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The total synthesis of the proposed structures of the prevezols B and C
thesisposted on 2017-02-17, 00:18 authored by Leung, Anna Elizabeth
The brominated diterpenes known as the ‘prevezols’, isolated from Laurencia obtusa obtained from the Ionian sea, have molecular frameworks unlike any that have been reported previously. Embedded within the carbon skeleton of each of the prevezols is a tertiary syn bromohydrin, posing a significant challenge to synthetic chemists. The synthesis of these compounds is further complicated by their partially-defined stereochemistry. The first chapter of this thesis discloses the previous work which has provided us with an arsenal of chemical transformations upon which to establish synthetic routes to the prevezols B and C, stereoisomers of one another. The proposed synthetic route to the prevezols B and C was based upon a convergent strategy, employing diastereoselective alkylation reactions between four stereochemically-divergent limonene-1,2-diol derivatives, and a key allylic iodide intermediate. Chapter 2 describes the synthesis of the key allylic iodide intermediate in eight steps from the commercially available mixture of cis/trans-(−)-limonene oxide. Chapter 3 discloses the asymmetric total synthesis of two of the proposed structures of prevezol C, via diastereoselective alkylation reactions employing the allylic iodide. Chapter 4 details the synthesis of two of the proposed structures of prevezol B in an analogous fashion. Inconsistency between the published data for the natural products and the synthetic diterpenes demands a structural revision of the prevezols B and C.