Total synthesis of (-)-elisapterosin B and on towards the metabolites of Pseudopterogorgia elisabethae

Demurtas, Daniela (2005) Total synthesis of (-)-elisapterosin B and on towards the metabolites of Pseudopterogorgia elisabethae. University of Southampton, Doctoral Thesis.

Abstract

This thesis is concerned with the synthesis of natural products isolated from the Caribbean Sea whip, Pseudopterogorgia elisabethae.  A new total synthesis of (-)-elisapterosin B is described.  This metabolite possesses an unprecedent cagelike (elisapterane) carbon skeleton and is particularly interesting because it displayed strong in vitro inhibitorial activity against Mycobacterium tuberculosis H37Rv and stronger antiplasmodial activity against Plasmodium falciparum, the parasite responsible for the most severe form of malaria.  Previous synthesis and synthetic approaches to (-)-elisapterosin B and (-)- colombiasin A, which is another target of this work, are reported in Chapter 1.  in Chapter 2 we describe the synthesis of a number of different spirolactones, rigid molecular scaffolds, which we firstly intended to use to synthesize colombiasin A and elisapterosin B. Problems with this method made us devise a different approach.  Studies directed towards (-)- colombiasin A using boron mediated coupling reactions together with a more classical approach and an approach towards elisabethadione, are described in Chapter 3.  in Chapter 4 the total synthesis of (-)-elisapterosin B from (S)-(+)-carvone is described.  Key steps are a Shapiro reaction, followed by a reagent free cascade reaction and an intramolecular [5+2]-cycloaddition to access (-)-elisapterosin B.  Experimental procedures are outlined in chapter 5.

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