New 2-oxosparteine derivatives: Synthesis and spectroscopic characterization

New 2-oxosparteine derivatives with alkyl (n-propyl-, n-pentyl-, n-hexyl- and n-heptyl-) substituent at C-17 position have been synthesized and studied by 1H, 13C NMR, MS, FT-IR and theoretical methods. It has been shown that alkyl substituent introduced at C-17 position is equatorially oriented and does not change the boat conformation of ring C. All newly obtained derivatives, when treated with HClO4 give only monoperchlorate salts.

► NMR spectra of new 17-alkyllupanine derivatives and their perchlorates. ► EI-MS and ESI-MS mass spectral behaviour of 17-alkyl substituted lupanines. ► According to DFT calculations boat–chair conformation is energetically favourable. ► All compound gives only monoperchlorate salts with protonated nitrogen atom N-16.