Chemistry of the Mitragyna Genus

Ongley, Patrick A (1951) Chemistry of the Mitragyna Genus. PhD thesis, University of Glasgow.

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Previous work on the Mitragyna alkaloids was largely haphazard, and very little attempt had been made to correlate the known properties. The first task in this investigation, therefore, was to do this. The properties of mitragynine, mitragynol, mitraphylline, rhynchophylline, and rotundi-foline, and of formosanine, from a species of the closely-related genus Ourouparia, have now been more completely examined. Concerning the occurrence of the alkaloids, several interesting results were encountered. There has been controversy as to whether or not mitrinermine from M. inermis and "rhynchophylline" from O. rhynchophylla are the same alkaloid. It has now been shown conclusively that they are the same. The hitherto unknown d-form of mitraphylline has been found in the bark of M. rubrostipulacea, and in M. ciliata, previously uninvestigated, notundifoline has been found in the leaves, and rhynchophylline in the bark. Sitosterol has been identified in the bark of M. inermis, and quinovic acid in the bark and leaves of various Mitragyna species. As far as functional groups are concerned, it is now known that the alkaloids contain no N-methyl groups, but are methyl esters and often contain additional methoxyl groups. Although neither mitraphylline nor rotundifoline gives hydroxyl or keto derivatives, acetyl-rhynchophylline is known. While neither mitragynine, mitraphylline, rotumdifoline, nor formosanine reacts with diazomethane, rhynchophylline does to give a methyl derivative. Mitragynol deserves special mention. This alkaloid, because of its solubility in sodium hydroxide, formation of azo dyes, and giving of several phenolic colour reactions, seems to be phenolic, but several reactions are difficult to explain on this hypothesis. Diazomethane, acetic and propionic anhydrides, and acetyl chloride with mitragynol all give the same reaction product, possibly the result of isomerisation. Such isomerisation occurs in the hydrolysis and re-esterification of ester alkaloids, e.g., other Mitragyna alkaloids, and Yohimbe and Seneco alkaloids. Two known degradation products have been re-examined. The base C9H13N resulting from the selenium degradation of rotundifoline has been shown to be 3:4-diethylpyridine, and the neutral compound C10H9NO formed in the calcium oxide distillation of rhynchophyllic acid and formerly considered a carbostyril is shown by its spectrum to be an indole. The various known properties of the compound suggest that it may be a 2:3-dimethyl-hydroxy-indole. Prom a detailed study of colour reactions and of ultra-violet spectra, it is concluded that the alkaloids are indolic. If this is so, and if they have the skeleton of any known indolic alkaloid, it is possibly that of the Pseudocinchona, but more probably that of the Yohimbe type. Since at lower temperatures there was difficulty in determining the number of active hydrogen atoms in the various alkaloids, an investigation was made of the effect of temperature on the determination of active hydrogen atoms. Examination of a range of 38 compounds each at the temperatures: room 50-60, 100, and 160 in phenetole showed that at elevated temperatures no abnormal values resulted. Low values were met in fluorene compounds. A smaller range of compounds, where low values had been either reported in the literature or encountered in this investigation, was investigated also in butyl ether and in mixed solvents. In these cases the expected values were obtained, if not at room temperature, then at least at higher temperatures. Although some hydrogen atoms, e.g., the second in an amino group, do become active only at higher temperatures, it is felt that many low values reported are due not to inactivity but either to insolubility of reactant preventing complete reaction, or insolubility of reaction product adsorbing the methane produced In one case where this could happen, mechanical stirring during the reaction led to the expected value being obtained.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry
Date of Award: 1951
Depositing User: Enlighten Team
Unique ID: glathesis:1951-79747
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 31 Mar 2020 09:09
Last Modified: 31 Mar 2020 09:09

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