Anticholinesterases and antioxidant alkamides from Piper nigrum fruits

The anticholinesterase and antioxidant effects of five different extracts of Piper nigrum were evaluated. Twenty-one known alkamides were isolated from active ethyl acetate extract and investigated for their cholinesterase inhibitory and antioxidant effects. Among them, piperine (2), piperettine (5) and piperettyline (20) exhibited dual inhibition against AChE and BChE, and feruperine (18) was the most potent selective inhibitor of BChE. Molecular docking simulation was performed to get insight into the binding interactions of the ligands and enzymes. In addition, N-trans-feruloyltyramine (3) contributed to the strongest DPPH radical-scavenging activity. The self-induced Aβ aggregation inhibition of 2, 5 and 18 was further evaluated. Results indicated that some alkamides could be multifunctional lead candidates for Alzheimer’s disease therapy.     

无机过氧化物在有机反应中作用的研究 I: 利用过硼酸钠进行烯烃环氧化反应

本文报导利用无机过氧化物(过硼酸钠)进行烯烃环氧化反应过硼酸钠对多数烯烃的环氧化反应可得到较为满意的结果, 但对α-蒎烯, 过硼酸钠可导致产物的异构化, 反应结果得到一含有四种组份的混合物, 总得率为85%, 而使用有机过氧酸对它进行环氧化反应时其产率可达90%。     

Constructing Ordered Three‐Dimensional TiO2 Channels for Enhanced Visible‐Light Photocatalytic Performance in CO2 Conversion Induced by Au Nanoparticles

As a typical photocatalyst for CO₂ reduction, practical applications of TiO₂ still suffer from low photocatalytic efficiency and limited visible‐light absorption. Herein, a novel Au‐nanoparticle (NP)‐decorated ordered mesoporous TiO₂ (OMT) composite (OMT‐Au) was successfully fabricated, in which Au NPs were uniformly dispersed on the OMT. Due to the surface plasmon resonance (SPR) effect derived from the excited Au NPs, the TiO₂ shows high photocatalytic performance for CO₂ reduction under visible light. The ordered mesoporous TiO₂ exhibits superior material and structure, with a high surface area that offers more catalytically active sites. More importantly, the three‐dimensional transport channels ensure the smooth flow of gas molecules, highly efficient CO₂ adsorption, and the fast and steady transmission of hot electrons excited from the Au NPs, which lead to a further improvement in the photocatalytic performance. These results highlight the possibility of improving the photocatalysis for CO₂ reduction under visible light by constructing OMT‐based Au‐SPR‐induced photocatalysts.     

Synthesis of 6- to 10-membered ring (E)-hydroxyiminohydroazaazoniabenzocycloalkenes derivative from cyclization of 2-nitromethylene-1-(ω-phenylalkyl)imidazolidine or 2-nitromethylene-1-(ω-phenylalkyl)hexahydropyrimidine in trifluoromethanesulfonic acid

In trifluoromethanesulfonic acid, 2-nitromethylene-1-(ω-phenylalkyl)imidazolidine or 2-nitromethylene-1-(ω-phenylalkyl)hexahydropyrimidine derivatives undergo an intramolecular cyclization to afford (E)-hydroxyiminohydroazaazoniabenzocycloalkenes, in their trifluoromethanesulfonate salt form. The reaction probably occurres via the formation of an electrophilic transient hydroxynitrilium ion (or O-protonated nitrile oxide). The yields are generally good, except for the higher-membered ring derivatives.     

One-step synthesis of diazadihydroacenaphthylene derivatives with an isoxazoline ring, starting from 1-benzylamino-1-methylsulfanyl-2-nitroethenes

At low temperature in trifluoromethanesulfonic acid, 1-benzylamino-1-methylthio-2-nitroethene derivatives form hydroxynitrilium ions (or O-protonated nitrile oxides) observed by NMR. Quenching with water leads to the formation of a reactive nitrile oxide, dipole which undergoes an unexpected INOC reaction leading to new 3-methylsulfanyl-8a,8b-dihydro-5H-1-oxa-2,4-diazaacenaphthylenes.     

A classification of subgroups of odd unitary groups

In this paper, under the Λ-stable rank condition, we discuss the classification of subgroups of odd unitary groups and get an analogue of Sandwich Theorem.     

Site‐Selective 1,2‐Dicarbofunctionalization of Vinyl Boronates through Dual Catalysis

A modular, site‐selective 1,2‐dicarbofunctionalization of vinyl boronates with organic halides through dual catalysis is described. This reaction proceeds under mild conditions and is characterized by excellent chemo‐ and regioselectivity. It thus represents a complementary new technique for preparing densely functionalized alkyl boron architectures from simple and accessible precursors.     

Stereoselective Base‐Catalyzed 1,1‐Silaboration of Terminal Alkynes

A base‐catalyzed reaction that enables stereoselective 1,1‐silaboration of terminal alkynes is described. This method not only offers a new strategy to functionalize simple and readily accessible alkynes beyond 1,2‐difunctionalization, but also provides an unconventional atom‐ and step‐economical approach to rapidly and reliably access versatile geminal silylboranes in the absence of transition metals and with exquisite stereoselectivity.     

Hierarchically porous Cu current collector with lithiophilic CuxO interphase towards high-performance lithium metal batteries

Lithium metal is one of the most promising anode materials for next-generation electrochemical energy storage due to low electrochemical potential and high spec...     

Preparation of Disperse Silver Particles by Chemical Reduction

Mastery over the microscopic shape and size of a nanoparticle enables accurate control of its properties for some strict application. The mechanism of shape-controlled synthesis was discussed by investigating the formation of silver nanospheres prepared by chemical reduction method using Ag(NH₃)₂⁺ as metal source, ascorbic acid as reducing agent and polyvinylpyrrolidone (K-30) as dispersant. The effects of temperature, PVP/AgNO₃ mass ratio, pH value and the interaction between PVP and silver on the shape and particle size were studied by XRD and SEM. The results show that the morphology of silver particles could transform from branched to spherical and the particle size gradually decrease with the increase of PVP/AgNO₃ mass ratio. The particles size can also be significantly influenced by pH value and temperature. The key point for preparing high dispersity spherical silver powder is that the growth rate of each plane of the particle must be uniform and synchronous. Silver powders with spherical particles with mean size of 0.2 μm were synthesized under the optimum conditions (PVP/AgNO₃ mass ratio 0.6, pH 7, reaction temperature of 40°C).