Variable-temperature ¹H-NMR studies on two C-glycosylflavones

Two known C-glycosylflavones, swertisin and embinoidin, were isolated from the leaves of Anthurium aripoense, and characterized by room temperature 1D and 2D NMR experiments. At this temperature, the 1H- and 13C-NMR spectra of these C-glycosylflavones revealed doubling of signals, which suggested the presence of two rotamers in solution. Variable-temperature (VT) 1H-NMR studies supported this hypothesis. The T-ROESY data, in addition to the theoretical (MM2) calculations utilizing the Chem3D Pro software, confirmed the hypothesis that the two rotamers interchange via rotation about the C-glycosidic bond.     

CRYSTAL STRUCTURE OF p—PROPIONYLCALIX [4]ARENE

<正> The title compound was synthesized by Friedel-Crafts reaction of tetrahydroxycalix [4] arene and propionyl choride, and its crystal structure was determined by X-ray diffraction technique. C10O8H40,Mr = 648. 75, triclinic, space group P1 with cell parameters, a = 9. 930(5), b = 11. 838(3), c=14. 522(7) A,α= 94. 92(3),β=102. 96(4),γ= 98. 32(3)°, V = 1635A3, Z = 2, Dc = 1. 399g/ cm3, μ(CuKa) = 3. 27cm-1, F (000) = 344. The final R = 0. 075, Rw = 0.092 for 5716 independent reflections with I>3σ(I). The crystal structure analysis shows that the molecule exists in fine cone conformation.     

pH Dependent plasmon-driven surface-catalysis reactions of p,p′-dimercaptoazobenzene produced from para-aminothiophenol and 4-nitrobenzenethiol

In this paper,we studied the pH dependent plasmon-driven surface-catalysis(PDSC) reactions of p,p’-dimercaptoazobenzene(DMAB) produced from para-aminothiophenol(PATP) and 4-nitrobenzenethiol(4NBT) both theoretically and experimentally.The surface enhanced Raman spectrum(SERS) of DMAB produced from PATP and 4NBT on Ag films in solutions with various pH values has been measured.The simulation and experimental results indicated that the pH dependence of PATP appeared in acidic environment and came from the amino group NH2.Furthermore,the ratio of intensity of Raman peak caused by PATP and DMAB indicated that this acidic sensor had higher pH sensitivity when it was excited by photons of higher energy.     

Trivinylphosphine and trivinylphosphine chalcogenides: stereochemical trends of ³¹P-¹H spin-spin coupling constants

A combined theoretical and experimental study of the stereochemical behavior of (31)P-(1)H spin-spin coupling constants has been performed in the series of trivinylphosphine and related trivinylphosphine oxide, sulfide and selenide. Theoretical energy-based conformational analysis of the title compounds performed at the MP2/6-311G** level reveals that each of the four compounds of this series exists in the equilibrium mixture of five true-minimum conformers, namely s-cis-s-cis-s-cis, s-cis-s-cis-gauche, syn-s-cis-gauche-gauche, anti-s-cis-gauche-gauche and gauche-gauche-gauche, which were taken into account in the conformational averaging of (31)P-(1)H spin-spin couplings calculated at the second-order polarization propagator approach/aug-cc-pVTZ-J level of theory. All (31)P-(1)H spin-spin coupling constants involving phosphorus and either of the vinyl protons are found to demonstrate a marked stereochemical dependences with respect to the geometry of the coupling pathway and internal rotation of the vinyl group around the P-C bond which is of major importance in the stereochemical studies of the unsaturated phosphines and phosphine chalcogenides.     

IR Study of p–π Conjugation in 2-Substituted 4-Methylene-1,3-dioxolanes and 4-Methyl-1,3-dioxoles

Selected group frequencies of the IR spectra of a number of 2-substituted 4-methylene-1,3-dioxolanes (a) and their endocyclic isomers, 2-substituted 4-methyl-1,3-dioxoles (b), have been studied to establish their usefulness as a measure of the strength of p– conjugation in the O—C=C moieties of the title compounds. In the exo compounds (a), the C=C stretching frequencies C=C and the in-phase, out-of-plane bending (wagging) frequencies CH₂ w of the =CH₂ group were found to be linearly related, besides to each other, also to the electron-donating character of the substituents and the ¹³C NMR chemical shift of the C atom of the exocyclic CH₂ group. This suggests that the two IR group frequencies of the exo isomers are linearly related to the strength of p– conjugation in the O—C=C moiety. The C=C stretching absorption of the exo compounds in the 1600–1700 cm^–1 region appeared as a doublet, shown to arise from Fermi resonance of the C=C fundamental with the CH₂ w overtone. The C=C frequencies of the endo compounds support some previous findings of an unexpected strength of p– conjugation in the 2-alkoxy derivatives. Finally, DFT calculations at the B3LYP/6-31G* level of theory are shown to give accurate predictions of the effect of 2-substituents on the group frequencies.     

¹H-nuclear magnetic resonance analysis of the triacylglyceride composition of cold-pressed oil from Camellia japonica

Camellia japonica (CJ) has oil-rich seeds, but the study of these oils has received little attention and has mainly focused only on their health properties. In the present work the relative composition of the fatty acid (FA) components of the triglycerides in cold-pressed oil from CJ is studied by 1H-NMR. The results obtained were: 75.75%, 6.0%, 0.17% and 18.67%, for oleic, linoleic, linolenic and saturated FA respectively. Levels of C?? unsaturated FA found in CJ oil were similar to those reported for olive oils. We also checked the possibility of using 13C-NMR spectroscopy; however, the results confirmed the drawback of 13C over 1H-NMR for the study of FA components of CJ triglycerides due to its low gyromagnetic ratio and its very low natural abundance.     

Studies on Properties of p—Nitrophenylazo Calix[4]arene Derivatives

The p-nitrophenylazo calix[4] arene derivatives la-ld with nonlinear optical(NLO)properties were prepared by the diazo-coupling reaction of calix[4]arene with p-nitrophenyl diazonium.The diazotization reaction of p-nltroaniline was caried out with isoamyl nitrite as a source of nitrous acid in EtONa/EtOH under refluxing conditon.X-Ray crystallographic analysis and ^1H NMR sptectra reveal that they exist as cone conformation in crystal state or in soution.HRS measurements at 1064 nm in THF indicate that p-nitrophenylazo calix[4]arenes have higher hyperpolarizability βz values than the corresponding reference compound 4-(4-nitrophenylazo)-2,6-dimethyl-phenol,without red shift of the charge transfer band.The tetrakis p-nitropheylazo calix[4]arene(2)with longer alkyl chains can form monolayer aht the air/water interface.     

Benzylidene-bis-(4-hydroxycoumarin) and benzopyrano-coumarin derivatives: synthesis, ¹H/¹³C-NMR conformational and X-ray crystal structure studies and in vitro antiviral activity evaluations

We report on the synthesis of 4-hydroxycoumarin dimers 1-15 bearing an aryl substituent on the central linker and fused benzopyranocoumarin derivatives 16-20 and on their in vitro broad anti-DNA and RNA virus activity evaluations. The chemical identities and structure of compounds 1-20 were deduced from their homo- and heteronuclear NMR measurements whereas the conformational properties of 5, 14 and 20 were assessed by the use of 1D difference NOE enhancements. Unequivocal proof of the stereostructure of compounds 7, 9, 16 and 18 was obtained by single crystal X-ray diffraction method. The X-ray crystal structure analysis revealed that two 4-hydroxycoumarin moieties in the 4-trifluoromethylphenyl- and 2-nitrophenyl derivatives (compounds 7 and 9, respectively) are intramolecularly hydrogen-bonded between hydroxyl and carbonyl oxygen atoms. Consequently, the compounds 7 and 9 adopt conformations in which two 4-hydroxy-coumarin moieties are anti-disposed. Antiviral activity evaluation results indicated that the 4-bromobenzylidene derivative of bis-(4-hydroxycoumarin) (compound 3) possesses inhibitory activity against HSV-1 (KOS), HSV-2 (G), vaccinia virus and HSV-1 TK? KOS (ACVr) at a concentration of 9-12 μM and at a minimum cytotoxic concentration (MCC) greater than 20 μM. Compounds 4-6, 8, and 20 were active against feline herpes virus (50% effective concentration, EC?? = 5-8.1 μM), that is at a 4-7-fold lower concentration than the MCC.     

¹H and ¹³C-NMR data of the simplest plumeran indole alkaloids isolated from Aspidosperma species

Indole alkaloids are the chemotaxonomic markers of the Aspidosperma genera. Those that have the simplest plumeran skeleton are classified as the precursors of biosynthetic routes and the intermediates for several synthetic reactions. This work aims to review the 1H and 13C-NMR data, up to 2011, describing the skeleton of 35 different plumeran indole alkaloids, from a group of 46 of them, and highlight the main spectral differences amongst them.     

Synthesis of （p—Substituted phenyl）azo Calix[4] arenes

A novel method for the preparation of chromogenic calixarenes with azo groups was reported.p-Substituted(-NO2,-CH3,-Cl)amilines were diazotized with isoamyl nitrite in EtONa/EtOH under refluxing condition.Fifteen mono-,bis-,tris-and tetrakis(p-substituted phenyl)azo calix[4]arenes (including proximal and distal isomers) were obtainged respectively by diazo-coupling in different molar ratio to calix[4]arenes(1) under pH=7.5-9.0 in non-aqueous solution at 0-5℃.^1H NMR and ^13C NMR spectra of (p-substtituted phenyl)azo calix[4]-arenes indicated that they existed in cone conformation in solution.     

Potentials of the D¹0u⁺ (6¹S₀) and F³1u(6³P₂) electronic Rydberg states of Cd₂ from ab initio calculations and laser-induced fluorescence excitation spectra

The method of supersonic free-jet expansion beam combined with techniques of laser spectroscopy was used in an investigation of vibronic and isotopic structures in the D10(u)? (61S?) and F31(u)(63P?) electronic energy Rydberg states of Cd?. Laser-induced fluorescence excitation spectra recorded using the D10(u)? ← X10(g)?(51S?) and F31(u) ← X10(g)? transitions in the region of 206-218 nm provided spectroscopic characteristics of the excited states and allowed constructing of their intratomic potentials. Isotopic structures recorded in the (υ',υ') bands of the D10(u)? ← X10(g)? transition were used in determination of the D10(u)? state vibrational characteristics (ω'(e)x'(e), ω'(e)x'(e)) and υ' assignment. The ν(0,0) recorded directly in the F31(u) ← X10(g)? transition enabled determination of the bottom of the F31(u) state potential well. Valence ab initio calculations of Cd? interatomic potentials were performed with relativistic and spin-orbit effects taken into account. The experimental results were compared with results of the ab initio calculations. A free-jet expansion of Cd? as a source of entangled atoms for a test of Bell's inequality was analyzed.     

聚N－（4，4＇－联吡啶盐）－p－乙烯基吡啶的电还原及光还原行为

合成了三种新型的主链为聚４－乙烯基吡啶的侧链型紫精聚合物和相应的小分子紫精，研究了它们的电还原及光还原行为。结果表明这类侧链型紫精聚合物的电还原和在异丙醇水溶液中的光还原都存在明显的聚合物效应，还原后生成的自由基正离子分子内缔合的倾向比相应的小分子紫精大得多．     

Optimisation of pressurised liquid extraction for the determination of p,p′-DDT and p,p′-DDE in aged contaminated Ethiopian soils

The effectiveness of extracting p,p′-DDT and p,p′-DDE from aged contaminated soil samples by means of pressurized liquid extraction (PLE) was evaluated. Two soil samples, which were contaminated more than 10 years ago, were used in the investigation. The static extraction time was optimised and then validated against the total sum of target analytes obtained from multiple sequential extractions. The PLE results were also compared with Soxhlet extraction (SOX). PLE for 3×10 min at 100 °C was proven to be more exhaustive than SOX in the determination of p,p′-DDE from both soil samples. In the case of p,p′-DDT, PLE was found to be equally as exhaustive as SOX. Additionally, most of the previous PLE investigations used hazardous organic solvents such as n-hexane, toluene and dichloromethane mixed with acetone, whereas in this investigation the less toxic solvent combination n-heptane/acetone has been employed.     

Synthesis of p,p ′-Phenolphthaleinbis(trimellitic) Dianhydride

p,p′-Phenolphthalein-bis(trimellitic) dianhydride was obtained by the reaction of diacetyloxyphenolphthalein with trimellitic anhydride. The structure of the new compound was proved by elementary analysis, infrared spectroscopy, and acid value determination. The course of acidolysis reaction was examined in the temperature range of 240–280°C. The compound obtained is a powder having a melting point of 135–138° C, has high thermal stability, and is easily soluble in many organic solvents and low-molecular epoxy resins. Application of p,p′-phenolphthalein-bis(trimellitic) dianhydride in synthesis of soluble polyester-imides and as a hardening agent for low molecular weight epoxy resins is proposed.     

Edta-linked 5p–4f trinuclear heterometallic complex: syntheses,X-ray structure and luminescent properties

A new heterometallic antimony–samarium complex, [Sb₂(edta)₂Sm(H₂O)₄]NO_3?·?3.55H₂O (edta?=?ethylenediaminetetraacetate) (1), has been synthesized and characterized by elemental analyses (EA), Fourier transform infrared spectroscopy, thermogravimetry-differential scanning calorimetry, and X-ray crystallography. The X-ray crystal structure analysis reveals that in 1 the bridging carboxylate-O,O′ of edta^4? connects samarium(III) and antimony(III) to form 2-D sheets. The 2-D sheets are further linked by bridging carboxylates from adjacent layers, resulting in 3-D coordination polymers. Complex 1 exhibits fluorescence in the solid state at room temperature.