Quantitative NMR of Bioactive Natural Products
As natural products research evolves from a basic chemistry-oriented science into an interdisciplinary effort located on the chemistry-biology (“bioactivity”) interface, the requisite technology is advancing rapidly. Today, the concerted acquisition of a standard set of one dimensional (1D) 1H/13C and two dimensional (2D) COSY, HSQC, NOESY/ROESY, and HMBC NMR spectra, together with other spectroscopic and spectrometric information, in particular MS/MSn, allows for almost routine structural identification of known, or elucidation of unknown, “small” organic molecules with varying degrees of structural complexity. From the perspective of interdisciplinary research groups with a keen interest in the overarching theme of bioactive natural products, the wealth of structural NMR methodology already seems sufficiently complex. Consequently, the addition of yet another implement to the NMR toolbox can appear to be excessive at first sight.