Benzo- and indolo-quinolizine derivatives XI—The configurational and conformational study of 1,2,3,4,4a,6,7,8,9,13b-decahydro-9aH-pyrido[1,2-f]phenanthridine isomers by 270 MHz 1H n.m.r.

The preferred conformations of the four isomers of 1,2,3,4,4a,6,7,8,9,13b-decahydro-9aH-pyrido[1,2-f] phenanthridine have been determined by 270 MHz ¹H n.m.r. and i.r. spectroscopy. N.m.r. assignments are based on the specific chemical shifts of the protons adjacent to the nitrogen atom, their geminal coupling constants and on the shifts induced by the C? C bonds and by the benzene nucleus. Specifically deuterated derivatives and double resonance experiments confirm the assignments unequivocally. These data are completed by solvent and temperature studies.