Natural abundance15N-NMR spectra were obtained from quinidine, quinine and epiquinidine. Correlation of the15N chemical shifts with X-ray studies and minimal energy conformer calculations, reported previously, enabled definite conclusions about the solution conformations of these alkaloids. Also the protonation of quinidine in CDCl3was studied. It was determined that the first protonation occurs on the quinuclidine nitrogen and not on the quinoline nitrogen as was reported by Yanuka et al.1