The alkaloids of ipecacuanha. Pt. 3 / by Frank Lee Pyman.

  • Pyman, Frank Lee.
Date:
1918.]
Catalogue details

Licence: Public Domain Mark

Credit: The alkaloids of ipecacuanha. Pt. 3 / by Frank Lee Pyman. Source: Wellcome Collection.

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    XXVI. — The Alkaloids of Ipecacuanha. Tart III. By Frank Lee Pyman. Tn the previous paper of this series (T., 1917, 111, 424), it was shown that O-methylpsychotrine gave a mixture containing emetine and ?’soemetine* on reduction. The formation of /.s-oemetine was demonstrated by the isolation of its benzoyl deriv alive, for neither Loemetine nor any of its salts had at that time been obtained in a crystalline form. Later, however, the hydro- bromide became crystalline, and was readily purified by crystal¬ lisation from water, and, from the pure salt, the base, hydro chloride, and hydroyen oxalate were prepared in the usual manner, and also obtained in crystalline form. On benzoylation, the base gave the benzoylfsoemetine previously described. Since emetine and /soemetine are produced by the reduction of methylpsychotrine, it was to be expected that Loemetine, like emetine, could be oxidised to methylpsychotrine and rubremetine, and this proved to be the case. The view that emetine and zsoemetine are stereo isomerides was thus confirmed, and it appeared to be of interest to determine whether an equilibrium between the two bases could be established by boiling with amyl alcohol and sodium amyloxide. Experiments to this end were unsuccessful, for, after fourteen hours’ boiling, no evidence of partial racemisation was obtained, each base being recovered unchanged except in so far as it had been hydrolysed to phenolic bases. ’the fact that psychotrine gives cephaeline and Locephaeline on reduction, whilst the methyl ether of psychotrine gives emetine and i.soemetine, indicated the probability that isoemetine was the methyl ether of isocephaeline, and this has now been proved by preparing isoemetine by the methylation of Locephaeline. When methylated under suitable conditions, isoemetine gives a well-crystallised W-methyl derivative, N-?nethylisoemetine, which proves to be the O-methyl ether of the isomeride of iV-methyl cephaeline previously described (T., 1914, 105, 1624); this sub stance is therefore Nonethyli&ocephaelime. * The term woemetine is clearly appropriate to this compound, which is the methyl ether of the isocephaeline described in 1914 (Carr and Pyman, T., 1914, 105, 1591), and the parent of the substance already named benzoyl- isoemetine (Pyman, T., 1917, 111, 424). It has since been employed by Karrer (Ber., 1917, 50, 582) for a reduction product of rubremetine. Whilst the coincidence is unfortunate, it does not appear to be important, for Karrer’s 4 isoemetine ’—an amorphous base from which no crystalline derivatives were prepared—is probably a mixture of stereoisomerides.