Advanced NMR Methods to Solve Complex Molecular Structures

Standard small and medium-sized molecules can typically be characterized by conventional NMR techniques. However, when facing unknowns and/or more complex molecular structures – especially proton-deficient compounds, an assignment strategy beyond the "normal" suite of NMR experiments is often required. Increasing natural products as well as synthetic molecular complexity often leads to an increase of the probability of mistakes in assigning the constitution and configuration of the molecule in question. In such cases, routine 2D NMR experiments often prove insufficient – with cases where even computer-assisted structure elucidation (CASE) methods fail. These situations partly explain the large number of mistakenly reported structures and the rise of number of structure revisions appearing in the literature.
Enormous advances have been made over the last years in terms of development of sophisticated pulse sequences, acquisition and analysis of anisotropic NMR data, and the application of computational tools. Combined, these methodologies provide a state-of-the-art road map for the unequivocal structure elucidation of complex natural products, synthetic organics and pharmaceuticals. This presentation will showcase the utilization of these techniques and their impact in solving challenging structural problems.