Magnetic Resonance in Chemistry

Cover image for Vol. 50 Issue 12

December 2012

Volume 50, Issue 12

Pages 779–834

  1. Research Articles

    1. Top of page
    2. Research Articles
    3. MRC Letters
    4. Errata
    1. A simple method for the determination of the partitioning of nitroxide probes in microheterogeneous media (pages 779–783)

      Carolina Aliaga, Paulina Torres and Fernanda Silva

      Article first published online: 24 SEP 2012 | DOI: 10.1002/mrc.3871

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      An easy and clean assessment for partitioning constant for spin labels in microheterogeneous media based on ESR g-factor is described. The method is a valuable alternative in those cases where the classical Benesi-Hildebrand treatment, based on UV-vis measurements, is difficult or not feasible. This simple method constitutes a valuable alternative for the assessement of antioxidant capabilities of phenols or polyphenols by spin labels.

    2. Spatial structure of heptapeptide Aβ16–22 (beta-amyloid Aβ1–40 active fragment) in solution and in complex with a biological membrane model (pages 784–792)

      Konstantin S. Usachev, Sergej V. Efimov, Ajdar R. Yulmetov, Andrey V. Filippov, Oleg N. Antzutkin, Sergii Afonin and Vladimir V. Klochkov

      Article first published online: 4 OCT 2012 | DOI: 10.1002/mrc.3880

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      The spatial structure of an active fragment of beta-amyloid Aβ1-40 heptapeptide Aβ16-22 (Lys-Leu-Val-Phe-Phe-Ala-Glu) in aqueous buffer solution and in complex with sodium dodecyl sulfate micelles as a model membrane system was investigated by 1H NMR spectroscopy and two-dimensional NMR (TOCSY, HSQC-HECADE, NOESY) spectroscopy. Complex formation was confirmed by the chemical shift changes of the heptapeptide's 1H NMR spectra, as well as by the signs and values of the NOE effects in different environments. We compared the spatial structure of the heptapeptide in borate buffer solution and in complex with a model of the cell surface membrane.

    3. Intermolecular dynamics and paramagnetic properties of ethylenediaminetetraacetate complexes with the yttrium subgroup rare earth elements using nuclear magnetic resonance (pages 793–797)

      Sergey P. Babailov

      Article first published online: 28 OCT 2012 | DOI: 10.1002/mrc.3884

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      Temperature dependencies of the 1H NMR spectra of paramagnetic [Ln3+(EDTA4−)] complexes have been analyzed (Ln3+ = Tb3+, Ho3+, Tm3+, Yb3+). The activation free energies (△G298) of the intermolecular EDTA ions exchange at [Ln3+(EDTA4−)] complexes are 60±3, 66±3, 69±3 and 74±3 kJ/mol (respectively). A monotonic increase of △G298 along the series of lanthanide [Ln3+(EDTA4−)] complexes is probably related to the lanthanide contraction.

  2. MRC Letters

    1. Top of page
    2. Research Articles
    3. MRC Letters
    4. Errata
    1. Two new triterpenoid saponins from Pittosporum senacia Putterlick (Pittosporaceae) (pages 798–802)

      Jens Linnek, Anne-Claire Mitaine-Offer, Thomas Paululat and Marie-Aleth Lacaille-Dubois

      Article first published online: 27 SEP 2012 | DOI: 10.1002/mrc.3876

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      Two new triterpenoid saponins, senaciapittosides A (1) and B (2), were isolated from the dried branches of Pittosporum senacia Putterlick (Pittosporaceae). Their structures were established mainly by 600-MHz two-dimensional nuclear magnetic resonance techniques and mass spectroscopy.

    2. Preparation and complete 1 H and 13C assignment of some pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-dione (PCUD) derivatives (pages 803–808)

      Alan M. Kenwright and Jonathan D. Sellars

      Article first published online: 4 OCT 2012 | DOI: 10.1002/mrc.3879

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      General synthesis of substituted pentacyclo[5.4.0.02,6.03,10.05,9]undecane-8,11-diones.

    3. Discrimination of pseudo-meta and pseudo-para diamino-octafluoro[2.2]paracyclophanes by 1H, 19F, and 13C NMR (pages 809–812)

      Alex J. Roche and Alexander A. Marchione

      Article first published online: 4 OCT 2012 | DOI: 10.1002/mrc.3882

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      The mixture of 1 and 2 is challenging to separate, but 1H COSY, 1H-19F HOESY, 1H-13C HSQC, 1H-13C HMBC, and 19F-13C HSQC techniques allowed the identification of either individual 1 or 2, and also permitted their atomic spectroscopic assignments.

    4. Steroidal saponins and pregnane glycosides from Smilax microphylla (pages 813–817)

      Tao Lin, Hui-Lian Huang, Rong-Hua Liu, Ji-Cheng Shu, Gang Ren, Feng Shao and Li-sha Liu

      Article first published online: 8 OCT 2012 | DOI: 10.1002/mrc.3883

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      Six steroidal saponins and two pregnane glycosides were isolated from the BuOH subfraction of 70% EtOH extract of Smilax microphylla C.H.Wright, in which two compounds were new.

    5. Stereostructure of mycoheptin A2 (pages 818–822)

      Marcin Płosiński, Tomasz Laskowski, Paweł Sowiński and Jan Pawlak

      Article first published online: 19 OCT 2012 | DOI: 10.1002/mrc.3890

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      The absolute configurations of all the stereogenic centers of the antibiotic mycoheptin A2 were established upon previously elaborated general procedure, consisting of DQF-COSY, NOESY, ROESY, HSQC and HMBC experiments as a major tools.

    6. 1H, 13C and 15N NMR assignments for N- and O-acylethanolamines, important family of naturally occurring bioactive lipid mediators (pages 823–828)

      Roberta Ottria, Silvana Casati and Pierangela Ciuffreda

      Article first published online: 28 OCT 2012 | DOI: 10.1002/mrc.3891

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      The complete 1H, 13C and 15N NMR signal assignments of some N- and O-acylethanolamines were achieved using one-dimensional and two-dimensional experiments (gs-HMQC and gs-HMBC).

    7. WYE-120318, a ring contraction product of methylnaltrexone, and structure revision of coniothyrione (pages 829–833)

      Fangming Kong, Tianmin Zhu, Weitao Pan, Russ Tsao, Thomas G. Pagano, Bao Nguyen and Brian Marquez

      Article first published online: 8 NOV 2012 | DOI: 10.1002/mrc.3892

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      A contracted ring degradation product, WYE-120318 (compound 2), was discovered during the development phase for methylnaltrexone bromide (compound 1) drug substance. The compound was isolated, and its structure was determined by spectroscopic data analyses. Remisporine A (compound 3) is envisioned as a naturally occurring ring contraction compound that autocatalytically dimerizes to dimer 4. Coniothyione (compound 5) can be considered as the first example of a stable natural product bearing the remisporine A skeleton. However, the regiochemistry of the chlorosubstituent needs to be revised to compound 6.

  3. Errata

    1. Top of page
    2. Research Articles
    3. MRC Letters
    4. Errata
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