Abstract

1H, 13C and in some cases also 15N chemical shifts of quaternary benzo[c]phenanthridine alkaloids (fagaronine, chelerythrine, chelilutine, chelirubine, nitidine, sanguilutine, sanguinarine, and sanguirubine) were systematically studied by NMR spectroscopy and ab initio calculations. The assignment of signals in the 1H and 13C NMR spectra was obtained from 2D NOE and gradient-enhanced single-quantum multiple bond correlation (GSQMBC) experiments. The ab initio geometry optimization using Gaussian 94 at the RHF/6–31 G** level, followed by the calculation of chemical shielding using the deMon/NMR code at the IGLO II level, were carried out in order to rationalize the assignment of individual experimentally determined resonances. Copyright © 1999 John Wiley & Sons, Ltd.

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