New materials and strategies for NMR based structural elucidation of organic molecules

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For many decades, NMR-based structural elucidation of organic molecules was dominated by the evaluation of chemical shifts, J-couplings and nuclear Overhauser effects (NOEs). In the last years it has been proved that the measurement of anisotropic NMR parameters such as residual dipolar couplings (RDCs) or more recently residual chemical shift anisotropies (RCSAs) can lead to accurate determination of constitution, configuration and conformation of complex and challenging molecules. The technique is based on the introduction of a weak molecular order using anisotropic system, e.g. lyotropic phases or mechanically strained polymer gels. Brazilian-German teams have long-term collaborations on following aspects of this field: (i) development of new chiral aligning media materials with improved mechanical and spectroscopical properties and compatible with a variety of solvents; (ii) Development of new pulse sequences and methodologies for more accurate extraction of anisotropic parameters; (iii) Development of new analysis and software tools for the determination of relative and absolute configuration using anisotropic NMR parameter; (iv) Application to demanding structural problems. The presented proposal will aim at strengthening their collaborations and put special effort on developing new alignment media for efficient and accurate measurement of carbon, proton, and even heteronuclei RCSAs. Furthermore, they will develop new strategies for interpreting anisotropic NMR data of highly flexible molecules. These new methods will be applied to solve structural problems of heterocyclic molecules, antimicrobial peptides, as well as novel natural products that exist only in very limited amounts.