天然结晶辣椒碱的NMR谱研究

用一维¹H NMR谱、¹H-¹H COSY谱和一维¹³C NMR谱、DEPT谱研究辣椒碱分子和二氢辣椒碱分子及其混合物,得到¹H和¹³C的化学位移,采用¹H NMR谱测定天然辣椒碱中辣椒碱和二氢辣椒碱的相对含量.     

A 19F NMR Study on the Interaction of the Hexafluoroanions of Group IV Elements with Cations in Solutions

In view of previous studies of tetrafluoroborate solutions¹, it appeared interesting to continue further investigations on the interactions of fluorocomplexes with different cations, in general, and of the MF₆ ^2- fluoro complexes, in particular. In this communication, the high resolution ¹⁹F NMR data are given for the aqueous and water-acetone solutions of silicon, germanium, tin and titanium hexafluorocomplexes, containing paramagnetic (Co²⁺, Ni²⁺, Cu²⁺, Cr³⁺) and diamagnetic (Be²⁺, Mg²⁺, Zn²⁺, NH₄ ⁺) cations.     

吡啶酰胺类化合物中酰胺键异构化的变温核磁共振研究

合成了一系列六氢吡啶酰胺化合物以研究酰胺键的双键性质. 采用¹H 及¹³C NMR 技术确证了不同取代的酰胺化合物中酰胺键的双键性质. 进一步采用变温核磁共振技术对2-(3,5- dinitrophenyl)-1-(piperidin-1-yl)ethanone(化合物1)进行了¹H 及¹³C NMR研究. 结果表明,在20 ℃（293 K）时,a, b及c, d上的氢和碳原子具有不同的化学位移,且距酰胺键越近,化学位移的差异越大. 随着温度的升高,两种异构体的转换速率增加,酰胺双键的性质越来越不明显,导致化学位移的差异逐渐减小,直至融合为一个峰. 经计算,在融合温度下两种异构体的相互转换的速率常数是380 s-¹,能垒约为67 kJ• mol^-1.       

A Refinement of the Hg2F2 Structure by the Use of NMR Data

Abstract

The crystal structure of Hg₂F₂ was studied in works.^1,2 The Hg₂F₂elementary cell of the tetragonal syngony with a=3.66 Å and c=10.89 Å contains two formula units, the space-group being 14/mmm. Hg₂F₂ belongs to those types of structures which possess one non-fixed coordinate (z_F and zHg); hence, the position of the fluorine nuclei may be determined from the value of the second moment of the NMR spectrum of ¹⁹F for powder sample.³ In this case it is ostensibly important, inasmuch as determining the positions of fluorine nuclei near the heavy mercury atoms presents a difficulty for X-ray analysis.     

A Refinement of the InF3.3H2 O Structure by the Use of NMR Data

Bokij and Khodashova' derived from X-ray diffraction study and coordination considerations that InF.3H₂O is pseudotetragonal with a=7.90, c=4.14 8, 2=2, space group PII2/n. each indium atom is surrounded by six ligands (F and H₂O) to form nearly are gular octahedron. The adjacent octahedra have common a pices forming in finitechains along the c-axis. Since the F and O scattering factors are much the same, the identification of F atoms and H₂O molecules was performed on the basis of coordination considerations. The bridges between In atoms were unambiguously identif iedas fluorine atoms (F). The fouro the rligands of each octahedron are two fluorine atoms (F) and two water molecules (H₂O equatorial plane of the octahedra (fluorines under fluorines in order to retain 2=2). estimated as oxygens of H₂O_I molecules due to the irspecifictetrahedral surrounding by F_II and H₂O_I In such a lamellar structure, the layers of H₂O_I and H₂O_II molecules interchange with the layers of F atoms. The existence of H₂O layersin the InF₃.3H₂structure, claimed by B. and K., is notin agreement with the factth that the crystals of this fluoride have needle-like habitus and do not exhibit excellent cleavage in the plane (110). In order toresolve this contradiction and find out the proton position sin the InF.3H ₂o structure, we have applied the NMR method     

一维核磁共振谱数据的小波变换压缩

本成功地将小波变换的多尺寸信号分解（ＭＲＳＤ）方法用于一维核磁共振（ＮＭＲ）信号的数据压缩。将一幅由３２７６８个数据点构成的ＮＭＲ谱图压缩至５１２个数据点,仍能在均方差很小（２．７７６９×１０＾－４）的情况下很好地重建原始谱图。     

31P AND 2H NMR Spectra of A Lyomesophase Containing Phosphoric Acid Monodecylester and H3PO4

This is a report on ³¹P nmr spectra of phosphoric acid monodecylester, PDE, and ²H quadrupolar splitting of D₂O in a lyomesophase developed from n-decylammonium chloride, PDE/H₃PO₄ and D₂O.Polarizing microcopic and ²H nmr studies showed that the mesophase was of lamellar-like structure but alignes as the temperature is increased. As the mesophase contained a minute amount of free H₃PO₄, the ³¹P nmr spectra gave a sharp peak and a hump. The latter was interpreted to arise from a slow tumbling process of PDE between different agglomerates in this system.     

Application of NMR spectroscopy for analysis of the composition of pine needle essential oil

We have used ¹H and ¹³C NMR spectroscopy to analyze the chemical composition of essential oils of pine needles grown in different regions of the Republic of Belarus. We consider the change in the composition of the oils depending on the area where the pines were grown. We suggest using pine essential oil as a biological indicator of environmental conditions. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 2, pp. 246–249, March–April, 2006.     

Solution Conformation of a Pentapeptide by NMR and Molecular Modeling Studies

High resolution NMR studies and molecular modeling calculations were performed on a linear pentapeptide BOC-Tyr-Gly-Gly-Pro-Leu-OMe. This molecule exhibits two conformations in the solution state. While the ¹³C spectrum in nonpolar solvents such as acetonitrile shows only one form, in DMSO-d₆ and MeOD there are two forms. The appearance of the major (M) and minor (m) resonances is attributed to cis-trans isomerization about the X-Pro bond.

The assignments of several proton resonances for the major conformer were made through the combined analysis of two dimensional (2D) homonuclear correlated spectroscopy (COSY) and available data on similar peptides. The solution conformation of the major moiety was probed using the distance constraints obtained from 2D-NOE spectroscopy (NOESY). In addition, other information such as presence of internal hydrogen bonds and dihedral angle values from coupling constants for the amide protons were also used.     

A Review of NMR Studies in RCo3 Systems Presenting d-Moment Instability

For the past few years, intermetallic systems with the formula RCo₃, where R is a rare earth, have attracted the attention of the magnetism community. In these systems, the magnetism associated to the Co ions presents a magnetic instability which gives rise to metamagnetic phase transitions observed as a change on the Co magnetic moment for some critical values of the molecular field acting on this sublattice. A number of publications about these systems is concerned with basic magnetic measurements and ⁵⁹Co NMR in compounds such as Y_1–x R _x Co₃, where R = Gd, Nd, Er. The Co ions are distributed among three crystal sites with different symmetries, one of these sites being further split into two magnetic sites, a fact in itself that considerably complicates the NMR spectra. Besides, as we have observed, the linewidths and even the number of lines appearing on the NMR spectra are strongly dependent on some NMR features, such as the radiofrequency power applied to the sample. Adding to this fact, these magnetic peculiarities depend on the compounds stoichiometry; therefore it is no surprise to find conflicting results in the literature. In the present paper a review of the NMR published data will be made, including some new results of our own.     

蚕丝蛋白的NMR研究Ⅲ.天蚕茧层固态13C CP-MASNMR研究

本文分别测定了东北天蚕茧和龙蛓天蚕茧各内,中,外三层茧层的固态¹³C CP-MASNMR波谱,对其谱峰进行了归属,估算了谱峰区主要谱线在该区所占的比例,还计算了各个茧层丝蛋白中无定形状态所占的百分含量。谱图显示了东北天蚕茧层与龙(蛓)天蚕茧层丝蛋白结构的差异。     

Structure determination of aligned systems by solid-state NMR magic angle spinning methods

Single crystal rotational echo double resonance (REDOR) experiments can be used to determine the three-dimensional orientation of heteronuclear bond vectors in an amino acid, as well as the crystal's orientation relative to the rotor fixed frame (RFF). We also demonstrate that for samples uniaxially aligned along the rotor axis, the polar tilt angle of a bond vector relative to the RFF can be measured by use of an analytical expression that describes the REDOR curve for that system. These bond orientations were verified by X-ray indexing of the single crystal sample, and were shown to be as accurate as +/- 1 degrees .     

没药中一呋喃倍半萜的核磁共振研究

从没药氯仿提取物中分离得到一呋喃倍半萜类化合物：2-甲氧基-5-乙酰氧基呋喃吉马-1(10)E-烯-6-酮．通过1D NMR和2D NMR（¹H-¹H COSY,HSQC和HMBC）等技术确定了该化合物的结构,利用2D NMR技术对其核磁共振信号进行了全归属,修正了文献中的归属错误. 通过NOESY实验以及偶合常数的分析,确定了其结构中1,10位双键和甲氧基、乙酰氧基、 甲基等基团的相对构型.     

基于最大隶属原则的核磁共振波谱模糊识别

介绍了基于最大隶属原则的核磁共振(NMR)波谱模糊识别原理与方法. 提出了关于核磁共振波谱模糊集合的概念,并给出了相应的隶属函数. 通过建立标准谱数据库和相应的模糊识别算法,实现了核磁共振波谱的快速自动定性分析. 对苯酚、邻苯二酚、间苯二酚及对苯二酚4种化合物及其11种混合物样品的¹H NMR谱进行了定性分析. 结果表明,在粗略找峰和隶属度阈值在0.45~0.85之间较大范围内取值的情况下,方法均给出了准确的识别结果.     

Visualization of residual anisotropic interactions in crosslinked natural rubbers by dipolar local field measurements and H natural abundance NMR spectroscopy

An extension of the exploitation of indirect observation of ¹H nuclei through ¹³C resonances is presented in the case of crosslinked elastomers. It is demonstrated that, by using this method in vulcanized elastomers above T_g a direct visualization of residual dipolar interactions on different functional groups as well as their dependence on motional constraints is available. It is also shown that ²H natural abundance NMR spectra of elastomers provide similar information on motional constraints by way of residual quadrupolar interactions.     

High-Resolution Solid-State NMR Spectroscopy of Steroids and Their Derivatives

Abstract: Steroids are an important class of organic compounds containing a vast array of biologically and physiologically essential molecules. Due to their availability, relatively straightforward derivatizability, and endogeneity, they are widely used in pharmacological applications. The investigation of molecular and physicochemical properties of active pharmaceutical ingredients (APIs) in the solid state is important, because these properties are directly related to their pharmacological activity. Several methods are available for this purpose. Solid-state NMR spectroscopy offers a nondestructive and flexible technique, providing both structural and dynamic information. It can be applied to every solid physical state (both crystalline and amorphous) as well as to materials with different compositions. The current article aims at gathering together some of the recent and most important studies in the area of high-resolution solid-state NMR spectroscopy of steroids and their derivatives completed with related theoretical reports not forgetting to outline the future remarks.     

DFT,FT‐Raman,FT‐IR and NMR studies of 2‐fluorophenylboronic acid

The experimental and theoretical vibrational spectra of 2‐fluorophenylboronic acid (2fpba) were studied. The Fourier transform Raman and Fourier transform infrared spectra of the 2fpba molecule were recorded in the solid phase. The structural and spectroscopic analysis of the molecule was carried out by using Hartree‐Fock and density functional harmonic calculations. For the title molecule, only one form was found to be the most stable structure, by using B3LYP level with the 6‐31++G(d,p) basis set. Selected experimental bands were assigned and characterized on the basis of the scaled theoretical wavenumbers by their total energy distribution (TED). The ¹H and ¹³C nuclear magnetic resonance (NMR) chemical shifts of the 2fpba molecule were calculated using the Gauge‐Invariant‐ atomic orbital (GIAO) method in DMSO solution using IEF‐PCM model and compared with the experimental data. Finally, geometric parameters, vibrational wavenumbers and chemical shifts were compared with available experimental data of the molecule. Copyright © 2009 John Wiley & Sons, Ltd.