强偶合体系异核二维相关NMR谱解析

本文对异核二维相关NMR谱中强偶合的影响进行了分析,给出量子力学的定量描述。用所建立的计算机NMR谱解析系统模拟了AB(X)自旋体系以及蔗糖的异核二维相关谱。     

核自旋偶合常数2JC-C-F的量子化学计算

用密度泛函B3LYP方法,在6-311G基组上对36个化合物进行构型优化、频率分析,计算了C-C-F的核自旋偶合常数^2JC-C-F。由此拟合出一个基于该方法和相同水平上计算^2JC-C-F的公式,选取四种化合物进行验证,计算值与文献值吻合。     

西尼地平核磁共振碳谱氢谱的谱峰归属

利用普通1H-NMR,13C-NMR,极化转移谱(DEPT)以及同核相关谱(COSY)、异核相关谱(HSQC),特别是远程偶合谱(HMBC)等多种核磁研究方法对新型的血管扩张药西尼地平的1H、13C信号进行完全归属。对由于分子结构对称而引起的化学位移相差最小为0．94Hz的两个碳加以区分,解决了由于样品的近似对称性而导致几组谱峰难以归属的问题。     

聚甲基丙烯酸正丁酯的核磁共振异核相关二维谱

<正> 核磁共振二维谱是研究高聚物分子结构的有力工具.有时一张谱图,就能得到高聚物序列结构或共聚物构型的直接证据.对高聚物结构分析有重要意义.自1983年Brown首次报道聚氯乙烯的二维J谱以来.美国Macromolecules等杂志竟相报道各种聚合物的二维谱图.目前已经报道过的聚合物核磁共振二维谱有二维J谱、~(19)F-~1H异核相关谱、~(13)C-~1H异核相关谱、~1H COSY谱、~(19)F COSY谱、NOESY     

荧光法测定核黄蛋白-核黄素的解离常数

本文推荐一个用荧光法测定配合物解离常数的实验,实验原理简单,知识内容跨学科,兼有生物化学和化学知识,有利于生化专业和化学专业的学生知识面的拓宽.     

相敏远程碳-氢相关技术在季碳归属中的应用

基于作者的二维相敏INEPT（insensitive nuclei enhanced by polarization transfer）实验,提出了相敏模式的远程碳－氢相关实验,称为相敏COLOC（heteronuclear correlation via logn-range couplings）实验,改善了远程碳－氢相关（COLOC）谱的分辨率。相敏COLOC实验可用于测定远程碳－氢相关信息,对季碳化学位移的归属具有一定的意义。作者给出了头孢呋辛钠的相敏COLOC谱。     

取代芳基吡唑和取代芳基异噁唑结构的核磁共振波谱表征

用1 H,13 C NMR和多种二维核磁共振谱表征了本系列化合物的结构,完成了1 H和13 C NMR 谱带的归属,测定了氟原子对各质子和碳原子的偶合常数,探讨了影响偶合常数大小的因素.     

Ab initio study of the NMR shielding constants and spin-spin coupling constants in cyclopropene

Summary Ab initio calculations of parameters which characterize the NMR spectrum are presented for the cyclopropene molecule. The London orbitals CHF (or GIAO-CHF, Gauge-Independent Atomic Orbital Coupled Hartree-Fock) results for the shielding constants are in good agreement with the experimental data, accurately determined, and with otherab initio values. The calculations of the NMR spin-spin coupling constants have been performed using the Multiconfiguration Time-Dependent Hartree-Fock (MC TDHF) approach. Different basis sets and MC SCF wavefunctions were used to estimate the accuracy of the results. Good agreement is obtained with the coupling constants estimated using the available experimental data.Dedicated to Professor Werner Kutzelnigg on the occasion of his 60th birthday     

Unrestricted Hartree-Fock instabilities in nuclear spin-spin coupling calculations. The MNDO method

The MNDO wavefunction is used to calculate the Fermi contact term of nuclear spin-spin coupling constants. Owing to the presence of non-singlet unrestricted Hartree-Fock instabilities of the wavefunction, convergence problems arise in a rather large set of molecules, especially those containing molecular orbitals. A special technique to cope with this situation is presented. The MNDO and transmitted components of the coupling constants in the ethylene molecule are also calculated and compared with those previously obtained with the INDO and INDO/S methods.Part of a Ph.D. thesis (G.E.S.) to be presented to the University of Buenos Aires.Commission of Scientific Research (CIC, Pcia. Bs. As.) fellow.Argentine National Research Council (CONICET) fellow.Member of the Argentine National Research Council (CONICET).     

Long-range carbon-carbon connectivity via unsymmetrical indirect covariance processing of HSQC and HMBC NMR data

It was recently demonstrated that an IDR- (Inverted Direct Response) HSQC-TOCSY data set could be decomposed into a negatively phased direct response spectrum and a positively phased relayed response spectrum that could then be subjected to unsymmetrical indirect covariance processing for the removal of artifacts due to response overlap in the proton NMR spectrum of the molecule. Using experimentally discrete HSQC and HMBC data sets, it is shown that unsymmetrical indirect covariance processing of the pair of NMR spectra affords a presentation containing long-range carbon-carbon connectivity information. The method is demonstrated using strychnine as a model compound. The resulting data are largely free of artifacts although artifacts can arise due to proton response overlap, as previously reported.     

一种新的四糖柴胡皂苷结构的NMR研究

本文报道从小叶黑柴胡(Bupleurum Smithii Wolff Var. Parvitolium Shanet Y. Li)分离出的一种新皂苷, 应用COSY, CH-COSY, TOCSY, HMQC-COSY, HMBC等NMR方法对其结构进行了研究, 确定该化合物为3β, 16β, 23, 28-四羟基齐墩果烷-11,13(18)-二烯-3-O-β-D-吡喃葡萄糖基-(1→2)-β-D-吡喃葡萄糖基-(1→6)-[β-D-吡喃葡萄糖基-(1→2)]-β-D-吡喃葡萄糖苷(1), 命名为柴胡皂苷O(Saikosaponin O)。