Nature Catalysis最新文献

Molecular catalysts play a significant role in chemical transformations, utilizing changes in redox states to facilitate reactions. To date molecular electrocatalysts have efficiently produced single-carbon products from CO₂ but have struggled to achieve a carbon–carbon coupling step. Conversely, copper catalysts can enable carbon–carbon coupling, but lead to broad C₂₊ product spectra. Here we subvert the traditional redox-mediated reaction mechanisms of organometallic compounds through a heterogeneous nickel-supported iron tetraphenylporphyrin electrocatalyst, facilitating electrochemical carbon–carbon coupling to produce ethanol. This represents a marked behavioural shift compared with carbon-supported metalloporphyrins. Extending the approach to a three-dimensional porous nickel support with adsorbed iron tetraphenylporphyrin, we attain ethanol Faradaic efficiencies of 68% ± 3.2% at −0.3 V versus a reversible hydrogen electrode (pH 7.7) with partial ethanol current densities of −21 mA cm⁻². Separately we demonstrate maintained ethanol production over 60 h of operation. Further consideration of the wide parameter space of molecular catalyst and metal electrodes shows promise for additional chemistries and achievable metrics.

Sulfur stereogenic molecules have a significant impact on drug development. Among them, sulfilimines are chiral molecules bearing S(IV) stereocentres, which exhibit great value in chemistry and biology but have so far been synthetically challenging to achieve. Similarly, it has also been a challenge to control the stereochemistry in Chan–Lam coupling, which has been widely used to construct C–N, C–O and C–S bonds by coupling nucleophiles with boronic acids using copper complexes. Here we report a highly chemoselective and enantioselective Chan–Lam S-arylation of sulfenamides with arylboronic acids to deliver an array of thermodynamically disfavoured aryl sulfilimines containing a sulfur stereocentre. A copper catalyst from a 2-pyridyl N-phenyl dihydroimidazole ligand has been designed that enables effective enantiocontrol by means of a well-defined chiral environment and high reactivity that outcompetes the background racemic transformation. A combined experimental and computational study establishes the reaction mechanism and unveils the origin of chemoselectivity and stereoselectivity.

SbzP is a unique pyridoxal-5′-phosphate-dependent enzyme, which catalyses a [3+2] annulation between the pyridinium ring of β-nicotinamide adenine dinucleotide (β-NAD) and an electron rich β,γ-unsaturated quinonoid derived from S-adenosylmethionine in natural product azaindane antibiotics biosynthesis. The SbzP-mediated annulation has been proposed to be a rare tandem C–C bond formation, but its structural basis and catalytic mechanism remain largely unknown. Here we report the β-NAD-complexed structure of PseP (SbzP homologue), identified by cryo-electron microscopy. Structure-based mutagenesis, stopped-flow analysis, thermal shift and surface plasmon resonance analysis identified the important residues for the substrate binding. Molecular dynamics simulations provided insights regarding how the enzyme orients the Cγ of the unsaturated quinonoid to β-NAD. In addition, density functional theory calculations confirmed that the proposed stepwise mechanism is more likely than a pericyclization mechanism. This study provides the structural basis of a pyridoxal-5′-phosphate-dependent enzyme that catalyses nucleophilic Cγ addition and β-NAD processing in natural product biosynthesis.

Generating large omics datasets has become routine for gaining insights into cellular processes, yet deciphering these datasets to determine metabolic states remains challenging. Kinetic models can help integrate omics data by explicitly linking metabolite concentrations, metabolic fluxes and enzyme levels. Nevertheless, determining the kinetic parameters that underlie cellular physiology poses notable obstacles to the widespread use of these mathematical representations of metabolism. Here we present RENAISSANCE, a generative machine learning framework for efficiently parameterizing large-scale kinetic models with dynamic properties matching experimental observations. Through seamless integration of diverse omics data and other relevant information, including extracellular medium composition, physicochemical data and expertise of domain specialists, RENAISSANCE accurately characterizes intracellular metabolic states in Escherichia coli. It also estimates missing kinetic parameters and reconciles them with sparse experimental data, substantially reducing parameter uncertainty and improving accuracy. This framework will be valuable for researchers studying metabolic variations involving changes in metabolite and enzyme levels and enzyme activity in health and biotechnology.

Achieving the selective electrocatalytic activation of C(sp³)–C(sp³) and C(sp³)−H bonds is key to enabling the electricity-driven synthesis of chemicals, the sustainable upgrading of plastics and the development of fuel cells operating on energy-dense liquid fuels. When exposed to electrodes under oxidative bias, hydrocarbons undergo both C–C bond fragmentation and oxygenation. Currently, we lack control over the bifurcation of these pathways. Here we provide insights into the complex network of alkyl transformation reactions, showing that under oxidizing potentials, adsorbed butane transforms to adsorbed CH_x fragments, which can be desorbed as methane before oxidation to adsorbed CO. Identifying the branchpoint between C‒C fragmentation and oxygenation allowed us to steer selectivity by applying pulsed potentials tailored to the desorption potential of specific adsorbates and the kinetics of intermediate oxidation. Our findings provide design criteria for improved fuel cell catalysts and open the door to selective C‒C cleavage in electrosynthetic pathways.