Reinvestigation of the conformations of a variety of hexahydrobenzo[c]phenanthridine alkaloids by 470 MHz PMR and 50 MHz CMR spectroscopy.

ABSTRACT

The high resolution pmr and cmr spectra of a variety of benzo[c]phenanthridine alkaloids and their CF3COOD salts were examined. The chemical shift of H-14 was found to be a reliable indicator of the orientation of the N-methyl group. The conformations of the C rings were assigned on the basis of the coupling constants between H-11 and the two H-12 protons. On the basis of the pmr spectra of (+)-14-epicorynoline (9) and (+/-)-14-epicorynoline-6,6,12 alpha-d3 (13), a revision of certain previous C ring conformations is indicated.