LONG-RANGE H-1-N-15 2-DIMENSIONAL HETERONUCLEAR SHIFT CORRELATION OF THE ALKALOID VINCAMINE AT NATURAL-ABUNDANCE

Long-range H-1-N-15 heteronuclear correlation pathways in the alkaloid vincamine, a structural constituent or biogenetic congener of numerou s Vinca alkaloids, are reported. Correlations were observed through th e use of the GHNMQC (Gradient-enhanced Hydrogen-Nitrogen Multiple Quan tum Coherence) 2D nmr experiment at natural abundance. An unanticipate d four-bond coupling between the H15a resonance and N4 was observed in contrast to the typical two- and three-bond coupling pathways. Nitrog en-15 chemical shift comparisons are drawn between vincamine and struc turally related alkaloids including ajmaline and the velbanamine porti on of the semi-synthetic alkaloid vinorelbine (Navelbine(TM)).