INVERSE-DETECTED 2-DIMENSIONAL NMR METHODS - APPLICATIONS IN NATURAL-PRODUCTS CHEMISTRY

Applications of inverse-detected 2D nmr methods are reviewed. Sequences presently available for direct (one-bond) heteronuclear correlation via 1J(XH) (HMQC and others) are discussed individually followed by examples of applications to natural products presented by class. Correlations of heteronuclear pairs other than H-1-C-13 and H-1-N-15 are briefly considered. Optimization of parameters necessary in the acquisition of inverse-detected heteronuclear chemical shift correlation data are considered, followed by an illustration using the degradation product of 1-bromomaaliol. Methods for performing HMQC-COSY (RELAY) and HMQC-TOCSY experiments are considered with examples. Various ways of utilizing HMQC-TOCSY data are discussed followed by an illustration of the assembly of the protonated portion of the carbon skeleton of the degradation product of 1-bromomaaliol by varying the mixing times in a series of HMQC-TOCSY experiments. Long-range proton-detected heteronuclear chemical shift correlation experiments (HMBC) are presented with extensive examples of the application of these experiments to a diverse assortment of natural products, which are presented by class of compounds. A practical example of the application of the HMBC experiment to the degradation product of 1-bromomaaliol follows. The relatively new HMQC-NOESY experiment is presented followed by a discussion of the relatively few examples of this experiment presently contained in the literature. Finally, examples of proton-detected one-dimensional analogues of 2D nmr experiments are described; these include SELINCOR, selective one-dimensional HMQC-TOCSY, and SIMBA (selective inverse multiple bond analysis).