FT-IR spectroscopic, AM1 and PM3 computational studies of conformation of natural products: cytisine.

Infrared spectra were recorded for cytisine (1) and its model compounds: N-methyl-2-pyridone (2) and piperidine (3) in solution. Eight solvents of different polarity, polarizability and acid-base properties: CCl(4), CS(2), CHCl(3), CDCl(3) (for comparison with the NMR spectra), CH(2)Cl(2), MeOH, Et(2)O and Et(3)N were chosen. Experimental FT-IR spectra were analysed with the help of those calculated for isolated derivatives at the AM1 and PM3 levels.