Solid-state C NMR and molecular modeling studies of acetyl aleuritolic acid obtained from Croton cajucara Benth

Solid-state ¹³C nuclear magnetic resonance (¹³C NMR) with magic-angle spinning (MAS) and with cross-polarization and magic-angle spinning (CP/MAS) spectra, and differential scanning calorimetry (DSC) techniques were used to obtain structural data from a sample of acetyl aleuritolic acid (AAA) extracted from the stem bark of Croton cajucara Benth. (Euphorbiaceae) and recrystallized from acetone. Since solid-state ¹³C NMR results suggested the presence of more than one molecule in the unitary cell for the AAA, DSC analysis and molecular modeling calculations were used to access this possibility. The absence of phase transition peaks in the DSC spectra and the dimeric models of AAA simulated using the semi-empirical PM3 method are in agreement with that proposal.     

The Synthesis of Novel Crown Ethers, Part VII [1]. Coumarin Derivatives of Benzocrowns and Cation Binding from Fluorescence Spectra

4-[3-(1-benzopyran-2-one)] derivativesof benzo[12]crown-4, benzo[15]crown-5 andbenzo-[18]crown-6 were synthesized from4-[3-(1-benzopyran-2-one)]-1,2-dihydroxy-benzenereacting with bis-ethyleneglycol dihalides orpentaethylene glycol ditosylate in alkali carbonate/DMF/water. The original products were identified byhigh resolution EI-mass spectra as well as IR,¹H-NMR and ¹³C-NMR spectroscopy. The 1 : 1binding constants of Mg²⁺, Li⁺, Na⁺ andK⁺ with the coumarin-benzocrowns were estimated usingfluorescence emission spectroscopy in acetonitrile.The complexing enhanced quenching fluorescence spectra(CEQFS) and complexing enhanced fluorescence spectra(CEFS) exhibited the ion binding powers due tocationic recognition rules of the macrocycles.     

A comparative study of NMR chemical shifts of sparteine thiolactams and lactams

The ¹³C and ¹H NMR spectra of the four possible thiolactams of sparteine (1) were recorded and the thiolactam group effects were determined. Most of the effects are greater than those of the lactam group in the oxo analogs. A good linear correlation between the ¹³C chemical shifts of CS and those of CO was found. The effects could help in assignment of the spectra and determination of conformation of thiolactams and related thiocarbonyl compounds.     

CO LMR spectrum of14N16O and its analysis with spectra of14N17O and14N18O

LMR spectra for v=1←0 transitions of¹⁴N¹⁶O in X²II_{1/2, 3/2} states were observed at 5.6 μm and 5.4 μm of CO laser. Introducing the advanced isotopic molecular constant scaling function to Hund’s case (a) diatomic structure model, these spectra were analyzed and fitted together with all reliable previous spectral data of¹⁴N¹⁶O as well as¹⁴N¹⁷O and¹⁴N¹⁸O. A full set of precise molecular parameters and their vibrational dependencies have been determined with much higher precision (1–2 orders for most parameters). Many of them have been obtained for the first time. Using isotopic scaling function, the molecular constants of¹⁴N¹⁷O and¹⁴N¹⁸O were deduced.     

Ketendithioacetal-S-imide

Starting from 2-isopropylidene-1,3-dithiane, various ketene-dithioacetal-S-imides have been prepared and characterized by¹H- and¹³C-NMR spectra.

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Ketendithioacetal-S-imideKurze Mitteilung

     

The13C NMR spectra of some polychlorinated dibenzo-p-dioxins. A calculation of13C chemical shifts

The¹³C NMR spectra of a number of polychiorinated dibenzo-p-dioxins (PCDD) were measured. These and previously known spectra were used for the development of a method for calculation of¹³C NMR spectra of chloroaromatics in the framework of a two-particle increment scheme for carbon chemical shifts. The scheme one allows to calculate¹³C chemical shifts for all 75 PCDD.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 760–761, April, 1994.     

1H, 13C,and 14N NMR study of 3-methylfurazans with nitrogen-containing substituents at position 4

3-Methylfurazans with nitrogen-containing substituents at position 4 were studied by ¹H, ¹³C, and ¹⁴N NMR spectroscopy. A correlation between the chemical shifts in ¹³C NMR spectra of these furazans and monosubstituted benzenes with the same substituents was found. The increments for a number of furazan-containing substituents were determined for the first time.     

MnCl+ and MnSO4 association constants to 170°C

Changes in electron spin resonance (ESR) spectra of the manganese (II) ion are used to determine thermodynamic association constants for MnCl⁺ and MnSO ₄ ⁰ complexes from 25 to 170°C. The technique employed requires minimal sample handling and preparation. Pressure increase had a negligible effect on the association constants which increase from 4 m^–1 at 50°C to 200 m^–1 at 170°C for MnCl⁺ and from 200 m^–1 at 25°C to 5700 m^–1 at 170°C for MnSO ₄ ⁰ . The ratio of inner to outer sphere complexes decreases with increasing temperature to 120°C and then increases from 120 to 170°C for both chloride and sulfate complexes. Enthalpies, entropies, heat capacities, and Gibb's free energies determined for each of the reactions compare well with values determined by other methods. These results confirm the validity of the high temperature and pressure ESR approach, which can be used to study other high temperature association reactions of Mn⁺² and, by competitive effects, association reactions of metals that do not have an ESR signal.     

Beryllium(II) Complexes with Bis(dimethylamino)phosphorylfluoride: A Multinuclear NMR (31P, 19F,and 9Be) Characterization in Solution

Complexes of beryllium chloride and nitrate with (Me₂N)₂P(O)F were characterized in solution by multinuclear NMR spectroscopy and in some cases by IR spectroscopy and conductimetry. ³¹P and ¹⁹F NMR spectra were informative of changes associated with complex formation revealing resonances consistent with different species in solution and suggest an equilibrium between these species in both beryllium derivatives. These compounds show narrow lines in the solution ⁹Be NMR spectra, indicative of a highly symmetric environment for beryllium. The presence of the different species was more pronounced in beryllium chloride complexes. The results are compared to those reported in the literature for hexamethylphosphoramide (HMPA).     

Solid state13C NMR spectra of metal carbonyl clusters

The solid state¹³C NMR spectra of four¹³CO enriched carbonyl clusters having a tri-iron metallic core have been analyzed to provide structural and dynamic information. In Fe₃(CO)₁₂ (1), the high temperature spectra suggest the occurrence of large amplitude motions of the CO groups around their position at the vertexes of the coordination polyhedron in addition to the motion involving the Fe₃-triangle previously detected in the VT-¹³C MAS spectra.¹³C and³¹P NMR data of Fe₃(CO)₁₁PPh₃ (2) indicates the presence of one molecule in the asymmetric unit in apparent disagreement with the previously reported X-ray data. Furthermore, we show that structural information can be obtained from the chemical shift tensor components readily available from the analysis of the spinning sideband manifold.     

13C and19F NMR study of α,β-difluorostyryl derivatives of transition metal carbonylates. A method of signal assignment based on the carbon—fluorine spin-spin coupling constants

The¹³C and¹⁹F NMR spectra ofZ- andE-isomers of β-X-substituted α,β-difluorostyrenes (X=F, Cl, CpFe(CO)₂, Re(CO)₅, Re₂(CO)₉Na) were studied. Direct and long-range (across 1–5 bonds) spin-spin coupling constants and the (¹³C−¹²C) isotope shifts in the¹⁹F NMR spectra were determined. The study of the¹³C satellites in the¹⁹F NMR spectra of substituted difluorostyrenes permitted assignment of the¹³C NMR signals of the vinylic carbon atoms. Similarly, the signals in¹⁹F NMR spectra were assigned based on coupling constants of fluorine withipso-carbon. These assignments were found to be in good agreement with the data available from the literature (X=F, Cl). The developed approach was applied to the elucidation of the structure ofZ−PhCF=CClFe(CO)₂Cp. Translated fromIzvestiya Akademii Nauk, Seriya Khimicheskaya. No. 8, pp. 1575–1579, August, 1998.     

In Vitro 31P MR Chemical Shifts of In Vivo-Detectable Metabolites at 3T as a Basis Set for a Pilot Evaluation of Skeletal Muscle and Liver 31P Spectra with LCModel Software

Most in vivo ³¹P MR studies are realized on 3T MR systems that provide sufficient signal intensity for prominent phosphorus metabolites. The identification of these metabolites in the in vivo spectra is performed by comparing their chemical shifts with the chemical shifts measured in vitro on high-field NMR spectrometers. To approach in vivo conditions at 3T, a set of phantoms with defined metabolite solutions were measured in a 3T whole-body MR system at 7.0 and 7.5 pH, at 37 °C. A free induction decay (FID) sequence with and without ¹H decoupling was used. Chemical shifts were obtained of phosphoenolpyruvate (PEP), phosphatidylcholine (PtdC), phosphocholine (PC), phosphoethanolamine (PE), glycerophosphocholine (GPC), glycerophosphoetanolamine (GPE), uridine diphosphoglucose (UDPG), glucose-6-phosphate (G6P), glucose-1-phosphate (G1P), 2,3-diphosphoglycerate (2,3-DPG), nicotinamide adenine dinucleotide (NADH and NAD⁺), phosphocreatine (PCr), adenosine triphosphate (ATP), adenosine diphosphate (ADP), and inorganic phosphate (Pi). The measured chemical shifts were used to construct a basis set of ³¹P MR spectra for the evaluation of ³¹P in vivo spectra of muscle and the liver using LCModel software (linear combination model). Prior knowledge was successfully employed in the analysis of previously acquired in vivo data.     

XPS and XAES of polyethylenes aided by line shape analysis: The effect of electron irradiation

X-ray photoelectron spectroscopy (XPS) and X-ray induced Auger electron spectroscopy (XAES) have been used to investigate different polyethylene surfaces, i.e. low density polyethylene (PELD), high density polyethylene (PEHD) and polyethylene of ultra high molecular weight (PEUHMW). The ratio of Csp²/sp³ was evaluated from (i) fitting of XPS C 1s spectra, (ii) the width of XAES C KLL spectra (parameter D) and (iii) line shape analysis by the pattern recognition (PR) method using the fuzzy k-nearest neighbors (fkNN) rule. The proposed approaches investigate: (i) the differences between various polyethylene surfaces, (ii) their surface changes and degradation due to electron irradiation under various doses and (iii) their stability under electron beam irradiation.The results of proposed approaches, i.e. C 1s fitting, C KLL width evaluation and PR line shape analysis applied to C 1s and C KLL transitions, are qualitatively consistent. The unirradiated polyethylenes indicate nearly Csp³ hybridizations. Under an electron dose a rapid decrease of Csp³ is observed, starting at a dose of 100 Cm⁻². The quantitative differences observed between results obtained from analyses using the C KLL and C 1s spectra, can be explained with a smaller average information depth of C KLL transition. However, quantitative discrepancies between results of various approaches using the same electron transition, i.e. C KLL or C 1s, are smaller. The surface degradation due to X-ray irradiation was negligible in comparison to electron beam irradiation. The PR method was efficient in identifying the polyethylene surfaces under various electron doses. The largest stability under an electron beam is exhibited by the PEUHMW.     

Kinetic Study of Radical Polymerization VI. Copolymer Composition and Kinetic Parameters for Coplymerization of Styrene‐Itaconic Acid by On‐Line 1H‐NMR

Free radical solution copolymerization of styrene (St) and itaconic acid (IA) in dimethylsulfoxide‐d₆ (DMSO‐d₆) as the solvent and the use of 2,2′‐azobisisobutyronitrile (AIBN) as the initiator at 78°C was investigated by an on‐line ¹H‐NMR spectroscopy technique. Individual monomer conversion vs. reaction time, which was calculated from the ¹H‐NMR spectra data, was used to study the drift in monomer mixture composition vs. conversion. It was found that in general, both monomers were incorporated almost equally into the copolymer. However, when the mole fraction of IA was low, the tendency of IA toward incorporation into the copolymer chain was somewhat higher than St and by increasing the mole fraction of IA in the reaction mixture, the inverse tendency was observed. Overall monomer conversion as a function of time was calculated from individual monomer conversion data and used for the estimation of k_p /k_t ^0.5 for various monomer mixture compositions. This ratio was decreased with increasing the amount of IA in the initial feed, indicating a decrease in the rate of copolymerization. Changes in the copolymer composition vs. overall monomer conversion were investigated experimentally from the NMR spectra. This was in good agreement with the changes in monomer mixture composition vs. reaction progress. Plotting the copolymer composition vs. initial monomer feed showed tendency of the system toward alternating copolymerization.     

Solid-state C NMR and SAXS characterization of the amorphous phase in low-molecular weight poly(ethylene oxide)s

Low-molecular weight poly(ethylene oxide)s (PEO) with extended, once or twice folded chains (as characterized by SAXS), were investigated by solid-state ¹³C NMR spectra measured under conditions to detect only the signal of the narrow line component. The direct detection and integrated intensities of the signals from hydroxy-terminated chain-end units in these spectra confirm that the narrow line component corresponds to the noncrystalline (amorphous) phase. The NMR line of PEO carbons adjacent to the hydroxy end-groups was used as an intensity standard to obtain information on the mean number of carbons per chain contributing to the amorphous phase. Assuming that amorphous phase is formed by chain ends (cilia) and folds it follows from the spectra that the length of folds is 6-7 monomer units; cilia are 2-3 monomer units long.     

The fully deprotonated anion of 1,3,5-benzene-triphosphonic acid: 1H, 31P,and 13C{1H} NMR and some comments on corresponding [AX]3 and AXX′2 spin systems and spectra

Abstract

The fully deprotonated anion of 1,3,5-benzene-triphosphonic acid 1,3,5-C₆H₃[PO₃^2?]₃ gives rise to deceptively simple ¹H and ³¹P NMR spectra due to a corresponding [AX]₃ spin system. The ¹³C{¹H} NMR spectrum reveals two ¹³C isotopomers which are identified via AXX′₂ systems. Results from analysis and iteration are described.     

FTIR and NMR studies of bis(oxaalkyl) sulphates(IV) and their complexes with proton and some metal cations

The complexation of Li⁺ and Na⁺ cations by three bis(oxaalkyl) sulphates(IV) was studied by FTIR and NMR on ¹H, ¹³C, ⁷Li and ²³Na nuclei. The NMR results have proved the formation of complexes and the fluctuation of Li⁺ and Na⁺ cations in respective circular arrangements. In the FTIR spectra of protonated sulphates intense continuous absorptions were observed indicating fast fluctuation of the protons in the respective multiminima potentials. The continuous absorptions in the far infrared region of the FTIR spectra of Li⁺ or Na⁺ complexes with three bis(oxaalkyl) sulphates(IV) indicate fast fluctuations of Li⁺ or Na⁺ cations between O-atoms of the oxaalkyl chains. The independence of the shape of the continua on the length of the oxaalkyl chains, i. e. the number of minima in the multiminima potential, demonstrates that the fluctuation of cations occurs in the respective circular arrangements.     

Nitropyrazoles

The structures of substitutedN-aminonitropyrazoles and 1- and 2-amino-4-nitro-1,2,3-triazoles as well as the site of protonation of 1-aminopyrazole were determined based on the¹H,¹³C, and¹⁵N (¹⁴N) NMR spectra. The¹³C NMR spectra were recorded under conditions of¹³C-{¹H,¹⁴N} triple resonance. Effects of substituents in the pyrazole ring on the¹³C and¹⁴N chemical shifts were studied. The¹³C,¹H and¹⁵N,¹H spin-spin coupling constants, obtained using techniques of [¹H]¹³C and [¹H]¹⁵N polarization transfer (SPT, INEPT), were measured, fully assigned, and discussed.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 11, pp. 2181–2186, November, 1995.For Part 8, see Ref. 1.     

Synthese und Konformation einiger Azaspirane mit Alkyl-bzw. Aryl-Sulfonamid-Gruppen

Preferred conformations of some azaspiran systems substituted with large groups at the nitrogen atoms were established by UV absorption spectroscopy. These groups prohibit the inversion at nitrogen, as was deduced from the¹H NMR spectra.

     

表柔比星-镁体系与DNA相互作用初步研究

表柔比星是临床上用于治疗快速增殖肿瘤的药物。本文应用紫外、荧光、圆二色、黏度、凝胶电泳等方法研究了表柔比星-Mg2+体系与DNA的作用。结果发现:在pH=7.4时,表柔比星可与Mg2+形成稳定体系。加入DNA后表柔比星-Mg2+体系的紫外吸收明显降低;Scatchard图表明表柔比星-Mg2+体系对溴化乙锭(EB)与DNA的结合为竞争性抑制;同时此体系可使DNA-EB体系荧光偏振度增大;使DNA的热变性温度(Tm)上升;黏度增大;凝胶电泳表明表柔比星-Mg2+体系对pBR322DNA有非常好的切割活性;圆二色谱法表明随着表柔比星-Mg2+体系的加入,DNA碱基间作用能迅速减弱,二级结构发生了显著的变化。综上所述:表柔比星-Mg2+体系与DNA之间为嵌插作用;且表柔比星-Mg2+体系具有更好的切割活性。这些结果,可为合理改善药效和设计新药提供依据。