Using unsymmetrical indirect covariance processing to calculate GHSQC-COSY spectra

GHSQC-TOCSY experiments allow sorting of proton-proton connectivity information as a function of C-13 chemical shift. GHSQC-TOCSY is a relatively insensitive 2D NMR experiment. Given two coherence transfer experiments, A -> B and A -> C, it is possible to indirectly determine B <-> C. Unsymmetrical indirect covariance processing of a H-1-C-13 GHSQC and a GCOSY spectrum afforded a GHSQC-COSY spectrum, with an information content analogous to a GHSQC-TOCSY experiment. However, GHSQC-TOCSY is of significantly lower sensitivity and the data require considerably more time to acquire than either of the component experiments. Investigators needing access to GHSQC-TOCSY type data can, in principle, access it from more readily acquired 2D NMR data. Strychnine (1) was used as a model compound to illustrate this capability.