Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.581183
Title: Alkaloids from transannular iodoaminations
Author: Brock, Elizabeth Anne
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2012
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Abstract:
This thesis is concerned with the development of transannular iodoamination methodology for the synthesis of pyrrolizidine, indolizidine and tropane alkaloids. Chapter 1 introduces the concept of a ‘transannular cyclisation’ and outlines the utility of such cyclisations in the synthesis of a range of [x.y.z]-azabicyclic alkaloids. Chapter 2 describes the development of a three step lithium amide conjugate addition, ring-closing metathesis and transannular iodoamination protocol for the preparation of the pyrrolizidine scaffold ([3.3.0]-azabicycle). Cyclisation of a hexahydroazocine occurs with concomitant N-debenzylation to give a single diastereoisomer of the corresponding C(7)-iodopyrrolizidine product, which is then elaborated to the known pyrrolizidine, (−)-7a-epi-hyacinthacine A1. Chapter 3 delineates an extension of the methodology described in Chapter 2, and an investigation into accessing alternate diastereoisomeric pyrrolizidine scaffolds via the transannular iodoamination process. These studies culminate in the synthesis of two pyrrolizidine alkaloids, (−)-hyacinthacine A1 and (−)-hyacinthacine A2. Chapter 4 details investigations into the further elaboration of the C(7)-iodopyrrolizidine scaffold synthesised in Chapter 2. A nucleophilic displacement reaction with azide leads to the synthesis of novel 7-deoxy-7-aminoalexine analogues, whilst radical-mediated substitution of the iodide by oxygen allows the synthesis and isolation of the pyrrolizidine alkaloid (−)-1-epi-alexine. Chapter 5 outlines the development of the transannular iodoamination reaction to facilitate the synthesis of the tropane architecture ([3.2.1]-azabicycle). A tandem lithium amide conjugate addition and aldol reaction sequence is followed by ring-closing metathesis to give the required aminocycloheptene. Subsequent treatment with iodine results in transannular cyclisation to give a single iodotropane product which, following elaboration culminates in the synthesis of (+)-pseudococaine. Chapter 6 contains full experimental procedures and characterisation data for all compounds synthesised in Chapters 2, 3, 4 and 5.
Supervisor: Davies, Steve Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.581183  DOI: Not available
Keywords: Chemistry & allied sciences ; Organic chemistry ; Organic synthesis ; Synthetic organic chemistry ; transannular ; iodoamination ; pyrrolizidine ; tropane ; alkaloids ; asymmetric synthesis ; iodocyclisation ; cocaine
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