Part I: The Structural Chemistry of the Triterpene beta-Amyrin. Part II: Routes to 11-Oxygenated Steroids From Ergosterol

Budziarek, Richard (1954) Part I: The Structural Chemistry of the Triterpene beta-Amyrin. Part II: Routes to 11-Oxygenated Steroids From Ergosterol. PhD thesis, University of Glasgow.

Abstract

PART I: The Structural Chemistry of the Triterpene beta-Amyrin. The reactions of the enol acetate of iso-beta-amyrenonyl acetate show that the parent aB-unsaturated ketone is correctly formulated as 2-acetoxyolean-10-en-12-one. iso-beta-Amyrin acetate, derived from iso-beta-amyrenonyl acetate by catalytic or Clemmensen reduction, is shown to be 2-acetoxyolean-10-ene and it is concluded that the locking of rings B/C in beta-Amyrin corresponds to the more stable configuration. Clemmensen reduction of iso-beta-amyradienonyl acetate gives beta-amyradienyl-II acetate which contains the same carbon skeleton as beta-Amyrin. In contrast to the behaviour of iso-a-amyradienonyl acetate, iso-beta-amyradienonyl acetate is reduced catalytically to neo-beta-Amyrin acetate, a monoene, which differs from each of the previously described isomers. Treatment of beta-amyrenonyl benzoate with strong alkali gives 18-iso-beta-amyrenonol. Catalytic hydrogenation of 18-iso-beta-amyrenonyl acetate yields 18-iso-beta-Amyrin acetate, oxidation of which with hydrogen peroxide yields a saturated ketone, 18-iso-beta-amyranonyl acetate. The orientation at C13 in the last compound is shown to represent the sterically stable configuration. Bromo-18-iso-beta-amyranonyl acetate is considerably more stable than the isomeric bromo-beta-amyranonyl acetate, and yields the corresponding alpha,beta-unsaturated ketone on heating in pyridine. Reduction of 18-iso-ft-amyranonyl a acetate by the Kishner-Wolff procedure gives 18-iso-beta-amyranol which differs from the saturated pentacyclic triterpenoid alcohols hitherto described. PART II: Routes to 11-Oxygenated Steroids from Ergosterol. Ergosterol has been converted by various procedures into 11alpha-hydroxy and 11-keto-steroids. The action of oxidising agents on ergosteryl-D acetate has been investigated: treatment with chromic acid giving 3beta-acetoxyergosta-9(11):22-dien-7-one and 3beta-acetoxyergosta-8:22-dien-7-one, with one mol. of per-formic acid giving 3beta-acetoxy-8alpha-ergosta-9(11):22-dien-7-one, with two mols. of performic acid giving 3beta-acetoxy-9alpha:11alpha-epoxyergost-22-en-7-one, and with perbenzoic acid giving 9alpha:11alpha-epoxyergosta-7:22-dien-3beta-yl acetate. By using mild alkaline conditions, hydrolysis of the ketoxide is accompanied by rearrangement to give 3beta:11alpha-dihydroxyergosta-8:22-dien-7-one, whereas treatment with strong alkali also effects a rearrangement, to give in this case, after acetylation, 7:11-diketoergost-22-en-3beta-yl acetate. 9alpha:11alpha-Epoxyergosta-7:22-dien-3beta-yl acetate has been converted into 3beta-acetoxy-9alpha:11alpha-dihydroxy-ergost-22-en-7-one characterised by its conversion into 3beta:11alpha-diacetoxyergosta-8:22-dien-7-one on treatment with strong alkali followed by acetylation. Oxidation of ergosteryl-D acetate 22:23-dibromide with one mol. of perbenzoic acid gives 22 :23-dibromo-9alpha: 11alpha-epoxyergost-7-en-3beta-yl acetate, whereas with two mols. a corresponding 7E:8E,9alpha:11alpha-diepoxide is obtained. Treatment of the former compound with sulphuric acid gives 22:23-dibromo-7E:11alpha-dihydroxyergost-8-en-3beta-yl acetate. Oxidation of this diol with chromic acid yields 22:23-dibromo-7:11-diketoergost-8-en-3beta-yl acetate and 22:23-dibromo-8alpha:9alpha-epoxy-7:11-diketoergostan-3beta-yl acetate, treatment of which with zinc and acetic acid gives in each case 7:11-diketoergost-22-en-3beta-yl acetate. 22:23-Dibromo-9alpha:11alpha-epoxyergost-7-en-3beta-yl acetate has been rearranged to 3beta-acetoxy-22-23-dibromoergost-8-en-7-one by-treatment with dilute hydrochloric acid and to 3beta-acetoxy-22:23-dibromoergost-8-en-ll-one by treatment with boron trifluoride. (Abstract shortened by ProQuest.).

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Keywords: Physical chemistry, Organic chemistry
• Date of Award: 1954
• Depositing User: Enlighten Team
• Unique ID: glathesis:1954-79074
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 31 Mar 2020 09:09
• Last Modified: 31 Mar 2020 09:09
• URI: https://theses.gla.ac.uk/id/eprint/79074