LongLarf

Nature Catalysis, Published online: 18 December 2023; doi:10.1038/s41929-023-01065-5

Merging photoredox and biocatalysis provides opportunities to address challenges in synthetic chemistry. Now the combination of a ruthenium photocatalyst for oxidative radical formation and ‘ene’-reductases for radical interception enables an enantiodivergent decarboxylative alkylation reaction.

Nature, Published online: 18 December 2023; doi:10.1038/s41586-023-06822-x

Enzyme-bound ketyl radicals derived from thiamine diphosphate are selectively generated through single-electron oxidation by a photoexcited organic dye and shown to lead to enantioselective radical acylation reactions.

Nature, Published online: 14 December 2023; doi:10.1038/d41586-023-03876-9

Stubborn compounds called PFAS in drinking water put health at risk. Technologies based on plasmas, pressure, sound or fungus could finally degrade these chemicals.

Intermolecular functionalization of tertiary C–H bonds to construct fully substituted stereogenic carbon centers represents a formidable challenge: without the assistance of directing groups, the state-of-the-art catalysts struggle to introduce chirality to racemic tertiary sp3-carbon centers. Direct asymmetric functionalization of such centers is a worthy reactivity and selectivity goal for modern biocatalysis. Here we present an engineered nitrene transferase (P411-TEA-5274), derived from a bacterial cytochrome P450, that is capable of aminating tertiary C–H bonds to provide chiral α-tertiary primary amines with high efficiency (up to 2300 total turnovers) and selectivity (up to >99% enantiomeric excess (e.e.)). The construction of fully substituted stereocenters with methyl and ethyl groups underscores the enzyme’s remarkable selectivity. A comprehensive substrate scope study demonstrates the biocatalyst’s compatibility with diverse functional groups and tertiary C–H bonds. Mechanistic studies, incorporating both experimental and computational data, elucidate how active-site residues distinguish between the enantiomers and enable the enzyme to perform this transformation with excellent enantioselectivity.

The enolization of 2-arylacetamides, followed by an enantioselective intramolecular conjugate addition to tethered 2,5-cyclohexadienones, yielding saturated fused N-heterocycles, is described. The transformation is achieved by employing a bifunctional iminophosphorane (BIMP) superbase catalyst and represents the first unactivated carboxamide deprotonation in a metal-free, catalytic, and enantioselective transformation.

Abstract

The organocatalytic enolization of 2-arylacetamides, followed by an enantioselective intramolecular conjugate addition to tethered 2,5-cyclohexadienones, yielding 3D fused N-heterocycles, is described. The transformation represents the first strong activating group-free activation of carboxamides via α-C−H deprotonation in a metal-free, catalytic, and enantioselective reaction, and is achieved by employing a bifunctional iminophosphorane (BIMP) superbase.

Nature Catalysis, Published online: 05 December 2023; doi:10.1038/s41929-023-01063-7

Low-carbon chemicals generated from CO2 provide a possible path to improve the sustainability of microbial bioproduction of food and chemicals. Now, using a metabolic engineering approach, yeast is engineered to produce glucose, myo-inositol, glucosamine, sucrose and starch from C1–3 molecules.

TCEP immobilized on agarose is widely used for efficient reduction of cysteines in peptides and proteins, but the reducing capacity is rather low. Herein, we have compared different solid supports for TCEP immobilization and found that silica-TCEP has an 8-fold higher reduction capacity, allowing thiol reduction of peptides at millimolar concentrations.

Abstract

Tris-(2-carboxyethyl)phosphine (TCEP) linked to agarose beads is widely used for reducing disulfide bridges in proteins and peptides. The immobilization of TCEP on beads allows efficient removal after reduction to prevent its reaction with alkylating reagents and thus interference with conjugation reactions. However, a limitation of agarose TCEP is its relatively low reduction capacity per milliliter of wet beads (about 15 μmol/ml), making it unsuitable for the reduction of disulfides from molecules at millimolar concentrations. In this work, we tested the immobilization of TCEP to a range of different solid supports and found that conjugation to silica gel offers TCEP beads with about 8-fold higher reduction capacity (129±16 μmol/ml wet beads). We show that it allows reducing disulfide-cyclized peptides at millimolar concentrations for subsequent cyclization by bis-electrophile linker reagents. Given the substantially higher reduction capacity, the robust performance in different solvents, the low cost of the silica gel, and the ease of functionalization with TCEP, the silica gel-TCEP is suited for reducing disulfide bridges in essentially any peptide and is particularly useful for reducing peptides at higher concentrations.

The synthesis of a phosphonium-substituted diphosphaindenylide, PPI, is reported. Introduction of two P atoms to the indenyl core results in considerable biradical character. Moreover, the ligand properties of PPI are investigated using a chromium tricarbonyl complex as model compound.

Abstract

Starting from C₆H₄(PCl₂)₂ and the TMS-substituted ylide (TMS)₂C=PR₃ (TMS=trimethylsilyl, R=p-tolyl), the phosphonium-substituted diphosphaindenylide PPI was prepared in two steps. CASSCF calculations as well as the reactivity toward diphenyl acetylene suggest a notable biradical character in PPI. Reaction with [Cr(CO)₃(MeCN)₃] affords the complex [Cr(CO)₃(η ⁵-PPI)] (5). This complex was employed to explore the ligand properties of PPI, which demonstrates considerable potential through the combination of strong metal-ligand interactions and the possibility of a pronounced indenyl effect.

Science, Volume 382, Issue 6674, Page 1026-1031, December 2023.

Science, Volume 382, Issue 6674, Page 987-987, December 2023.

Science, Volume 382, Issue 6674, Page 1056-1065, December 2023.

Machine learning approaches allow the creation of protein adaptive landscapes and the identification of catalytic modes using limited experimental data to establish relationships between enzyme, substrate and catalytic performance, and have been used for data-driven protein engineering to improve their catalytic activity and selectivity.

Abstract

Protein engineering is essential for altering the substrate scope, catalytic activity and selectivity of enzymes for applications in biocatalysis. However, traditional approaches, such as directed evolution and rational design, encounter the challenge in dealing with the experimental screening process of a large protein mutation space. Machine learning methods allow the approximation of protein fitness landscapes and the identification of catalytic patterns using limited experimental data, thus providing a new avenue to guide protein engineering campaigns. In this concept article, we review machine learning models that have been developed to assess enzyme-substrate-catalysis performance relationships aiming to improve enzymes through data-driven protein engineering. Furthermore, we prospect the future development of this field to provide additional strategies and tools for achieving desired activities and selectivities.