silicon and cornexistin

The synthesis of 5-epi-hydroxycornexistin (44), a diastereoisomer of the herbicidal natural product hydroxycornexistin (2) has been completed. Palladium mediated sp(2)-sp(3) coupling of the stannane 25 and the chloride 31 and ring-closing metathesis of the resulting diene 32 has been used to construct the tricyclic lactone 34a, which possesses the nine-membered carbocyclic core found in the natural product, in good yield. The synthesis of 5-epi-hydroxycornexistin (44) has established the feasibility of using a furan as precursor for the cyclic anhydride unit present in the natural product and has demonstrated the viability of other late-stage transformations that will be used to prepare hydroxycornexistin (2).

Topics: Alkenes; Crystallography, X-Ray; Furans; Heterocyclic Compounds, 3-Ring; Lactones; Nitrobenzoates; Silicon; Stereoisomerism