School of Chemistry - Theses

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    Studies towards the synthesis of rhizopodin
    Loits, Darran Andrew ( 2014)
    The asymmetric synthesis of the C1 – C18 fragment of rhizopodin is described. Initial work focused on the construction of the C9 – C18 fragment utilising the addition of the anion derived from 2-methyloxazole 195 to an aldehyde (235) to construct the C15 – C16 bond. The synthesis of iodide fragment 259 began with known aldehyde 244 and utilised a stereoselective novel acetylide addition to install the C3 stereocentre as well as a regioselective hydrostannylation of the terminal alkyne followed by tin-iodide exchange to install the vinyl iodide. Attempted construction of the C7 – C8 bond by intramolecular Heck coupling lead to the preferential formation of 6E, 8Z macrocycle 262 over the desired 6E, 8E 261 whilst an intermolecular Heck coupling between alkene 240 and iodide 259 resulted in the formation of a mixture of 6E, 8E (263) and 6E, 8Z (264) dienes with a slight preference towards the desired 6E, 8E (263). Due to the low selectivity, an alternative method for the construction of the C6 – C9 diene was then utilised. Suzuki coupling between boronate 311 and iodide 259 installed the diene (310), which was then esterified with acid 316. Installation of the azide by a Mitsunobu reaction (318) allowed for the application of an O, N-acyl shift to provide hydroxy amide 319 that was subjected to oxidation and cyclodehydration to give oxazole (320). This completed the synthesis of the C1 – C18 fragment of rhizopodin with NMR spectral analysis showing good correlations with literature values for the relevant fragments in rhizopodin (4) itself.