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Studies towards the asymmetric synthesis of Dictyoxetane

Ahmadipour, Sanaz (2016)
Ph.D. thesis, University of Birmingham.

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Abstract

The brown alga, Dictyota dichotoma, collected from the Indian Ocean has proven to be a prolific source of new diterpenes. The diterpene, dictyoxetane, isolated from the brown alga, is structurally related to the dollabellane class of natural products. Dictyoxetane is the only known natural product having the 2,7-dioxatricyclo[4.2.1.0]nonane ring subunit.

Chapter 1 of this thesis describes the isolation, structure and proposed biosynthesis of dictyoxetane. The methods reported in the literature for the preparation of the dioxatricyclic framework are discussed, which might be applied in a synthesis of dictyoxetane. The Grainger group has previously reported the synthesis of the trans-hydrindane core of dictyoxetane starting from a Robinson annulation-derived bicyclic enone. Asymmetric approaches to the starting hydrindanone in this synthesis and the Hajos-Parrish ketone are also presented.

Chapter 2 reports the efforts to address the current limitations of this approach, namely the low-yielding Robinson annulation of an expensive starting material, 2-methylcyclopentanone. An asymmetric synthesis of the trans-hydrindane ring system starting from the Hajos-Parrish ketone, involving chemoselective radical-based deoxygenation, is reported.

Studies towards dioxatricyclic ring annulation are described in Chapter 3. A number of strategies such as radical cyclisation, ring-expansion and [4+3] cycloaddition are investigated towards 7-membered ring formation. The Lee [5+2] annulation using allylsilane acetals and olefin metathesis both provided a way to annulate a 7-membered ring to the hydrindanone system en route to dictyoxetane.

Type of Work:Ph.D. thesis.
Supervisor(s):Grainger, Richard S. and Simpkins, Nigel
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Chemistry
Subjects:QD Chemistry
Institution:University of Birmingham
ID Code:6982
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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