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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

New synthetic methods in an approach to taxinine

Bonnert, Roger Victor January 1987 (has links)
A series of studies were undertaken directed towards the synthesis of taxinine. As part of these studies the need arose for a stepwise synthesis of a highly substituted butadiene from an aldehyde. The initial approach used the Peterson elimination to control the regio-chemistry in the formation of tri- and tetra-substituted dienes. The generality of this method appeared to be hampered by the basicity of 2-lithio-2-trimethylsilyl propane, which was required to undergo nucleophilic attack at an aldehyde. A study of the Diels-Alder reactions of a 3-alkyl-2,4-penta-l,3-diene and a 3-alkyl-4-methyl-penta-1,3-diene showed the former to react more efficiently. A deuterium labelling experiment eliminated the degeneracy of this diene in a 1,5-hydrogen shift as a reason for its increased reactivity. A more reliable route to the preparation of highly substituted butadienes was attained using the highly nucleophilic 2-lithio-2-phenyl- seleno-propane reagent. This route was used to prepare a triene system which underwent an intramolecular Diels-Alder reaction to enable the preparation of the taxane model compound 8,12,15,15-tetra- metllyltricyclo[9. 3. 1 .03,8] pentadec-ll-en-2-one which has the same stereochemistry and methyl group substitution as the naturally occurring taxanes. Attempts were then made to prepare taxinine using a carbohydrate derivative. A key step in the route to taxinine involved a Robinson annulation of a carbohydrate derived ketone. Alkylations of a carbohydrate derived enolate were studied initially. The Robinson annulation was then carried out using 3-trimethylsilyl-3-buten-2-ol and the enolate derived from methyl 4,6-O-benzylidene-3-deoxy-3-C- methyl-D-arabino-hexapyranosid-2-ulose.

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