Synthetic Studies on Gibberellins

Lyall, William J. S (1977) Synthetic Studies on Gibberellins. PhD thesis, University of Glasgow.

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Abstract

Based upon the serendipitous conversion of carbomethoxy-2-(p-methoxyphenyl)-cyclohexane-1-carboxylic acid into endo-2-(p-methoxyphenyl)-cyclohexane-cis-1,5-dicarboxylic acid anhydride, a stereospecific synthesis of 1,2,3,4,4a(betaH),9a(betaH)-hexahydro-7-methoxy-o-oxofluorene-2-carboxylic acid has been achieved in excellent yield, originating from the regiospecific and stereoselective Diels Alder cyclisation between acrylyl chloride and 5-(p-methoxyphenyl)-trans, trans-penta-2,4-dienoyl chloride. The Diels Alder reaction between related dienes and dienophiles was also investigated. A detailed investigation of the intramolecular Dieckmann cyclisation of methyl (1,2,3,4,4a(betaH),9a-hexahydro-2-carbomethoxy-7-methoxy-9-oxofluorenyl-9abeta)-acetate and of its 9-desoxy and 9alpha-hydroxy derivatives as a route to 3-methoxy-6,16-dioxo-9(betaH)-gibb-A-triene suggests that strain factors are the cause of failure of this cyclisation. 3-methoxy-16-oxogibba-1(10),2,4 ,9(11)-tetraene was obtained by acid catalysed cyclisation of the olefinic diazo ketone, 1,2,3,4,4a(betaH)-tetrahydro-Delta9,11-2-diazoacyl-7-methoxyfluorene. A keto-carbenoid C-H insertion reaction applied to the corresponding hexahydro and 9alpha-hydroxy-hexahydro derivatives failed to yield any tetracyclic material. An attempt to extend the Parham hydrofluorene synthesis failed at an early stage when 2-bromo-5-methoxybenzyl alcohol, or its 1-alkoxy-l-ethoxyethane acetal derivative failed to undergo electrophilic halogen exchange. A similar lack of success was experienced with the corresponding Grignard reagent.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Organic chemistry
Date of Award: 1977
Depositing User: Enlighten Team
Unique ID: glathesis:1977-78772
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 30 Jan 2020 14:55
Last Modified: 30 Jan 2020 14:55
URI: http://theses.gla.ac.uk/id/eprint/78772

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