Natural product syntheses
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| Title: | Natural product syntheses |
|---|---|
| Authors: | Li, Ivan Chan Kwong |
| Summary: | This thesis is concerned with synthetic approaches towards the indole alkaloid koumine and the sesquiterpene quadrone. An intramolecular Diels-Alder reaction is the key step in our synthetic approaches to koumine. Chapter one describes some aspects of indole alkaloids including a general background, biosynthesis of strychnos alkaloids as well as the discovery of koumine and its pharmacological action. Chapter two deals with three potential routes to koumine and the important intermediate rel-(1R,6R,10S)-N-methyl-1-allyl-3-aza-2-oxobicyclo[4.4.0]dec-7-ene-10-y1-methanol has been prepared by way of a Diels-Alder reaction of maleic anhydride and (E)-3,5-hexadienylamine with further functionalisation. Quadrone, a sesquiterpene with a novel tetra cyclic system as well as antitumour activity, has become a popular synthetic target since its discovery and the main theme of our approach is a carbene cyclisation to form and basic skeleton. Chapter three describes the discovery of quadrone, its biogenetic origin and some previous sytheses. Chapter four explores 2 routes to the bicyclic intermediate 4-t-butyl-dimethyl-silyloxy-6,6-dimethyl-2-(2-oxo-2-propyl)bicyclo[3.2.1]octan-8-one which has been synthesised via a Michael addition of 4,4-dimethyl-2-(2-methyl-2-propyl) cyclopentanone with acrolein and subsequent intramolecular aldol condensation. Attempted preparation of the required carbene precursor (from this intermediate) using either a Horner-Wittig reagent or several halomethyltriphenylphosphonium halides proved unsuccessful. |
| URL: | https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375675 |
| Database: | OpenDissertations |
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