Researches into the structure of emetine

Abstract

The first crude preparation of the alkaloid emetine was obtained in 1817 by Pelletier from the plant species Cephaelis ipecacuanha. Since that day many workers have turned their attentions to the structural problem presented by this alkaloid, among them being such famous chemists as Karrer, Pyman, Späth, and Reichstein. Their failure to complete the elucidation of the structure cannot be ascribed to a lack of time or to the substance being uninteresting in itself, for, during the century or so that emetine has been known, the structure of many alkaloids with considerably more complex molecules have been solved. Furthermore, emetine has always aroused considerable interest because of its unique position as therapeutic agent for the treatment of amoebic dysentery. It seems more probable that the great difficulty experienced by the early workers of obtaining pure emetine accounts partly for the slow rate of progress; the reluctance of the derivatives and degradation products of the alkaloid to crystallise, must also be taken in to account. Again, the oxidation technique, so powerful a weapon with many other alkaloidal problems, failed to cast any light on what might be called the core of the molecule.

A knowledge of the structure of emetine will obviously be of considerable value in view of its pharmacological properties, and the present researches have been planned with that end in view. The mode of attack, different from these previously employed, will be described in this thesis. Part of the author’s early work on the emetine problem was presented for a Higher Degree (M.Sc., Manchester), and will be described briefly in this historical survey.