聚甲氧基二甲醚合成研究现状

以聚甲氧基二甲醚(简称PODE)合成原料为出发点,系统介绍了PODE合成的反应机理、催化剂和工艺,概述了目前的研究现状,总结了影响PODE合成的因素,展望了PODE合成的研究方向。PODE3-4的理化性质接近柴油,适合用于柴油添加剂,合成PODE3-4研究重点在于开发高活性和高选择性的固体酸催化剂。     

Papain-specific activating esters in aqueous dipeptide synthesis

Enzymatic peptide synthesis has the potential to be a viable alternative for chemical peptide synthesis. Because of the increasing commercial interest in peptides, new and improved enzymatic synthesis methods are desirable. In recently developed enzymatic strategies such as substrate mimetic approaches and enzyme-specific activation, use of the guanidinophenyl ester (OGp) group has been shown to suffer from some drawbacks. OGp esters are sensitive to spontaneous chemical hydrolysis and the group is expensive to synthesize and therefore not suitable for large-scale applications. On the basis of earlier computational studies, we hypothesized that OGp might be replaceable by simpler ester groups to make the enzyme-specific activation approach to peptide bond formation more accessible. To this end, a set of potential activating esters (Z-Gly-Act) was designed, synthesized, and evaluated. Both the benzyl (OBn) and the dimethylaminophenyl (ODmap) esters gave promising results. For these esters, the scope of a model dipeptide synthesis reaction under aqueous conditions was investigated by varying the amino acid donor. The results were compared with those obtained from a previous study of Z-X(AA) -OGp esters. Computational docking analysis of the set of esters was performed in order to provide insight into the differences in the reactivities of all the potential activating esters. Finally, selected ODmap- and OBn-activated amino acids were applied in the synthesis of two biologically active dipeptides on preparative scales.     

5-(4-(二氟甲氧基)苯基)-1H-吡咯-2-甲酸的合成研究

标题化合物是一种重要的医药及农药等精细化工产品的中间体,该化合物暂无文献报道其合成工艺,具有非常好的研究价值。根据文献报道,具有类似结构的化合物对IDO具有良好的抑制作用,能够有效地治疗、减轻或预防由免疫抑制引起的各种疾病,包括由肿瘤或病毒感染引起的自身免疫性疾病。设计并优化了该化合物的合成工艺,以N-Boc-2-吡咯硼酸为原料,经Suzuki反应、脱保护、羧酸化等步骤合成标题化合物,其结构经1HNMR、13CNMR和MS确证,总收率为40.8%。     

Progress in the synthesis of carbon nanotube- and nanofiber-supported Pt electrocatalysts for PEM fuel cell catalysis

This paper reviews the literature on the synthesis of carbon nanotube- and nanofiber-supported Pt electrocatalysts for proton exchange membrane (PEM) fuel cell catalyst loading reduction through the improvement of catalyst utilization and activity, especially focusing on cathode nano-electrocatalyst preparation methods. The features of each synthetic method were also discussed based on the morphology of the synthesized catalysts. It is clear that synthesis methods play an important role in catalyst morphology, Pt utilization and catalytic activity. Though some remarkable progress has been made in nanotube- and nanofiber-supported Pt catalyst preparation techniques, the real breakthroughs have not yet been made in terms of cost-effectiveness, catalytic activity, durability and chemical/electrochemical stability. In order to make such electrocatalysts commercially feasible, cost-effective and innovative, catalyst synthesis methods are needed for Pt loading reduction and performance optimization.     

Greener synthesis and medical applications of metal oxide nanoparticles

Over the past decade, the subject of “greener chemistry" and chemical processes has been emphasized. The “greener chemistry” improves environmental efficiency in reducing the consumption of resources and energy and achieving a stable economic development of the environment. Nanotechnology is investigating nanoscale materials that have applications in the area of biotechnology and nanomedicine alongside several other significant applications such as cosmetics, drug delivery, and biosensors. The different shapes and sizes of nanoparticles can be synthesized with physical, chemical, or biological methods. The tendency to produce nanomaterials, especially metal oxides, and use them, is increasing because of their exciting properties in the nanoscale. However, metal oxide nanoparticles produced by chemical methods have significant concerns due to hazardous and toxic chemicals and their environmental damage. The production of metal oxide nanoparticles using the principles of greener chemistry has found a special place in research. Increased awareness of greener chemistry and biological processes has necessitated using environmentally friendly methods for the production of non-toxic nanomaterials. Plants and polymeric materials as renewable and inexpensive sources have received particular attention to prepare nano biomaterials. The use of plants to synthesize metal oxide nanoparticles because of the non-use toxic pollutants is one of the environmentally friendly methods, and that's why this type of synthesis is called greener synthesis. In this review, we exhibit a total sight of greener synthesis methods for producing metal oxide nanoparticles and their medical applications.     

A review of the advancements in the synthesis and modification of mesoporous carbon and its application to electrochemistry

In the 21st century, materials science has developed rapidly. Mesoporous carbon is now among the most attractive substances due to its enormous specific surface area, high porosity, and structured pore structure. There are many methods to synthesize mesoporous carbon, among which the template method is widely used because of the variety of templates and synthesis pathways. Mesoporous carbon has been used in many fields. Its good electrical conductivity, lightweight nature, and low price have led to many applications in electrochemistry, such as capacitors, electrodes, and materials for electric vehicles. This work contains a literature overview on the synthesis methods and modification techniques for mesoporous carbon, as well as its application in electrochemistry, which serves as a guide for the future growth of mesoporous carbon research.     

Synthesis of Al-doped ZnO nanomaterials with controlled luminescence

Due to the combination of interesting piezoelectric, electric, optical and thermal properties ZnO-doped nanomaterials are of high interest for multifunctional applications in gas sensors, ultrasonic oscillators or transparent electrodes in solar cells. Their implementation and utilisation is strongly dependant on the microstructure and surface nanochemistry characteristics. New processes for the synthesis and sintering are required to control and optimize the chemical composition, component distribution, crystalline and grain sizes. We present the results on the synthesis of zinc oxide powders with different Al content by two different procedures: hydrothermal route and evaporation–condensation in a solar furnace.The influence of the synthesis parameters on the chemical and microstructural characteristics of nanophases synthesized in the two methods has been systematically studied using chemical methods, XRD, BET, picnometric density, SEM and TEM. The combination of the two methods is demonstrated to be a powerful way to obtain nanomaterials with controlled composition and morphology that could not be successfully realised using classical routes. Al doping leads to a lower material density and to a smaller grain size. The first results on the luminescence properties of Al-doped ZnO nanopowders are also presented.     

酶法合成棕榈酸异辛酯

目前棕榈酸异辛酯的工业化生产方法以化学合成法为主,其反应温度高、副反应多、酸对设备腐蚀严重、产物不易分离。本工艺采用酶法合成棕榈酸异辛酯,与化学合成法相比,具有反应条件温和、设备简单、能耗低的特点。脂肪酶经固定化后活力显著提高,酯化率可达95％,固定化酶可重复使用5批以上,具有良好的工业放大前景。     

Research progress in the electrochemical synthesis of ferrate(VI)

There is renewed interest in the +6 oxidation state of iron, ferrate (VI) (Fe^VIO₄²⁻), because of its potential as a benign oxidant for organic synthesis, as a chemical in developing cleaner (“greener”) technology for remediation processes, and as an alternative for environment-friendly battery cathodes. This interest has led many researchers to focus their attention on the synthesis of ferrate(VI). Of the three synthesis methods, electrochemical, wet chemical and thermal, electrochemical synthesis has received the most attention due to its ease and the high purity of the product. Moreover, electrochemical processes use an electron as a so-called clean chemical, thus avoiding the use of any harmful chemicals to oxidize iron to the +6 oxidation state. This paper reviews the development of electrochemical methods to synthesize ferrate(VI). The approaches chosen by different laboratories to overcome some of the difficulties associated with the electrochemical synthesis of ferrate(VI) are summarized. Special attention is paid to parameters such as temperature, anolyte, and anode material composition. Spectroscopic work to understand the mechanism of ferrate(VI) synthesis is included. Recent advances in two new approaches, the use of an inert electrode and molten hydroxide salts, in the synthesis of ferrate(VI) are also reviewed. Progress made in the commercialization of ferrate(VI) continuous production is briefly discussed as well.     

Conifer-Derived Metallic Nanoparticles: Green Synthesis and Biological Applications

The use of metallic nanoparticles in engineering and biomedicine disciplines has gained considerable attention. Scientists are exploring new synthesis protocols of these substances considering their small size and lucrative antimicrobial potential. Among the most economical techniques of synthesis of metallic nanoparticles via chemical routes, which includes the use of chemicals as metal reducing agents, is considered to generate nanoparticles possessing toxicity and biological risk. This limitation of chemically synthesized nanoparticles has engendered the exploration for the ecofriendly synthesis process. Biological or green synthesis approaches have emerged as an effective solution to address the limitations of conventionally synthesized nanoparticles. Nanoparticles synthesized via biological entities obtained from plant extracts exhibit superior effect in comparison to chemical methods. Recently, conifer extracts have been found to be effective in synthesizing metallic nanoparticles through a highly regulated process. The current review highlights the importance of conifers and its extracts in synthesis of metallic nanoparticles. It also discusses the different applications of the conifer extract mediated metallic nanoparticles.     

新型强力甜味剂纽甜的合成研究进展

介绍了新型强力甜味剂纽甜的结构、性能、合成方法及发展前景,对纽甜的合成方法进行了综述.对具体的合成路线作了比较:化学合成法工艺简单,但收率较低;化学-酶联合法专一性强,但发酵成本较高.阿斯巴甜经济易得,以阿斯巴甜为原料合成纽甜是目前最具有发展前景的工艺.     

基于分子筛绿色合成的天然硅铝矿物介尺度活化研究进展

传统的水热合成分子筛的工艺在源头上并不环保,因为其所使用的硅、铝试剂是由天然硅铝矿物通过复杂的反应与分离过程制备而来的。以天然矿物直接作为分子筛合成的硅、铝源而不经化学试剂中间体被视为分子筛绿色合成的发展方向之一,其关键在于天然矿物的介尺度活化,即通过物理、化学或物理与化学作用相结合的方式破坏天然硅铝矿物的高聚合度结构,将其解聚为具有不同介尺度结构的分子筛合成原料。为此,本文综述了天然矿物介尺度活化方法的研究进展,从能耗、活化机理和所得活化产物的介尺度结构的角度,对比分析了机械活化、热活化、碱熔活化、亚熔盐活化和拟固相活化的优缺点,总结了以不同介尺度活化产物为原料合成高性能分子筛的研究现状,为以天然硅铝矿物为原料高性能分子筛的合成提供思路。     

Unerwünschte Reaktionen organischer Stoffe als Gefahren in Chemieanlagen

Undesired reactions of organic substances as sources of danger in chemical plant . In chemical production processes, danger can arise both from the intended exothermal reaction and from unintended exothermal reactions. Such “undesired” reactions may be exothermal reactions of the substances themselves (e.g. decomposition, polymerization) or reactions of the substances involved with one another (e. g. of a reactant with the solvent). Differential thermal analysis and warm storage have been successfully used in various modifications as experimental methods for the study of such reactions. For exothermal decomposition reactions, correlations can be made between the chemical constitution of the substances and the energy released on decomposition, as well as the temperature of incipient decomposition. In mixtures with other substances a modified decomposition behaviour must be expected, usually of such a kind that the temperature range of decomposition is lowered. There are many possible exothermal reactions of substances with one another; only a few have hitherto been studied in detail.     

Li–Y doped and codoped TiO2 thin films: Enhancement of photocatalytic activity under visible light irradiation

Sol−gel synthesis based on the self-assembling template method has been applied to synthesize Li–Y doped and co-doped TiO₂ not only to improve simultaneously the structural and electronic properties of TiO₂ nanomaterials but also to achieve Li–Y doping of titania with high photocatalytic reactivity. The characterization of the samples was performed by GXRD, GSDR, FT-IR, and Raman spectroscopy. According to the GXRD patterns, all the observed reflections can be indexed using the anatase form of TiO₂, Which is confirmed by ground state diffuse reflectance and micro-Raman spectra. The Li–Y doped titania materials immobilized as nanostructured thin films on glass substrates exhibit high photocatalytic efficiency for the degradation of toluidine and benzoic acid under visible light irradiation. The development of these visible light-activated nanocatalysts has the potential of providing environmentally benign routes for water treatment.     

TiC粉体合成的研究现状与展望

TiC具有高熔点、高硬度、高化学稳定性、高耐磨性等优良性能,在多个行业具有广阔的应用前景。目前合成TiC粉体的方法较多,本文综述了碳/金属热还原法、熔盐辅助合成法、机械合金化法等几种主要合成方法,并分析了各种合成方法的优缺点,可为低成本、大规模合成高纯度、形貌可控的TiC粉体提供参考,还对TiC粉体未来合成研究进行了展望。     

液相化学法制备纳米粉体材料的研究进展

液相化学法是制备纳米粉体材料的常用方法。从方法的改进与完善、技术的组合与创新方面综述了液相法制备纳米粉体材料的研究进展。总结了我国在纳米粉体材料研究中所取得的成果 ,最后指出了今后急需解决的问题     

Review: hydrothermal technology for smart materials

In broad terms, hydrothermal synthesis is a technology for crystallising materials (chemical compounds) directly from aqueous solution by adept control of thermodynamic variables (temperature, pressure and composition). The objective of this review is to introduce the field of hydrothermal materials synthesis and show how understanding solution thermodynamics of the aqueous medium can be used for engineering hydrothermal crystallisation processes. In this review, powder synthesis, and their applications are introduced. In Section ‘Introduction’, we will focus on the hydrothermal synthesis as a materials synthesis technology by providing history, process definitions, technological merits and comments on its current implementation in the laboratory. In Section ‘Scope of hydrothermal synthesis in future’, we will describe the development of hydrothermal technology for materials synthesis, their results and comparison with other methods.     

Structure-guided saturation mutagenesis of N-acetylneuraminic acid lyase for the synthesis of sialic acid mimetics

Analogues of N-acetylneuraminic acid (sialic acid, NANA, Neu5Ac), including 6-dipropylcarboxamides, have been found to be selective and potent inhibitors of influenza sialidases. Sialic acid analogues are, however, difficult to synthesize by traditional chemical methods and the enzyme N-acetylneuraminic acid lyase (NAL) has previously been used for the synthesis of a number of analogues. The activity of this enzyme towards 6-dipropylcarboxamides is, however, low. Here, we used structure-guided saturation mutagenesis to produce variants of NAL with improved activity and specificity towards 6-dipropylcarboxamides. Three residues were targeted for mutagenesis, Asp191, Glu192 and Ser208. Only substitution at position 192 produced significant improvements in activity towards the dipropylamide. One variant, E192N, showed a 49-fold improvement in catalytic efficiency towards the target analogue and a 690-fold shift in specificity from sialic acid towards the analogue. These engineering efforts provide a scaffold for the further tailoring of NAL for the synthesis of sialic acid mimetics.     

Review of chemical syntheses of 7-keto-Δ<Superscript>5</Superscript>-sterols

Steroids bearing ketone functionality at carbon-7 are found commonly in nature, and the most prevalent of these are the 7-keto-Δ⁵-sterols. These substances have diverse biological properties and are present in biological samples and food products. For the purpose of studying this class of oxysterols, many chemical methods, involving the chemical oxidation of Δ⁵-sterols to the corresponding 7-keto-Δ⁵-sterols derivatives have been developed to produce these compounds. We have undertaken a review and evaluation of chemical methods for the synthesis of these compounds and have endeavored to enhance one of these procedures to yield products for chemical and biological investigations.