Isoxerophilusins A and B, Two Novel Polycyclic Asymmetric Diterpene Dimers from Isodon xerophilus: Structural Elucidation, Modification, and Inhibitory Activities against α-Glucosidase.

Isoxerophilusins A (1) and B (2), two unprecedented diterpene heterodimers biogenetically from ent-atisanes and abietanes, were isolated from the rhizomes of Isodon xerophilus. Their structures were determined by extensive spectroscopic analysis and single-crystal X-ray diffraction. Selective esterification of 1 generated 11 new derivatives. All derivatives showed excellent α-glucosidase inhibitory activity in comparison to acarbose. Compounds 12 and 13 demonstrated significant inhibition against α-glucosidase with IC50 values of 4.92 and 3.83 µM, respectively.

Non-classical Deactivation Mechanism in a Supported Intermetallic Catalyst for Propane Dehydrogenation.

Platinum-based supported intermetallic alloys (IMAs) demonstrate exceptional performance in catalytic propane dehydrogenation (PDH) primarily because of their remarkable resistance to coke formation. However, these IMAs still encounter a significant hurdle in the form of catalyst deactivation. Understanding the complex deactivation mechanism of supported IMAs, which goes beyond conventional coke deposition, requires meticulous microscopic structural elucidation. In this study, we unravel a nonclassical deactivation mechanism over a PtZn/γ-Al2O3 PDH catalyst, dictated by the PtZn to Pt3Zn nanophase transformation accompanied with dezincification. The physical origin lies in the metal support interaction (MSI) that enables strong chemical bonding between hydroxyl groups on the support and Zn sites on the PtZn phase to selectively remove Zn species followed by the reconstruction towards Pt3Zn phase. Building on these insights, we have devised a solution to circumvent the deactivation by passivating the MSI through surface modification of γ-Al2O3 support. By exchanging protons of hydroxyl groups with potassium ions (K) on the γ-Al2O3 support, such a strategy significantly minimizes the dezincification of PtZn IMA via diminished metal-support bonding, which dramatically reduces the deactivation rate from 0.2044 to 0.0587 h-1.

Immunosuppressive leucosesterterpane and penta-nor-leucosesterterpane sesterterpenoids from Leucosceptrum canum.

Five undescribed leucosesterterpane sesterterpenoids, leucosceptrines A-E, two undescribed penta-nor-leucosesterterpane (C20) sesterterpenoids, nor-leucosceptrines A and B, and three known analogues, were obtained from the aerial parts of Leucosceptrum canum of Chinese origin. Leucosceptrines A-C are the first examples of leucosesterterpane-type sesterterpenoids with unclosed dihydropyran rings and reverse configurations at chiral centers C-4 and/or C-12. Nor-leucosceptrines A and B possesses an unusual penta-nor-leucosesterterpane skeleton. Their structures were unambiguously elucidated through comprehensive spectroscopic analyses and single-crystal X-ray diffraction. A plausible biogenetic pathway for these sesterterpenoids was proposed. The immunosuppressive effects of these isolates on the secretion of the cytokine IFN-γ by T cells stimulated with anti-CD3/CD28 monoclonal antibodies were observed with different potencies.

Thermally stable Ni foam-supported inverse CeAlOx/Ni ensemble as an active structured catalyst for CO2 hydrogenation to methane.

Nickel is the most widely used inexpensive active metal center of the heterogeneous catalysts for CO2 hydrogenation to methane. However, Ni-based catalysts suffer from severe deactivation in CO2 methanation reaction due to the irreversible sintering and coke deposition caused by the inevitable localized hotspots generated during the vigorously exothermic reaction. Herein, we demonstrate the inverse CeAlOx/Ni composite constructed on the Ni-foam structure support realizes remarkable CO2 methanation catalytic activity and stability in a wide operation temperature range from 240 to 600 °C. Significantly, CeAlOx/Ni/Ni-foam catalyst maintains its initial activity after seven drastic heating-cooling cycles from RT to 240 to 600 °C. Meanwhile, the structure catalyst also shows water resistance and long-term stability under reaction condition. The promising thermal stability and water-resistance of CeAlOx/Ni/Ni-foam originate from the excellent heat and mass transport efficiency which eliminates local hotspots and the formation of Ni-foam stabilized CeAlOx/Ni inverse composites which effectively anchored the active species and prevents carbon deposition from CH4 decomposition.

Unified Strategy Enables the Collective Syntheses of Structurally Diverse Indole Alkaloids.

Natural products and their analogues are significant sources of therapeutic lead compounds. However, synthetic strategies for generating large collections of these molecules remain a significant challenge. The most difficult step in their synthesis is the design of a common intermediate that can be easily transformed into natural products belonging to different families. This study demonstrates the evolution of synthetic tactics designed to assemble the functionalized piperidines present in indole alkaloids from a common intermediate. More importantly, we also report a previously unknown Ir- and Er-catalyzed dehydrogenative spirocyclization reaction that enables direct access to spirocyclic oxindole alkaloids. As a practical application, the asymmetric total syntheses of 29 natural alkaloids belonging to different families were accomplished by following a uniform synthetic route. The proposed methodology extends the capability of the iridium-catalyzed dehydrogenative coupling reaction to the realm of indole-alkaloid synthesis and provides new opportunities for the efficient preparation of natural product-like molecules.

Reaction-Driven Dynamic and Reversible Transformations of Au Single Atoms and Au-Zr Alloys on Zirconia for Efficient Acetylene Hydrochlorination.

Catalysis involving gold supported on metal oxides has undergone extensive examination. However, the nature of the catalytic site under actual reaction conditions and the role of the support continue to be vigorously debated. This study addresses these issues through experimental investigations and theoretical simulations. We explore a novel catalytic mechanism that employs dynamic single-atom catalysis for the hydrochlorination of acetylene. This catalytic mechanism occurs in defective ZrO2-supported Au-Zr single-atom alloys. Specifically, the dynamic single-atom catalysis is a result of the mobility of the gold cation, which is accelerated by Cl radicals and strongly couples with the abundant unsaturated surface sites of ZrO2 in a synergistic manner. As a result, the Au electronic structure dynamically evolves, leading to a decrease in the addition reaction energy barrier. Notably, the Au cation can detach from the Au-Zr alloy structure to catalyze the hydrochlorination of acetylene near the Zr-Ov-Zr sites and then reintegrate back into the Au-Zr alloy structure upon completion of the reaction. This study underscores the significance of dynamic active sites under reaction conditions and their pivotal role in catalysis.

Aromatic Ethers Induced Electronic Structure Reconstruction on Encapsulated Nickel Catalysts for High-Performance Catalytic Hydrogenation.

Carbon-encapsulated metal (CEM) catalysts effectively address supported metal catalyst instability by protecting the active metal with a shell. However, mass transfer limitations lead to reduced activity for catalytic hydrogenation reaction over most CEM catalysts. Herein, we introduce a dopant strategy aimed at incorporating nickel metal within graphene-like shells (GLS) featuring oxygen-containing functional groups (OFGs). The core of this strategy involves precise control of GLS modification and the demonstrated pivotal influence of aromatic ether linkages (═C-O-C) in GLS for significant enhancement of catalytic performance. The introduction of ═C-O-C into GLS with stability was beneficial to improve the work function of the catalyst and promoted electron transmission from Ni metal core to GLS, further elevating the catalytic activity, based on the Mott-Schottky effect. In addition, the experimental characterization and density functional theory (DFT) calculations showcased that the ═C-O-C reconstructed the electronic state of GLS, imparting it highly specific for the adsorption of hydrogen and para-chloronitrobenzene (p-CNB) to obtain para-chloroaniline (p-CAN) with high selectivity. This work manifested a feasible direction for the precise modulation and design of the OFGs in CEM catalysts to achieve highly efficient catalytic hydrogenation.

Iron-Based Catalysts with Oxygen Vacancies Obtained by Facile Pyrolysis for Selective Hydrogenation of Nitrobenzene.

The development of preparation strategies for iron-based catalysts with prominent catalytic activity, stability, and cost effectiveness is greatly significant for the field of catalytic hydrogenation but still remains challenging. Herein, a method for the preparation of iron-based catalysts by the simple pyrolysis of organometallic coordination polymers is described. The catalyst Fe@C-2 with sufficient oxygen vacancies obtained in specific coordination environment exhibited superior nitro hydrogenation performance, acid resistance, and reaction stability. Through solvent effect experiments, toxicity experiments, TPSR, and DFT calculations, it was determined that the superior activity of the catalyst was derived from the contribution of sufficient oxygen vacancies to hydrogen activation and the good adsorption ability of FeO on substrate molecules.

Discovery and bioinspired total syntheses of unprecedented sesquiterpenoid dimers unveiled bifurcating [4 + 2] cycloaddition and target differentiation of enantiomers.

[4 + 2] cycloaddition has led to diverse polycyclic chiral architectures, serving as novel sources for organic synthesis and biological exploration. Here, an unprecedented class of cadinane sesquiterpene [4 + 2] dimers, henryinins A-E (1-5), with a unique 6/6/6/6/6-fused pentacyclic system, were isolated from Schisandra henryi. The divergent total syntheses of compounds 1-5 and their enantiomers (6-10) were concisely accomplished in eight linear steps using a protection-free approach. Mechanistic studies illustrated the origin of selectivity in the key [4 + 2] cycloaddition as well as the inhibition of reaction pathway bifurcation via desymmetrization. The chemical proteomics results showed that a pair of enantiomers shared common targets (PRDX5 C100 and BLMH C73) and had unique targets (USP45 C588 for 4 and COG7 C419 for 9). This work provides experimental evidence for the discovery of unprecedented cadinane dimers from selective Diels-Alder reaction and a powerful strategy to explore the biological properties of natural products.

Discovery of Natural Potent HMG-CoA Reductase Degraders for Lowering Cholesterol.

Exploitation of key protected wild plant resources makes great sense, but their limited populations become the major barrier. A particular strategy for breaking this barrier was inspired by the exploration of a resource-saving fungal endophyte Penicillium sp. DG23, which inhabits the key protected wild plant Schisandra macrocarpa. Chemical studies on the cultures of this strain afforded eight novel indole diterpenoids, schipenindolenes A-H (1-8), belonging to six diverse skeleton types. Importantly, semisyntheses suggested some key nonenzymatic reactions constructing these molecules and provided targeted compounds, in particular schipenindolene A (Spid A, 1) with low natural abundance. Remarkably, Spid A was the most potent HMG-CoA reductase (HMGCR) degrader among the indole diterpenoid family. It degraded statin-induced accumulation of HMGCR protein, decreased cholesterol levels and acted synergistically with statin to further lower cholesterol. Mechanistically, transcriptomic and proteomic profiling suggested that Spid A potentially activated the endoplasmic reticulum-associated degradation (ERAD) pathway to enhance the degradation of HMGCR, while simultaneously inhibiting the statin-activated expression of many key enzymes in the cholesterol and fatty acid synthesis pathways, thereby strengthening the efficacy of statins and potentially reducing the side effects of statins. Collectively, this study suggests the potential of Spid A for treating cardiovascular disease.

Boron-intercalation-triggered crystalline transition of Pd nanosheet assemblies for an enhanced oxygen reduction reaction.

The development of effective and stable cathode electrocatalysts is highly desired for fuel cells. Controlling the composition and morphology of Pd-based materials can provide a great opportunity to improve their oxygen reduction reaction (ORR) performance. Here, we report the synthesis of hexagonal close-packed (hcp) Pd2B nanosheet assemblies (Pd2B NAs) via the boronation reaction between as-synthesized Pd NAs and N,N-dimethylformamide. The hcp Pd2B NAs with uniform pore distribution can provide sufficient active sites for ORRs. The insertion of B atoms can induce the phase transition from face-centered cubic structure to hcp structure, as the most thermodynamically stable phase in the Pd-B alloy, which is beneficial for enhancing the ORR stability and toxicity resistance. Therefore, the hcp Pd2B NAs exhibit superior mass activity, specific activity and excellent stability for ORR. The present strategy of boron-intercalation-triggered crystalline transition of Pd-based nanomaterials is valuable for the design of metal-nonmetal catalysts with enhanced performance.

Revolutionizing the structural design and determination of covalent-organic frameworks: principles, methods, and techniques.

Covalent organic frameworks (COFs) represent an important class of crystalline porous materials with designable structures and functions. The interconnected organic monomers, featuring pre-designed symmetries and connectivities, dictate the structures of COFs, endowing them with high thermal and chemical stability, large surface area, and tunable micropores. Furthermore, by utilizing pre-functionalization or post-synthetic functionalization strategies, COFs can acquire multifunctionalities, leading to their versatile applications in gas separation/storage, catalysis, and optoelectronic devices. Our review provides a comprehensive account of the latest advancements in the principles, methods, and techniques for structural design and determination of COFs. These cutting-edge approaches enable the rational design and precise elucidation of COF structures, addressing fundamental physicochemical challenges associated with host-guest interactions, topological transformations, network interpenetration, and defect-mediated catalysis.

Electron Regulation of Heterostructured Pt/Rh Metallene Boosts Ethylene Glycol Electrooxidation and Hydrogen Evolution.

The research on high-efficiency two-dimensional (2D) catalytic materials for the small-molecule oxidation-assisted hydrogen evolution reaction (HER) is prospective for efficient hydrogen production. Herein, we report heterostructured Pt/Rh metallene with Pt nanoparticles (NPs) uniformly anchored on Rh metallene for the HER and ethylene glycol oxidation reaction (EGOR). The ultrathin sheet structure of the Pt/Rh metallene offers high surface areas and sufficient active sites. More importantly, the Pt/Rh heterostructure can optimize catalytic active centers and adjust electronic structure. Thus, Pt/Rh metallene exhibits superior electrocatalytic HER activity with a low overpotential of 28 mV in 1 M KOH at 10 mA cm-2 and EGOR activity with a specific activity of 8.39 mA cm-2 in 1 M KOH with 3 M EG, along with outstanding CO tolerance. In a two-electrode system, Pt/Rh metallene requires a low potential of 0.51 V for stable and efficient hydrogen production at 10 mA cm-2 in 1 M KOH + 3 M EG, with the simultaneous production of high-value-added products. The job proposes an attractive strategy for the synthesis of 0D/2D metallene toward simultaneous energy-saving hydrogen production and chemical update.

Phosphorus-induced activation of Ir metallene for efficient acidic overall water electrolysis.

In this work, we synthesize P-doped Ir metallene (P-Ir metallene) with rich defects as a highly active bifunctional catalyst towards the hydrogen evolution reaction and oxygen evolution reaction, requiring overpotentials of 28 and 279 mV to drive 10 mA cm-2 in 0.5 M H2SO4, respectively. Moreover, P-Ir metallene exhibits excellent electrocatalytic performance for overall water splitting, producing hydrogen at 10 mA cm-2 with a low operation voltage of 1.508 V. This study proposes the incorporation of phosphorus into noble metals to improve the electrocatalytic performance for water splitting.

Discovery and Biomimetic Semisynthesis of Spirophyllines A-D from Uncaria rhynchophylla.

Spirophyllines A-D (1-4), four new spirooxindole alkaloids all characterized by the spiro[pyrrolidin-3,3'-oxindole] core and a rare isoxazolidine ring, were isolated from Uncaria rhynchophylla. Their structures were determined by spectroscopic methods and confirmed by X-ray crystallography. Based on the biomimetic semisynthesis strategy, compounds 1-8 were synthesized in three steps via the key reactions of 1,3-dipolar cycloaddition and Krapcho decarboxylation from corynoxeine. Interestingly, compound 3 showed moderate inhibitory activity against the Kv1.5 potassium channel (IC50 = 9.1 µM).

Sustainable Ammonia Electrosynthesis from Nitrate Wastewater Coupled to Electrocatalytic Upcycling of Polyethylene Terephthalate Plastic Waste.

Integrating the nitrate reduction reaction (NO3RR) with polyethylene terephthalate (PET) hydrolysate oxidation to construct the nitrate/PET hydrolysate coelectrolysis system holds a great promise of realizing the simultaneous upcycling of nitrate wastewater and PET plastic waste, which, however, is still an almost untouched research area. Herein, we develop an ultralow content of Ru-incorporated Co-based metal-organic frameworks as a bifunctional precatalyst, which can be in situ reconstructed to Ru-Co(OH)2 at the cathode and Ru-CoOOH at the anode under electrocatalytic environments, and function as real active catalysts for the NO3RR and PET hydrolysate oxidation, respectively. With a two-electrode nitrate/PET hydrolysate coelectrolysis system, the current density of 50 mA cm-2 is achieved at a cell voltage of only 1.53 V, realizing the simultaneous production of ammonia and formate at a lower energy consumption. This study provides a concept for the construction of coelectrolysis systems for upcycling of nitrate wastewater and PET plastic waste.

Interfacial engineering of hydrophobic octadecanethiol/Pd metallene toward electrocatalytic nitrogen reduction.

In this work, we propose the modification of ultrathin and wrinkled Pd metallene by hydrophobic octadecanethiol (Pdene@C18) via Pd-S bonds for the nitrogen reduction reaction. The hydrophobic self-assembled monolayer C18 can effectively capture more N2 and inhibit the hydrogen evolution reaction. As a result, a high NH3 yield and Faraday efficiency of 27.97 µg h-1 mgcat.-1 and 14.29% are achieved for Pdene@C18 under neutral conditions, respectively, highlighting the modification of hydrophobic monolayers for efficient nitrogen electro-reduction to ammonia.

Chromium-Doped Nickel Oxide and Nickel Nitride Mediate Selective Electrocatalytic Oxidation of Sterol Intermediates Coupled with H2 Evolution.

Replacing the oxygen evolution reaction (OER) with the thermodynamically favorable electrooxidation of organics is considered a promising approach for the simultaneous production of hydrogen (H2 ) and high-value chemicals. However, exploring and optimizing efficient electrocatalysts remains a challenge for large-scale production of value-added steroid carbonyl and H2 . Herein, Cr-NiO/GF and Cr-Ni3 N/GF (GF: graphite felt) electrocatalysts were designed as anode and cathode for the production of steroid carbonyls and H2 , respectively. The cooperative Cr-NiO and ACT (4-acetamido-2,2,6,6-tetramethyl-1-piperidine-N-oxyl) electrocatalyst can be extended to the electrooxidation of a series of steroid alcohols to the corresponding aldehydes. Additionally, Cr-Ni3 N displays superior electrocatalytic activity for hydrogen evolution reaction (HER), with a low overpotential of 35 mV to deliver 10 mA cm-2 . Furthermore, the system coupled with anodic electrooxidation of sterol and cathodic HER exhibited excellent performance with high space-time yield of 48.85 kg m-3 h-1 for steroid carbonyl and 1.82 L h-1 for H2 generation in a two-layer stacked flow cell. Density Functional Theory (DFT) calculations indicated that Cr doping effectively stabilizes ACTH on the NiO surface, and ACTH molecule could be captured via the ketonic oxygen interaction with Cr, resulting in excellent electrocatalytic activity. This work develops a novel approach to the rational design of efficient electrocatalysts for the simultaneous production of H2 and large-scale value-added pharmaceutical carbonyl intermediates.

Cytotoxic C-20 non-oxygenated ent-kaurane diterpenoids from Isodon wardii.

Twenty new ent-kaurane diterpenoids, wardiisins A-T (1-20), along with two previously undescribed artefactual compounds (21 and 22) and twelve known analogues (23-34), were isolated from the aerial part of Isodon wardii. Their structures were elucidated by comprehensive analysis of spectroscopic data and single-crystal X-ray diffraction, and most of them were found to bear unusual C-12 oxygenation. Compounds 4, 7, 8, 19, 20, 21 exhibited remarkable cytotoxicity against the cancer cell lines HL-60, SMMC-7721, A-549, MDA-MB-231, and SW480, with IC50 values ranging from 0.3 to 5.2 µM. Moreover, 7 was found to induce G2/M cell cycle arrest and promote apoptosis in SW480 cell lines.

Selective CO2 Electroreduction to Formate on Polypyrrole-Modified Oxygen Vacancy-Rich Bi2 O3 Nanosheet Precatalysts by Local Microenvironment Modulation.

Challenges remain in the development of highly efficient catalysts for selective electrochemical transformation of carbon dioxide (CO2 ) to high-valued hydrocarbons. In this study, oxygen vacancy-rich Bi2 O3 nanosheets coated with polypyrrole (Bi2 O3 @PPy NSs) are designed and synthesized, as precatalysts for selective electrocatalytic CO2 reduction to formate. Systematic material characterization demonstrated that Bi2 O3 @PPy precatalyst can evolve intoBi2 O2 CO3 @PPy nanosheets with rich oxygen vacancies (Bi2 O2 CO3 @PPy NSs) via electrolyte-mediated conversion and function as the real active catalyst for CO2 reduction reaction electrocatalysis. Coating catalyst with a PPy shell can modulate the interfacial microenvironment of active sites, which work in coordination with rich oxygen vacancies in Bi2 O2 CO3 and efficiently mediate directional selective CO2 reduction toward formate formation. With the fine-tuning of interfacial microenvironment, the optimized Bi2 O3 @PPy-2 NSs derived Bi2 O2 CO3 @PPy-2 NSs exhibit a maximum Faradaic efficiency of 95.8% at -0.8 V (versus. reversible hydrogen electrode) for formate production. This work might shed some light on designing advanced catalysts toward selective electrocatalytic CO2 reduction through local microenvironment engineering.