The Occurrence and Chemistry of Certain Triterpenes, with Particular Reference to the alpha-Amyrin Group

Manson, William (1950) The Occurrence and Chemistry of Certain Triterpenes, with Particular Reference to the alpha-Amyrin Group. PhD thesis, University of Glasgow.

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Part I - The Structures of alpha-Amyrenol and Ursolic Acid. Investigations have been carried out on the naturally occurring triterpene, alpha-amyrenol, C30H50O, and the related substance ursolic acid, C30H48O3, with a view to the elucidation of the structure of the alpha-amyrin group of triterpenes Oxidation with chromic anhydride of the unsaturated hydrocarbon l-alpha-amyradiene C30H48, yielded l-alpha-amyradiene oxide, C30H48O, which on further oxidation with the same reagent was converted to l-alpha-amyrenone oxide C30H46O2. In addition a number of well-defined mixed crystals of the hydrocarbon and each of its oxidation products were obtained, and one of these was identified with a product previously obtained by treatment of l-alpha-amyradiene with perbenzoic acid. An examination of molecular rotational differences between certain derivatives of alpha-amyrenol and the corresponding derivatives of alpha-amyrenol has been made, from which, in conjunction with the oxidation experiments on l-alpha-amyradiene, a partial formulation for alpha-amyrenol has been derived. Treatment of acetylursolyl chloride, C32H49O3Cl, with phenylmagnesium bromide yielded the diphenylcarbinol, C44H60O3, which could not be dehydrated to the corresponding diphenylethylene derivative, and hence confirmed the tertiary nature of the carboxyl group of ursolic acid. Ketoacetylursolic acid when refluxed with quinoline in presence of oxygen has been shown to yield nor-alpha-amyradienonyl acetate, C31H46O3, while in the absence of air nor-alpha-amyrenonyl acetate was produced. Under similar conditions, ursonic acid C30H46O3, acetylursolic acid C32H50O4 , and alpha-amyrenonyl acetate C32H50O3 have been shown to be stable, from which the relative locations of the ketone group and the carboxyl group of ketoacetylursolic acid have been tentatively fixed. Oxidation of acetylursolic acid with hydrogen peroxide produced an oxido-lactone C32H48O5, identical to that obtained by Jeger, Borth, and Ruzicka (Helv. Chim. Acta,1946,29,1999). In addition, there was produced an acid which on methylation yielded methyl oxido-acetyl-ursolate C33H52O5, previously designated methyl ketodihydro-acetylursolate (Jeger, Borth, and Ruzicka,loc. cit.). Methyl acetylursolate on treatment with hydrogen peroxide yielded methyl oxido-acetylursolate, C33H52O5, which by the action of dilute mineral acid was converted to the isomeric methyl ketodihydro-acetylursolate. The compound described in the literature as methyl ketodihydro-acetylursolate was identified as methyl oxido-acetylursolate described above. Treatment of methyl oxido-acetyl-ursolate and methyl ketodihydro-acetylursolate with bromine yielded the same bromo compound C33H51O5Br, which on dehydrohalogenation gave methyl iso-ketoacetyl-ursolate, C33H50O5. Oxidation of this with selenium dioxide gave methyl iso-ketodehydro-acetylursolate C33H48O5, and from a comparison of the behaviour of this compound with that of similar derivatives of alpha- and beta-amyrenol, a structure incorporating the partial structures already obtained, has been derived. Part II - The resin from Canarium Schweinfurthii. The resin from the tree Canarium Schweinfurthii has been examined analytically. The steam volatile portion was found to consist of the terpene d-limonene containing a trace of a phellandrene. The non-volatile portion contained the triterpenes alpha-amyrenol, beta-amyrenol, alpha-elemolic acid, beta-elemonic acid and a diol, C30H50O2, which like alpha-elemolic and beta-edemonic acids contained two unconjugated double bonds but which could not be identified with any of the known triterpene diols.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry
Date of Award: 1950
Depositing User: Enlighten Team
Unique ID: glathesis:1950-79817
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 03 Mar 2020 10:33
Last Modified: 03 Mar 2020 10:33

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