Stereostructure assignment of flexible five-membered rings by GIAO 13C NMR calculations:: Prediction of the stereochemistry of elatenyne
Stereostructure assignment of flexible five-membered rings by GIAO 13C NMR calculations:: Prediction of the stereochemistry of elatenyne
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DOI：
10.1021/jo8003138
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发表时间：
2008-06-06
影响因子：
3.6
通讯作者：
Goodman, Jonathan M.
中科院分区：
文献类型：
--
作者：
Smith, Steven G.;Paton, Robert S.;Goodman, Jonathan M.
The stereochemistry of conformationally mobile five-membered rings is often hard to assign from NMR data, and [2,2']bifuranyl systems are even more challenging. GIAO C-13 NMR chemical shifts have been calculated for a series of [2,2']bifuranyl and pyranopyran species, taking into account their conformational flexibility using weighted averages of the data for all low energy conformers. We show that calculation of C-13 NMR chemical shifts using the geometries obtained using molecular mechanics greatly reduces the computational expense without a significant loss of accuracy, even in this demanding system. The results were sufficiently accurate to distinguish not only the pyran and furanyl isomers; but also between all the diastereoisomeric forms. As a result of this validation, we predict the stereochemistry for the recently proposed revised structure of the natural product elatenyne, which contains a [2,2']bifuranyl core.
