共查询到19条相似文献,搜索用时 181 毫秒
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本工作利用手性位移试剂Eu(hfc)Eu(tfc)_3和Pr(hfc)_3对通式为剂进行了~1H、~(13)C和~(31)P NMR研究,观察了对映异构体在手性条件下在NMR谱图上的反映。结果表明,在手性位移试剂作用下,用~1H NMR谱仅能测定结构简单例如R为CH_3的化合物的光学纯度,但采用~(31)P{~1H}技术则可方便有效地测定结构复杂的该类化合物的光学纯度。本工作还对硫酮式和硫醇式两类硫代磷酰胺酯与手性位移试剂的络合模型作了初步讨论。 相似文献
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ω-溴代芳香基乙酮与3-(D-葡萄糖-1-基)-4-氨基-5-巯基-1,2,4-三唑反应 合成了一系列新颖的3-(D-葡萄糖-1-基)-6-芳基-7H-1,2,4三唑并[3,4-b[1,3 ,4]噻二嗪.用元素分析,IR,NMR,MS对其结构进行了表征,研究了其NMR波谱特 征,并以^1H-^1H COSY,^13C-^1H COSY,COLOC二维NMR技术对其^1H NMR,^13C NMR的谱峰进行了全归属 相似文献
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《Magnetic resonance in chemistry : MRC》2003,41(2):115-122
3α‐Acetyl‐β‐boswellic acid ( 1 ), 3α‐acetyl‐α‐boswellic acid ( 2 ), 3α‐acetyl‐9,11‐dehydro‐β‐boswellic acid ( 3 ), 3α‐acetyl‐9,11‐dehydro‐α‐boswellic acid ( 4 ) and 3α‐acetyl‐11‐keto‐β‐boswellic acid ( 5 ) were isolated from the gum resin of Boswellia serrata. 1D and 2D NMR (COSY45, HMQC, HMBC, ROESY) spectra at 500 MHz were used for shift assignments and structure verification. All boswellic acids investigated share the cis conformation at ring D/E and the 3α orientation of the acetyl ester group. Owing to high‐order spectra, NMR could not determine the exact conformation of H‐20/H‐30 of the β‐boswellic acids. 3α‐Acetyl‐β‐boswellic acid methyl ester ( 1 ′) was synthesized for experiments with a shift reagent, Eu(fod)3, that enhanced the resolution considerably. The oxygen atoms of the 3α‐acetyl group form the apparent complex binding site for the shift reagent. Copyright © 2003 John Wiley & Sons, Ltd. 相似文献
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The equimolar mixtures of typical lanthanide shift reagents such as Eu(fod)3, Pr(fod)3 or Yb(fod)3 with silver trifluoroacetate, previously used to induce paramagnetic shifts in the 1H NMR spectra of alkenes, have been successfully applied to simple aromatic hydrocarbons such as benzene, toluene, ethylbenzene and xylenes. In benzene and p-xylene the signals of all the aromatic protons are shifted identically. In other substituted benzenes the magnitude of the induced shift depends on the distance between the proton and the substituents. In addition, the different behaviour of the signals of the methyl groups in meta-and para-xylene on the addition of the complex shift reagent allows the quantitative analysis of the two xylenes in their mixtures. 相似文献
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The complete assignment of the proton NMR spectra of several α-, β- and γ- naphthoflavones at 100 MHz using Eu(fod), and double resonance experi- ments has been carried out. The compounds were found to associate at the carbonyi oxygen, by analogy with flavones where complete structural assignment can be attained using Pr(fod)3, at 60MHz. The three types of naphthoflavones can be distinguished by observation of the quantitative lanth- anide-induced shifts at H-3 and/or H-5, combined with their chemical shift values in the absence of shift reagent. 相似文献
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The 1H and 13C NMR spectra of methyl (-)-zanzibarate (1), an ent-labdanic diterpene isolated from the epicarp of Hymenaea courbaril var. altissima (Leguminosaea, Cesalpinoideae, Detariae), was fully assigned by COSY experiments, 13C/1H shift correlation diagrams and NOE experiments. 相似文献
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Afonin A. V. Kuznetsova S. Yu. Ushakov I. A. Petrova O. V. Voronov V. K. Mikhaleva A. I. 《Russian Chemical Bulletin》2001,50(3):551-553
The reactions of 2-, 3-, and 4-(1-vinylpyrrol-2-yl)pyridines with methyl iodide afford the corresponding quaternary salts. Analysis of their 1H and 13C NMR spectra showed that the quaternization of the nitrogen atom considerably enhances the -acceptor effect of the pyridine ring on the pyrrole ring and on the vinyl group. 1-Methyl-2-(1-vinylpyrrol-2-yl)pyridinium iodide contains no weak intramolecular C--H...N hydrogen bond present in the starting compound. 相似文献
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Tashiro M Furihata K Fujimoto T Machinami T Yoshimura E 《Magnetic resonance in chemistry : MRC》2007,45(6):518-521
Structural elucidation of a malate-aluminum(III) complex has been carried out using 1H and 27Al NMR spectroscopy. The 1H chemical shift perturbation clearly indicated the interaction between malate and Al(III) ion. The measurements of 27Al NMR and 1H-13C HSQC spectra demonstrated that the major form of a complex comprised two equivalent malate ions and two unequivalent Al(III) ions. With this constraint, an equilibrium geometry of the complex was proposed by a semi-empirical molecular orbital calculation. 相似文献
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Aromatic methyl ethers appear to bind strongly to the NMR shift reagent Eu(fod)3 only when there are at least two ether groups ortho to each other. Isolated or lone methyl ethers are very weakly bound to shift reagent as compared to an ester group. It is proposed that europium is involved in strong bidentate binding to ortho oxygens in veratrole, 1,2,3-trimethoxybenzene, methyl veratrate, methyl 3,4,5-trimethoxybenzoate and reserpine. The resultant shifts in molecules with several sites of comparable binding ability are subjected to population analysis using shifts from model compounds. Populations of individual substrate-lanthanide complexes are calculated and demonstrate the additivity of lanthanide induced shifts in these systems. 相似文献