Synthesis of the Non-adjacent Bis-THF Core of Cis-sylvaticin Using a Double Oxidative Cyclisation

A short synthesis of the non-adjacent bis-THF core of the Annonaceous acetogenin cis-sylvaticin (1) is described. C(2) Symmetrical (Z,E,E,Z)- and (E,E,E,E)-tetraenes and were synthesised in six and three steps respectively from (1E,5E,9E)-cyclododeca-1,5,9-triene. Subsequent permanganate promoted asymmetric bi-directional oxidative cyclisation of tetraene was used to create the non-adjacent bis-THF core of 1, installing seven of the nine stereogenic centres present in the natural product in a single step. Desymmetrization of the oxidative cyclisation product by mono-tosylation gave access to a C11-C32 fragment of cis-sylvaticin.