Synthesis of Natural Products by the Oxidation of Phenols

Davidson, Thomas A (1961) Synthesis of Natural Products by the Oxidation of Phenols. PhD thesis, University of Glasgow.

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Introduction - The oxidative coupling of phenols, as a biogenetic route to many natural products is discussed and an account of the recent evidence in support of the theory is given. Part I - The synthesis of the depside dihydropicrolichenic acid from olivetol aldehyde is described. Several reagents were tried with a view to causing the oxidative coupling to picrolichenic acid. The vital coupling reaction was finally achieved by using manganese dioxide suspended in benzene. A partial resolution of picrolichenic acid was obtained via the quinine methohydroxide salt. Part II - The total syntheses of the mould metabolites, geodin and erdin, were attempted. Two routes to the intermediate benzo-phenones, dihydrogeodin and dihydroerdin, were unsuccessful. The first route required the condensation of a dichloro-p-orsellinic acid with a suitable derivative of methyl 3-hydroxy-5-methoxy-benzoate by a Friedel and Craft's reaction. The second route reversed the roles of the reactants by using the anhydrides of 5-benzyloxy- and 5-hydroxy-3-methoxyphthalic acid and attempting to condense them with 2,6-dichloroorcinol. Partial syntheses of geodin and erdin were achieved by oxidative coupling of the dihydro compounds, obtained from natural geodin and erdin, with alkaline potassium ferricyanide. Part III - The synthesis of colchicine by oxidative coupling of a phenolic precursor, 1-(3',4'-dimethoxy-5'-hydroxyphenyl)-3-(beta-tropolonyl)-propane, was attempted. The precursor was obtained by condensation of a suitably substituted phenylacetaldehyde with the anhydride of 2-carboxy-4-hydroxy-3-oxocycloheptatrienyl-acetie acid with subsequent pyrolysis, reduction and hydrolysis. All attempts to induce ring closure to the tricyclic system of desaoetylamidocolchiceine by a variety of oxidants were unsuccessful.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry
Date of Award: 1961
Depositing User: Enlighten Team
Unique ID: glathesis:1961-79400
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 05 Mar 2020 10:05
Last Modified: 05 Mar 2020 10:05

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