The biosynthesis of ephedrine

• Published in: Canadian journal of chemistry 1989-06, Vol.67 (6), p.998-1009
• Main Authors: Grue-Sørensen, Gunnar, Spenser, Ian D
• Format: Article
• Language: English
• Subjects: Chemistry; Exact sciences and technology; Noncondensed benzenic compounds; Organic chemistry; Preparations and properties
• ISSN: 0008-4042; 1480-3291
• DOI: 10.1139/v89-152

It is shown by 13 C nuclear magnetic resonance spectroscopy that the labelled C 2 fragment of [2,3- 13 C 2 ]pyruvic acid is transferred intact into the C-methyl group and the adjacent carbon atom of the Ephedra alkaloids, norephedrine, ephedrine, norpseudoephedrine, and pseudoephedrine, in growing plants of Ephedragerardiana. This finding serves to identify pyruvate as the elusive precursor of the aliphatic C 2 terminus of the skeleton of the alkaloids. In earlier experiments with C-labelled substrates, label from [3- 14 C]pyruvic acid was incorporated mainly, but not exclusively, into the C-methyl group of ephedrine, and label from [2- 14 C]pyruvate was incorporated similarly into the carbon atom adjacent to the C-methyl group. A C 6 -C 1 unit related to benzaldehyde or benzoic acid has long been known to generate the benzylic fragment of the carbon skeleton of the Ephedra alkaloids. It is likely that the carbon skeleton of ephedrine is generated from pyruvate and either benzaldehyde or benzoic acid, by a reaction analogous to the formation of acetoin or diacetyl from pyruvate and acetaldehyde or acetic acid, respectively. Keywords: biosynthesis of ephedrine, Ephedra alkaloids, 13 C NMR spectra, ephedrine, biosynthesis of pyruvic acid, incorporation into ephedrine 13 C NMR spectra.