Studies in the Chemistry of Natural Products

Wagner, Hans M (1951) Studies in the Chemistry of Natural Products. PhD thesis, University of Glasgow.

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Part I: The non-basic constituents of the plant Ephedra vulgaris were examined by chromatographic methods. An extract of the plant from which the alkaloids had been removed was saponified and the non-saponifiable matter was isolated. The latter was dissolved in ethanol and on chilling part of the material was precipitated. In this way an alcohol soluble portion and an alcohol insoluble portion was separated. Chromatography of the latter yielded a mixture of long chain paraffins, a secondary alcohol, a primary alcohol mixture and a small quantity of a phytosterol as well as some recalcitrant gums. The paraffins were shown to be probably a mixture of nonacosane and hentriacontane, the secondary alcohol was identified as (+)-n-nonacosan-10-ol, the primary alcohol was shown to be a mixture of long chain aliphatic alcohols with a mean chain length of 28 carbon atoms and the phytosterol proved to be beta-sitosterol. Chromatography of the alcohol soluble fraction yielded an unidentified oil analysis of which gave the formula C22H40O and which appeared to have a conjugated diene system. A second primary alcohol mixture was also isolated with a mean chain length of 22 carbon atoms. Finally a large phytosterol fraction was isolated from the chromatogram. This was shown to consist of beta-sitosterol only, for the absence of sitostanol was proved by the method of Anderson and Nabenhauer (J.A.C.S., 1924, 46, 1958) and the absence of stigmasterol was shown by the method of Windaus and Hauth (Ber., 1906, 39. 4378). The negative Tortelli-Jaffe test showed the absence of alpha-sitosterol and ergosterol. Furthermore oxidation of the sterol from Ephedra by the method of Barton and Jones (J., 1943, 599) led to the isolation of sitost-4-en-3-one only. The residual gums from the chromatogram were examined for the presence of ketones by Girard's reagent but no ketonic material was isolated. Part II: Three crystalline substances, which gave a positive Liebermann-Burchard test and which were obtained from a petroleum extract of the bark of the tree Alstonia verticillosa were examined chromatographically. The first material was shown to consist of a mixture of the triterpenes alpha- and beta-amyrin and lupeol. The second fraction was hydrolysed and benzoylated and chromatography of the benzoates afforded alpha-amyrin-benzoate and lupeol- benzoate. Similar treatment of the third fraction yielded alpha-amyrin, beta-amyrin-benzoate and lupeol-benzoate. A further quantity of beta-amyrin was isolated from Manila Elemi resin. A new beta-amyrene was prepared which can be used as a starting point in the study of the stereochemistry of rings A and B of -amyrin. The latter was oxidised as acetate with hydrogen peroxide to the saturated ketone beta-amyranonyl-acetate. Reduction of this by the Kischner-Wolff technique yielded the saturated alcohol beta-amyranol. Dehydration of the latter yielded a new hydrocarbon, beta-amyrene. Hydrogenation of this unsaturated compound gave a saturated hydrocarbon which was not identical with beta-amyran, the saturated hydrocarbon previously obtained from beta-amyrin by Ruzicka and Jeger (Helv. Chim. Acta, 1941, 24, 1179). It was therefore concluded that the dehydration probably took place by a retrapinacolone mechanism with a change in the structure of ring A of beta-amyrin.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry
Date of Award: 1951
Depositing User: Enlighten Team
Unique ID: glathesis:1951-78890
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 14:44
Last Modified: 30 Jan 2020 14:44

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