炔酰胺类缩合剂研究进展

缩合剂是指用于促成羧酸与胺或者醇直接缩合构建酰胺键或酯键的一类试剂的总称.由于酰胺和酯的重要性,缩合剂的开发成为了学术界与工业界广泛关注的一个重要研究方向.多肽合成就是α-氨基酸在缩合剂的作用下反复形成酰胺键的过程,因此,缩合剂在多肽合成中发挥着至关重要的作用.当前多肽合成所使用的试剂和技术大多是20世纪50~80年代发展起来的,这些试剂和技术的天生弊端逐渐显现出来.比如传统多肽缩合剂过度活化α-氨基酸而诱发的外消旋化和其它副反应导致的副产物成为药物多肽生产过程中一个极为关切的问题.另外固相多肽合成的低原子经济性给可持续发展带来了极大的挑战.这些问题只能依靠原始创新的颠覆性技术和全新的缩合方法来解决.我们课题组致力于通过发展新试剂和新反应来解决多肽与蛋白质化学合成领域的难题.本文系统介绍了我们发展的一种结构全新的炔酰胺类缩合试剂及其在酰胺、酯、大环内酯、多肽、硫代多肽合成中的应用研究进展.     

多肽在金纳米粒子表面偶联反应效率研究

通过1-(3-二甲氨基丙基)-3-乙基碳二亚胺(EDC)与N-羟基琥珀酰亚胺(NHS)活化反应将多肽偶联到金纳米粒子表面,采用荧光光谱研究其形成的酰胺键的反应偶联效率.考察了实验条件,包括缓冲液的种类(HEPES、Tris-HCl、硼酸、PBS缓冲液)、pH值(pH 6.5~9.0)、缓冲液浓度(10, 25, 40和50 mmol/L)、NHS和EDC的浓度(NHS 0.2~1.0 mol/L,EDC 0.01~0.5 mol/L)及二者比例(0,0.5,1.0,2.0和2.5)、偶联反应时间(4, 8, 12, 24和36 h)等对偶联效率的影响,筛选出最佳实验条件.实验结果表明, 25 mmol/L 4-羟乙基哌嗪乙磺酸(HEPES)缓冲液(pH 7.0), NHS/EDC浓度为0.4 mol/L/0.2 mol/L和24 h的反应时间为EDC-NHS活化反应将多肽偶联到金纳米粒子上的最佳实验条件.本研究结果可为相关研究提供技术参考.     

Coupling techniques in speciation analysis

Summary Direct coupling techniques in speciation analysis lead to reproducible results with lower risks of trace contamination or losses of analytes in a shorter period of time. The direct coupling mode seems to be most promising for liquid chromatographic separation methods — especially gel permeation chromatography — and for some electrophoretic methods — as flow-through and capillary techniques. Promising detection methods are Flame-AAS and ICP-OES but also hydride-generation AAS and chemical reaction detectors in continuous-flow technique.     

Coupling Principles in Organic Dyes

Dye molecules containing two or more polymethine structural units, or at least one polymethine and one polyene structural unit, generally exhibit coupling effects that determine the spectroscopic behavior and other physicochemical properties of the substance. The coupling concept can be used inter alia to fit the quinone dyestuffs, the indigoids, and the indanthrenes into a general poymethine color system and to perdict new dye structures.     

Nickel-Catalyzed Coupling Reactions of Alkenes

Several reactions of simple, unactivated alkenes with electrophiles under nickel(0) catalysis are discussed. The coupling of olefins with aldehydes and silyl triflates provides allylic or homoallylic alcohol derivatives, depending on the supporting ligands and, to a lesser extent, the substrates employed. Reaction of alkenes with isocyanates yields N-alkyl acrylamides. In these methods, alkenes act as the functional equivalents of alkenyl- and allylmetal reagents.     

Measurements of Long-Range Homonuclear Coupling Constants

Coupling constants in proton systems provide access to useful structural information. Several methods have been proposed to measure these constants in high-resolution spectra, but many of them are not well suited when the coupling constants are comparable to the spectral linewidth. In such a case the measurement of the apparent splitting, obtained from conventional NMR or from two-dimensional correlation spectroscopy (COSY), can cause a miscalculation of the true coupling constant value. In this work, data processing for extracting small coupling constants is described. Signals are obtained from spin-echo experiments and analysed in the time domain in such a way that couplings are apparently multiplied by n+1, where n is positive. Small coupling constants in 4-methyl-1,3-dioxane were obtained by this method. © 1997 John Wiley & Sons, Ltd.     

Coupling effects in optical metamaterials

Metamaterials have become one of the hottest fields of photonics since the pioneering work of John Pendry on negative refractive index, invisibility cloaking, and perfect lensing. Three-dimensional metamaterials are required for practical applications. In these materials, coupling effects between individual constituents play a dominant role for the optical and electronic properties. Metamaterials can show both electric and magnetic responses at optical frequencies. Thus, electric as well as magnetic dipolar and higher-order multipolar coupling is the essential mechanism. Depending on the structural composition, both longitudinal and transverse coupling occur. The intricate interplay between different coupling effects in a plasmon hybridization picture provides a useful tool to intuitively understand the evolution from molecule-like states to solid-state-like bands.     

氨水介质中金属锌促进醛的呐偶联反应

传统的呐偶合反应必须在无水有机溶剂条件下, 由金属或金属化合物促进羰基化合物进行呐偶合反应. 曾经报道过金属锌在强碱介质或弱酸介质中, 促进羰基化合物进行水相呐偶合反应. 本文报道一种简便、有效的水相呐偶合反应, 它是在含有少量冠醚的稀氨水溶液中, 使用锌粉促进醛基化合物进行水相呐偶合反应, 其中加入少量的冠醚有助于提高反应的产率, 呐醇产率由63%提高到84%. 然而, 呐偶合反应的产率受到羰基周围环境的立体位阻影响较大, 在此条件下, 锌粉能有效地促进芳香族醛类化合物进行水相呐偶合反应, 得到的呐醇产率高, 但非对映异构体选择性差, 而脂肪族醛类化合物得到的呐醇产率较低, 在同样的条件下, 酮类化合物不能顺利进行呐偶合反应.     

氨水介质中金属锌促进醛的(口片)呐偶联反应

传统的(口片)呐偶合反应必须在无水有机溶剂条件下,由金属或金属化合物促进羰基化合物进行(口片)呐偶合反应.曾经报道过金属锌在强碱介质或弱酸介质中,促进羰基化合物进行水相(口片)呐偶合反应.本文报道一种简便、有效的水相(口片)呐偶合反应,它是在含有少量冠醚的稀氨水溶液中,使用锌粉促进醛基化合物进行水相(口片)呐偶合反应,其中加入少量的冠醚有助于提高反应的产率,(口片)呐醇产率由63%提高到84%.然而,(口片)呐偶合反应的产率受到羰基周围环境的立体位阻影响较大,在此条件下,锌粉能有效地促进芳香族醛类化合物进行水相(口片)呐偶合反应,得到的(口片)呐醇产率高,但非对映异构体选择性差,而脂肪族醛类化合物得到的(口片)呐醇产率较低,在同样的条件下,酮类化合物不能顺利进行(口片)呐偶合反应.     

金属催化端炔与亚胺衍生物亲核加成制备炔丙基胺的研究进展

综述了端炔与C=N双键亲核加成制备炔丙基胺的合成方法的研究进展.其中包括醛亚胺的间接或直接偶联反应,烯胺的间接偶联反应,酮亚胺的间接或直接偶联反应等.参考文献30篇.     

Efficient Pd-Catalyzed Direct Coupling of Aryl Chlorides with Alkyllithium Reagents

Organolithium compounds are amongst the most important organometallic reagents and frequently used in difficult metallation reactions. However, their direct use in the formation of C−C bonds is less established. Although remarkable advances in the coupling of aryllithium compounds have been achieved, Csp²−Csp³ coupling reactions are very limited. Herein, we report the first general protocol for the coupling or aryl chlorides with alkyllithium reagents. Palladium catalysts based on ylide-substituted phosphines (YPhos) were found to be excellently suited for this transformation giving high selectivities at room temperature with a variety of aryl chlorides without the need for an additional transmetallation reagent. This is demonstrated in gram-scale synthesis including building blocks for materials chemistry and pharmaceutical industry. Furthermore, the direct coupling of aryllithiums as well as Grignard reagents with aryl chlorides was also easily accomplished at room temperature.     

Interaction of Silane Coupling Agents with CaCO3

A study of eight silane coupling agents showed very different effect of these compounds on the mechanical properties of PP/CaCO₃composites. The application of aminofunctional silane coupling agents resulted in the reactive coupling of the two inactive components leading to increased strength and decreased deformability. A detailed study of the interaction between CaCO₃and the various coupling agents was carried out in order to find an explanation for the strong coupling effect. The amount of coupling agent creating a monolayer coverage was determined by a dissolution method for each coupling agent. The obtained values changed between 0.3 and 1.0 wt% calculated for the CaCO₃. An attempt was made to determine the orientation of the adsorbed molecules to the filler surface. Most of the coupling agents are oriented perpendicularly to the surface with the exception of a methacryl functional silane compound. Possible interactions between hydrolyzed or condensed silane coupling agents and the filler were studied by Fourier transform infrared spectroscopy using transmitting (FTIR-TS) and diffuse reflectance (DRIFT) modes, as well as gel permeation chromatography (GPC). The results showed that bulky organofunctional groups form a caged, polycyclic, low-molecular-weight structure on the surface, while silanes with smaller groups tend to condense into open, ladder type, high-molecular-weight polysiloxane chains. Polymer/filler adhesion, however, depends primarily on the chemical character of the organofunctional group. Aminofunctional silane coupling agents adhere well to the filler surface and react also with the polymer. In the case of similar functionality the size of the organofunctional group determines the strength of the adhesion.     

金属催化下芳基磺酸酯偶联反应的研究进展

综述了金属催化下芳基磺酸酯作为底物参与形成碳—碳键、碳—氮键的偶联反应, 如Suzuki-Miyaura反应、Sonogashira反应等方面的研究进展.     

Coupling reactions of zirconocene complexes and heterosubstituted alkenes

This tutorial review surveys recent advances in the field of zirconium promoted coupling reactions of unsaturated molecules (and/or organolithium compounds) and heterosubstituted alkenes. This reaction has recently emerged as a powerful tool in organic chemistry to access a variety of synthetically useful building blocks not easily available by other methods. In particular, three different reaction pathways are discussed: i) the reaction involving alkyne-zirconocene and aryne-zirconocene complexes which allows access to dienyl and aryl zirconocene complexes; ii) the reaction of alkene-zirconocene complexes and enol ethers which has shown to be highly dependent on the structure of the enol ether used, allowing the synthesis of simple vinyl zirconocenes or multicomponent coupling products, and; iii) the reaction involving imine-zirconocene complexes which supposes a new entry to allylic amines.     

Theoretical Design of High－spin Organic Molecules with Heterocycles as Ferromagnetic Coupling Units

IntroductionThe design and the syntheses of organicmolecules with very high- spin ground states havebeen a topic of great interest[1— 5] .One of rationalapproaches to designing high- spin molecules,which has been proposed and studied by severalgroups[6,7] ,consists in conceptually dividing themolecules into two components,i.e.,a spin- con-taining( SC) fragment which provides the unpairedelectron and a ferromagnetic coupling ( FC) unitwhich is connected with radical centers ferromag-netically…     

Coupling of vinyl aziridines and phenyl isocyanate

Thermal coupling of vinyl aziridines and phenyl isocyanate was evaluated. Although oxazolidinone products were predominant, some reactions afforded a seven-membered ring heterocycle. When Ni/IMes was employed as a catalyst, a wider array of vinyl aziridines underwent coupling reactions. The Ni catalyzed reactions generally afforded vinyl imidazolidinones as major products.     

4个新型有机磷缩合试剂的合成及其在生物活性肽合成中的应用

报道了4个新型有机磷化合物：N-二乙氧基磷酰苯并唑酮(DEPBO)、N－(2-氧-1,3,2-二氧杂磷杂环乙烷基)-苯并唑酮(DOPBO)、3－(2'-氧-1',3',2'-二氧杂磷杂环己烷基)-氧-1,2,3-苯共三嗪-4(3H)-酮(DOPBT)和3－(二乙氧基磷酰基)-氧-1,2,3-苯并三嗪-4(3H)-酮(DEPBT)的合成,并研究了它们作为缩会试剂在多肽合成中的应用. 研究结果表明,它们可以成功地用于固相法和溶液法合成多肽,其中DEPBT还可用于环肽的合成. 应用DEPBO和DEPBT合成了促睡眠肽的类似物及从云南中草药繁缕中分离鉴定的一个环七肽等生物活性肽.     

钯催化卤代芳烃Ullmann偶合反应

Ullmann偶合反应是有机合成中构建碳—碳键最重要的方法之一. 综述了钯催化卤代芳烃Ullmann偶合反应的研究进展, 其中包括钯催化还原Ullmann偶合反应和钯催化氧化Ullmann偶合反应等两部分.     

Palladium‐Catalyzed Cross‐Coupling of Alkenyl Carboxylates

Carboxylate esters have many desirable features as electrophiles for catalytic cross‐coupling: they are easy to access, robust during multistep synthesis, and mass‐efficient in coupling reactions. Alkenyl carboxylates, a class of readily prepared non‐aromatic electrophiles, remain difficult to functionalize through cross‐coupling. We demonstrate that Pd catalysis is effective for coupling electron‐deficient alkenyl carboxylates with arylboronic acids in the absence of base or oxidants. Furthermore, these reactions can proceed by two distinct mechanisms for C?O bond activation. A Pd^0/II catalytic cycle is viable when using a Pd⁰ precatalyst, with turnover‐limiting C?O oxidative addition; however, an alternative pathway that involves alkene carbopalladation and β‐carboxyl elimination is proposed for Pd^II precatalysts. This work provides a clear path toward engaging myriad oxygen‐based electrophiles in Pd‐catalyzed cross‐coupling.     

Pinacol Coupling Reactions Catalyzed by Active Zinc

The facile carbon-carbon bond formation is a forever goal and indispensable tool in organic synthesis1. Metal-mediated coupling reactions as highly efficient processes are always a major focus of directed synthesis2. Pinacol coupling reactions have been recognized to be efficient and selected alternatives for preparing several kinds of compounds3, not to mention those can be as versatile tools for preparing building blocks or exerted on synthesizing natural products in several key steps4. The …