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有机反应的立体选择性和有机化合物的立体异构现象不仅在有机化学,在药物科学和生命科学等相关学科领域中也是具有极其重要意义的研究课题之一。本文介绍了表达有机反应立体选择性高低和立体异构体纯度的几个重要描述术语——对映体过量百分数(percent enantiomeric excess,简写为%ee)、非对映体过量百分数(percent diastereomeric excess,简写为%de)、对映体比例(enantiomeric ratio,简写为er)和非对映体比例(diastereomeric ratio,简写为dr)的历史由来、含义及其在学术使用中存在的争议,给大学有机化学课程相关内容的教学提出建议。 相似文献
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亚胺的对映选择性催化还原研究进展 总被引:1,自引:0,他引:1
亚胺的对映选择性催化氢化是近年来不对称催化反应中的一个新热点, 本文综述了自1973 年Kagan 等人首次报道亚胺对映选择性催化还原以来本领域的研究进展。 相似文献
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大量手性药物分子均具有D-和L-对映异构体, 呈镜像结构的对映体通常表现出截然不同的生理学反应. 青霉胺(Pen)是从青霉素中获取的一种常见的手性药物, 研究者为了实现这两种对映异构体严格区辨和分析一直在不断付出努力. 基于含有NH功能基的手性席夫碱大环化合物具有合成条件温和、结构收敛的优点, 本工作报道了含NH功能基的手性单Schiff碱大环对映异构体的合成(CR和CS)及其对小分子青霉胺对映体(D-Pen和L-Pen)的键合作用及对映体识别选择性. 通过X射线单晶衍射技术解析了单Schiff碱大环对映异构体的晶体结构, 结果表明这两个大环对映体均具有扭曲的非平面构型, 环状骨架中与环己基手性碳相连的亚胺(NH)质子均指向环腔内侧. 采用紫外可见光吸收光谱(UV-Vis)和核磁共振氢谱(1H NMR)滴定技术对手性大环与青霉胺对映体之间相互作用行为进行考察, 表明手性大环与青霉胺不同对映体键合比均为1∶1, 键合常数接近107 L•mol-1, 电喷雾电离质谱法(ESI-MS)表征观察到大环与青霉胺按1∶1键合的缔合物[C-Pen+H]+的分子离子峰. 1H NMR滴定表明手性大环与青霉胺对映体之间的缔合源于大环结构中不对称NH功能基与青霉胺对映体之间形成分子间氢键作用. 通过手性大环与青霉胺对映异构体之间的键合常数比较, 表明大环CR对L-Pen具有更高的选择性键合能力, 而CS则对D-Pen表现出更高的选择性键合能力, 选择性键合常数比均接近2倍. 进一步通过圆二色光谱(CD)滴定考察, 阐释了手性大环与青霉胺对映体选择性键合作用能力与两者之间对映体结构的手性匹配性质密切相关, 主体大环对与其手性相匹配青霉胺对映体表现出较高的键合作用能力, 而与手性不相匹配的青霉胺对映体键合作用则相对较弱. 相似文献
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综述了环糊精在酶促不对称反应、诱导不对称光化学反应、手性化合物的对映体选择性控释与包结和手性农药的对映体选择性毒性领域中的对映体选择性作用的研究进展,并对其前景作了简要展望(引用文献46篇)。 相似文献
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手性和手性物质的重要性已不言而喻,手性药物的开发也已成为主要发展趋势,但目前仍有部分手性药物以消旋体的形式出售和使用。如何合理、有效地使用这些消旋体药物,一直是值得深入研究的课题。对映体选择性释放将手性拆分和控释两个概念结合于一体,有望为消旋体药物的使用提供新的途径。基于本课题组的研究,本文综述了近年来对映体选择性释放研究领域所取得的主要进展。为便于讨论,本文根据构成药物控释载体的手性分子或结构(手性因素),将手性药物释放体系分为有机材料(水凝胶和粒子等)、无机材料和分子印迹材料等控释体系。关于对映体选择性释放以及释放过程中的对映选择性作用的研究,可进一步提升我们对于手性、手性物质和手性作用的认识。 相似文献
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用溶胶-凝胶法以磷钼酸(MPA)的镍盐溶液水解钛酸四丁酯制备了NiPMo/TiO2催化剂.使用ICP、 XRD、 TG-DTA、 IR、 TPD-MS和微反应技术研究了催化剂的化学组成、热稳定性、化学吸附性质和催化反应性能.杂多钼酸盐与TiO2通过O2-在TiO2表面发生了键合.在623 K下,杂多阴离子仍保持原有的Keggin结构.CO2在Lewis酸位Ni(Ⅱ)和Lewis碱位Ni-O-Mo的桥氧协同作用下生成CO2卧式吸附态Ni(Ⅱ)←O-(CO)←(O--Ni).丙烯有多种吸附态在催化剂上吸附.在563 K、 1 MPa和空速1500 h-1的反应条件下,丙烯的摩尔转化率为3.2%,产物MAA选择性为95%. 相似文献
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Different approaches for the synthesis of 1-benzyloxypyrazin-2(1H)-one derivatives from simple amino acids have been investigated. A library of 33 precursors for the preparation of N-hydroxy pyrazinones was obtained in moderate to good yields. 相似文献
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Toward new camptothecins. Part 6: Synthesis of crucial ketones and their use in Friedländer reaction
Laurent Gavara Thomas Boisse Jean-Pierre Hénichart Adam Daïch Philippe Gautret 《Tetrahedron》2010,66(38):7544-5571
In the context of the preparation of camptothecin and luotonin A analogs, the synthesis of some key keto-precursors and their use in Friedländer condensation are described. This paper also focuses on the stability of these keto intermediates and emphasizes the major differences between indolizinones and pyrroloquinazolinones series. Noteworthy is also the report of some original structures isolated as by-products of some experiments. 相似文献
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The Langevin paramagnetic theory can’t describe the relation between magnetization of ferrofluids and applied magnetic field. The structuralization of ferrofluids, which is considered the main influence factor of the magnetization, is regarded. The part of magnetization works is deposited when the structure is forming. This action influences the magnetization of ferrofluids directly or indirectly. On the base of the “compressing” model, the Langevin function that usually describes the magnetization of ferrofluid is modified, and a well-fitted curve is obtained. An equation of the relation between the equivalent volume fraction after being “compressed” and the intensity of magnetic field is discovered, which approximately describes the process of magnetization. The relation between the approximate initial susceptibility and the volume fraction can be obtained from modified formula. 相似文献
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Rebecca J. Burton Mandy L. CrowtherNeal J. Fazakerley Shaun M. FilleryBarry M. Hayter Jason G. KettleCaroline A. McMillan Paula PerkinsPeter Robins Peter M. SmithEmma J. Williams Gail L. Wrigley 《Tetrahedron letters》2013
The highly regioselective Buchwald–Hartwig amination at C-2 of the cheap and readily accessible reagent, 2,4-dichloropyridine with a range of anilines and heterocyclic amines is described. This new methodology is robust and provides a facile access to 4-chloro-N-phenylpyridin-2-amines on 0.25 mol scale. These intermediates undergo a further Buchwald–Hartwig amination at higher temperature to enable rapid exploration of the chemical space at C-4 and to provide a library of 2,4-bisaminopyridines. 相似文献
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KMnO4-mediated oxidative CN bond cleavage of tertiary amines producing secondary amine was introduced, which was trapped by electrophiles (acyl chloride and sulfonyl chloride) to form amides and sulfonamides. The reaction could take place at mild condition, tolerating a wide range of function groups and affording products in moderate to excellent yields. 相似文献
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N. A. Nedolya 《Chemistry of Heterocyclic Compounds》2008,44(10):1165-1219
The review contains a concise historical account and information on the most significant researches undertaken by the staff
at the A. E. Favorsky Irkutsk Institute of Chemistry, Siberian Branch of the Russian Academy of Sciences on the Chemistry
of Heterocyclic Compounds.
Dedicated to Academician of the Russian Academy of Sciences B. A. Trofimov on his 70th jubilee.
Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1443–1502, October, 2008. 相似文献
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A general synthesis of previously unknown semicarbazone-based α-amidoalkylating reagents, 4-(tosylmethyl)semicarbazones, has been developed. The synthesis involved three-component condensation of semicarbazones of aliphatic or aromatic aldehydes with the same or other aldehydes and p-toluenesulfinic acid. The scope and limitations of this reaction were investigated. The compounds obtained were demonstrated to be an efficient α-(4-semicarbazono)alkylating agents. They were reacted with H- (sodium borohydride), O- (sodium methylate), S- (sodium phenylthiolate), N- (pyrrolidine, sodium succinimide), P- (trialkyl phosphites), and C-nucleophiles (sodium diethyl malonate) to give the corresponding products of the tosyl group substitution, 4-substituted semicarbazones, including analogues of nitrofurazone. Among the prepared compounds tested in vitro for antibacterial and antifungal activity, three nitrofuryl-containing semicarbazones exhibited high biological activities with minimum inhibitory concentration (MIC) values of 8–32 μg/mL. 相似文献
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Regiospecific and direct imidation of the methyl C(sp3)–H bond of thioanisoles is realized under mild and metal-free conditions with N-fluorobis(benzenesulfonyl)imide as an oxidant and nitrogen source. Proposed mechanism suggests that thionium ion intermediates and a Pummerer-type reaction are involved. The imidation has advantages such as high step-economy, excellent functionality tolerance, and regiospecificity, giving structurally diverse imidation products. 相似文献
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A small library of new chiral bidentate hydroxyalkyl-imidazolium salts 1 is conveniently synthesized on multi-gram scale from inexpensive and commercially available chiral pool amino acids. The corresponding carbenes, generated by deprotonation of imidazolium salts 1, in combination with palladium(II) chloride were tested in the Mizoroki–Heck coupling reaction. The most significant results in terms of yields and reactivities were achieved with low catalyst loading. The catalytic activities of these imidazolium salts were also investigated in the asymmetric addition of diethylzinc to benzaldehyde. The use of MgO nanoparticles as an additive in conjunction with these ligands played a crucial role in increasing the efficiency of these reactions. 相似文献