REVISED ASSIGNMENT OF THE H-1-NMR SPECTRUM OF THE QUINOLIZIDINE ALKALOID LUPININE

The H-1 NMR spectrum of the quinolizidine alkaloid lupinine was studied at 200 and 600 MHz. A full assignment of the H-1 signals was achieved by application of a variety of NMR techniques, including homonuclear H-1 NOE difference, 2D delta(H)/delta(H) COSY and direct delta(C)/delta(H) correlation experiments. This results in some changes to the current literature assignments; particularly important is the conclusion that the chemical shift difference between the equatorial (beta) and axial (alpha) protons at C-9 is negative (-0.47 ppm) rather than positive. The currently accepted assignment of the C-13 NMR spectrum has been confirmed by independent, and more direct, means.