A total synthesis of zoapatanol

Liverton, Nigel John (1983) A total synthesis of zoapatanol. University of Southampton, Doctoral Thesis.

Abstract

The novel structure and contragestational activity of zoapatanol, an oxepane ring containing diterpene make it an interesting synthetic target. Chapter Two describes the synthesis of a model compound, 2,2-dimethyl6E-(2-hydroxyethylidene)oxepan-3-ol. The alkylation of an anion equivalent of diethyl fumarate with a homoallylic halide and the acid catalysed cyclisation of an epoxy-diol to give, under optimised conditions, only the desired oxepane derivative were the key steps. Chapter Three is concerned with some attempted routes to zoapatanol, using geraniol as the starting material. Functionalisation at the 10-position was achieved by reaction with hypochlorous acid, terminal epoxidation or reaction with selenium dioxide. The ultimate failure of these approaches was due to a lack of stereospecificity in the onecarbon homologation at the 1-position. A successful synthesis of zoapatanol is the subject of Chapter Four. Carboalumination of 7-benzyloxy-6-methylhept-l-yne and quenching of the vinyl alane with ethylene oxide produced the key homoallylic alcohol. By the use of a similar sequence of reactions to that employed in the model compound synthesis, this alcohol was transformed into an epoxydiol which was cyclised to give an oxepane derivative with a functionalised side chain. Further elaboration afforded the title compound.

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