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Title: Steroselective synthesis and transformations of medium-ring lactones and ethers
Author: Anderson, E. A.
Awarding Body: University of Cambridge
Current Institution: University of Cambridge
Date of Award: 2000
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This thesis details work on the development of understanding of the effects of medium ring conformation on the outcome of ring functionalisation reactions. An overview of the applications of medium-ring stereocontrol towards the synthesis of natural products is presented in Chapter 1. The synthesis of the disubstituted lactone 2.43 via a tandem carbonate methylenation/Claisen rearrangement ring-expansion is detailed in Chapter 2. Comparison of the selectivity of functionalisation of this lactone at C-3, C-5 and C-6 was made with the corresponding ring-opened methyl ester 2.69. Correlation of the results with molecular modelling studies revealed interesting and contrasting diastereoselectivities of functionalisation. (Fig. 6780A) The use of a medium-ring lactone as a scaffold for the construction of a second tethered Claisen rearrangement ring-expansion allowed the synthesis of the 8,8-trans-fused bicyclic lactone 3.2. This model polyether submit resembles the medium ring portions of ciguatoxins and brevetoxins. (Fig. 6780B) A medium-ring lactone can also act as temporary scaffold for the stereocontrolled introduction of functionality onto a carbon skeleton. Studies towards the synthesis of C-1-C-8 of (+)-discodermolide led to the synthesis of the 8-membered lactone 4.77, which was functionalised en route to an advanced precursor of the 6-membered δ-lactone target fragment.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available