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NMR assignments and X‐ray diffraction spectra for two unusual kaurene diterpenes from Erythroxylum barbatum
Author(s) -
dos Santos Claudio Costa,
Sousa Lima Mary Anne,
BrazFilho Raimundo,
de Simone Carlos Alberto,
Silveira Edilberto Rocha
Publication year - 2005
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1700
Subject(s) - chemistry , two dimensional nuclear magnetic resonance spectroscopy , methylene , stereochemistry , proton nmr , chemical shift , carbon 13 nmr , x ray , crystallography , organic chemistry , physics , quantum mechanics
The structural characterization of two new, unusual kaurene diterpenes isolated from roots of Erythroxylum barbatum is described. 1D NMR and several 2D shift‐correlated NMR pulse sequences ( 1 H, 1 H‐COSY, HMQC, HMBC and NOESY) were used for structure elucidation and the unambiguous 1 H and 13 C chemical shifts assignments. Single crystal X‐ray diffraction analysis was also used to confirm the final relative configuration of the compounds possessing the C‐20 methyl and the CH 2 ‐15 methylene groups in cis‐orientation. Copyright © 2005 John Wiley & Sons, Ltd.