a better efficiency‐with higher reaction kinetics, a better stability and expand the substrate scope compared to its solution counterpart. Designing crystalline artificial enzymes represents a good alternative to soluble or supported enzymes for the future of synthetic biology

Mimicking biocatalysis for the design of artificial oxygenases based on a versatile protein scaffold

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Mimicking biocatalysis for the design of artificial oxygenases based on a versatile protein scaffold

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Oxidation Catalysis by Rationally Designed Artificial Metalloenzymes

International audienceThe principle of enzyme mimics has been raised to its pinnacle by the design of hybrids made from inorganic complexes embedded into biomolecules. The present review focuses on the design of artificial metalloenzymes for oxidation reactions by oxygen transfer reactions, with a special focus on proteins anchoring inorganic complexes or metal ions via supramolecular interactions. Such reactions are of great interest for the organic synthesis of building blocks. In the first part, following an overview of the different design of artificial enzymes, the review presents contributions to the rational design of efficient hybrid biocatalysts via supramolecular host/guest approaches, based on the nature of the inorganic complex and the nature of the protein, with special attention to the substrate binding. In the second part, the original purpose of artificial metalloenzymes has been twisted to enable the observation of transient intermediates, to decipher metal-based oxidation mechanisms. The host protein crystals have been used as crystalline molecular-scale vessels, within which inorganic catalytic reactions have been followed, thanks to X-ray crystallography. These hybrids should be an alternative to enzymes for sustainable chemistry

A new chiral diiron catalyst for enantioselective epoxidation

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The reductive decyanation reaction : chemical methods and synthetic applications

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Clear-cut difference in the rearrangement of 1-bromo-2-(2-phenyl-3-butenyl)benzene under anionic or radical conditions

International audienceThe o-(3-butenyl)phenyl system bearing a phenyl group on the 2-position of the side chain was studied as a potential mechanistic probe for distinguishing between radical and carbanion intermediates. The Bu3(S)nH reduction of 1-bromo-2-(2-phenyl-3-butenyl)benzene, 4, yields mainly the 1,5-cyclization product, 6, with a preference for the trans-isomer. Treatment of 4 with Mg or t-BuLi leads to double-bond isomerization and yields (E)-1,2-diphenyl-2-butene, 8, along with 3,4-diphenyl-1-butene, 5

Functionalization of silicon oxide using supercritical fluid deposition of 3,4-epoxybutyltrimethoxysilane for the immobilization of amino-modified oligonucleotide

International audienceThe functionalization of silicon oxide based substrates using silanes is generally performed through liquid phase methodologies. These processes involve a huge quantity of potentially toxic solvents and present some important disadvantages for the functionalization of microdevices or porous materials, for example the low diffusion. To overcome this drawback, solvent-free methodologies like molecular vapor deposition (MVD) or supercritical fluid deposition (SFD) have been developed. In this paper, the deposition process of 3,4-epoxybutyltrimethoxysilane (EBTMOS) on silicon oxide using supercritical carbon dioxide (scCO2) as a solvent is studied for the first time. The oxirane ring of epoxy silanes readily reacts with amine group and is of particular interest for the grafting of amino-modified oligonucleotides or antibodies for diagnostic application. Then the ability of this specific EBTMOS layer to react with amine functions has been evaluated using the immobilization of amino-modified oligonucleotide probes. The presence of the probes is revealed by fluorescence using hybridization with a fluorescent target oligonucleotide. The performances of SFD of EBTMOS have been optimized and then compared with the dip coating and molecular vapor deposition methods, evidencing a better grafting efficiency and homogeneity, a lower reaction time in addition to the eco-friendly properties of the supercritical carbon dioxide. The epoxysilane layers have been characterized by surface enhanced ellipsometric contrast optical technique, atomic force microscopy, multiple internal reflection infrared spectroscopy and X-ray photoelectron spectroscopy. The shelf life of the 3,4-epoxybutyltrimethoxysilane coating layer has also been studied. Finally, two different strategies of NH2-oligonucleotide grafting on EBTMOS coating layer have been compared, i.e. reductive amination and nucleophilic substitution, SN2. This EBTMOS based coating layer can be used for a wide range of applications such as the preparation of new supported and recoverable catalysts and new integrated silicon microdevices for healthcare purposes

Iron Coordination Chemistry of N2Py2 ligand substituted by carboxylic moieties and their impact on Alkene Oxidation Catalysis

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