Magn. Reson. Chem.; Volume 43, Issue 12 , Pages 999 - 1007

"Analysis and Elimination of Artifacts in Indirect Covariance NMR Spectra via Unsymmetrical Processing"

Kirill A. Blinov, Nicolay I. Larin, Mikhail Kvasha, Arvin Moser, Antony J. Williams, and Gary E. Martin

Abstract

Indirect covariance NMR offers an alternative method of extracting spin-spin connectivity information via the conversion of an indirect-detection heteronuclear shift correlation data matrix to a homonuclear data matrix. Using an IDR (Inverted Direct Response)-HSQC-TOCSY spectrum as a starting point for the indirect covariance processing, a spectrum is obtained that can be described as a carbon-carbon COSY experiment. These data are analogous to the autocorrelated ¹³C-¹³C double quantum INADEQUATE experiment except that the indirect covariance NMR spectrum establishes carbon-carbon connectivities only between contiguous protonated carbons. Cyclopentafuranone and the complex polynuclear heteroaromatic naphtho[2',1':5,6]-naphtho[2',1':4,5]thieno[2,3-c]quinoline are used as model compounds. The former is a straightforward example due to a well resolved proton spectrum while the latter, which has considerable resonance overlap in its congested proton spectrum, gives rise to two types of artifact responses that must be considered when using the indirect covariance NMR method.