Spectral reassignment and structure elucidation of scopolamine free base through two‐dimensional NMR techniques

Abstract

Abstract The combination of 1D and 2D NMR techniques, especially the long‐range heteronuclear chemical shift correlation experiment, has permitted the reassignment of some carbons and protons of scopolamine free base in CDCl 3 solution and the differentiation of each atom of the piperidine ring. In contrast to literature data, and to the protonated state conformation, these studies showed that the methyl group is equatorially disposed relative to the piperidine ring. NMR and IR spectroscopic results demonstrated that the OH group is connected by a hydrogen bond to the phenyl ring at a low concentration, but an intermolecular hydrogen bond is formed at high concentration.