Imaging Gas-Involved Structural Dynamics by Environmental Electron Microscopy.

Understanding gas-involved physicochemical reactions is undoubtedly one of the most significant challenges in the modern chemical industry. To clarify how those reactions precede requires deep insights into the real-time visualization of reaction dynamics within a gas environment. The emergence and rapid development of in situ environmental electron microscopy (EEM) including scanning electron microscopy (ESEM) and transmission electron microscopy (ETEM) have enabled multiscale observation of dynamic gas-involved physicochemical reactions.

Unravelling nonclassical beam damage mechanisms in metal-organic frameworks by low-dose electron microscopy.

Recent advances in direct electron detectors and low-dose imaging techniques have opened up captivating possibilities for real-space visualization of radiation-induced structural dynamics. This has significantly contributed to our understanding of electron-beam radiation damage in materials, serving as the foundation for modern electron microscopy. In light of these developments, the exploration of more precise and specific beam damage mechanisms, along with the development of associated descriptive models, has expanded the theoretical framework of radiation damage beyond classical mechanisms.

Alstoscholarisine L, a novel caged monoterpenoid indole alkaloid with antifungal activity from Alstonia scholaris.

Alstoscholarisine L is an architecturally complex monoterpenoid indole alkaloid with a unique ring fusion pattern, isolated from the leaves of Alstonia scholaris. The 6/5/5/6/6/6-membered rings contain two lactonic rings and one aminal carbon and possess seven contiguous aligned stereocenters, three of which are quaternary. Its structure was elucidated by extensive spectroscopic data analyses, quantum chemical computations, and single-crystal X-ray diffraction.

Heterocyclic pseudoguaianolide oligomers and seco-pseudoguaianolide derivatives from the inflorescence of Ambrosia artemisiifolia.

Two heterocyclic sesquiterpenoid oligomers (1, 2) and four previously undescribed seco-pseudoguaianolide derivatives (3-6) were isolated from the inflorescence of Ambrosia artemisiifolia. Ambrosiadimer A (1) is an unprecedented dimer featuring a hexahydropyrrolizine core scaffold and two pseudoguaianolide units. Ambrosiatrimer A (2) is a trimer formed from three pseudoguaianolide units via a pyrrolidine ring.

A new terpestacin-type sesterterpenoid with tricyclic 3/15/5 scaffold from an endophytic fungus sp. J019.

ABSTACTChemical investigation of an endophytic fungus, sp. J019, isolated from the plant species R. Br.

New ent-cleistanthanes and ent-pimaras diterpenoids with potential cytotoxicity from Phyllanthus franchetianus H. Lév.

Seven diterpenoids including five ent-cleistanthanes (1, 2, 4-6) and two ent-pimaranes (3, 7) were isolated for the first time from the aerial part of Phyllanthus franchetianus H. Lév. Their structures were elucidated on the basis of the extensive spectroscopic analyses, single-crystal X-ray diffraction and ECD analysis.

Isosativene and sativene sesquiterpene derivatives from Dendrobium nobile.

Two unusual isosativene sesquiterpene derivatives, named dendronobilol A (1) and dendronobilside A (2), and two unusual sativene sesquiterpene derivatives, named dendronobilsides B (3) and C (4), had been isolated from the stems of Dendrobium nobile. The structures of all the compounds were established using spectroscopic methods and by comparison with literature data, and their absolute configurations were confirmed via single-crystal X-ray diffraction data and electronic circular dichroism (ECD) calculations. Dendronobilol A (1) and dendronobilside A (2) possessed a unique tricyclo[4.

Sabatier Principle Driving Interface Defect Engineering on 3D Graphene-Like Encapsulated Cobalt Structure for Hydrogenation Reaction.

Establishing structural defects is a perspective way to increase the catalytic hydrogenation reaction. Toward Sabatier optimization for hydrogenation reaction with defect density offers guidance for designing optimal catalysts with the highest performance. A controllable synthesis strategy is reported for Co@NC-x catalyst induced by defect density.

Selenium dioxide promoted selenylation/cyclization of leucosceptrane sesterterpenoids.

A novel selenium dioxide promoted selenylation/cyclization of leucosceptrane sesterterpenoids was reported. Two types of leucosceptrane derivatives with different valence states of selenium atoms (Se and Se) were obtained. The mechanisms of these two processes were proposed, and the selenium-containing derivates may serve as intermediates of Riley oxidation that could be trapped with appropriate substrates.

Silvaticusins A-D: ent-kaurane diterpenoids and a cyclobutane-containing ent-kaurane dimer from Isodon silvaticus.

Three new ent-kaurane diterpenoids, silvaticusins A-C (1-3), along with a new ent-kaurane dimer silvaticusin D (4) were isolated from the aerial parts of Isodon silvaticus. The structures of these new compounds were established mainly by comprehensive analysis of their NMR and MS data. The absolute configuration of compounds 1 and 4 were determined using a single-crystal X-ray diffraction and computational methods, respectively.

Structurally diverse ent-clerodanoids from the aerial parts of Isodon scoparius.

Scoparodane C (1), a diterpenoid with a rare 3,4-seco-3-nor-2,11-epoxy-ent-clerodane scaffold, was obtained from the aerial parts of Isodon scoparius, along with isocopariusines A-E (2-6), five ent-clerodanoids featuring a 5/6-fused ring system, and isocopariusines F-H (7-9), three common ent-clerodanoids. The structures of these previously undescribed compounds were established by a combination of spectroscopic analysis, X-ray diffraction, chemical derivatization, and quantum chemical calculation. Remarkably, isocopariusine B (3) showed strong resistance reversal activity against fluconazole-resistant Candida albicans.

Undobolins A-L, Ophiobolin-Type Sesterterpenoids from .

Twelve previously undescribed ophiobolin-type sesterterpenoids, undobolins A-L (-), were isolated from , and their structures were elucidated by spectroscopic analysis, ECD calculations, and single-crystal X-ray diffraction experiments. Compound was the second example of 20-nor-ophiobolin reported, while compounds - were notable for oxygenation of C-2, and compound showed significant inhibitory activity against ConA-induced T lymphocyte proliferation with an IC value of 2.3 μM, which suggests a promising new direction in the quest for immunosuppressive agents.

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

Isoxerophilusins A () and B (), two unprecedented diterpene heterodimers biogenetically from -atisanes and abietanes, were isolated from the rhizomes of . Their structures were determined by extensive spectroscopic analysis and single-crystal X-ray diffraction. Selective esterification of generated 11 new derivatives.

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.

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

Five undescribed leucosesterterpane sesterterpenoids, leucosceptrines A-E, two undescribed penta-nor-leucosesterterpane (C) 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.

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

Nickel is the most widely used inexpensive active metal center of the heterogeneous catalysts for CO hydrogenation to methane. However, Ni-based catalysts suffer from severe deactivation in CO 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 CeAlO/Ni composite constructed on the Ni-foam structure support realizes remarkable CO methanation catalytic activity and stability in a wide operation temperature range from 240 to 600 °C.

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).

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.

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.

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.

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 . 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.

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) PdB nanosheet assemblies (PdB NAs) via the boronation reaction between as-synthesized Pd NAs and N,N-dimethylformamide.

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.

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.

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.