1H and 13C NMR assignments for four triterpenoid saponins from Albizziae cortex

Four triterpenoid saponins were isolated from Albizziae cortex, and a complete assignment of their (1)H and (13)C NMR spectra was carried out using 1D and 2D NMR ((1)H-(1)H COSY, HSQC, HMBC, and HSQC-TOCSY) methods. Their (1)H NMR assignments were reported for the first time and some of their (13)C NMR spectral data reported in literature were corrected.     

一维多重接力COSY和选择性远程DEPT核磁共振技术在新分子骨架生物碱结构测定和谱峰归属研究中的应用

自防已科千金藤根中分得一个新型分子骨架的四氢异喹啉类生物碱-excentricine(1)。本工作采用一维多重接力COSY和选择性远程DEPT核磁共振新技术成功地确定谱峰归属, 鉴别和连结被季碳和杂原子分割开的自旋体系, 测定了其结构。     

一维多重接力COSY和选择性远程DEPT核磁共振技术在新分子骨架生物碱结构测定和谱峰归属研究中的应用

自防已科千金藤根中分得一个新型分子骨架的四氢异喹林类生物碱—excentricine(1)。本工作采用一维多重接力COSY和选择性远程DEPT核磁共振新技术成功地确定谱峰归属,鉴别和连结被季碳和杂原子分割开的自旋体系,测定了其结构。     

Complete assignment of 19F, 1H and 13C NMR spectra of monomers and precursors towards bridge trifluoromethylated poly(p-phenylenevinylene)

The complete assignment of 19F, 1H and 13C NMR spectra of 11 trifluoromethylated and four bistrifluoromethylated monomers for bridge trifluoromethylated poly(p-phenylenevinylene) is described. The combination of one-dimensional 19F, 1H and 13C spectra, long-range fluorine couplings and the two-dimensional techniques of direct and long-range HETCOR (J = 140 and 8 Hz) permitted full resonance assignment.     

Comprehensive 1H and 13C NMR assignment of 13 protobassic acid saponins

This study aimed to carry out complete ¹H and ¹³C NMR assignment of 13 protobassic acid saponins, including arganins A–C ( 1 – 3 ) and F ( 4 ), butyrosides B–D ( 5 – 7 ), tieghemelin ( 8 ), 3′-O-glucosyl-arganin C ( 9 ), Mi-saponins A–C ( 10 – 12 ), and mimusopsin ( 13 ), recorded in methanol-d₄. This was accomplished by the analysis of high-resolution one-dimensional (1D) NMR (¹H and ¹³C), two-dimensional (2D) NMR (¹H–¹H COSY, HSQC, and HMBC), and selectively excited 1D TOCSY spectra. Before this study, ¹H and ¹³C NMR data of arganins A–C ( 1 – 3 ) and F ( 4 ) were partially assigned. Our effort leads to their complete assignment, especially the glycon residue, and revises some reported data. Some revisions of the ¹H and ¹³C NMR data in the glycon part of butyroside C ( 6 ), tieghemelin ( 8 ), Mi-saponin A ( 10 ), and mimusopsin ( 13 ) were made. Those data of butyrosides B and D ( 5 & 7 ) and Mi-saponin B ( 11 ), which had not been recorded in methanol-d₄, are provided. In addition, the ¹H and ¹³C NMR data of Mi-saponin C ( 12 ) are reported for the first time. These data, being recorded in methanol-d₄, should be more friendly for use as a reference for identifying the related triterpenoid saponins.     

青蒿素的二维核磁共振研究

报导了采用二维核磁共振技术研究青蒿素的核磁氢谱和碳谱的谱线归属,以今后为^1^3C中间体的生物转化产物提供鉴定的基础.     

1-(2,6-二氟苯甲基)-N-甲基-1H-1,2,3-三唑-4-甲酰胺核磁共振峰的归属

采用一维(1D)和二维(2D)核磁共振(NMR)技术对一种抗癫痫活性的化合物1-(2,6-二氟苯甲基)-N-甲基-1H-1,2,3-三唑-4甲酰胺的1H和13C NMR信号进行了归属。     

(s)-多沙唑嗪的核磁共振理论和实验研究

报道了(s)-多沙唑嗪的1H、13C、DEPT、1H-1H COSY等的NMR波谱数据, 并对1H、13C NMR信号进行了指认. (s)-多沙唑嗪分子中含有9个季碳原子, 其中绝大部分通过常规实验的方法难以指认. 应用量子化学规范不变原子轨道(GIAO)的Becke-3-Lee-Yang-Parr(B3LYP)和Hartree-Fock(HF)方法, 分别在6-21G基组下计算了标题化合物的13C NMR化学位移值. 计算结果表明, 理论计算数据与实验结果吻合较好, 可以帮助对(s)-多沙唑嗪季碳原子NMR位移信号进行指认.     

选择性远程DEPT技术用于吡咯里西啶类生物碱的结构测定和核磁共振研究

本文从峨眉千里光(Sencic Fubcri Hensl)中分得二个吡咯里西啶类生物碱。经测定,一个为阔叶千里光碱(1),另一个为新阔叶千里光碱(2)。它们的~(1)H NMR研究尚未见报道。两者的~(13)C NMR研究已有报道,但1的许多~(13)C谱峰归属,不同的作者所得的结果不一致,而2的~(13)C谱峰归属与本文的二维NMR实验结果不一致。这二个化合物的NMR谱较为复杂,部分谱峰相互重选,其归属用一般方法不易确定。本文采用最近由我们提出的选择性远程~(13)CDEPT技术对这二个化合物的结构及其     

Complete 1H- and 13C NMR assignments of saponins from roots of Gypsophila trichotoma Wend

The assignments of 1H and 13C NMR spectra of two new aminoacyl triterpene saponins from roots of Gypsophila trichotoma Wend. are reported. In addition to 1D NMR methods, 2D NMR techniques (COSY, TOCSY, ROESY, HSQC, HMBC, and HSQC-TOCSY) were used for the assignments. The structures were completed by analysis of HR-ESI-MS and ESI-MS(n).     

氧氟沙星的核磁共振波谱性质研究

结合1H, 13C NMR, DEPT, COSY, HSQC, HMBC谱和碳氟偶合裂分行为, 对酸性及碱性溶液中氧氟沙星(Ofloxacin, OFL)的1H和13C谱分别进行归属, 研究了哌嗪环亚甲基构成的AA'BB'复杂自旋体系中各H的化学位移. 发现噁嗪环上的甲基处于直立键; 5H在酸性溶液中化学位移移向低场, 这可能与形成C—H…O弱氢键有关; 在碱性溶液中, OFL的羧基变为羧酸根, 造成羧基和羰基周围碳原子上π电子重新分布, 导致相应C的化学位移和碳氟偶合常数发生明显变化.     

新药普卢利沙的核磁共振研究

应用同核化学位移相关谱(1H-1H COSY)、氢检出异核多量子相关谱(HMQC)、氢检出多键异核多量子相关谱(HMBC)等二维谱核磁共振技术,参考19F-1H和19F-13C的偶合裂分情况对抗菌新药普卢利沙的1H NMR、13C NMR谱的信号进行了全归属。     

Configurational assignment of N-arylsulfonylimines of alpha-polychloroaldehydes

Configurational assignment of seven synthesized N-arylsulfonylimines of alpha-polychloroaldehydes has been carried out by means of experimental measurements and high-level ab initio calculations of their (13)C--(13)C, (13)C--(1)H and (15)N--(1)H spin-spin coupling constants. The title compounds were shown to exist in solution solely in the form of E isomers, in line with thermodynamic reasoning.     

二维接力HOHAHA和—维多重接力COSY研究苷类化合物的结构

苷类化合物的糖体质子大多相互有自旋偶合作用,构成一个复杂的自旋系统。糖体端基质子(H-1)NMR 信号大多为双峰,出现在较     

Determination of heteronuclear coupling constants from 3D HSQC-TOCSY experiment with optimized random sampling of evolution time space

An application of 3D version of HSQC-TOCSY experiment for the measurement of heteronuclear coupling constants of organic compounds yielding complex spectra is proposed. The approach presented here is based on the optimized random sampling of the evolution time space followed by Multidimensional Fourier Transform (MFT). In this study, we show that the interpretation of omega(3)-(13)C coupled (1)H-(13)C 3D HSQC-TOCSY spectra with E.COSY-type multiplets allows one to evaluate heteronuclear coupling constants of strychnine with high accuracy, whereas the employment of 2D methods is associated with signal overlap and use of conventionally recorded 3D NMR spectra cannot provide accurate results in an overnight experiment.     

Interleaved Dual NMR Acquisition of Equivalent Transfer Pathways in TOCSY and HSQC Experiments

A dual NMR data acquisition strategy to handle and detect two active equivalent transfer pathways is presented and discussed. We illustrate the power of this time-efficient approach by collecting two different 2D spectra simultaneously in a single experiment: i) TOCSY or HSQC-TOCSY spectra with different mixing times, ii) F2-¹³C-coupled and decoupled HSQC spectra, iii) conventional and pure-shift HSQC spectra, or iv) complementary HSQC and HSQC-TOCSY spectra.     

Complete assignments of (1)H and (13)C NMR data for two 3beta,8beta-epoxymexicanolides from the fruit of a Chinese mangrove Xylocarpus granatum

Three 3beta,8beta-epoxymexicanolides, including xyloccensin K, 6-acetoxycedrodorin and a new one named xyloccensin W, were isolated from the fruit of a Chinese mangrove Xylocarpus granatum. Their structures were determined by spectroscopic analyses. The first complete assignment of (1)H and (13)C NMR data for xyloccensin W was achieved by means of 2D NMR techniques, including (1)H-(1)H COSY, HSQC, HMBC and NOESY spectra. In addition, the confusion of (1)H and (13)C NMR data previously reported for xyloccensin K was clarified.     

Assignment of the major and minor components of gentamicin for evaluation of batches

The antibiotic agent gentamicin sulfate is a mixture of several structurally very similar aminoglycosides. The major components of gentamicin are gentamicin C1, C1a, C2 and C2a. These major components were separated by means of column chromatography. The ¹H and ¹³C NMR spectra of the free bases and the corresponding sulfates were assigned using HMQC, HMBC and selective TOCSY experiments. Additionally, the ¹H and ¹³C NMR spectra of the sulfates and hydrochlorides, respectively, of the minor components were assigned. The full assignment of all components of gentamicin is necessary for the quantitative analysis of batches of gentamicin. By means of coupled liquid chromatography–NMR, several different batches were studied, revealing different compositions of batches from various sources. Copyright © 2003 John Wiley & Sons, Ltd.     

单-马来二腈基二硫烯-β-环糊精异构体在溶液中的不同组装行为

通过单-2-对甲苯磺酰基-β-环糊精(1)与马来二腈基二硫烯钠盐的取代反应制得单-2-马来二腈基二硫烯-β-环糊精(2),并经红外光谱、紫外光谱、热重分析、1H和13C NMR等手段对产物进行了表征.虽然化合物2的异构体--单-6-马来二腈基二硫烯9-β-环糊精在溶液中因为相互包合作用而在圆二色性光谱中产生分裂的Cot...     

Towards the automatic analysis of NMR spectra: part 7. Assignment of 1H by employing both 1H and 1H/13C correlation spectra

A reliable method of automatically assigning one-dimensional proton spectra is described. The method relies on the alignment of the proton spectrum with an associated heteronuclear single-quantum coherence (HSQC) spectrum, transferring the stoichiometry and couplings to the HSQC. The HSQC spectrum is then assigned using a linear assignment procedure in which a fitness function incorporating (1)H chemical shifts, (1)H couplings and (13)C shifts are employed. The method uniquely employs a sequential procedure in which only correlations of like stoichiometry are assigned at the same time.