Latest ArticlesA new strategy for the metal-free coordination–insertion ring-opening polymerization of tetrahydrofuran by the central metalloid Boron has been first identified. Bis(pentafluorophenyl)(phenoxy)borane was used as a catalyst for the polymerization reaction system. And polytetrahydrofuran with high molecular weight and narrow molecular weight distribution could be obtained. The proposed mechanism was studied by MALDI-TOF, ESI-MS and O-18 isotope labeling analyses as a metal-free coordination insertion mechanism.
Biomass is the most bountiful renewable carbon resource on earth. Photocatalytic transformation is a promising method to utilize biomass to obtain high-value-added chemicals and it has more obvious advantages compared with thermochemical and biological processes due to the milder operational conditions, fewer reagents and equipment. Semiconductor material is one of the most common kinds of heterogeneous biomass photocatalysts, which has the advantages of high selectivity, stable catalytic performance, long activation time, and low cost. In this paper, the significant research progress on the photocatalytic transformation of biomass with semiconductor materials to produce high-value-added chemicals is reviewed, and the three most typical semiconductor photocatalysts (TiO2, CdS, and g-C3N4) are detailed. The photocatalytic mechanism and photocatalytic system optimization including structural modification, metal co-catalyst loading, and introduction of heterojunction are presented. Besides, the main problems, the development direction and trend of semiconductor materials in photocatalytic transformations of biomass in the future are prospected, which provide guidance and inspiration for the further development of semiconductor photocatalysts and make contributions to the progress in efficient utilization of biomass.
Nitrene transfer reactions are powerful tools in synthetic organic chemistry. In recent years, transition-metal catalyzed nitrene transfer reactions with carbamates as the nitrene precursors have been widely pursued. Such species undergoes facile C−H amination, aziridination, and bifunctionalization of alkenes under the catalysis of different transition metals including Rh, Fe, Ru and others, enabling the efficient construction of various nitrogen-containing molecules. In this review, the recent developments in nitrene transfer reactions with carbamates via N−O bond cleavage were introduced based on different types of reaction, and the key mechanistic information and synthetic applications of the methodologies were discussed.
Fungal symbionts co-evolve with hosts and microbial co-inhabitants to acquire an unpredictable potential for producing novel bioactive metabolites, but the knowledge about the topic remains patchy and superficial. Here we present the chemical characterization of acatulides A−G (1−7) as architecturally unprecedented macrolides from the solid-state culture of Acaulium album H-JQSF, an arthropod-associated fungus. The acatulide structures were elucidated by spectroscopic analysis, modified Mosher's method and single-crystal X-ray diffraction. The plausible biosynthetic pathways for compounds 1−4 are proposed. Interestingly, acatulides B−D (2−4) and G (7) were demonstrated to be neuroprotective against the 1-methyl-4-phenylpyridinium (MPP+)-induced damage to SH-SY5Y cells and nematode Caenorhabditis elegans (C. elegans).
Early pathogenesis of ischemia-reperfusion (I/R)-induced acute kidney injury (AKI) is dominated by intracellular calcium overload, which induces oxidative stress, intracellular energy metabolism disorder, inflammatory activation, and a series of pathologic cascaded reactions that are closely intertwined with self-amplifying and interactive feedback loops, ultimately resulting in cell damage and kidney failure. Currently, most nanomedicines originate from the perspective of antioxidant stress, which can only quench existing reactive oxide species (ROS) but cannot prevent the continuous production of ROS, resulting in insufficient efficacy. As a safe and promising drug, BAPTA-AM is hydrolyzed into BAPTA by intracellular esterase upon entering cells, which can rapidly chelate with overloaded Ca2+, restoring intracellular calcium homeostasis, thus inhibiting ROS regeneration at the source. Here, we designed a KTP-targeting peptide-modified yolk-shell structure of liposome–poly(ethylene glycol)methyl ether-block-poly (l-lactide-co-glycolic) (mPLGA) hybrid nanoparticles (<100 nm), with the characteristics of high encapsulation rate, high colloid stability, facile modification, and prolonged blood circulation time. Once the BA/mPLGA@Lipo-KTP was targeted to the site of kidney injury, the cholesteryl hemisuccinate (CHEMS) in the phospholipid bilayer, as an acidic cholesterol ester, was protonated in the simulated inflammatory slightly acidic environment (pH 6.5), causing the liposomes to rupture and release the BA/mPLGA nanoparticles, which were then depolymerized by intracellular esterase. The BAPTA-AM was diffused and hydrolyzed to produce BAPTA, which can rapidly cut off the malignant loop of calcium overload/ROS generation at its source, blocking the endoplasmic reticulum (ER) apoptosis pathway (ATF4–CHOP–Bax/Bcl-2, Casp-12–Casp-3) and the inflammatory pathway (TNF-α–NF-κB–IL-6 axes), thus alleviating pathological changes in kidney tissue, thereby inhibiting the expression of renal tubular marker kidney injury molecule 1 (Kim-1) (reduced by 82.9%) and also exhibiting prominent anti-apoptotic capability (TUNEL-positive ratio decreased from 40.2% to 8.3%), significantly restoring renal function. Overall, this research holds huge potential in the treatment of I/R injury-related diseases.
Catalytic Michael addition reaction represents a fundamental importance in organic synthetic chemistry. Whereas corresponding conversions toward intrinsically low reactive enamide remains an ongoing challenging. We herein report a copper-catalyzed conjugate addition of allenes to β-substituted alkenyl amides, one of the most challenging Michael acceptors. The present method utilizes readily available allenes as the latent carbon-based nucleophiles and simple, common β-substituted alkenyl amides as starting materials, unlike previous methods that usually preinstall an activating group to improve the reactivity of amide or uses highly reactive stoichiometric quantities of organometallics. Hence, this approach shows good functional group compatibility and can be implemented under mild reaction conditions with excellent level of chemo- and regioselectivities.
Developing new functional explosives that display high stability, good energy performance, and low sensitivity are one of the key directions of energetic materials research. In this work, two-dimensional (2D) Schiff-based energetic covalent organic frameworks (COFs) are prepared based on triaminoguanidine salts with different anions as building blocks. Benefiting from the robust covalent bond in 2D extended polygons and strong π-π interactions in the eclipsed interlayers, the synthesized energetic COFs showed higher thermal stability and lower mechanical sensitivity than their precursor salts. More importantly, incorporating triaminoguanidine salts into COFs effectively increase the corrosion resistance to metal under high humidity conditions, which is due to the imine moieties in COFs functioning as π acceptors and offering strong bonding with metallic ions. This work provides a new pathway for the development of high-performance energetic materials.
Tuberculosis (TB) is a chronic infectious disease, which is caused by the pathogen Mycobacterium tuberculosis (Mtb) and reemerged as a global health risk with a significant proportion of multi-drug resistant and extensively drug resistant TB cases. It is very urgent to find some novel high-confidence drug targets in Mtb for discovering the effective anti-TB agents. Thioredoxin reductase (TrxR) has been identified to be a highly viable target for anti-TB drugs for its important role in protecting the pathogen from thiol-specific oxidizing stress, regulating intracellular dithiol/disulfide homeostasis and DNA replication and repair. In the present work, a near-infrared (NIR) fluorescent probe DDAT was developed for the detection of TrxR activity and used to high-throughput screen the TrxR inhibitors from natural products. Two screened TrxR inhibitors from Sappan Lignum and microbial metabolites that were further used to inhibit Mycobacterium tuberculosis. All the results indicate that DDAT is a practical fluorescent molecular tool for the discovery of potential anti-TB drugs.
Artificial Z(S)-scheme photocatalytic water splitting systems have attracted extensive attention due to their advantages such as wide light absorption range, high charge separation efficiency and strong carrier redox ability. However, it is still challenging to design and prepare Z(S)-scheme photocatalysts with low-cost and highly stability for efficiently photocatalytic overall water splitting using solar energy. This review mainly introduces various strategies to improve the photocatalytic water splitting performance of Z(S)-scheme systems. These strategies mainly focus on enhancing or extending the range of light absorption, promoting charge separation, and enhancing surface redox reaction in Z(S)-scheme systems. Finally, the main challenges of Z(S)-scheme photocatalytic water splitting systems and their future development directions are pointed out. This review would be beneficial to understanding the challenges and opportunities faced by the research field of Z(S)-scheme photocatalytic systems, and has important guiding significance for the development and utilization of high-performance Z(S)-scheme photocatalytic reaction system in the future.