Can my NMR Correlations determine your Structure unambiguously??

Results shown

The structure elucidation of an unknown organic compound remains a challenging task. Whilst NMR correlation data is relatively accessible, it's interpretation can still be hard. The difficulty of the structure elucidation problem depends more on the type of the investigated molecule than on its size. Saturated compounds can usually be assigned unambiguously using only COSY and 13C-HMBC data, whereas condensed heterocycles are problematic due to their lack of protons that could show interatomic connectivities.

Computer tools have been developed to make a chemist's life a lot easier. One of them is Cocon[1,2], which uses NMR correlation data and, to a small extend, chemical shift information to generate structural proposals. Since 2003 Cocon has been available online as WebCocon at http://cocon.nmr.de . In 2005 WebCocon was presented as tool for the discussion of structural proposals, using theoretical correlation datasets that were generated based on the proposals. Now we present the results of a survey of publications from JNP in recent years, featuring new natural products whose structure has been determined solely by NMR. The published constitutions (at least one for each publication) have been submitted to a structure discussion with WebCocon.

As example, follows data for the publication year 2007: out of 198 publications, a total of 111 (~55%) had new compounds that verified straight forward, and 47 (~25%) had at least one compound with more then one possible structural assignment. A total of 40 (~20%) publications had compounds that could not be verified, because WebCocon did not produce any results. One part of the process of theoretical correlation data generation in WebCocon is the generation of carbon chemical shifts that are in agreement with Cocon's chemical shift rules. Unfortunately the inversion of the chemical shift rules sometimes fails and the result does not fit. Currently this is being improved, and we hope to obtain better results in the future.

Literature cited

The following literature references are used for this poster:

  1. Lindel, T; Junker, J; Köck, M; Journal of Molecular Modeling, 3 (8), 364-368, 1997
  2. Lindel, T; Junker, J; Köck, M; European Journal of Organic Chemistry, (3), 573-577, 1999
The Poster

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