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Alcobendas, Spain

Gil S.,University of Barcelona | Espinosa J.F.,Research Center Lilly | Parella T.,University of Barcelona
Journal of Magnetic Resonance | Year: 2010

A new NMR approach is proposed for the measurement of long-range heteronuclear coupling constants (nJXH, n > 1) in natural abundance molecules. Two complementary in-phase (IP) and anti-phase (AP) data are separately recorded from a modified HSQMBC experiment and then added/subtracted to provide spin-state-selective α/β-HSQMBC spectra. The magnitude of nJXH can be directly determined by simple analysis of the relative displacement between α- and β-cross-peaks. The robustness of this IPAP-HSQMBC experiment is evaluated experimentally and by simulation using a variety of different conditions. Important aspects such as signal intensity dependence and presence of unwanted cross-talk effects are discussed and examples on the measurement of small proton-carbon ( nJCH) and proton-nitrogen (nJNH) coupling constants are provided. © 2010 Elsevier Inc. All rights reserved. Source


Parella T.,Autonomous University of Barcelona | Espinosa J.F.,Research Center Lilly
Progress in Nuclear Magnetic Resonance Spectroscopy | Year: 2013

A general review of novel NMR methods to measure heteronuclear long-range proton-carbon coupling constants (nJCH; n > 1) in small molecules is made. NMR experiments are classified in terms of NMR pulse scheme and cross-peak nature. A discussion about simplicity, general applicability and accuracy for each particular NMR experiment is presented and exemplified. Important aspects such as the sign determination and measurement of very small coupling values involving protonated and non-protonated carbons as well as the complementarity between different experiments are also discussed. Finally, a compilation of applications in structural and conformational analysis of different types of molecules since 2000 is surveyed. © 2013 Elsevier B.V. All rights reserved. Source


Sauri J.,Autonomous University of Barcelona | Parella T.,Autonomous University of Barcelona | Espinosa J.F.,Research Center Lilly
Organic and Biomolecular Chemistry | Year: 2013

A user-friendly 2D NMR approach denoted as CLIP-HSQMBC is proposed for the very easy, direct and accurate measurement of long-range proton-carbon coupling constants in organic molecules and natural products. The J value can be extracted directly from the analysis of resolved in-phase 1H multiplets that show an additional splitting arising from the proton-carbon coupling. In cases of unresolved peaks, a simple fitting analysis using the internal satellite lines as a reference is performed. Addition of a spin-lock period results in a CLIP-HSQMBC-TOCSY experiment that is suitable for the measurement of very small coupling values or to observe correlations from overlapped resonances. This journal is © The Royal Society of Chemistry 2013. Source


Gil S.,University of Barcelona | Espinosa J.F.,Research Center Lilly | Parella T.,University of Barcelona
Journal of Magnetic Resonance | Year: 2011

A simple proton-selective α/β-HSQMBC experiment is proposed for the accurate measurement of long-range proton-carbon coupling constants ( nJ CH) in small molecules without need for an individualized and time-consuming post-processing fitting procedure. The method acquires two pure-phase In-phase (IP) and Anti-phase (AP) multiplets completely free of any phase distortion due to the absence of J HH evolution. Accurate nJ CH values can be directly measured analyzing the relative displacement of the resulting IPAP cross-peaks. Discussion about signal intensity dependence and cross-talk is made for a range of experimental conditions. The robustness of the method is evaluated by comparing the nJ CH value measured from the analysis of the three available IP, AP and IPAP multiplet patterns. Multiple-frequency and region-selective versions of the method can also be efficiently recorded provided that excited protons are not mutually coupled. © 2011 Elsevier Inc. All rights reserved. Source


Sauri J.,Autonomous University of Barcelona | Espinosa J.F.,Research Center Lilly | Parella T.,Autonomous University of Barcelona
Angewandte Chemie - International Edition | Year: 2012

Simply successful: A proton-selective HSQMBC-TOCSY experiment can be used to measure small proton-carbon ( nJ CH; n>1) coupling constants on both protonated and non-protonated carbon atoms (see spectrum). The method combines in a single pulse scheme all the benefits of the widely used HSQMBC and HSQC-TOCSY experiments. The magnitude and the sign of nJ CH can be determined simply with excellent accuracy. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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