共查询到16条相似文献,搜索用时 78 毫秒
1.
对系列手性salen-Ni(Ⅱ)络合物的电子圆二色(ECD)光谱及其绝对构型关联进行了概述.根据晶体结构和对固、液ECD光谱的表征,结合理论计算,着重探讨了准平面型手性[Ni(salen)]的固态结构及其在溶液中的绝对构型和优势构象.在此基础上通过若干实例说明了平面四方形[M(salen)]络合物两种绝对构型命名法,并给出了我们的建议.对[Ni(sal-R, R-chxn)] [sal-R, R-chxn = (R, R)-N, N'-双(亚水杨基)-1, 2-二亚氨基环己烷]的二氯甲烷溶液ECD光谱的计算结果表明,可见区第一个ECD吸收带主要是π →d荷移跃迁(LMCT)所致,而不是通常认为的d-d跃迁: [Ni(sal-R, R-chxn)]的绝对构型为Λ,其在可见区第一个ECD吸收带为正.将此ECD指纹应用于具有“闭壳层”电子结构的其它平面型手性[Ni(salen)]和六配位trans-[CoⅢ(salen)L2]络合物的绝对构型指认,具有一定的普适性.本文的研究结果对于深入理解手性[M(salen)]络合物的配位立体化学、手征光学性质及其手性识别和不对称催化机理具有重要科学意义. 相似文献
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与电子能级跃迁相关的电子圆二色(ECD)光谱因其研究对象宽泛,与涉及振动能级的振动圆二色(VCD)光谱互补,已成为应用于手性立体化学研究的集成手性光谱的主流表征手段。本文概述了确定手性金属配合物绝对构型的三种主要方法,详细介绍了ECD光谱法在确定手性金属配合物绝对构型中的应用,其中着重强调了激子手性方法,并对集成手性光谱学未来的发展趋势做出了展望。 相似文献
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振动圆二色谱: 一种确定手性分子绝对构型的新方法 总被引:2,自引:0,他引:2
手性分子绝对构型的确定是一个极其重要且长期存在的问题. 振动圆二色谱是在红外波长区域测定分子圆二色性的一种新方法, 极大地扩展了圆二色谱的应用范围. 振动圆二色谱法通过构象搜索、量子化学计算等手段准确预测手性分子的振动圆二色谱图, 进而与实测谱图进行比较确定其绝对构型. 该方法已经得到了越来越广泛的应用, 必将成为一种有效测定手性分子绝对构型的常规方法. 相似文献
4.
本文采用该方法将α 羟基酮分别与(R)和(S)-2-甲氧基-2-苯基-2-三氟甲基乙酸(MTPA)反应, 得到(S)和(R)-Mosher酯, 再分别测定其 1H NMR谱, 通过计算化学位移差值确定其绝对构型. 相似文献
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手性化合物的结构确定,尤其是新型手性化合物的绝对构型测定一直是不对称研究的重要工作.除单晶测试外,光谱学方法近年来被广泛应用于手性分子结构鉴定,主要包括电子和振动圆二色谱、旋光光谱、旋光拉曼谱等.本文对上述测试方法的原理、应用范围和相关理论计算方法做了介绍.把谱学测试与理论计算相结合,将成为手性分子结构鉴定的重要发展方向. 相似文献
6.
Mo_2(OAc)_4试剂在邻二醇类结构绝对构型确定中的应用 总被引:1,自引:0,他引:1
环状及非环状邻二醇结构的绝对构型的确定是一个令人关注的研究领域.目前国外文献介绍了一种通过使用过渡金属试剂Mo2(OAc)4进行环状及非环状邻二醇结构绝对构型研究的方法,只需将该试剂与溶液中的被测化合物混合即可形成螯合物,无需制备和分离,且立刻可以进行圆二色谱测定,通过诱导产生的一定波长下的Cotton效应与被测化合物的手性中心的关系,可以方便地应用螺旋规则完成绝对构型的研究.将系统地介绍这一方法学,包括对方法学的研究思路、实验步骤、对影响因素的研究结果,以及一些应用的实例. 相似文献
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采用经典柱色谱法从三七内生真菌Talaromyces purpureogenus中分离得到2个化合物(1和2),经核磁共振波谱和质谱确认其结构均为Drimane倍半萜.通过量子化学计算比较电子圆二色谱(ECD)、旋光(OR)与实验值的方法鉴定了化合物1和2的绝对构型.生物活性测试结果显示,化合物1对大肠杆菌(E.coli)具有一定的抗菌活性(MIC=25μmol/L). 相似文献
10.
在研究天然产物绝对构型的过程中,筛选了一些绝对构型未确定的生物碱类化合物,利用密度泛函理论(DFT)在不同的计算水平下得出其旋光和碳氢谱数据.理论值与实测值对比分析结果表明,二者基本符合,从而鉴定出这些化合物的绝对构型. 相似文献
11.
Buagafuran is a novel drug candidate derived from natural product.Its absolute configuration has been confirmed by electronic circular dichroism combined with modern quantum-chemical calculation using time-dependent density functional theory.The predicted UV absorbance peak is underestimated by several nanometers compared with the experimental data.The applicability of empirical rule for the C=C-C-O system in Buagafuran has also been discussed.Our results show that electronic circular dichroism could be a useful tool for the absolute configuration assignment of chiral drugs,especially for the oily or semisolid substances,whose crystal structures are impossible to obtain. 相似文献
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Wen-Qiang Liu Fang-Fang Lai Jie Zhang Li Sheng Yan Li Li Li Xiao-Guang Chen 《Tetrahedron》2018,74(24):3045-3051
NLG919 (1) with two chiral carbon atoms on its chemical structure is a potent indoleamine 2,3-dioxygenase 1 (IDO1) inhibitor. We developed an effective way to prepare all stereoisomers of 1, the key step being the chiral resolution of racemic intermediate 2. The optimal resolution solvent system was identified as dichloromethane and n-pentane or petroleum ether. Using (?)-di-p-toluoyl-d-tartaric acid as resolution reagent, optical pure (R)-2 (e.e.?>?99%, yield?=?70%) was obtained. The mechanism of chiral resolution was clarified through single-crystal X-ray diffraction of the diastereomeric salt. The absolute configurations of four stereoisomers of 1 were established through electronic circular dichroism spectra, quantum chemical calculation and transition metal method. Their IDO1 inhibitory activity was assessed by pharmacological experiments in vitro and in mouse, demonstrating that S configuration of C5 played an important role on the inhibition of IDO1, while the stereochemistry on C2′ exerted little effect on the IDO1 inhibitory activity in mouse. 相似文献
13.
Christin Worch Iuliana Atodiresei Dr. Gerhard Raabe Prof. Dr. Carsten Bolm Prof. Dr. 《Chemistry (Weinheim an der Bergstrasse, Germany)》2010,16(2):677-683
Straightforward syntheses of enantiopure N‐benzoyl‐ and N‐tert‐butyloxycarbonyl‐protected sulfonimidamides, which can be used as building blocks in newly designed catalysts, are presented. Key synthetic step is a dynamic resolution of a racemic sulfinic acid sodium salt. All subsequent transformations proceed stereospecifically. The absolute configurations at the sulfur atoms of both sulfonimidamides were determined by comparison of measured and calculated CD spectra. An X‐ray crystal structure determination of a sulfonimidoylguanidine derivative confirmed this result. 相似文献
14.
Absolute configurations (+)-(4S), (+)-(3S,4R), (−)-(2S,4S), and (−)-(1R,2R,4S) were assigned, for the first time, to bioactive furanogermacranes extracted from Commiphora erythraea resin by DFT computational analysis of their ORD curves and ECD spectra. This analysis established that all of these compounds share the same absolute configuration at the methyl-substituted carbon thus allowing us to hypothesize a biosynthetic relationship among these structurally related metabolites. 相似文献
15.
Marcelo A. Muñoz Cristina Chamy María A. Bucio Angelina Hernández-Barragán Pedro Joseph-Nathan 《Tetrahedron letters》2014
The absolute configuration of the diterpenoid 13-acetoxyscopadulane, also known as demalonyl thyrsiflorin A acetate (5), isolated from several Calceolaria species has been established by vibrational circular dichroism spectroscopy in combination with density functional theory calculations, as well as by evaluation of Flack and Hooft single crystal X-ray parameters. It follows 5 belongs to the normal enantiomeric series of diterpenes, and that at least 11 out of 13 scopadulanes, for which chemical and biogenetical relationships with 5 are established, also belong to the same stereochemical series. 相似文献
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Dr. Lu Zheng Yulin Zhan Lin Ye Dan Zheng Dr. Ying Wang Prof. Kun Zhang Prof. Hua Jiang 《Chemistry (Weinheim an der Bergstrasse, Germany)》2019,25(62):14162-14168
Two pentameric foldamers, Q5 and Q5C-S , containing a C−F bond were synthesized based on quinoline oligamide foldamers for the measurement of enantiomeric excess and for the determination of absolute configuration of chiral amines, diamines, amino alcohols, and α-amino acid esters. Chiral induction of Q5 was triggered in situ when the chiral analytes reacted with the C−F bond in Q5 by a N-nucleophilic substitution reaction, leading to a linear correlation between the CD amplitude at the region of quinoline chromophores and the ee values of the chiral analytes, which can be used for the ee determination of chiral analytes. Furthermore, the CD intensity of Q5C-S containing a chiral motif at its C-terminus enhances via remote, favorable chiral communication when the chiral induction was triggered in situ by chiral analytes at the N-terminus matches the original helicity of Q5C-S , but decreases via remote, conflicted chiral communication when the chiral induction is triggered in situ by chiral molecules at the N-terminus mismatches the original one. The system can thus be used for determination of the absolute configuration of chiral analytes, given that the chirality of the chiral motif at the C-terminus of Q5C-S is known. 相似文献