Magnetic Resonance in Chemistry

Cover image for Vol. 49 Issue 8

August 2011

Volume 49, Issue 8

Pages 459–542

  1. Rapid Communications

    1. Top of page
    2. Rapid Communications
    3. Research Articles
    4. MRC Letters
    1. Selective J-resolved-HMQC-1 and -2, new methods for measuring proton–proton coupling constants in strongly coupled spin systems (pages 459–463)

      Kazuo Furihata and Mitsuru Tashiro

      Article first published online: 12 JUL 2011 | DOI: 10.1002/mrc.2778

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      Efficient pulse sequences for measuring 1H–1H coupling constants (JHH) in strongly coupled spin systems, named selective J-resolved-HMQC-1 and -2, have been developed. The new pulse sequences utilize selective excitation of the target portion in the spin system of interest, which changes the complicated spin system into a simple one.

    2. A NMR reverse diffusion filter for the simplification of spectra of complex mixtures and the study of drug receptor interactions (pages 464–468)

      M. Vega-Vázquez, J. C. Cobas, F. F. Oliveira de Sousa and M. Martin-Pastor

      Article first published online: 12 JUL 2011 | DOI: 10.1002/mrc.2786

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      A reverse diffusion filter NMR experiment (Drev) is proposed for the study of small molecules in binding with macromolecules. The filtering efficiency of Drev to eliminate the signals of the macromolecule is superior to conventional relaxation filters. The Drev filter it is also a useful complement for ligand-based NMR screening in combination with the STD experiment.

  2. Research Articles

    1. Top of page
    2. Rapid Communications
    3. Research Articles
    4. MRC Letters
    1. 1H and DOSY NMR spectroscopy analysis of Ligusticum porteri rhizome extracts (pages 469–476)

      Alejandra León, María Isabel Chávez and Guillermo Delgado

      Article first published online: 14 JUL 2011 | DOI: 10.1002/mrc.2767

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      The presence of tokinolide B (3), diligustilide (4), riligustilide (5) and some additional constituents in the extracts from Ligusticum porteri rhizomes was established by NMR spectroscopy. DOSY experiment provided virtual separation and structural information for the natural products in an acetone extract. Complementary, a procedure for quantification by 1H NMR of 3, 4 and others constituents in L. porteri extracts was developed.

    2. A double-Fourier approach to enhance the efficiency of the indirect domain sampling in 2D NMR (pages 477–482)

      Srinivasan Chandrashekar, Yoav Shrot and Lucio Frydman

      Article first published online: 14 JUL 2011 | DOI: 10.1002/mrc.2769

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      Partial prior knowledge regarding the position of the NMR resonances along the indirect domain together with customized excitations for every particular t1 increment, allow one to achieve optimized samplings in terms of resolution and bandwidth in a minimum number of scans.

    3. Sensitivity enhancement for maximally resolved two-dimensional NMR by nonuniform sampling (pages 483–491)

      David Rovnyak, Mark Sarcone and Ze Jiang

      Article first published online: 12 JUL 2011 | DOI: 10.1002/mrc.2775

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      Nonuniform sampling has a fundamental, but perhaps counterintuitive, advantage in sensitivity over uniform sampling when the time domain spans πT2. Specifically, enhancements on the order of two fold in the intrinsic SNR of the time domain data can be obtained for nonuniform sampling vs. uniform sampling when the number of transients is adjusted such that the total experimental times are identical.

    4. Geminal 2J(29Si-O-29Si) couplings in oligosiloxanes and their relation to direct 1J(29Si-13C) couplings (pages 492–501)

      Milan Kurfürst, Vratislav Blechta and Jan Schraml

      Article first published online: 14 JUL 2011 | DOI: 10.1002/mrc.2779

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      Relationships are found between 79 measured 2J(29Si-O-29Si) couplings in oligosiloxanes and 29Si chemical shifts, number of oxygenous substituents and 1J(29Si-13C) couplings. In selected compounds the signs of the 2J couplings are positive, it is argued that all the 2J(29Si-O-29Si) couplings are positive. Density functional calculations failed to reproduce the signs and trends in the couplings.

    5. Measurement of long-range proton–carbon coupling constants from pure in-phase 1D multiplets (pages 502–507)

      Juan F. Espinosa, Paloma Vidal, Teodor Parella and Sergi Gil

      Article first published online: 12 JUL 2011 | DOI: 10.1002/mrc.2782

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      A double-selective variant of the SELINCOR pulse sequence yields 1D proton multiplets that exhibit pure absorptive in-phase lineshapes for precise measurement of specific long-range proton–carbon coupling constants in small organic molecules at natural abundance.

    6. Radical anions of flavonoids (pages 508–513)

      Tamara I. Vakulskaya, Lyudmila I. Larina and Alexander V. Vashchenko

      Article first published online: 12 JUL 2011 | DOI: 10.1002/mrc.2783

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      Some natural flavonoids and their synthetic nitro-derivatives have been investigated by polarography and EPR spectroscopy under electrochemical reduction in acetonitrile, DMF, DMSO and 1,2-dimetoxyethane. All studied compounds, apart from flavanone, which accepts two electrons at once, are reduced on the first stage with one-electron transfer. Nevertheless, the primary radical anions were detected by the EPR spectroscopy only for 4′-nitroflavone. Radical anions of other flavonoids are quickly dimerized. The analysis of the temperature dependence of the superfine interaction constants and broadening lines in EPR spectra of 4′-nitroflavone radical anions has shown that the distribution of spin density is due to both the change of medium polarity and rotation of the nitrophenyl moiety.

    7. The structural and dynamic properties of 1-bromodecane in urea inclusion compounds investigated by solid-state 1H, 13C and 2H NMR spectroscopy (pages 514–522)

      Xiaorong Yang and Klaus Müller

      Article first published online: 12 JUL 2011 | DOI: 10.1002/mrc.2785

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      The structural and dynamic properties of 1-bromodecane in urea are studied by solid-state 1H, 13C and 2H NMR spectroscopy. The results show the end groups of 1-bromodecane in urea are randomly arranged. The dynamic properties of the guest molecules can be described in a quantitative way using a 3-site jump process, in combination with the small-angle wobbling motion. The bromine substituents in guest molecules induce stronger guest-host, guest-guest interactions.

  3. MRC Letters

    1. Top of page
    2. Rapid Communications
    3. Research Articles
    4. MRC Letters
    1. Structure elucidation of the dye Acid Red 131: complete 1H, 13C and 15N NMR data assignment (pages 523–528)

      Elisabetta Schievano, Ileana Menegazzo, Ester Marotta and Stefano Mammi

      Article first published online: 6 MAY 2011 | DOI: 10.1002/mrc.2765

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      The chemistry of dyes and pigments is relevant to the textile industry, because of the importance to establish the best conditions for the finishing process and to understand the interactions among various compounds to yield the correct hue and nuances. For this reason, the molecular structure of a monoazo acid dye, C.I. Acid Red 131, was elucidated and characterized by homo- and hetero-nuclear NMR, MS, IR and UV spectroscopy techniques.

    2. Structure elucidation of a sodium salified anthraquinone from the seeds of Cassia obtusifolia by NMR technique assisted with acid–alkali titration (pages 529–532)

      Chen Zhang, Rufeng Wang, Bin Liu and Guangzhong Tu

      Article first published online: 14 JUL 2011 | DOI: 10.1002/mrc.2771

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      A new sodium salt of anthraquinone named sodium emodin-1-O-β-gentiobioside, together with nine known compounds was isolated from the seeds of Cassia obtusifolia and its structure was elucidated by 1H and 13C NMR technique assisted with acid-alkali titration. The chemical shift change of sodium emodin-1-O-β-gentiobioside before and after acid-alkali titration was also characterized.

    3. Structure elucidation of the new citharoxazole from the Mediterranean deep-sea sponge Latrunculia (Biannulata) citharistae (pages 533–536)

      Grégory Genta-Jouve, Nellie Francezon, Alexandre Puissant, Patrick Auberger, Jean Vacelet, Thierry Pérez, Angelo Fontana, Ali Al Mourabit and Olivier P. Thomas

      Article first published online: 14 JUL 2011 | DOI: 10.1002/mrc.2772

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      Citharoxazole, the first oxazole derivative in the pyrrolo[4,3,2-de]quinoline family, was isolated from a Mediterranean deep sponge. Its structure was completely and unambiguously assigned by one- and two-dimensional NMR techniques (1H NMR, 13C NMR, HMBC). The regiochemistry of the oxazole was determined using HMBC intensities cross peaks related to 3J values.

    4. Complete assignment of NMR data of 22 phenyl-1H-pyrazoles' derivatives (pages 537–542)

      Aline Lima de Oliveira, Carlos Henrique Alves de Oliveira, Laura Maia Mairink, Francine Pazini, Ricardo Menegatti and Luciano Morais Lião

      Article first published online: 14 JUL 2011 | DOI: 10.1002/mrc.2773

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      Complete assignment of 1H and 13C NMR chemical shifts and J(1H/1H and 1H/19F) coupling constants for 22 1-phenyl-1H-pyrazoles' derivates were performed using the concerted application of 1H 1D and 1H, 13C 2D gs-HSQC and gs-HMBC experiments. All 1-phenyl-1H-pyrazoles' derivatives were synthesized as described by Finar and co-workers. The formylated 1-phenyl-1H-pyrazoles' derivatives were performed under Duff's conditions.

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