Ergot alkaloids : a triple radical cyclisation approach to the synthesis of lysergic acid

Cladingboel, David Edward (1990) Ergot alkaloids : a triple radical cyclisation approach to the synthesis of lysergic acid. University of Southampton, Doctoral Thesis.

Abstract

A novel free radical approach to the synthesis of lysergic acid and the ergot alkaloids has been investigated. The homolytic cleavage of carbon-halogen bond, mediated by tri-n-butyltin hydride, followed by cyclisation, resulted in the development of synthetic routes to several classes of organic compounds: 3,4-disubstituted dihydroindoles via single cyclisation; hexahydrobenz[cd]indoles via tandem cyclisation and both octahydroindolo[6,5,4-cd]indoles and decahydroindolo[4,3-fg]quinolines via triple radical cyclisation. Chapter 1 introduces lysergic acid and briefly describes past total syntheses of this molecule. A retrosynthetic plan is outlined and some literature precedent for its successful application to lysergic acid synthesis is given. Chapters 2 and 3 describe work carried out which leads to the synthesis of highly functionalised phenylacetaldehyde derivatives and allylic amines respectively. The coupling of aldehyde and amine to give various enamines and the radical cyclisation of these enamines is described in chapter 4. Some further ideas for future work are outlined in chapter 5.

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