含苯并咪唑环N-酰腙衍生物的NMR研究

应用¹H NMR、¹³C NMR、¹H-¹H COSY、NOESY、¹H-¹³C HSQC、¹H-¹³C HMBC和变温¹H NMR等多种NMR技术,对新化合物1,即N'-[（4-N,N-二甲基）苯基]亚甲基-2-（4-甲基苯氧甲基）苯并咪唑-1-乙酰肼的两种异构体（E/trans和E/cis）的¹H和¹³C NMR信号进行了全归属,测量了相应的偶合常数（J值）以及异构体所占的比例.实验结果表明,此新化合物在DMSO-d₆中存在着E/trans和E/cis两种异构体的互变,且E/cis异构体含量为74.2%.     

高分子化学位移的量化计算与固体NMR实验研究

该文以2种不同立构聚丙烯（iPP和sPP）为讨论对象,首先研究了量化计算方法在预测高分子¹³C 各向同性和各向异性化学位移（CSA）中的应用,然后讨论了近年来发展的测定¹³C CSA粉末线形的2种重要固体NMR实验技术（SUPER和RAI）的特点和实验优化问题. 最后,利用可获得接近无扭曲线形的SUPER技术测定了等规立构聚丙烯样品的¹³C CSA粉末线形,并与量化计算理论结果比较. 结果表明：¹³C 各向同性化学位移及CSA粉末线形的理论计算结果均与固体NMR实验结果有很好的符合,预示通过¹³C CSA量化计算结合固体NMR实验是阐明高分子微观结构的有力工具.     

聚醚酰亚胺(YS-30)链结构的1D和2DNMR谱分析

聚醚酰亚胺(YS-30)是一种可溶性的聚酰亚胺,本文对它的¹³C NMR谱,¹NNMR谱和COSY谱进行了研究.经过分析,对¹³C NMR和¹H NMR谱作出了归属,确认了聚醚酰亚胺的链结构.     

靶向新药吉非替尼的核磁共振波谱研究

应用1D、2D NMR实验技术（¹H NMR、¹³C NMR、DEPT、¹H-¹H COSY、¹H-¹³C HMQC、¹H-¹³C HMBC等）研究了靶向新药吉非替尼的结构,对其1H NMR和¹³C NMR谱峰作了全归属,并讨论了F原子对吉非替尼的¹H、¹³C NMR的影响.     

南海海绵Dysidea fragilis中两个倍半萜内酯的NMR研究

用一维¹H、¹³C NMR谱、DEPT ¹³C NMR谱、选择性远程DEPT ¹³C NMR、¹H-¹H COSY和¹³C-¹H COSY二维核磁共振技术研究了南海海绵Dysidea fragilis中的两个倍半萜herbadysidolide(1)和furodysinin lactone(2),确认了化学结构,并对其¹³C NMR和¹H NMR谱进行了归属.药理活性试验表明:1和2具有一定的心血管活性.     

果糖二丙酮的结构全归属

2,3：4,5-双-O-（1-甲基亚乙基）-β-D-吡喃果糖又称为果糖二丙酮（diacetonefructose）,是一类重要的药物合成中间体,它是抗癫痫药物托吡酯中的母体部分,在药物合成中具有重要的作用.果糖二丙酮结构中含有手性碳原子,核磁共振（NMR）谱图较为复杂,本文首先应用¹H NMR、¹³C NMR、DEPT135、¹H-¹³C HMBC、¹H-¹³C HSQC、¹H-¹H COSY和NOESY实验对果糖二丙酮的¹H和¹³C NMR信号进行了指认归属,确定了其空间构型.然后,利用计算化学的方法对其结构进行了模拟,进一步佐证了该构型的正确性.     

苯基哌嗪衍生物的NMR波谱研究

通过¹H NMR、¹³C NMR、及HMBC、HSQC、¹H-¹H DQFCOSY等2D NMR方法对新合成的10个苯基哌嗪衍生物类抗高血压药物进行结构鉴定, 并对这些化合物的¹H NMR和¹³C NMR信号进行了全归属. 初步探讨了取代基对分子¹³C化学位移的影响.      

Lasiodonin Acetonide的NMR数据解析

对lasiodonin acetonide进行了¹H和¹³C NMR检测,参考lasiodonin, maoecrystal T, wikstroemioidin B和rabdocoetsin A的¹H、¹³C NMR数据,通过DEPT和¹H-¹H COSY、HSQC、HMBC等2D NMR技术对该化合物所有的¹H和¹³C NMR信号进行了全归属和详细解析.     

取代喹啉的13C NMR研究

报道了14种新的取代喹啉的¹³C NMR谱.应用¹³C NMR等谱确定了这14种新化合物的分子结构,并对全部谱峰进行了归属,初步探讨了分子结构对¹³C NMR化学位移的影响.     

一种新型的莪术醇衍生物的波谱学分析

莪术醇进行环外双键断裂氧化和酸催化氧桥开环加成2步反应后,经硅胶柱层析分离,得到一种新型的莪术醇衍生物（2）. 应用1D NMR和2D NMR测试了化合物2的¹H NMR、¹³C NMR、¹H-¹H COSY、gHSQC、gHMBC,对化合物2的¹H和¹³C化学位移进行了全归属,结合其红外光谱和质谱,推得化合物2为8-羟基-12-异丙基-2-甲基-三环[6.2.2.0^1,5]十二烷-10-氧杂-6,9-二酮,并比较了莪术醇,莪术醇双键断裂氧化产物(化合物1),化合物2的¹H NMR、¹³C NMR数据变化.     

Effect of Stereodefects Distribution on Rheological Behavior of Isotactic Polypropylene

A series of five isotactic polypropylenes (iPP) used commercially for producing biaxial oriented polypropylene film (BOPP), which had similar average degrees of isotacticity but different stereodefects distribution, was studied. Xylene solubles (XS) at different temperatures and high temperature solution ¹³C NMR were used to characterize the stereodefects distribution of the five samples. These samples gradually became more random following the order of sample A to E. The plateau modulus (G ⁰ _N ≈ 0.2 MPa at 190°C) of these samples was lower than those of metallocene-catalyzed polypropylenes with very narrow molecular weight distributions (MWD) (G ⁰ _N ≈ 0.4 MPa at 190°C), indicating that the influence of MWD on G ⁰ _N cannot be neglected. The storage modulus and complex viscosity of the five samples decreased gradually with the widened stereodefects distribution, due to the formation of a less constrained network that finally caused the reduction of G ⁰ _N and the increase of the flow activation energy. The rheological behavior of the BOPP resin samples could be well related to the results of XS and ¹³C NMR, implying that the rheological measurement can be adopted as a simple and efficient method to characterize the stereodefects distribution of isotactic polypropylene.     

MORPHOLOGY OF STEREOBLOCK POLYPROPYLENE

The microstructure and morphology of stereoblock polypropylenes containing sequences of isotactic (i) and syndiotactic (s) polypropylene (PP) were studied by ¹³C NMR spectroscopy, wide angle x-ray scattering (WAXS), size exclusion chromatography (SEC) combined with FT-IR analysis of the fractions, and atomic force microscopy. The ¹³C NMR spectra show the presence of long stereoregular sequences in the respective stereoblock polypropylene which are able to form the crystal modification known from the respective stereoregular homopolymers as revealed by WAXS measurements. A bimodal molar-mass distribution is detected by SEC. All SEC fractions contain i-PP and s-PP sequences, proven by FT-IR spectroscopy. It is shown by atomic-force microscopy that the stereoblock polypropylene, synthesized by homopolymerization of propylene using iso- and syndiotactic catalysts, form a microphase-separated morphology. The microphase separation is preserved also after treatment with hot toluene. A parallel investigation was conducted on a blend of i-PP and s-PP; it exhibits macrophase separation. Treatment of the blend with hot toluene results in the dissolution of the s-PP phase.     

INFLUENCE OF THERMAL TREATMENTS ON THE POLYMORPHISM IN STEREOIRREGULAR ISOTACTIC POLYPROPYLENE: EFFECT OF STEREO-DEFECT DISTRIBUTION

The influence of cooling rate from the melt on the polymorphism and crystallinity is investigated as a function of isotacticity and stereo-defect distribution in polypropylenes. Detailed analysis of wide angle x-ray diffraction patterns shows that crystallinity in the materials used is nearly independent of the experimental cooling rates (0.5–40°C/min). At high cooling rates, the materials exist mainly in the α-phase, whereas the amount of the γ-phase increases at the lower cooling rates. With an increasing amount of stereo-defects, this cooling-rate dependence of the polymorphism is enhanced. The effect of different stereo-defect distributions, as observed in metallocene-(random) and Ziegler–Natta (blocklike) derived isotactic polypropylenes, was investigated. The formation of the γ-phase is more prevalent in materials with a random defect distribution compared to the materials in which the stereo-defects have a blocklike distribution. The crystallinity decreases more rapidly as a function of the tacticity in the random defect-distributed materials.     

Impact of remote protonation on 13C CPMAS NMR quantitation of charred and uncharred wood

The impact of inefficient cross polarization (long TCH values), caused by long 13C-1H internuclear distances, on 13C CPMAS NMR spectra of charred and uncharred woods is determined by simultaneously fitting data from complementary variable spin lock and variable contact time experiments. As expected, the impact is minimal for uncharred woods, but is very significant for the charred woods. Quantification of the decrease in CPMAS signal intensity caused by both inefficient cross polarization and rapid T1rhoH relaxation is achieved using an advanced spin counting methodology, for which the term "spin accounting" is proposed. 13C CPMAS NMR observabilities determined using the spin accounting methodology were close to 100% for the uncharred samples, and 69-82% for the charred samples. This represents a large improvement on the 30-40% observabilities determined using other spin counting techniques. Furthermore, it is shown that remote protonation and rapid T1rhoH relaxation are roughly equally responsible for the low signal intensity of standard (I ms contact time) 13C CPMAS spectra of charcoal.     

13C]aminopyrine and [13C]caffeine breath test: influence of gender,cigarette smoking and oral contraceptives intake

The [13C]aminopyrine breath test ([13C]ABT) measures the global activity of cytochrome P450 in vivo and is a sensitive indicator of liver metabolic dysfunction. The present study aims to determine whether gender and cigarette smoking influence the results of [13C]ABT as well as to confirm the effect of oral contraceptive steroids (OCS) intake on this metabolic test. Hundred and ten healthy subjects, including men and women, smoker and non-smoker, women taking OCS or not, were phenotyped for CYP1A2 using the [13C]caffeine breath test and underwent a [13C]ABT. Both tests showed large inter-individual variations in accordance with that of CYP450 liver content. [13C]ABT was sensitive enough to point out a significant induction or inhibition related to cigarette smoking habits or OCS. The combined effect of smoking and OCS resulted in an overall unchanged metabolic activity. Consequently, the impact of the studied conditions on the [13C]ABT parameters must be considered by clinicians or clinical investigators.     

ON MORPHOLOGY AND MULTIPLE MELTING IN POLYPROPYLENE

A series of polypropylenes, including two modern high crystallinity materials (HCPP) were subjected to a stepwise crystallization procedure as a guide to their properties. The results were complicated by the development of double melting endotherms at the highest crystallization temperature. Both HCPP, when grown at the temperature of 145°C, give a double melting peak, but the proportions of the two peaks varied according to the density of nucleation. By partially melting a specimen between the two peaks, it was possible to assign the higher peak to radial dominant lamellae and the lower peak to mostly tangential subsidiary lamellae filling the space in between. Uniformly cross-hatched lamellae at the center of spherulites melt along with the lower melting population in the outer regions of the spherulites. Even if differences in crystallization temperature are eliminated, the properties of nucleated as opposed to nonnucleated PP may therefore be influenced by differences between the center and periphery of spherulites, with “central” properties much more in evidence in nucleated material. The development of these double endotherms is related to morphological constraint, rather than molecular fractionation. Their form is strongly influenced by cross-hatching, but the phenomenon is still found at 160°C where cross-hatching does not form.     

[13C]Aminopyrine and [13C]Caffeine Breath Test: Influence of Gender,Cigarette Smoking and Oral Contraceptives Intake

Abstract

The [¹³C]aminopyrine breath test ([¹³C]ABT) measures the global activity of cytochrome P450 in vivo and is a sensitive indicator of liver metabolic dysfunction. The present study aims to determine whether gender and cigarette smoking influence the results of [¹³C]ABT as well as to confirm the effect of oral contraceptive steroids (OCS) intake on this metabolic test. Hundred and ten healthy subjects, including men and women, smoker and non-smoker, women taking OCS or not, were phenotyped for CYP1A2 using the [¹³C]caffeine breath test and underwent a [¹³C]ABT. Both tests showed large inter-individual variations in accordance with that of CYP450 liver content. [¹³C]ABT was sensitive enough to point out a significant induction or inhibition related to cigarette smoking habits or OCS. The combined effect of smoking and OCS resulted in an overall unchanged metabolic activity. Consequently, the impact of the studied conditions on the [¹³C]ABT parameters must be considered by clinicians or clinical investigators.     

Solid state NMR study of carbon bonding in amorphous hydrogenated carbon films

Carbon bonding environments in hydrogenated amorphous carbon films (a-C:H) deposited from an rf-biased methane plasma onto various substrates have been quantified by application of solid state¹³C NMR. A family of films were prepared by systematically varying the substrate bias voltage. Quantitative data on carbon chemistry in these films is required for modeling the impact of structure on mechanical and optical properties. A variety of NMR acquisition pulse sequences have been investigated to determine the conditions under which quantitative¹³C NMR data can be acquired in this system. The results indicate that data acquisition from this material requires different protocols than for the study of polymeric hydrocarbon films. With proper experimental design, NMR is an excellent technique for structural studies of these materials.     

Terrigenous clay deposition on estuarine sandflats: using stable isotopes to determine the role of the mud crab, Helice crassa Dana, in the recovery process.

Clay slurries, mixed in seawater, were deposited on intertidal mudflats in two contrasting estuaries in an experiment designed to evaluate the potential impact of soil erosion from adjacent urban developments on the biodiversity of the benthic communities, and the subsequent recovery mechanisms. Profiles of the natural abundance of stable isotopes from sediment cores where examined to determine immediate and longer-term impacts of the clay on the ambient sediments. The source clays with delta13C values of about -26 per thousand were easily distinguished from natural sediments with delta13C values of -19.7 +/- 1.1 per thousand at site OK and -14.2 +/- 0.9 per thousand at site WP, and bioturbation was seen to generate a gradient between these values. Physical processes of burial, or erosion and dispersal by estuarine flows initiated the recovery process. Repeated drying cycles left the clay surface cracked and able to trap natural sediments and food on the otherwise barren surface. Colonisation of the clay plots by the mud crab, Helice crassa, was important to the recovery process and depended on proximity to adjacent crab colonies. Burrowing activity by larger crabs enhanced the erosion of the clay surface while the resultant bioturbation blended the clay into the underlying sediments. Smaller crabs had less effect on erosion and bioturbation from their burrowing was mostly confined within the clay layer. Where the clay was more than 3 cm thick, they did not break through the bottom of the clay and the interface between clay and sediment was still sharp after 12 months. 13C variations also indicated that crab burrows and cracking of the clay surface moved natural sediment deep into the plots where it could be worked into the clay by subsequent crab burrowing activities thus enhancing recovery from the clay impact.     

NMR studies of structure and dynamics in fruit cuticle polyesters

Cutin and suberin are support polymers involved in waterproofing the leaves and fruits of higher plants, regulating the flow of nutrients among various plant organs, and minimizing the deleterious impact of microbial pathogens. Despite the complexity and intractable nature of these plant biopolyesters, their molecular structure and development are amenable to study by suitable solid-state and solution-state NMR techniques. Interactions of tomato cutin with water were examined by solid-state 2H and 13C NMR, showing that water films enhance rapid segmental motions of the acyl chains and are associated with a fivefold increase in surface elasticity upon cutin hydration. The suberization of wounded potato tissues was studied by solid-state 13C NMR, revealing the likely phenylpropanoid structures that permit dense cross-linking of the suberin structure and their proximity to the cell-wall polysaccharides. Finally, two new approaches were developed to elucidate the molecular structures of these biopolymers: partial depolymerization followed by spectroscopic analysis of the soluble oligomers; and swelling of the intact materials followed by magic-angle spinning (MAS) NMR analysis.