Abstract Protecting-group (PG)-free S-glycosylation offers an attractive strategy for glycopeptide synthesis, yet practical methods for complex peptides remain limited. Here, we report a non-photochemical S-glycosylation strategy that directly couples unprotected glycosyl donors with unprotected cysteine-containing peptides, enabling efficient access to β-S-glycopeptides. The method shows broad compatibility with glycosyl donors and peptide substrates and enables direct glycosylation of a structurally complex 37-mer precursor bearing one free cysteine, four protected cysteines, and oxidation-sensitive functionalities, thereby facilitating the efficient synthesis of sublancin and diverse glycosylated analogues. In contrast to photochemical radical-based S-glycosylation, which produces α-S-glycopeptides and proved unsuitable for the full-length substrate, the present strategy allows efficient late-stage glycosylation of structurally complex peptides. Combined with a fragment-based native chemical ligation approach for α-S-glycoside synthesis, this platform provides stereochemically defined sublancin analogues and reveals that the configuration of the S-glycosidic linkage strongly influences antibacterial activity. These results establish a practical PG-free platform for complex S-glycopeptide synthesis and glycocin structure–activity studies.
Abstract Aryl-substituted azetidines are found in pharmacologically active compounds; however, efficient synthetic methods to access this scaffold remain limited. Existing approaches predominantly enable the synthesis of azetidines bearing electron-rich aryl substituents. Herein, we report a new and straightforward route to 3-substituted 1-azabicyclo[1.1.0]butanes (ABBs) from commercially available tert-butyl 3-oxoazetidine-1-carboxylate in four steps. The ABBs were then applied in a three-component photocatalytic ring-opening reaction, affording 3,3-diaryl-N-sulfonylazetidines with a variety of electron-poor (hetero)arene units, a previously inaccessible chemical space. Under the optimized conditions, 29 examples of 3,3-diaryl-N-sulfonylazetidines were prepared in yields of up to 72%.
Designing fluorescent small molecules requires simultaneous control over optical responses, brightness, and physicochemical constraints across vast, underexplored chemical spaces. Conventional generate-score-screen approaches become impractical under such realistic design specifications, owing to their low search efficiency, unreliable generalizability of machine-learning predictions, and the prohibitive cost of quantum chemical calculations. Here, we present LUMOS, a data- and physics-driven framework for inverse design of fluorescent molecules. LUMOS couples the generator and predictor within a shared latent representation, enabling direct specification-to-molecule design and efficient exploration. Moreover, LUMOS combines neural networks with a fast time-dependent density functional theory (TD-DFT) calculation workflow to build a suite of complementary predictors spanning different trade-offs in speed, accuracy, and generalizability, enabling reliable property prediction across diverse scenarios. Finally, LUMOS employs a property-guided diffusion model integrated with multiobjective evolutionary algorithms, enabling de novo design and molecular optimization under multiple objectives and constraints. Benchmarks across random, scaffold, and fluorophore splits show competitive or improved predictive accuracy together with enhanced physical consistency, while multiobjective optimization yields substantially improved Pareto fronts over representative baselines. Further validation using TD-DFT and molecular dynamics (MD) simulations demonstrates that LUMOS can generate valid fluorophores that meet various target specifications. Overall, these results establish LUMOS as a data-physics dual-driven framework for fluorophore inverse design.
Abstract G-quadruplex (G4) structures play key physiological roles and serve as functional building blocks in DNA/RNA-based aptamer biosensors. Their function critically depends on their structural stability and nonspecific interactions in cells. However, the behavior of exogenously delivered G4s in living cells remains poorly understood. Here, using 19F NMR, we monitored three representative G4 sequences, HT, hVEGFP, and TBA, in intact Xenopus laevis oocytes, HeLa cells, and derived lysates. We found that G4 structural stability, interactions, and NMR signal detectability are cell-type-dependent. In oocytes, all three G4s maintain detectable folded signals, with TBA showing slight time-dependent degradation. In HeLa cells, folded signals are absent for all three G4s due to intracellular interactions. HT and TBA undergo degradation in the cytoplasm rather than in the nucleus, whereas hVEGFP uniquely remains protected from degradation owing to both its higher thermal stability and protective interactions. These findings highlight the non-negligible effect of the cellular environment and the necessity of studying G4s in their native cellular context. Furthermore, we demonstrated that cell lysates can serve as a practical platform for reflecting G4 stability in intact cells. Collectively, this work deepens our understanding of G4 behavior in cells and provides a basis for improvement of G4-based agents.
Abstract Optoglycomics describes an emerging research field in which photoswitchable glycoconjugates are employed to probe and control carbohydrate–protein interactions with light. In most cases, azobenzene serves as the photoswitchable chromophore, which can be reversibly isomerized between its E and Z state, thereby substantially altering the spatial presentation of conjugated glycans. This light-induced conformational change can modulate the affinity of glycan ligands for their receptors and the inhibitory properties of glycosidase and glycosyltransferase inhibitors. Furthermore, glycosylated surfaces, including the cellular glycocalyx, as well as other glycosylated supramolecular assemblies, can be manipulated with the high spatial and temporal precision afforded by light. Although optoglycomics is still in its infancy, the remarkable success of photopharmacology suggests that it has the potential to become a powerful tool for investigating the still not conclusively understood complexity of glycobiology and to inspire new diagnostic and therapeutic strategies for glycan-associated diseases.
Abstract Achieving high ductility and toughness in semicrystalline polymers without sacrificing stiffness remains a longstanding challenge. Here we show that sparse precise ionic functionalization can fundamentally alter the mechanical behavior of a semicrystalline polymer. Ionic poly(ethylene glycol) (iPEGs) containing precisely spaced imidazolium groups (∼1.5 mol %, every 62 repeat units) undergo a striking transition from brittle to ultraductile behavior, which exhibits stable neck propagation and apparent strain hardening at moderate molecular weight of 41 kDa. Tensile behavior, melt rheology, and X-ray scattering spectra reveal that this highly ductile behavior arises from a coupled ionic-semicrystalline architecture. Dynamic ionic associations introduce long-lived transient constraints that enhance the amorphous phase resistance to deformation and sustain load-bearing connectivity between crystallites, while ionic incorporation suppresses lamellar thickening and produces thin PEG crystallites capable of deformation-induced reorganization. The resulting interplay between crystallite connectivity, tie-chain load transfer, and reconfigurable crystallites enable stable neck propagation rather than brittle fracture. These results establish sparse ionic “stickers” as a molecular design principle for strengthening crystal-mobile semicrystalline polymers without introducing additional phases or permanent covalent cross-links.
Abstract The transformation of electron-deficient pyridines into electron-rich Zincke imines is a well-established strategy for selective C3/C5 functionalization via electrophilic or radical pathways. Despite this, the reactivity of these imines toward metal nitrenoids has remained unexplored. Addressing this gap, we herein disclose an iron-catalyzed divergent reaction of Zincke imines with dioxazolones. Depending on the conditions, this protocol provides access to either C5-amidopyridines or substituted oxazoles, primarily starting from 2-substituted pyridines. This highly regioselective C5-amidation proceeds under mild conditions to furnish biologically relevant 2-substituted 5-amidopyridines, providing direct access to valuable scaffolds that are otherwise challenging and costly to access via conventional routes. Conversely, oxidative conditions at elevated temperatures favor the formation of oxazole derivatives with versatile synthetic handles. Mechanistic and theoretical insights support the generation of a reactive Fe(III)-imidyl intermediate that undergoes selective addition at the C5 position of the Zincke imine.
Abstract 6-acetyl-L-tryptophan (6Ac-Trp) was synthesized as a tryptophan (Trp) analog with an absorption spectrum extending to ca. 400 nm, an emission spectrum spanning the blue-to-green visible region. Its fluorescence quantum yield is environment-sensitive (i.e., ca. 0.54 in water and <0.01 in hydrophobic solvents). A highly active synthetase was evolved for site-specific incorporation of 6Ac-Trp into proteins in both Escherichia coli and mammalian cells. Moreover, the utility of 6Ac-Trp was demonstrated by two-photon excitation fluorescence microscopy imaging of cell-penetrating peptide distributions in live HeLa cells and nuclear localization of histone H3 in HEK293T cells. Given its structural similarity to tryptophan, compatibility with chemical peptide synthesis, and genetic encoding, 6Ac-Trp provides a useful minimal fluorophore for site-specific studies of protein dynamics, interactions, and localization in complex biological systems.
Abstract The global rise of antibiotic resistance poses a public health challenge, emphasizing the urgent need for novel antibiotics featuring unique chemical scaffolds and mechanisms of action. Here, we report the discovery and characterization of darumycins, guanidine-containing pentacyclic sesterterpene antibiotics that exhibit potent activity against high-priority Gram-positive pathogens and mycobacteria. The darumycin biosynthetic gene cluster was identified through genome mining in the Actinobacterium Micromonospora rubida and heterologously expressed in Streptomyces chassis strains. Gene cluster engineering facilitated the discovery of novel darumycin derivatives, thereby expanding the chemical diversity within the sesterterpene class of natural products and revealing nuanced variations in their bioactivity. Targeted gene deletions, along with LC–MS and NMR analyses, enabled us to propose a darumycin biosynthetic pathway, further complemented by in vitro biochemical characterization of two O-methyltransferase tailoring enzymes, DarM and DarG. The high-resolution crystal structure of DarM in complex with SAH provided valuable insights into the enzymatic mechanism and revealed a distinct architecture compared to other methyltransferases acting on terpene scaffolds.
Abstract Lindqvist-type polyoxovanadate-alkoxides are used as atomically precise, soluble analogs of metal oxides to interrogate site-dependent (e.g., μ2-oxido vs terminal oxido) tunneling in proton-coupled electron transfer (PCET). Variable-temperature kinetic isotope effect (VT-KIE) analysis reveals that H atom uptake at the μ2-oxido site of [TBA]2[V6O8(OCH3)11] proceeds via quantum mechanical tunneling in acetonitrile, evidenced by a temperature-independent KIE, a small isotopic effect on activation energy, and positive Arrhenius prefactor ratio. This behavior is in contrast to PCET at the terminal vanadyl site of [TBA][V6O7(OCH3)12], which follows a semiclassical, concerted proton–electron transfer mechanism. Tunneling effects are solvent dependent; switching to dimethylformamide, a more basic solvent, results in a reduction in H-bonding interactions with the acceptor, lowering the observed rate of H atom uptake at the bridging site. This work highlights the role of site-specific basicity on tunneling in metal oxides, where competitive H-bonding with solvent disrupts tunneling.
Abstract Mitochondrial DNA (mtDNA) has emerged as a promising target for the development of next-generation chemotherapeutics, as its damage can disrupt key processes that drive cancer progression and resistance to nuclear DNA (nDNA)-targeting drugs. However, achieving selective and direct targeting of mtDNA remains a significant challenge due to its nucleobase similarity to nDNA and necessitates mitochondria-directed delivery strategies. This study reports the identification of a novel N-heterocyclic carbene (NHC) rhenium (Re) complex 4 that selectively targets and damages mtDNA in cancer cells without the need for mitochondria-directed delivery, while sparing nDNA. This remarkable selectivity arises from the inherent reactivity preference of this complex toward mtDNA, rather than from distribution-driven effects. The in vitro potency of complex 4 outperformed that of nDNA-targeting cisplatin. In-depth mechanistic studies revealed that complex 4 forms covalent adducts with mtDNA, leading to disruption of mitochondrial gene replication and transcription. This triggers various downstream effects, including mitochondrial superoxide generation, dissipation of membrane potential, downregulation of nucleoid-associated proteins and polymerase γ expression, and depletion of OXPHOS proteins and ATP, leading to induction of mitophagy and endoplasmic reticulum stress. It induced necroptosis-mediated cell death and has the ability to overcome cisplatin resistance across multiple cancer cell lines. Furthermore, it significantly reduces the volume of 3D tumor spheroids, demonstrating efficacy in a physiologically relevant tumor model. Overall, this study identifies for the first time the unique mtDNA-targeting capability of [Re(I)(bisNHC)(CO)3Cl] complexes without the need for mitochondria-targeting vectors.
Abstract Mechanical force can often unlock chemical reactivity inaccessible under conventional conditions. However, understanding how molecular structure and environment govern mechanochemical reaction pathways in the solid state remains a significant challenge. In particular, establishing design principles to access heterolytic bond scission in nonpolar materials remains elusive. Here, we investigate a family of diarylmethane-based mechanophores embedded in polymer networks to elucidate how bond identity, substituent electronics, leaving-group stabilization, and matrix interactions collectively determine mechanochemical reactivity. By systematically varying the nature of the scissile bond (C–O vs C–C), the electronic properties of the diarylmethane core, and the presence or absence of hydrogen-bonding functionalities in the surrounding polymer matrix, we establish structure–reactivity relationships that govern the formation of radical and ionic species under tensile load. Mechanophores containing C–O bonds display environment-dependent behavior, with homolytic cleavage dominating in non-hydrogen-bonding matrices and heterolytic scission accessible only when both strongly donating substituents and hydrogen-bond donors are present. In contrast, mechanophores incorporating polarized C–C bonds with strongly stabilizing leaving groups undergo heterolytic cleavage to yield diarylcarbenium ions, even in matrices lacking hydrogen-bonding functionality. These results establish design principles linking molecular structure and polymer environment to mechanochemical reactivity and demonstrate that ionic pathways can be accessed and stabilized in the solid state. More broadly, this work provides guidelines for designing mechanoresponsive materials with distinct reaction pathways and mechanochromic responses.
Abstract Water electrolyzers are key technologies for enabling a carbon-neutral society by facilitating sustainable hydrogen production. Despite extensive efforts to develop highly active catalysts, a persistent gap remains between catalyst performance evaluated in rotating disk electrode (RDE) systems and that achieved in practical membrane electrode assembly (MEA) configurations. In this perspective, we highlight the origins of this discrepancy and emphasize that intrinsic catalytic activity alone is insufficient to predict electrolyzer performance. Using the acidic hydrogen evolution reaction (HER) as a model system, we demonstrate that apparent activity metrics such as mass activity and Tafel slope can be significantly influenced by catalyst loading, composition, and measurement conditions in RDE, often leading to misleading conclusions. In contrast, MEA performance is governed by complex interfacial phenomena including mass, electron, and charge transport. A similar behavior was also observed for alkaline HER and acidic oxygen evolution reaction (OER). We further present case studies illustrating the critical roles of electron transfer and durability in water electrolyzers. In addition, recent advances in proton-exchange-membrane water electrolyzer commercialization are discussed, highlighting the importance of system-level optimization, including ionomer distribution control and scalable manufacturing via slot-die coating, which enabled the deployment of a 2.5 MW system. Overall, bridging the gap between laboratory catalyst research and industrial water electrolyzer applications requires a shift from catalyst-centric design toward integrated system-level engineering.
Abstract The construction of C(sp2)-C(sp3) bonds is fundamental to pharmaceutical synthesis, yet metal-free approaches to electrophilic cross-coupling remain underdeveloped. Herein, we report a visible-light-driven, metal-free cross-coupling between heteroaryl nitriles and alkyl bromides enabled by a rationally designed aminosilane, (TMS)3SiNHPh. This reagent engages electron-deficient nitriles in an EDA complex via π–π interaction. Photoinduced electron transfer generates a silyl radical that triggers XAT from alkyl bromides, delivering alkyl radicals for subsequent decyanative coupling without the need for an external photocatalyst or transition-metal catalyst. The method accommodates a broad range of substrates, providing alkylated heteroarenes in moderate to good yields, and extends to Minisci-type C–H alkylations, underscoring the versatility of this platform. This work demonstrates that strategic EDA donor design can address a long-standing challenge in metal-free electrophilic coupling.
Abstract Traditional efforts in modulating the reactivity of metal centers focus on tuning parameters in the primary coordination sphere. The ability to embed stimuli-responsive functionality in the secondary coordination sphere to modulate metal center reactivity represents a distinct strategy for expanding transition metal reactivity while leaving the primary coordination sphere unmodified. Herein, we describe the incorporation of a photoresponsive unit, fluorenone, into the secondary coordination sphere of a Ni(II) complex resulting in a significant perturbation of the complex electronic structure, manifesting in distinct excited states that cannot be predicted by the metal complex or fluorenone unit alone. Using the activation of strong nickel(II) trifluoromethyl bonds as a readout of this strategy, the incorporation of latent ligand-centered radicals enabled near-quantitative generation of trifluoromethyl radical. Comparisons with a control complex lacking the appended fluorenone unit demonstrated the unique role of the appended fluorenone, showcasing the ability to endow photoreactivity to an otherwise unreactive complex. Mechanistic studies including TD-DFT calculations, cyclic voltammetry, and transient absorption spectroscopy support that irradiation with visible light leads to metal-to-ligand charge transfer followed by relaxation to a long-lived 3d–d state. The studies presented herein showcase a ligand design principle focused on secondary coordination sphere edits through the introduction of latent ligand-centered radicals, allowing for the direct tuning of the metal center reactivity.
Mass spectral molecular networking has become an indispensable tool for natural product discovery, yet its performance in distinguishing isomeric structures and recognizing unprecedented carbon skeletons remains challenging, especially for low-signal-to-noise ratio mass spectra. Herein, we introduce Fragment Ion Abundance-Based Molecular Networking (FIAMN), an advanced strategy that complements standard molecular networking by integrating mode-based spectral denoising, fragment ion abundance characterization, and cosine-spectral entropy dual similarity fusion. This integrated workflow enables more reliable skeleton-oriented clustering and preferential identification of novel scaffolds from complex mixtures. Application of FIAMN to the soft coral Sinularia australiensis afforded six structurally unique diterpenoids, simaustralenes A-F, representing four unprecedented carbon skeletons. Biomimetic photocyclization studies supported their proposed biosynthetic origins and further highlighted how precursor functional groups govern skeletal diversification. Notably, compound 6 exhibited potent antipulmonary fibrosis activity with efficacy comparable to the clinical drug Nintedanib. By enabling more reliable differentiation of isomeric and low-abundance metabolites, FIAMN provides a practical framework for expanding structurally distinct natural product chemical space through MS-guided discovery.
Cells execute complex biological functions through programmed biomolecular condensation, yet a general and programmable strategy for nucleic acid condensation in vitro remains challenging. Here, we demonstrate that carbon dots (CDs) function as an electrostatic-driven versatile chemical compiler that translates nucleobase sequence into programmed condensate architectures and functions. We found that citric acid-ethylene diamine carbon dots (CA-EDA CDs) drive the condensation of both ssDNA and mRNA via multiple weak interactions. Crucially, the spatially heterogeneous electrostatic potential on the CD surface decodes the distinct electrostatic properties of nucleobases through Coulomb-dominated interactions, establishing a definitive binding hierarchy (G > C > T > A), as revealed by systematic binding studies and molecular dynamics simulations. Based on this chemical compiler, we can achieve hierarchical control of the condensate structure. Furthermore, by programming condensate density via sequence engineering, we achieved switchable up- and down-regulation of GFP mRNA translation in a cell-free system, faithfully mimicking the regulatory role of natural ribonucleoprotein granules. This work establishes CDs as a versatile compiler platform for programmable nucleic acid condensation, transcending the limitations of nonspecific electrostatic neutralization and paving the way for constructing intelligent biomaterials and synthetic biological systems with encoded function.
Arene ring-opening (ARO) reaction via C-C bond cleavage remains a formidable challenge due to the exceptional thermodynamic stability of aromatic frameworks. Inspired by enzymatic lignin degradation in nature, we report an oxidative strategy that enables arene ring-opening of benzylic alcohols under mild conditions. Using hydrogen peroxide as oxidant and 2-nitro-4-(trifluoromethyl)-benzeneseleninic acid as the catalyst, we achieved the efficient conversion of benzylic alcohols into muconolactone or muconic acid derivatives, which contain multiple functional handles enabling diverse downstream derivatizations. Both of the exocyclic C-C bonds and the arene ring C-C bonds in benzylic alcohols were cleaved through the present Se-catalytic tandem oxidation and rearrangement processes.
Ensuring the enantiomeric purity of chiral compounds is crucial in pharmaceutical research. Chiral organic carboxylic acids are widely present in drug molecules, and the rapid and accurate differentiation of enantiomers of these compounds is vital for drug screening and quality control. Herein, we have developed a metal-free 19F-labeled NMR probe, combining the dynamic exchange capability of hypervalent iodine with chemical sensing to propose a strategy for the detection of chiral carboxylic acids. This method exhibits high tolerance to potentially competing functional groups, effectively distinguishing enantiomers in complex samples and providing a rapid and selective approach for pharmaceutical chiral analysis. The potential of this method in assessing enantiomeric excess and the selectivity of catalytic reactions underscores its application prospects in asymmetric synthesis and drug development.
Abstract Palladium-catalyzed cross-couplings are frequently limited by off-cycle deactivation pathways, particularly phosphine deligation followed by aggregation of Pd(0) to catalytically inactive palladium black. We report an “on-cycle enforcement” strategy that employs a cooperative, nonalloyed trimetallic assembly─Pd(0), Cu(I), and Mn(III)─confined within PS-750-M/HPMC micelles in water. In this architecture, Pd mediates the canonical oxidative addition and reductive elimination steps, Cu(I) accelerates transmetalation via a Cu-nucleophile intermediate, and Mn(II/III) serves as a redox buffer that likely continuously reoxidizes off-cycle Pd(0) to micelle-soluble Pd(II), followed by its religation and reduction, thereby preventing Pd black formation. Spectroscopic analysis─transmission electron microscopy, scanning transmission electron microscopy–high-angle annular dark-field imaging, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy─reveals that the three metals remain spatially separated in the assembly yet electronically complementary within a phosphorus-rich matrix, enabling persistent catalytic activity. The resulting platform supports rapid, selective C–C couplings at 45 °C with broad substrate compatibility, including heteroarenes and terminal olefin─containing partners, without olefin interference. The catalyst displays exceptional longevity, minimal metal leaching (<1 ppm), and robust scalability, with multicycle reactions and gram-scale processes proceeding efficiently even after extended catalyst storage. These findings establish redox-buffered, compartmentalized trimetallic assemblies as a general solution to enforcing on-cycle Pd catalysis in water.
