LUPIN ALKALOIDS .7. THE STRUCTURE OF ANGUSTIFOLINE, AN ALKALOID OF LUPINUS-ANGUSTIFOLIUS, IN SOLUTION

The H-1 and C-13 NMR spectra of the lupin alkaloid angustifoline 1 in four solvents (cyclohexane-d(12), CDCl3, CD3CN, and C6D6) were assigne d using 2D H,H and H,C COSY and 2D J-resolved spectra. The torsional H CCH angles calculated from the vicinal J(HH) coupling constants are es sentially in agreement with those expected for the deformed all-chair conformation with endo oriented N(12)-H bond, reported earlier for 1 i n the solid state. Some arguments seem to point, however, to a small c ontribution of other conformations: with ring A deformed in another di rection, deformed all-chair with exo oriented N(12)-H bond and/or a co nformation with ring C in the boat form.