Effect of substituents and structural modification on conformational equilibrium in bis-quinolizidine system

Abstract On the basis of literature interpretation of 13 C NMR and 1 H NMR spectra of bis-quinolizidine alkaloids, the values of free enthalpy Δ G of conformational equilibria of those compounds were calculated. The results were analysed together with the X-ray and DFT data to discuss the effects of different substituents attached to the sparteine system in various positions as well as the effects of structural modifications on conformational equilibria. The measure of the effect was expressed by ΔΔ G value, defined as the difference in Δ G of the compound under consideration and its parent compound without a given substituent.