Delocalized radical systems present a challenging yet appealing ground to test the control of multiple selectivity in organic synthesis. Despite some recent advancements, the issue of regioselectivity in delocalized radical system has largely centered on allylic radicals. To explore larger delocalized radical systems, we report the catalytic generation of extensively delocalized 4-vinylphenoxyl radicals and their involvement as key intermediates in regioselective radical C-N bond formation. Guided by the mechanistic principles of metalloradical catalysis, we develop a Co(II)-based enantioselective radical system for dearomative 1,7-conjugate amination of readily available 4-vinylphenols with aryl azides. This can afford valuable chiral α-tertiary amino acid derivatives in high yields with excellent enantioselectivities for the newly-created tetrasubstituted stereocenters. Unlike prior systems, this amination involves hydrogen-atom abstraction from O-H bonds. As demonstrated with 1,6-conjugate addition with various nucleophiles, the resulting α-tertiary amino acid derivatives, which bear additional -quinone methide (-QM) functionality, may find useful synthetic applications.

Carbon-sulfur bond-forming reactions in natural product biosynthesis largely involve Lewis acid/base chemistry with relatively few examples catalysed by radical -adenosyl-l-methionine (SAM) enzymes. The latter have been limited to radical-mediated sulfur insertion into carbon-hydrogen bonds with the sulfur atom originating from a sacrificial auxiliary iron-sulfur cluster. Here we show that the radical SAM enzyme AbmM encoded in the albomycin biosynthetic gene cluster catalyses a sulfur-for-oxygen swapping reaction, transforming the furanose ring of cytidine 5'-diphosphate to a thiofuranose moiety that is essential for the antibacterial activity of albomycin δ. Thus, in addition to its canonical function of mediating the reductive cleavage of SAM, the radical SAM catalytic cluster of AbmM appears to play a role in providing the sulfur introduced during the AbmM-catalysed reaction. These discoveries not only establish the origin of the thiofuranose core in albomycin δ but, more importantly, also emphasize the functional diversity of radical SAM catalysis.

Despite increasing demand for chiral fluorinated organic molecules, enantioselective C-H fluorination remains among the most challenging and sought-after transformations in organic synthesis. Furthermore, utilizing nucleophilic sources of fluorine is especially desirable for F-radiolabelling. To date, methods for enantioselective nucleophilic fluorination of inert C(sp)-H bonds remain unknown. Herein, we report our design and development of a Pd-based catalytic system bearing bifunctional MPASA ligands which enabled highly regio- and enantioselective nucleophilic β-C(sp)-H fluorination of synthetically important amides and lactams, commonly present in medicinal targets. The enantioenriched fluorinated products can be rapidly converted to corresponding chiral amines and ketones which are building blocks for a wide range of bioactive scaffolds. Mechanistic studies suggest that the C-F bond formation proceeds via outer-sphere reductive elimination with direct incorporation of fluoride, which was applied to late-stage F-radiolabelling of pharmaceutical derivatives using [F]KF.

Iminium-catalyzed cycloaddition is one of the most prominent examples of organocatalysis, yet a biological counterpart has not been reported despite the wide-spread occurrence of iminium adducts in enzymes. Here, we present biochemical, structural, and computational evidence for iminium catalysis by the natural Diels-Alderase SdnG that catalyzes norbornene formation in sordarin biosynthesis. A Schiff base adduct between the ε-nitrogen of active site K127 and the aldehyde group of the enal dienophile was revealed by structural analysis and captured under catalytic conditions via borohydride reduction. This Schiff base adduct positions the substrate into near-attack conformation and decreases the transition state barrier of Diels-Alder cyclization by 8.3 kcal/mol via dienophile activation. A hydrogen bond network consisting of a catalytic triad is proposed to facilitate proton transfer required for iminium formation. This work establishes a new mode of catalysis for Diels-Alderases and points the way to the design of novel iminium based (bio)catalysts.

Stereochemically controlled hydrogen bond donors play essential roles in the pharmaceutical industry. Consequently, organic molecules that bear difluoromethyl (CFH) groups at chiral centres are emerging as pivotal components in pharmaceuticals owing to their distinct hydrogen-bonding property. However, a general approach for introducing CFH groups in an enantioselective manner has remained elusive. Here we show that enantioconvergent difluoromethylation of racemic alkyl electrophiles, through alkyl radical intermediates, represents a strategy for constructing CFH-containing stereocentres. This strategy is enabled by using copper catalysts bound with a chiral diamine ligand bearing electron-deficient phenyl groups, and a nucleophilic CFH-zinc reagent. This method allows the high-yield conversion of a diverse range of alkyl halides into their alkyl-CFH analogues with excellent enantioselectivity. Mechanistic studies reveal a route involving asymmetric difluoromethylation of alkyl radicals and crucial non-covalent interactions in the enantiodetermining steps. This copper-catalysed difluoromethylation process opens an avenue for the efficient preparation of CFH-containing pharmaceuticals.

Heterologous expression of nitrogenase has been actively pursued because of the far-reaching impact of this enzyme on agriculture, energy and environment. Yet, isolation of an active two-component, metallocentre-containing nitrogenase from a non-diazotrophic host has yet to be accomplished. Here, we report the heterologous synthesis of an active Mo-nitrogenase by combining genes from and in . Metal, activity and EPR analyses demonstrate the integrity of the metallocentres in the purified nitrogenase enzyme; whereas growth, nanoSIMS and NMR experiments illustrate diazotrophic growth and N enrichment by the expression strain, as well as accumulation of extracellular ammonia upon deletion of the ammonia transporter that permits incorporation of thus-generated N into the cellular mass of a non-diazotrophic strain. As such, this study provides a crucial prototype system that could be optimized/modified to enable future transgenic expression and biotechnological adaptations of nitrogenase.

Sulfur-stereogenic molecules have a significant impact on drug development, but are underexplored largely due to our limited ability to construct such structures. Among them, sulfilimines are a class of chiral molecules bearing S(IV)-stereocenters, which exhibit great value in chemistry and biology but were synthetically intractable previously. We report a highly chemoselective and enantioselective Chan-Lam -arylation of sulfenamides with arylboronic acids to deliver an array of thermodynamically disfavored diaryl and alkyl aryl sulfilimines containing a sulfur stereocenter. Though Chan-Lam coupling has been widely used to construct C-N, C-O and C-S bonds by coupling nucleophiles with boronic acids using copper complexes in academia and industry, control of the stereochemistry in this textbook transformation has proven to be a formidable challenge. A new copper catalyst from a 2-pyridyl -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.

Intermolecular functionalization of tertiary C-H bonds to construct fully substituted stereogenic carbon centers represents a formidable challenge: without the assistance of directing groups, state-of-the-art catalysts struggle to introduce chirality to racemic tertiary s -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 -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 elucidate how active-site residues distinguish between the enantiomers and enable the enzyme to perform this transformation with excellent enantioselectivity.

Hybrid systems that integrate synthetic materials with biological machinery offer opportunities for sustainable and efficient catalysis. However, the multidisciplinary and unique nature of the materials-biology interface requires researchers to draw insights from different fields. In this Perspective, using examples from the area of N and CO fixation, we provide a unified discussion of critical aspects of the material-microbe interface, simultaneously considering the requirements of physical and biological sciences that have a tangible impact on the performance of biohybrids. We first discuss the figures of merit and caveats for the evaluation of catalytic performance. Then, we reflect on the interactions and potential synergies at the materials-biology interface, as well as the challenges and opportunities for a deepened fundamental understanding of abiotic-biotic catalysis.

Constructive functionalization of unstrained aryl-aryl bonds has been a fundamental challenge in organic synthesis due to the inertness of these bonds. Here we report a split cross-coupling strategy that allows two-fold arylation with diverse aryl iodides through cleaving unstrained aryl-aryl bonds of common 2,2'-biphenols. The reaction is catalyzed by a rhodium complex and promoted by a removable phosphinite directing group and an organic reductant. The combined experimental and computational mechanistic studies reveal a turnover-limiting reductive elimination step that can be accelerated by a Lewis acid co-catalyst. The utility of this coupling method has been illustrated in the modular and simplified syntheses of unsymmetrical 2,6-diarylated phenols and skeletal insertion of phenyl units.

Skeletal editing has received unprecedented attention as an emerging technology for the late-stage manipulation of molecular scaffolds. The direct achievement of functionalized carbon-atom insertion in aromatic rings is challenging. Despite ring-expanding carbon-atom insertion reactions, such as the Ciamician-Dennstedt re-arrangement, being performed for more than 140 years, only a few relevant examples of such transformations have been reported, with these limited to the installation of halogen, ester and phenyl groups. Here we describe a photoredox-enabled functionalized carbon-atom insertion reaction into indene. We disclose the utilization of a radical carbyne precursor that facilitates the insertion of carbon atoms bearing a variety of functional groups, including trifluoromethyl, ester, phosphate ester, sulfonate ester, sulfone, nitrile, amide, aryl ketone and aliphatic ketone fragments to access a library of 2-substituted naphthalenes. The application of this methodology to the skeletal editing of molecules of pharmaceutical relevance highlights its utility.

Catalytic metal clusters play critical roles in important enzymatic pathways such as carbon fixation and energy conservation. However, how ligand binding to the active-site metal regulates conformational changes critical for enzyme function is often not well understood. One carbon fixation pathway that relies heavily on metalloenzymes is the reductive acetyl-coenzyme A (acetyl-CoA) pathway. In this study, we investigated the catalysis of the last step of the reductive acetyl-CoA pathway by the CO-dehydrogenase (CODH)-acetyl-CoA synthase (ACS) complex from , focusing on how ligand binding to the nickel atom in the active site affects the conformational equilibrium of the enzyme. We captured six intermediate states of the enzyme by cryo-electron microscopy, with resolutions of 2.5-1.9 Å, and visualized reaction products bound to cluster A (an Ni,Ni-[4Fe4S] cluster) and identified several previously uncharacterized conformational states of CODH-ACS. The structures demonstrate how substrate binding controls conformational changes in the ACS subunit to prepare for the next catalytic step.

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 . 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.

Artificial metalloenzymes present a promising avenue for abiotic catalysis within living systems. However, their in vivo application is currently limited by critical challenges, particularly in selecting suitable protein scaffolds capable of binding abiotic cofactors and maintaining catalytic activity in complex media. Here we address these limitations by introducing an artificial metathase-an artificial metalloenzyme designed for ring-closing metathesis-for whole-cell biocatalysis. Our approach integrates a tailored metal cofactor into a hyper-stable, de novo-designed protein. By combining computational design with genetic optimization, a binding affinity (  ≤ 0.2 μM) between the protein scaffold and cofactor is achieved through supramolecular anchoring. Directed evolution of the artificial metathase yielded variants exhibiting excellent catalytic performance (turnover number ≥1,000) and biocompatibility. This work represents a pronounced leap in the de novo design and in cellulo engineering of artificial metalloenzymes, paving the way for abiological catalysis in living systems.

Catalytic enantioconvergent nucleophilic substitution reactions of alkyl halides are highly valuable transformations, but they are notoriously difficult to implement. Specifically, nucleophilic fluorination is a renowned challenge, especially when inexpensive alkali metal fluorides are used as fluorinating reagents due to their low solubility, high hygroscopicity and Brønsted basicity. Here we report a solution by developing the concept of synergistic hydrogen bonding phase-transfer catalysis. Key to our strategy is the combination of a chiral -urea hydrogen bond donor (HBD) and an onium salt-two phase-transfer catalysts essential for the solubilization of potassium fluoride-as a well-characterized ternary HBD-onium fluoride complex. Mechanistic investigations indicate that this chiral ternary complex is capable of enantiodiscrimination of racemic benzylic bromides and α-bromoketones, and upon fluoride delivery affords fluorinated products in high yields and enantioselectivities. This work provides a foundation for enantioconvergent fluorination chemistry enabled through the combination of a HBD catalyst with a co-catalyst specifically curated to meet the requirement of the electrophile.

The site-selective functionalization of C( )-H bonds represents a powerful strategy for the synthesis of structurally diverse compounds with broad applicability. Here we report efficient regioselective catalytic methods for the formation of benzyltrimethylsilanes through ruthenium-catalysed C( )-H silylmethylation. The developed protocols enable selective functionalization at both and positions within arenes bearing N-based directing groups. The resulting silylmethyl compounds can undergo diverse transformations, including nucleophilic aromatic substitution, carbonyl addition, olefination and desilylation. Significantly, the regiodivergent installation of silylmethyl synthetic handles allows for the synthesis of the pharmaceutical losmapimod and could further be applied in direct late-stage functionalizations. Mechanistically, an essential role for biscyclometallated ruthenium(II) species has been found, with the formation of intermediate ruthenium(III) species indicated by paramagnetic NMR experiments. These synthetic inventions and mechanistic elucidations signify a transformative step within ruthenium-catalysed C( )-H functionalization, enabling diverse syntheses and providing a framework for future development.

The Heck reaction, which is widely used for the construction of C‒C bonds, is a cornerstone of modern organic synthesis. Traditionally, this transformation relies on transition metal catalysts, whose frontier -orbitals cement the mechanism and scope of the reaction. Here we present a conceptually distinct Heck-type coupling strategy that replaces transition metals with a photoactive bismuth complex, marking an advance in main group catalysis. This approach leverages the distinctive electronic and photophysical properties of bismuth, providing a reimagined reaction pathway. The bismuth catalyst undergoes a photo-induced ligand-to-metal charge transfer processes, unmasking a Bi(II) species capable of halogen atom transfer (XAT) processes with alkyl iodides. The multifaceted redox-dependent photophysical properties of the bismuth catalyst facilitate the coupling of aryl and alkyl electrophiles with styrenes through an intricate interplay of mechanistic steps. The method provides a mechanistic blueprint for accessing coveted Bi(II) species, offering an alternative to transition metal catalysis in organic synthesis.

Methylthio-alkane reductases convert methylated sulfur compounds to methanethiol and small hydrocarbons, a process with important environmental and biotechnological implications. These enzymes are classified as nitrogenase-like enzymes, despite lacking the ability to convert dinitrogen to ammonia, raising fundamental questions about the factors controlling their activity and specificity. Here we present the molecular structure of the methylthio-alkane reductase, which reveals large metalloclusters, including the P-cluster and the [FeSC]-cluster, previously found only in nitrogenases. Our findings suggest that distinct metallocluster coordination, surroundings and substrate channels determine the activity of these related metalloenzymes. This study provides new insights into nitrogen fixation, sulfur-compound reduction and hydrocarbon production. We also shed light on the evolutionary history of P-cluster and [FeSC]-cluster-containing reductases emerging before nitrogenases.

Azetidines are four-membered saturated N-heterocycles that are of interest in discovery chemistry. However, the implementation of these structures is limited by their synthetic intractability, resulting from their inherent ring strain. An approach that circumvents this is the intermolecular [2 + 2] photocycloaddition between imines and alkenes. However, this is unworkable with simple acyclic imines and non-activated alkenes, due to the inability to generate suitably reactive imine-derived triplet intermediates. Here we show that simple acyclic imines bearing N-sulfamoyl fluoride substituents generate reactive triplet imines that react with a broad range of alkenes to produce azetidine products in high yields. Mechanistic and computational studies confirm the key role of the sulfamoyl fluoride unit in dictating the [2 + 2] pathway. In addition, the sulfamoyl fluoride substituents offer a convenient reaction site for product functionalization or for traceless removal. The advent of synthetically useful imine-derived triplets should initiate further research and applications of these elusive reactive intermediates.

The development of novel strategies to rapidly construct complex chiral molecules from readily available feedstocks is a long-term pursuit in the chemistry community. Radical-mediated alkene difunctionalizations represent an excellent platform towards this goal. However, asymmetric versions remain highly challenging, and more importantly, examples featuring simple hydrocarbons as reaction partners are elusive. Here we report an asymmetric three-component alkene dicarbofunctionalization capitalizing on the direct activation of C( )-H bonds through the combination of photocatalysed hydrogen atom transfer and nickel catalysis. This protocol provides an efficient platform for installing two vicinal carbon-carbon bonds across alkenes in an atom-economic fashion, providing a wide array of high-value chiral α-aryl/alkenyl carbonyls and phosphonates, as well as 1,1-diarylalkanes from ubiquitous alkane, ether and alcohol feedstocks. This method exhibits operational simplicity, broad substrate scope and excellent regioselectivity, chemoselectivity and enantioselectivity. The compatibility with bioactive motifs and expedient synthesis of pharmaceutically relevant molecules highlight the synthetic potential of this protocol.

Achieving substrate generality in asymmetric catalysis remains a long-standing goal, particularly for the selective construction of chiral heteroatoms. Compared with carbon, sulfur, phosphorus and silicon stereogenic centres, methods for the construction of their boron and germanium congeners remain very scarce. Chiral (hetero) spirocycles are of relevance in several research domains. Methods effective for constructing carbon-centred chiral spirocycles do not translate to boron and germanium, leaving these chiral centres unexplored. We describe a unified strategy for constructing carbon, boron and germanium-centred chiral spirocyclic skeletons via enantioselective hetero [2+2+2] cycloaddition of a bis-alkyne with a nitrile. A chiral designer Ni(0) -heterocyclic carbene complex enables the required long-range enantioinduction. The resulting enantio-enriched spirocycles feature a pyridine motif, making them exploitable for ligand design and functional materials featuring attractive photophysical and chiroptical properties.