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Moscow, Russia

Martin G.E.,Merck And Co. | Blinov K.A.,Molecule Apps LLC | Williamson R.T.,Merck And Co.
Magnetic Resonance in Chemistry | Year: 2013

Unsymmetrical and generalized indirect covariance processing methods provide a means of mathematically combining pairs of 2D NMR spectra that share a common frequency domain to facilitate the extraction of correlation information. Previous reports have focused on the combination of HSQC spectra with 1,1-, 1,n-, and inverted 1JCC 1,n-ADEQUATE spectra to afford carbon-carbon correlation spectra that allow the extraction of direct (1JCC), long-range (nJCC, where n ≥ 2), and 1JCC-edited long-range correlation data, respectively. Covariance processing of HMBC and 1,1-ADEQUATE spectra has also recently been reported, allowing convenient, high-sensitivity access to nJCC correlation data equivalent to the much lower sensitivity n,1-ADEQUATE experiment. Furthermore, HMBC-1,1-ADEQUATE correlations are observed in the F1 frequency domain at the intrinsic chemical shift of the 13C resonance in question rather than at the double-quantum frequency of the pair of correlated carbons, as visualized by the n,1, and m,n-ADEQUATE experiments, greatly simplifying data interpretation. In an extension of previous work, the covariance processing of HMBC and 1,n-ADEQUATE spectra is now reported. The resulting HMBC-1,n-ADEQUATE spectrum affords long-range carbon-carbon correlation data equivalent to the very low sensitivity m,n-ADEQUATE experiment. In addition to the significantly higher sensitivity of the covariance calculated spectrum, correlations in the HMBC-1,n-ADEQUATE spectrum are again detected at the intrinsic 13C chemical shifts of the correlated carbons rather than at the double-quantum frequency of the pair of correlated carbons. HMBC-1,n-ADEQUATE spectra can provide correlations ranging from diagonal (0JCC or diagonal correlations) to 4JCC under normal circumstances to as much as 6JCC in rare instances. The experiment affords the potential means of establishing the structures of severely proton-deficient molecules. Copyright © 2013 John Wiley & Sons, Ltd. Source

Martin G.E.,Merck And Co. | Blinov K.A.,Molecule Apps LLC | Reibarkh M.,Merck And Co. | Williamson R.T.,Merck And Co.
Magnetic Resonance in Chemistry | Year: 2012

Establishing the carbon skeleton of a molecule greatly facilitates the process of structure elucidation, leaving only heteroatoms to be inserted, heterocyclic rings to be closed, and stereochemical features to be defined. INADEQUATE, and more recently PANACEA, have been the only means of coming close to the goal of totally defining the carbon skeleton of a molecule. Unfortunately, the extremely low sensitivity and prodigious sample requirements of these experiments and the multiple receiver requirement for the latter experiment have severely restricted the usage of these experiments. Proton-detected ADEQUATE experiments, in contrast, have considerably higher sensitivity and more modest sample requirements. By combining experiments such as 1,1-ADEQUATE and 1,n-ADEQUATE with higher sensitivity experiments such as GHSQC through covariance processing, sample requirements can be further reduced with a commensurate improvement in the s/n ratio and F 1 resolution of the covariance processed spectrum. We now wish to report the covariance processing of an inverted 1J CC 1,n-ADEQUATE experiment with a non-edited GHSQC spectrum to afford a spectrum that can trace the carbon skeleton of a molecule with the exception of correlations between quaternary carbons. Copyright © 2012 John Wiley & Sons, Ltd. Source

Hanssen K.O.,University of Tromso | Schuler B.,IBM | Williams A.J.,Royal Society of Chemistry | Demissie T.B.,University of Tromso | And 13 more authors.
Angewandte Chemie - International Edition | Year: 2012

Turning a new leaf: The first structures isolated from Thuiaria breitfussi, the breitfussins, are presented. This structural class consists of indole-oxazole-pyrrole units. Limited quantities prevented crystallization; therefore, the structures were solved using a novel combination of AFM, computer-aided structure elucidation (CASE), and DFT calculations. Visualization by AFM determined all the connection points of the cyclic systems and the other substituents. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

Blinov K.A.,Molecule Apps LLC | Buevich A.V.,Merck And Co. | Williamson R.T.,Merck And Co. | Martin G.E.,Merck And Co.
Organic and Biomolecular Chemistry | Year: 2014

The impact of LR-HSQMBC very long-range nJCH heteronuclear shift correlation data as a supplement to HMBC data as input for the computer-assisted structure elucidation program, Structure Elucidator®, is assessed for the first time. The severely proton-deficient xanthone antibiotic cervinomycin A2 and the alkaloid staurosporine were employed as a model compounds. © 2014 The Royal Society of Chemistry. Source

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