An Evans-Tishchenko/Ring closing metathesis approach towards the medium ring lactone, Octalactin A
Medium-ring lactones have become important targets for synthesis as they have been isolated in an increasing number of biologically active natural products. The studies towards two 8-membered ring lactone natural products, octalactins A 1 and B 2, will be described.The first section of this thesis examines the application of key methodology (anti aldol reaction, Homer Wadsworth Emmons olefination, intermolecular Evans- Tishchenko coupling and Ring Closing Metathesis) towards the octalactins via the synthesis of a model lactone 3 (Chapter 2). The second section (Chapter 3) discusses the extension of the aldol methodology from Chapter 2 towards the development of a novel chiral auxiliary 4 to mediate the anti aldol reaction. The generality of this new auxiliary in anti aldol reactions will also be discussed. The final part of this thesis describes the synthesis of the octalactins based on the application of the methodology developed from the model studies using the key functionalised fragments: aldehyde 5, 3-ketophosphonate ester 6 and aldehyde 7.