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NMR assignments and X-ray diffraction spectra for two unusual kaurene diterpenes from Erythroxylum barbatum.

dos Santos CC, Sousa Lima MA, Braz-Filho R, de Simone CA, Silveira ER

Curso de Pós-Graduação em Química Orgânica, Departamento de Química Orgânica e Inorgânica, Centro de Ciências, Universidade Federal do Ceará, CP 12 200, Fortaleza-CE, 60451-970, Brazil.

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 (1H,1H-COSY, HMQC, HMBC and NOESY) were used for structure elucidation and the unambiguous 1H and 13C 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 CH2-15 methylene groups in cis-orientation.

Published 6 December 2005 in Magn Reson Chem, 43(12): 1012-5.
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