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Keywords:

  • HSQC;
  • 1,1-ADEQUATE;
  • HSQC–ADEQUATE;
  • unsymmetrical indirect covariance;
  • generalized indirect covariance;
  • indirect covariance;
  • HMBC

Abstract

Various experimental methods have been developed to unequivocally identify vicinal neighbor carbon atoms. Variants of the HMBC experiment intended for this purpose have included 2J3J-HMBC and H2BC. The 1,1-ADEQUATE experiment, in contrast, was developed to accomplish the same goal but relies on the 1JCC coupling between a proton–carbon resonant pair and the adjacent neighbor carbon. Hence, 1,1-ADEQUATE can identify non-protonated adjacent neighbor carbons, whereas the 2J3J-HMBC and H2BC experiments require both neighbor carbons to be protonated to operate. Since 1,1-ADEQUATE data are normally interpreted with close reference to an HSQC spectrum of the molecule in question, we were interested in exploring the unsymmetrical indirect covariance processing of multiplicity-edited GHSQC and 1,1-ADEQUATE spectra to afford an HSQC–ADEQUATE correlation spectrum that facilitates the extraction of carbon-carbon connectivity information. The HSQC–ADEQUATE spectrum of strychnine is shown and the means by which the carbon skeleton can be conveniently traced is discussed. Copyright © 2011 John Wiley & Sons, Ltd.