环丙基螺环硫巴比妥衍生物的合成、表征及抗惊厥活性

设计合成了2个刚性很强的结构对称性巴比妥酸类化合物———环丙基螺环硫巴比妥酸化合物。通过红外、核磁对其结构进行了表征。其中化合物1a和1b活泼氢(N—H)的化学位移有明显区别。利用二维氢氢相关谱观察到了化合物1a结构中,环丙烷上氢质子与酰胺环上氢质子由于螺环刚性屏蔽影响使其2个环上同侧较近质子之间存在相关性,异侧较远质子之间无相关性。初步测试了2个化合物的抗小鼠电击惊厥活性:化合物1a和1b的惊厥抑制率分别为50%和70%。     

氟烯的结构-特性关系 Ⅱ.某些含氟烷基取代环丙烷的核磁共振谱及质谱

本文报导了十七个新的含氟烷基单取代环丙烷的核磁共振谱及质谱数据,着重讨论了含氟烷基对环上质子的屏蔽效应.烷基取代基中α碳(与环直接相联的碳)上的氢为氟原子取代之后,不仅使所有环上质子的化学位移向低场移动,并且使环上之顺式质子与反式质子的化学位移差Δδ减小,对应于三种类型的环丙烷:和相应的Δδ值分别为～0. 4、～0. 2和<0. 1ppm.这说明除了与环直接相联的 C-C 键外,与α碳相联的键(如 C-F 键)对环上质子的化学位移也有重大影响.文中对质谱也作了简单的讨论.     

稠环芳烃系列化合物化学位移的计算——Ⅲ.稠环芳烃13C化学位移的加合性

本文在稠环芳烃质子化学位移及甲基稠环芳烃甲基质子化学位移加合性的基础上考虑到稠环芳烃分子中碳原子微环境的特点、π电子环流以及碳原子受到的范德华作用对¹³C化学位移的贡献机理,提出12种类型的六元碳环结构因素,并利用10个化合物的80个¹³C化学位移实验数据得出适合于稠环芳烃¹³C化学位移的普遍公式,按这一公式计算结果的标准误差为lppm,远小于现有的半经验量子力学方法的计算误差.说明稠环芳烃系列分子的¹³C化学位移也存在加合性规律.利用本计算方法可较准确地鉴别和预示已合成的稠环芳烃分子的¹³C化学位移值.本文计算了55个稠环芳烃分子的674个非等性的¹³C化学位移.     

三取代环丙烷的^1^3C核磁共振谱研究

前文曾报道三取代环丙烷的质子核磁共振谱及其解析结果,讨论了取代基对化学位移和偶合常数的影响.环丙烷的~(13)C核磁共振谱研究报道极少。Monti等人研究了甲基、溴代和乙炔基环丙烷的~(13)C核磁共振谱,发现在多取代的环丙烷中,取代基相互之间的影响是很显著的.Clague等人亦报道了一系列环丙烷的~(13)C核磁共振谱,但未有详细的分析.本文报道10种尚未见载于文献的三取代环丙烷的~(13)C核磁共振谱,数据见表1. 在1,2,3-三取代环丙烷中,由于取代基的相互作用,影响环上碳的化学位移的因素是比较复杂的.从我们测定化合物的数据来看,取代基为CH_3的环上碳的平均化学位移为29.24     

2－羟基2＇烷氧基－1，1＇－联萘化合物的~1HMNR研究

研究了２－羟基－２＇－异丙氧基－１。１－联萘（３）等联萘化合物的~１ＨＮＭＲ谱或ＣＯＳＹ谱。此类化合物因２及２＇位取代基不同，两个萘环上同位质子不再等价，萘环质子峰增至１２组。化合物３~１ＨＮＭＲ谱峰的归属表明，萘环环电流各向异性对另一萘环质子的屏蔽作用与作者早期研究结果［１］一致。２（或２＇）位取代基上的质子的化学位移也与另一萘环平面相对位置有关。     

1,4-二氢Hantzsch吡啶衍生物的合成及其1H NMR和荧光光谱研究

报道了N-甲基-4-芳基-2,6-二甲基-3,5-二乙酯基-1,4-二氢吡啶(2a-2f),4-芳基-2,6-二苯基-3,5-二乙酯基-1,4-二氢吡啶(3a-3f)及其相应的N-甲基化合物(4a-4f)的合成(芳基p-RC6H4-;R＝OCH3,CH3,H,Cl,CN,NO2).化合物4-芳基-2,6-二甲基-3,5-二乙酯基-1,4-二氢吡啶(1a-1f)可发射较强的荧光,化合物3呈现较弱的荧光,它们的氮甲基产物2和4没有荧光.化合物4氮甲基质子的化学位移值比其相对应的化合物2氮甲基质子的化学位移值向高场移动0.6～0.7.化合物3的4-位次甲基质子的化学位移变化与同碳苯基对位取代基的σ+P有相当好的关联.这些现象反映了化合物2-4的特征构象.     

稠环芳烃系列化合物化学位移的计算 Ⅱ.甲基稠环芳烃甲基质子化学位移的加合性

本文在稠环芳烃质子化学位移加合性的基础上提出八种类型的结构因素,对11种甲基稠环芳烃的29个非等性甲基质子的化学位移进行了计算.结果表明,甲基稠环芳烃的甲基质子化学位移也相当准确地服从加合性规律.计算值的标准误差为0.12ppm.该计算方法可用于计算稠环芳烃取代基的核磁共振谱。     

2,7,16,21-四氧[8.8]对环吩-1,8,15,22-四酮的~1H-NMR研究

2,7,16,21-四氧[8.8]对环吩-1,8,15,22-四酮是一个新的大环化合物。由于它的苯环不能自由转动,而苯环上的质子是化学位移不等价的。这给研究羰基的屏蔽和去屏蔽区域提供了一个很好的例证。     

几种芴衍生物(有机材料增感剂)的13C核磁共振研究

利用FX-60Q脉冲付里叶变换核磁共振波谱仪(磁场强度为14093高斯,观察频率为15.04MH_z)测定了四种劳衍生物的非去偶谱、偏共振谱和质子完全去偶谱。借助于偏共振技术、质子噪声(宽带)去偶、取代基化学位移加合规则以及模式化合物比较,确定了各峰的化学位移和一键、二键及三键偶合常数。实验结果表明,用化学位移和偶合常数的值除帮助识别各峰的归属外,还能推断未知化合物的碳键状态及取代基电负性的大小,对鉴别化合物结构可提供有用的线索。     

B环对位取代异黄酮化合物的核磁共振研究

对14个合成的B环对位取代异黄酮化合物核磁共振氢谱进行了研究.利用超导核磁共振归属了B环无取代异黄酮质子的化学位移,根据取代基化学位移的变化影响规律考察了取代基对分子的影响方式.研究结果表明,2'(6'),3'(5')位质子共振迁移分别与取代基参数σ_p和S_o线性相关,说明4'位取代基主要通过电子效应影响其间位质子,其磁各向异性仅影响邻位质子,该取代基对A环质子影响不大,而对C环尤其是对2-H影响较明显.     

Computational NMR of natural products: On the way to super large molecules exemplified with alasmontamine A

¹H and ¹³C nuclear magnetic resonance (NMR) chemical shifts of a tetrakis monoterpene indole alkaloid alasmontamine A with a molecular formula of C₈₄H₉₁N₈O₁₂ have been calculated at the PBE0/pcSseg-2//pcseg-2 level of theory on M06-2X/aug-cc-pVDZ geometry. In the course of the preliminary conformational search, six true minimum energy conformers were identified that can contribute to the actual conformation of this huge alkaloid. Calculated chemical shifts generally demonstrated a good agreement with available experimental data characterized with a corrected mean absolute error of 0.10 ppm for the range of about 7 ppm for protons and 1.1 ppm for the range of about 160 ppm for carbons.     

Two-dimensional NMR studies of 2-substituted thioxanthene sulfoxides

2-Fluoro-, 2-chloro-, 2-bromo-, 2-methyl-, and 2-methoxythioxanthene have been prepared by borane reduction of the corresponding thioxanthone. The corresponding sulfoxides were prepared by m-chloroperoxybenzoic acid oxidation of these sulfides. Proton and carbon chemical shifts have been assigned to these thioxanthene sulfoxides with the aid of LROCSCM and SROCSCM experiments. Carbon chemical shifts in the unsubstituted rings occur at approximately 125 ppm (C5); 128 ppm (C6); 130 ppm (C7); 128 ppm (C8); and 36 ppm (C9). The methylene protons appears as AB doublets at approximately 4.2 and 3.8 ppm. All sulfoxides have the same, pseudo-equatorial geometry.     

1H NMR spectra part 31: 1H chemical shifts of amides in DMSO solvent

The ¹H chemical shifts of 48 amides in DMSO solvent are assigned and presented. The solvent shifts Δδ (DMSO‐CDCl₃) are large (1–2 ppm) for the NH protons but smaller and negative (?0.1 to ?0.2 ppm) for close range protons. A selection of the observed solvent shifts is compared with calculated shifts from the present model and from GIAO calculations. Those for the NH protons agree with both calculations, but other solvent shifts such as Δδ(CHO) are not well reproduced by the GIAO calculations. The ¹H chemical shifts of the amides in DMSO were analysed using a functional approach for near ( ≤ 3 bonds removed) protons and the electric field, magnetic anisotropy and steric effect of the amide group for more distant protons. The chemical shifts of the NH protons of acetanilide and benzamide vary linearly with the π density on the αN and βC atoms, respectively. The C=O anisotropy and steric effect are in general little changed from the values in CDCl₃. The effects of substituents F, Cl, Me on the NH proton shifts are reproduced. The electric field coefficient for the protons in DMSO is 90% of that in CDCl₃. There is no steric effect of the C=O oxygen on the NH proton in an NH…O=C hydrogen bond. The observed deshielding is due to the electric field effect. The calculated chemical shifts agree well with the observed shifts (RMS error of 0.106 ppm for the data set of 257 entries). Copyright © 2014 John Wiley & Sons, Ltd.     

Chemische Verschiebungen von Methylprotonen in 1H-NMR-Spektren von Alkylcyclohexanen

The chemical shifts of methyl protons of 51 methyl and tert-butyl substituted cyclohexanes were determined. The resonance range of axial methyls extends from δ = 0,63 to 0,98 ppm and equatorial groups from δ = 0,81 to 1,02 ppm. the chemical shifts of axial methyl groups are more greatly influenced by neighbouring groups than those of equatorial methyls. The shift effects of alkyl groups on the chemical shifts of methylprotons and ring protons were compared.     

几种硅烷及其氟取代衍生物的质子核磁共振

属于H_mF_2-mSi(CH₂CH₅)_n(CHCH₂)_2-n型的九个化合物可以系统地合成出来。本文报导它们的质子核磁共振谱。     

15N NMR chemical shifts for the identification of dipyrrolic structures

A variety of dipyrromethanes and dipyrromethenes have been prepared, and their 15N NMR chemical shifts have been measured by two-dimensional correlation to 1H NMR signals. The nitrogen atoms in five examples of dipyrromethanes consistently exhibit chemical shifts around -231 ppm, relative to nitromethane. Seven examples of hydrobromide salts of meso-unsubstituted dipyrromethenes consistently display 15N chemical shifts around -210 ppm, while their corresponding zinc(II) complexes exhibit chemical shifts around -170 ppm. The presence of electron-withdrawing substituents on one of the pyrrolic rings of dipyrromethenes affects the chemical shifts of both of the nitrogen nuclei in the molecule. Boron difluoride complexes of meso-unsubstituted dipyrromethenes display 15N chemical shifts around -190 ppm. Two examples of free-base dipyrromethenes bearing substituents at the meso-position exhibit 15N chemical shifts at approximately -156 ppm, and for the zinc complexes of these compounds at -162 ppm. One-bond nitrogen-hydrogen coupling constants, when measurable, were consistently in the range of -96 Hz. Since the measured 15N chemical shifts have such a high regularity correlated to structure, they can be used as diagnostic indications for identifying the structure of dipyrrolic compounds.     

A computer program for the automatic estimation of H NMR chemical shifts

A computer program has been developed for predicting ¹H NMR chemical shifts. It automatically finds the various substructures of a given molecule for which additivity rules are available. Several strategies have been used to widen the range of applicability. with 200 test compounds, over 90% of the assigned chemical shifts of protons bonded to a carbon atom could be predicted. The mean deviation between observed and predicted values was 0.08 ppm with a standard deviation of 0.19ppm.     

The 1H and 13C NMR chemical shifts of Strychnos alkaloids revisited at the DFT level

The density functional theory calculation of ¹H and ¹³C NMR chemical shifts in a series of ten 10 classically known Strychnos alkaloids with a strychnine skeleton was performed at the PBE0/pcSseg-2//pcseg-2 level. It was found that calculated ¹H and ¹³C NMR chemical shifts provided a markedly good correlation with experiment characterized by a mean absolute error of 0.08 ppm in the range of 7 ppm for protons and 1.67 ppm in the range of 150 ppm for carbons, so that a mean absolute percentage error was as small as ~1% in both cases.