Synthesis and conformational analysis of disubstituted sparteine derivatives

摘要

Synthesis of disubstituted sparteine derivatives and their diperchlorate salts was performed. Their IR and NMR spectra were analysed to determine the structure of these compounds, as well as the substituent and the protonation effects. It was shown that both unsaturated (2,17(beta-dimethyl-2,3-didehydrosparteine (12), 17p-isopropyl-2-methyl-2,3-didehydrosparteine (13)) and saturated (2,17beta-dimethylspaiteme (14), 17beta-isopropyl-2-methylsparteine (15)) newly obtained sparteine derivatives have the same configurational-conformational system: trans A/B chair/chair, trans C/D boat/chair. The methyl and the isopropyl (both equatorial) groups at C-17 appear the elements stabilizing the boat-chair system of the C/D rings, which does not change either on the introduction of the second substituent to the opposite quinolizidine system (the A/B rings) or on protonation. The protonation of the free bases obtained gives only disalts. The atoms undergoing the protonation are either C-3 and N-16 in 12 and 13 or both nitrogen atoms (N-l and N-16) in 14 and 15. The methyl group intro duced on the carbon atom C-2 takes equatorial position, as in 2-methylsparteine (2).