13C nuclear magnetic resonance spectroscopy of methylenedioxy group-containing C19-diterpenoid alkaloids and their derivatives

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Abstract
The natural abundance carbon-13 nmr spectra of some methylenedioxy group-containing C19-diterpenoid alkaloids and their derivatives (dictyocarpine, 14-acetyldictyocarpine, dictyocarpinine, 14-dehydrodictyocarpine, 14-dehydrodictyocarpinine, 6-dehydrodictyocarpinine, 6,14-didehydrodictyocarpinine, deltaline (eldeline), deltamine (eldelidine), 6-dehydrodeltamine, delcorine, 6-acetyldelcorine, and 6-dehydrodelcorine) have been determined. Self-consistent assignments of nearly all the resonances in these compounds have been made with the aid of single-frequency off-resonance proton decoupling techniques, additivity relationships, and the effects induced by certain structural changes. Particular attention is directed towards features of the spectra which are most useful for structure elucidation and identification of the C19-diterpenoid alkaloids.