Workshops – Saturday July 25, 2020
AMWS1 – 3D Structure Elucidation of Natural Products Using a Combination of Isotropic/Anisotropic NMR Parameters and Computational Methods – $30 with Registration
9:00 AM – 12:00 PM
Presenters
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The molecular constitution of most small molecules can in principle be straightforwardly determined by manual or automatic analysis of a set of 2D NMR data from experiments of homonuclear/heteronuclear through-bond correlations, in combination with their molecular formula. At this point, only atomic connectivities are established but no information about the spatial arrangement the them is known (Molecular Configuration/Conformation). This is the primary concept embedded in conventional CASE (Computer Assisted Structure Elucidation) protocols.[1] Once the constitution has been established, the determination of the relative configuration and preferred conformation is a more challenging task and was historically addressed in NMR by using NOE and proton-proton and proton-carbon 2,3J coupling constants analysis. The affordable access to fast and parallelized computing processors made molecular modeling and DFT calculations of NMR parameters (chemical shifts / J coupling constants) more accessible to the scientific community. In the group of anisotropic NMR parameters, the development of the application of Residual Dipolar Couplings (RDCs) and Residual Chemical Shift Anisotropy (RCSA) to the configurational and conformational analysis of small molecules has matured enough in the recent years to perform this task in an almost straightforward way. To complete the configurational/conformational analysis of small molecules, these parameters can be used individually, as needed, in order to solve a particular structural problem, or can be combined in multi-NMR parameter fitting protocol to select the correct configuration/conformational space from a complete set of computer-generated diastereoisomers. The latter is known as Computer-Assisted 3D Structure Elucidation (CASE-3D) protocol.
We assume that attendees know how to determine molecular constitution and to perform NMR assignments. The scope of the current workshop is to provide the attendees with state-of-the-art tools to confirm the 2D structure proposals and determine the 3D structure (configuration and conformational space) of small molecules in general. We will also provide tips about computational parameters.
The workshop will cover the following topics in detail and from very practical standpoint to determine configuration and conformational space:
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Application of 1H and 13C isotropic chemical shift
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Scalar coupling constant (J) based analysis using a variety of J proton-proton and proton-carbon
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Residual Dipolar Couplings (RDCs) and Residual Chemical Shift Anisotropy (RCSA): sample preparation, data collection and data analysis.
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1D and 2D Quantitative Nuclear Overhauser Enhancement (NOE)
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Multi-NMR parameters fitting to computer generated structures (CASE-3D)
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