Abstract
The 13C nuclear magnetic resonance (13C-NMR) spectra of the piperidine-type Nuphar alkaloids and their derivatives (I-V) were recorded with complete assignments. Two methyl groups of C-10 and C-11 in I and II were shown to be magnetically nonequivalent. The 13C-NMR spectroscopy was demonstrated to be more useful than 1H-NMR spectroscopy in studies on magnetic nonequivalence of dimethyl groups associated with molecular asymmetry. The shift values for some carbons caused by the introduction of the double bond, the hydroxyl group, and the acetyl group were examined.
