Optimizing NMR Methods for Structure Elucidation: Characterizing Natural Products and Other Organic Compounds
Chapter 12: Avoiding Getting the Wrong Structure
Published:26 Sep 2018
Special Collection: 2018 ebook collectionSeries: New Developments in NMR
2018. "Avoiding Getting the Wrong Structure", Optimizing NMR Methods for Structure Elucidation: Characterizing Natural Products and Other Organic Compounds, Darcy C Burns, William F Reynolds
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With all of the advances in NMR methodology, one might assume that the probability of deducing an incorrect structure by modern NMR methods would be very low. However, there have been a surprising number of structural assignment errors reported recently and there are undoubtedly more that have not yet been detected. This unique chapter focusses on the likely reasons for structural assignment errors and the ways by which the risk of this kind of error can be minimized. The chapter begins with a listing of possible reasons for structure assignment errors. This is followed by a related section which makes general recommendations of ways to minimize the risk of errors. The next section discusses two specific cases where incorrect natural product structures were reported. We analyze the probable causes of the initial errors, followed by a discussion of how the errors were detected and the correct structures assigned. The final section describes ten specific NMR spectroscopic ‘traps’ that could mislead one during structure elucidation and how they can be avoided. These represent real problems that were encountered by the senior author during over 30 years of natural product structure elucidation.