HPLC analysis of ecdysteroids in plant extracts using superheated deuterium oxide with multiple on-line spectroscopic analysis (UV, IR, 1H NMR, and MS).

HPLC, using superheated D20 as the mobile phase, combined with on-line characterization via a combination of diode array UV, 1H NMR, FT-IR spectroscopy, and mass spectrometry has been used for the analysis of a standard of 20-hydroxyecdysone- and ecdysteroid-containing plant extracts. This combination of spectrometers enabled the on-flow collection of UV, 1H NMR, IR, and mass spectra not only for pure 20-hydroxyecdysone (100-400 microg on column) but also the major ecdysteroids present in crude extracts of Silene otites, Silene nutans, and Silene frivaldiskyana. The ecdysteroids unequivocally identified in these extracts included 20-hydroxyecdysone, polypodine B, and integristerone A.     

Development of HPLC/ESI-MS and HPLC/1H NMR methods for the identification of photocatalytic degradation products of iodosulfuron

In the present study, HPLC/ESI-MS and stopped-flow HPLC/1H NMR methods were developed and applied to separate and characterize the byproducts arising from TiO2-catalyzed photodegradation of the herbicide iodosulfuron methyl ester (IOME) in aqueous solution under UV irradiation. Prior to identification, irradiated solutions of IOME (200 and 1000 mg.L(-1)) were concentrated by solid-phase extraction using two cartridges: Isolute C18 and Isolute ENV+. Analytical separation was achieved on a C18 reversed-phase column with ACN/H2O (HPLC/MS) or ACN/D2O (HPLC/NMR) as mobile phase and a linear gradient with a chromatographic run time of 35 min. The combination of UV and MS data allowed the structural elucidation of more than 20 degradation products, whereas 1H NMR data permitted an unequivocal confirmation of the identities of major products and the differentiation of several positional isomers, in particular, the hydroxylation isomers. The obtained results permitted us to propose a possible degradation scheme and to put in evidence the presence of privileged sites for the attack of OH radicals. This work shows, for the first time, the application of combined HPLC with UV, MS, and NMR detection for complete structural elucidation of photocatalytic degradation products, and it will be of particular value in studies on the elimination of pollutants in aqueous solutions by photocatalysis.     

Synthesis and properties of a solution-processable truxene derivative for OLED devices

A soluble truxene derivative (TR1) attached with triphenylamine at the peripheral position was designed and synthesized. The structure and purity of TR1 were carefully characterized by 1H NMR, UV/vis and photoluminescent spectroscopy, mass spectroscopy, and thermal analyses. It exhibited good solubility in common organic solvents and good film forming properties. The maximum absorption and emission peaks in THF solution were shown at 358 nm and 415 nm, respectively. Bright blue emission was observed in both solution and solid states under UV excitation. The fluorescent quantum efficiency was 0.46. The best luminous efficiency was found to be 3.65 cd/A with CIE coordinates of (0.163, 0.260) in electroluminescence devices.     

1, 5-Bis (2-hydroxyacetophenone)thiocarbohydrazone: A novel colorimetric and fluorescent dual-mode chemosensor for the recognition of fluoride

1,5-Bis (2-hydroxyacetophenone)thiocarbohydrazone (H₄L) has been synthesized and characterized by means of spectroscopic and single crystal X-ray diffraction methods. Interactions of the H₄L with a variety of anions were investigated using a combination of UV–visible and fluorescence spectroscopic methods in a biological competing solvent DMSO. The H₄L has a high degree of selectivity for fluoride over other anions. ¹H NMR titration experiments indicate that a deprotonation process is involved in the chemo sensing process.     

A novel pyromellitic diimide derivative: Synthesis,gelation and spontaneous colorimetric sensing of dihydroxybenzene isomers

We report on the synthesis and self-assembly of a new hydrazide derivative N′, N′-bis[4-octadecyloxybenzamido]pyromellitic diimide (compound 1) which formed gels in several apolar organic solvents such as benzene and 1, 2-dichloroethane. ¹H NMR, and FT-IR spectroscopy studies confirmed that the intermolecular hydrogen bonding and van der Waals interactions were major driving forces for the formation of self-assembling gels. The gelator can form noncovalent interactions with dihydroxybenzenes, exhibiting different colors when it complexes with different positional isomers, and thus can be used to sense the positional isomers of dihydroxybenzenes by the naked eyes. This sensing property was further investigated by UV/Vis, ¹H NMR, and ¹H NMR NOESY spectroscopy which revealed that the charge–transfer interaction between hydroxyl groups of the dihydroxybenzene isomers (donor) and compound 1 (acceptor) accounted for this property.     

LC-UV-solid-phase extraction-NMR-MS combined with a cryogenic flow probe and its application to the identification of compounds present in Greek oregano

Structure elucidation of natural products usually relies on a combination of NMR spectroscopy with mass spectrometry whereby NMR trails MS in terms of the minimum sample amount required. In the present study, the usefulness of on-line solid-phase extraction (SPE) in LC-NMR for peak storage after the LC separation prior to NMR analysis is demonstrated. The SPE unit allows the use of normal protonated solvents for the LC separation and fully deuterated solvents for flushing the trapped compounds to the NMR probe. Thus, solvent suppression is no longer necessary. Multiple trapping of the same analyte from repeated LC injections was utilized to solve the problem of low concentration and to obtain 2D heteronuclear NMR spectra. In addition, a combination of the SPE unit with a recently developed cryoflow NMR probe and an MS was evaluated. This on-line LC-UV-SPE-NMR-MS system was used for the automated analysis of a Greek oregano extract. Combining the data provided by the UV, MS, and NMR spectra, the flavonoids taxifolin, aromadendrin, eriodictyol, naringenin, and apigenin, the phenolic acid rosmarinic acid, and the monoterpene carvacrol were identified. This automated technique is very useful for natural product analysis, and the large sensitivity improvement leads to significantly reduced NMR acquisition times.     

双甲基丙烯酸聚乙二醇酯的合成及光聚合反应

合成了一系列新型的具有光引发聚合反应活性的单体；不同分子量的聚乙二醇的双甲基丙烯酸酯。单体在紫外光引发条件下进行自由基聚合，生成交联的聚合产物。用＾１Ｈ－ＮＭＲ对单体进行了表征。用ＩＲ对单体和聚合物进行了分析，研究了双甲基丙烯酸二乙二醇酯的聚合反应动力学，测定了聚合活化能。     

Photodegradation of nitrobenzene using 172 nm excimer UV lamp

Photodegradation of nitrobenzene (NB) using an excimer UV lamp at a wavelength of 172 nm is investigated. Experimental results show that high concentration nitrobenzene can be efficiently degraded with irradiation by excimer UV lamp, and confirm that degradation of nitrobenzene is more efficient by UV/H(2)O(2) combination than UV only. In the case of using UV only, 60 min of treatment was found to be sufficient to degrade the major part of NB solution with a concentration of less than 4mM. In the case of using the combination of UV/H(2)O(2) with a H(2)O(2) concentration of 7:1 molar ratio to NB, 4.07 mM NB solution drastically decreased to 0.41 mM after treatment for only 20 min. Degradation intermediate products are identified by analyzing the degradation products with GC/HRMS and possible degradation pathways of nitrobenzene are suggested.     

一种笼形超分子主体化合物Cryptophane E的合成与表征

以香草醛为原料,在乙醇介质中与1,3-二溴丙烷反应生成1,3-二(4-甲酰-2-甲氧基苯氧基)丙烷,然后在甲醇介质中进行硼氢化还原,最后在甲酸介质中聚合,合成笼形超分子主体化合物Cryptophane E.采用核磁共振谱(1H NMR、13C NMR)、质谱(MS)、紫外光谱(UV)荧光光谱、红外光谱、元素分析等测试技术对Cryptophane E进行表征,重点考察反应温度、时间及原料配比等因素对合成产率的影响,获得最佳反应条件,并深入探讨了合成机理.     

High-resolution capillary tube NMR. A miniaturized 5-microL high-sensitivity TXI probe for mass-limited samples,off-line LC NMR,and HT NMR

A new triple-resonance (TXI) (1H, 13C, 15N) high-resolution nuclear magnetic resonance (NMR) capillary probe with 2.5-microL NMR-active sample volume (V(obs)) was built and tested for applications with mass- and volume-limited samples and for coupling of microbore liquid chromatography to NMR. This is the first microliter probe with optimized coil geometry for use with individual capillary tubes with an outer diameter of 1 mm. The 90 degree pulse lengths of the 1-mm microliter probe were below 2 micros for proton, below 8 micros for carbon, and below 20 micros for nitrogen, and a spectral line width at signal half-height below 1 Hz was obtained. Compared to a conventional 5-mm probe, the new 600-MHz 1-mm TXI microliter probe with z-gradient shows an increase in mass sensitivity by a factor of 5, corresponding to a 25-fold reduction in measuring time. The consumption of costly deuterated solvent is reduced by at least 2 orders of magnitude. The 1-mm TXI microliter probe with z-gradient allows the measurement of one-dimensional 1H NMR and two-dimensional heteronuclear NMR spectra with a few nanomoles (micrograms) of compound with high sensitivity, speed, and quality. This is a breakthrough for discrete sample NMR spectroscopy with paramount importance for structure elucidation in natural compound chemistry and metabolic research. It offers also advantages for linking chromatographic methods to NMR in a nindustrial environment. Capillary tube NMR may find new applications in areas where high sample throughput is essential, e.g., in the quality control of large sample arrays from parallel chemistry, screening, and compound depositories. It has the potential to increase the sample throughput by 1 order of magnitude or more if new hardware for fast sample handling and exchange becomes available.     

聚(2,5-二丁氧基)对苯乙炔的合成、表征及发光性能研究

用强碱诱导的脱氯化氢法合成了发光聚合物聚（2，5－二丁氧基）对苯乙炔（PDBOPV），并与前聚物路线合成法进行了比较。脱氯化氢法具有反应时间短和产率高等优点，而且不需要进行高温处理，有利于相关器件的制备。用紫外、红外光谱和^1H-NMR对聚（2，5－二丁氧基）对苯乙进行了表征，测定了荧光（PL）光谱，讨论了烷氧基取代对聚合物光学性质和可溶性的影响。     

1,1,4,4-四苯基-1,3-丁二烯衍生物的合成

以苯乙酮和溴代苯为原料,通过格氏反应先制得1,1-二苯基乙醇(1),收率为91.3%;(1)经脱水和氯甲基化得到1,1-二苯基-3-氯丙烯(2),收率为92.9%;(2)再与二苯甲酮衍生物经格氏反应制得了1,1,4,4-四苯基-1,3-丁二烯衍生物(3a)和(3b),收率高于54.0%,并对各步合成的工艺条件进行了研究.HPLC测得(3a)和(3b)质量分数均高于99.0%.通过紫外光谱、红外光谱、质谱、1H NMR和元素分析对产物的组成和结构进行了鉴定.     

Synthesis of parent aniline tetramer and pentamer and redox properties

In this paper, the parent aniline tetramer and pentamer have been synthesized successfully through a novel method (one-step oxidative coupling reaction), and they were characterized by IR, MALDI-TOF-MS, elemental analysis and ¹H NMR. The chemical oxidation process of the tetramer and pentamer were studied by UV–Vis spectra. It was found the tetramer and pentamer were oxidized to EB form and then to the pernigraniline oxidation state.     

共反应剂法合成纤维素高级脂肪酸酯

采用乙酸酐为共反应剂合成了纤维素高级脂肪酸酯。用FT－IR，^1H-NMR对合成产物的结构进行了表征。结果表明，在纤维素分子骨架上同时接枝上了高级脂肪酸酯基以及乙酸酯基，产物为纤维素混合酸酯。产物的酯化度值通过^1H-NMR确定，酯化度可达到1．66。研究了纤维素与系列高级脂肪酸的酯化反应，结果表明，随着高级脂肪酸中碳原子数目的增加，产物的酯化度逐渐减小，而产的有一个先啬 －后减小的趋势。     

Synthesis and characterization of a novel photocrosslinkable fluorinated poly(arylene ether) for optical waveguide

To improve its chemical resistance and mechanical stability, a novel fluorinated poly(arylene ether) bearing a photocrosslinkable chalcone group in the main chain was successfully synthesized by means of polycondensation between 4,4′-dihydroxychalcone and decafluorobiphenyl in N,N-dimethylacetamide in the presence of the excess anhydrous potassium carbonate. The structure of polymer was characterized by ¹H NMR and ¹⁹F NMR spectroscopies. The resulting polymer shows excellent solubility in common organic solvents, high glass transition temperature and good thermal stability. Crosslinking of the resulted polymer has been demonstrated by UV irradiation. Near-IR spectra of polymer film before and after UV irradiation show no absorption at the telecommunication wavelengths of 1310 and 1550 nm, demonstrating that the resulting polymer is good candidate material for optical waveguide application.     

1-Alkylcarbonyl-5-fluorouracil Prodrugs: Synthesis,Thermal and Hydrolytic Stability

Abstract

Six homologous 1 -alkylcarbonyl derivatives of 5-fluorouracil (5-FU) have been synthesized and characterized by ¹H NMR, infrared and UV spectroscopy. The derivatives were found to hydrolyze rapidly in pH 7.1 buffer at 32°C (t_1/2 = 3-5 min). Although the hydrolysis was found to be catalyzed by hydrated formaldehyde, only 5-FU was observed as a product of the hydrolysis: no 1- or 3-alkylcarbonyloxymethyl products were observed. The 1 -alkylcarbonyl derivatives were recovered intact upon heating at 145°C for 1 h, but, upon heating at 205°C for 1 h, 25% of the sample decomposed to 5-FU with the assumed loss of ketene. The 1-alkylcarbonyl derivatives were stable when stored in a desiccator but decomposed to carboxylic acid and 5-FU upon exposure to atmospheric moisture.     

Highly fluorescent dendrimers containing stilbene, and 4-styrylstilbene with resorcinarene cores: synthesis and optical properties

Dendron conjugated branches of stilbene and 4-styrylstilbene groups have been attached to resor-cinarene cores. A noticeable effect in solution for all dendrimers was observed in the fluorescence quantum yield. The optical properties do not change with concentration in solution. The optical properties of thin films are identical to those of the solutions indicating the absence of intermolecular interactions. The dendrimers were characterized by 1H, 13C NMR, FTIR, UV-Vis, fluorescence spectroscopy, MALDI-TOF or FAB+ mass spectrometry, and elemental analysis.     

1-取代的4-硝基咪唑含能衍生物的合成、表征及热分解性能?

以4-硝基咪唑为原料,通过与2-氨基-3,5-二硝基-6-氯吡啶、2,6-二氯-3-硝基吡啶缩合,合成出未见文献报道的化合物6-(4-硝基-咪唑-1-基)-2-氨基-3,5-二硝基吡啶(1#)及6-氯-3-硝基-2-(4-硝基-咪唑-1-基)-吡啶(3#),收率分别为65%、52%;并采用此种方法优化了3-硝基-2-(4-硝基-咪唑-1-基)-吡啶(2#)的合成,收率为85%。进一步尝试了化合物3#的叠氮化反应,得到5-叠氮基-6-硝基四唑基[1,5-a]吡啶(4#)。采用核磁共振、质谱、红外光谱、元素分析等方法对相关化合物的结构进行了表征。利用TG和DSC分析法研究了化合物1#的热行为,结果表明:化合物1#的初始分解温度为221.83℃,分解放热总量为302.65 k J/mol,热失重温度范围为209.17~398.67℃,累计热失重71.84%。     

Quantification of organic and amino acids in beer by 1H NMR spectroscopy

The quantification of organic and amino acids in beer using 1H NMR spectroscopy is demonstrated. Quantification was made both by integration of signals in the spectra together with use of calibration references and by use of partial least-squares (PLS) regression. Results from the NMR quantifications were compared with those obtained from determinations by amino acid analysis on HPLC and organic acid analysis by capillary electrophoresis. The described NMR-based methods could satisfactorily be used for quantification of several of the investigated metabolites in beer down to approximately 10 mg/L and for most with a good to high accuracy compared to results obtained by HPLC and capillary electrophoresis (R2 0.90-0.99). This was achieved with a simple sample preparation and one-dimensional 1H NMR spectra obtained in a few minutes. The use of PLS clearly improves the accuracy of the quantifications, based on comparison to results obtained by HPLC and capillary electrophoresis, and furthermore permits the determination of components with partially overlapped signals in the spectrum. NMR spectroscopy in combination with PLS will be a useful tool for the quantification of metabolites, not only in beer but also in other beverages and biofluids.     

Isolation of n-decyl-alpha(1-->6) isomaltoside from a technical APG mixture and its identification by the parallel use of LC-MS and NMR spectroscopy

The identification of n-decyl alpha(1-->6)isomaltoside as a main component of technical alkyl polyglucoside (APG) mixtures by the parallel use of liquid chromatography-mass spectrometry (LC-MS) and nuclear magnetic resonance (NMR) spectroscopy is described. Following enrichment on a styrene-divinylbenzene-based solid-phase extraction material, unknown components were separated by reversed-phase liquid chromatography (LC). Chemical characterization was achieved by both mass spectrometry and NMR spectroscopy. It is demonstrated that the combination of LC-MS with various NMR techniques is very suitable for stereochemical assignment of unknown components in technical APG mixtures.