Angewandte Chemie最新文献

Ultrafine metal oxide nanoclusters (UMONs) exhibit remarkable catalytic potential due to their high specific surface area; however, achieving precise control over both the size and crystal phase of UMONs remains a significant challenge. Herein, we developed a dual-induced confined synthesis strategy that couples hydrophobic gating with thermally triggered phase transformation to precisely confine UMONs within the pores of a metal–organic framework (MOF). 13 UMONs@MOF composites were successfully synthesized with the metal cations in UMONs spanning different regions of the periodic table. Notably, sub-3 nm metastable γ-MnO₂ was stabilized and confined within MIL-101(Fe) for the first time. The optimized 15% γ-MnO₂@MIL-101(Fe) showed a durable 100% O₃ removal efficiency for over 100 h. This performance was maintained in a continuous air flow containing 40 ppm O₃ at a high gas hourly space velocity of 1.7 × 10⁵ h⁻¹ over a wide humidity range of 10%–90%. Mechanistic studies reveal that its superior catalytic activity originates from the synergistic effect between the confined γ-MnO₂ active sites and the Fe₃O clusters in the MIL-101(Fe). This work provides a universal approach for the precise control of the size and crystal phase of UMONs, paving the way for designing high-performance catalysts.

Gold catalysis provides access to a remarkable array of complex carbon scaffolds, but the use of silver salts to activate gold(I) chloride precatalysts can be problematic due to Ag(I) light sensitivity, hygroscopicity, redox activity, and interference with the desired catalysis. Although H-bond donors are a promising alternative to silver salts, they still suffer from much lower activity and narrower applicability, as Au–Cl cleavage remains rate limiting. To address these limitations, we have rationally designed a self-activating phosphine Au(I) chloride complex that incorporates a supramolecular chloride receptor in the form of an anthracene bisurea quintuple H-bond donor. In the absence of any additive, this complex promotes multiple intra- and intermolecular reactions, with a catalytic activity rivalling traditional inorganic chloride scavengers. Mechanistic studies for the model reaction show that the exceptional chloride binding ability of the anthracene bisurea unlocks access to a zwitterionic catalyst resting state where the Au─Cl bond has been cleaved, thus significantly reducing barriers for catalysis. The principles uncovered in this work show how supramolecular anion recognition moieties impact catalyst speciation and enhance performance, enabling for the first time H-bond donors to compete with inorganic chloride scavengers in terms of activity and generality.

Electrochemical nitrate reduction to ammonia (NO₃RR) offers a sustainable alternative to the energy-intensive Haber–Bosch process. However, its practical implementation is limited by the sluggish and energy-demanding oxygen evolution reaction at the anode. Herein, we report a strategically designed paired-electrolysis system coupling NO₃RR with the urea oxidation reaction (UOR), followed by chemical acidification, to establish an economical route of bipolar ammonia (NH₃) production, using a black CoWO₄ (B-CoWO₄) with abundant oxygen vacancies (OVs) as the electrocatalyst. B-CoWO₄ shows a record-breaking performance with a current density of ∼1.25 A cm⁻² at an ultra-low potential of 0 V versus reversible hydrogen electrode. Combined spectroscopic and electrochemical analyses reveal a “fill-restore” cycle of OVs during NO₃RR: oxygen from NO₃⁻ incorporates into the OVs, which are subsequently restored after the formation of NH₃. Theoretical calculations demonstrate that the OVs modify the electronic structure of the catalyst and facilitate the formation of key intermediate (NO₃H*). Importantly, in the coupled NO₃RR||UOR flow-cell system, B-CoWO₄ delivers an apparent bipolar NH₃ Faradaic efficiency of 173.12% and a production rate of 9.43 mmol h⁻¹ cm⁻². This integrated strategy boosts overall energy efficiency and enables simultaneous valorization of nitrate-contaminated water and urea-rich wastewater streams.

The synthesis and photophysical characterization of a new family of terbium(III) complexes called Imaging-crystallophore, substituted by π-conjugated antennas, is reported. Previous crystallophore variants (such as Tb-Xo4) have shown very interesting nucleating properties to obtain high-quality protein crystals. In addition, the Imaging-crystallophore emits in the green and accumulates in the protein crystals, enabling very easy crystal detection using fluorescence microscopy under one-photon but also under two-photon excitations. X-ray diffraction crystallography and molecular dynamics simulations demonstrate that the binding site of the Imaging-crystallophore in hen-egg white lysozyme (HEWL) is similar to that of the Tb-Xo4 but present additional hydrophobic interactions with the conjugated antennas. However, its nucleating properties are not as effective as those of Tb-Xo4. Finally, we emphasize the synergy between the two generations of crystallophore by preparing and analyzing the properties of the mix (10/0.2) corresponding to a mixture of Tb-Xo4 and Imaging-crystallophore. By combining the best of nucleating and imaging properties, we can easily obtain and detect high-quality protein crystals

Helicobacter pylori infection represents a major global health challenge, characterized by high prevalence, significant association with gastric cancer, and rising antibiotic resistance. Carbohydrate-based vaccines targeting the O-antigen of lipopolysaccharide (LPS) present a promising alternative to conventional antimicrobial therapies. To explore the immunogenicity of LPS O-antigen from clinical isolate H. pylori SS1, we report an integrated chemoenzymatic strategy for the first synthesis of its octadecasaccharide O-antigen and related fragments for antigenicity evaluation. Our strategy features modular chemical synthesis of a decasaccharide precursor containing a high-carbon sugar (D,D-Hep) residue, a unique oligomeric β1,2-linked ribofuranosyl tetrasaccharide motif and a switchable glucosamine (GlcNH₂) residue through stereoconvergent [6 + 4] assembly, followed by protecting-group-controlled enzymatic elongation to precisely install hybrid Lewis antigen moiety (Le^y-Le^x) in a site-specific fucosylation manner to afford the target octadecasaccharide bearing five challenging 1,2-cis-glycosidic linkages. Chemical stereoselective construction of 1,2-cis-glucosidic and 1,2-cis-fucosidic linkages was accomplished by reagent-controlled glycosylation and 4-O-acyl remote participation, respectively. Enzymatic site-specific installation of the remaining three 1,2-cis-fucosidic linkages was achieved using two robust fucosyltransferases and a strategically designed GlcNH₂ residue. Glycan microarray-based screening of the synthetic O-antigen and its subunits with H. pylori-infected patient sera identified an undecasaccharide as a simpler and key epitope for vaccine development.

Catalytic alkene cyclization initiated by carbon electrophiles represents an emerging strategy for constructing valuable and challenging molecular architectures. However, due to reactivity issues, the realization of such reactions with tertiary carbon electrophiles remains a formidable challenge. Herein, we report an efficient Brønsted acid-catalyzed system that overcomes this limitation. Using 1-adamantanols as precursors of tertiary carbocation electrophiles, and through TfOH catalysis, alkenes tethered with carboxyl, sulfonamide, and hydroxyl groups, including those with relatively low reactivity such as alkyl-substituted and terminal alkenes, can be converted into a variety of adamantylated heterocycles in hexafluoroisopropanol with good yields via 1,2-addition or formal 1,1-addition, with high regio- and stereoselectivity. The products serve as versatile synthetic building blocks and can be readily transformed into valuable adamantyl-containing compounds, including derivatives with anti-influenza A activity. Density functional theory (DFT) calculations and control experiments indicate that the moderate electrophilicity of the adamantyl carbocation and the hyperconjugative effect of the adamantyl group in stabilizing carbocations form the basis for achieving the electrophilic cyclization. Additionally, they also reveal that different nucleophilic groups can influence the progression of the reaction. These findings provide references for the design of new electrophilic reactions.

Among more than four thousand monoterpene indole alkaloids (MIAs) isolated to date, only a few feature a 2,2,3-trisubstituted indoline moiety. (+)-Melonine and (+)-N₄-oxy melonine possess a highly rearranged carbon framework, presumably arising from cyclization of a rearranged iminium ion of quebrachamine precursor. We report herein the first enantioselective total synthesis of (+)-melonine and (+)-N₄-oxy melonine featuring: a) a highly enantioselective CBS reduction followed by a stereospecific Johnson-Claisen rearrangement for the synthesis of enantioenriched β-substituted γ,δ-unsaturated ester; b) Bower's bis-cyclizative diamination of alkene, enabling the conversion of a functionalized cycloheptene to the tetracyclic core of the natural products; and c) an AlMe₃-mediated lactamization that concurrently achieves desymmetrization at the C20 prochiral center.

A notable characteristic of living organisms is their capacity to adapt to environmental changes and transform external signals into distinct responsiveness, facilitating the execution of diverse functions with motility as a key parameter. To better mimic such lifelike behavior, researchers have developed various supramolecular assembled systems with responsive behavior toward a variety of stimuli. However, exploiting motion along length scales and achieving collective control over the responsiveness to multiple stimuli in supramolecular systems is still challenging. Here we present the development of molecular motor based supramolecular polymers that are responsive toward multi-stimulus and exhibit multi-state assembly and chirality. Taking advantages of aldehyde functionalized motors, we realized photo-responsive supramolecular polymers featuring boosted photo-efficiency, near quantitative photoconversions, programmable behavior and responsiveness to multiple stimuli in a reversible manner in aqueous media. The various stimuli including light and different chemicals could act on the motor building blocks and subsequently trigger the transformation of the supramolecular polymers toward reversible polymerization, direct post-functionalization and chirality modulation. The interplay between the rotary molecular motion and the supramolecular systems assembly process, taking advantage of different external stimuli to govern the assembly state, provides a basis for multi-responsive supramolecular materials

Among more than four thousand monoterpene indole alkaloids (MIAs) isolated to date, only a few feature a 2,2,3-trisubstituted indoline moiety. (+)-Melonine and (+)-N₄-oxy melonine possess a highly rearranged carbon framework, presumably arising from cyclization of a rearranged iminium ion of quebrachamine precursor. We report herein the first enantioselective total synthesis of (+)-melonine and (+)-N₄-oxy melonine featuring: a) a highly enantioselective CBS reduction followed by a stereospecific Johnson-Claisen rearrangement for the synthesis of enantioenriched β-substituted γ,δ-unsaturated ester; b) Bower's bis-cyclizative diamination of alkene, enabling the conversion of a functionalized cycloheptene to the tetracyclic core of the natural products; and c) an AlMe₃-mediated lactamization that concurrently achieves desymmetrization at the C20 prochiral center.