Natural Abundance Nitrogen-15 NMR: A Study About the Conformation and Protonation Site of Some Quinoline Alkaloids

Abstract

Natural abundance ¹⁵N-NMR spectra were obtained from quinidine, quinine and epiquinidine. Correlation of the ¹⁵N 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 CDCl₃ was 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

Key Words:

• ¹⁵N-NMR
• quinoline alkaloids.