| The naturally occurring polyacetylenes Bupleurynol and (2E,8 E,10E)-heptadeca-2,8,10-triene-4,6-diyn-1-ol were synthesized in a convergent and stereospecific manner using a series of metal-mediated cross-coupling reactions. These syntheses demonstrate the utility of using a di-functional olefin template building block for the stereospecific synthesis of a disubstituted alkene product and its elaboration to a natural product target.; The syntheses utilize E-iodochloroethylene in a 'lynchpin' approach to guarantee the requisite E stereochemistry of the natural product. Palladium- and copper-catalyzed cross-coupling reactions form the body of the molecules, while hydroboration is used to create, in a stereospecific fashion, both cis and trans olefin constructs.; Hydrozirconation is used in a proposed 'second-generation' approach. This approach makes the synthetic route a tandem process, whereby an sp2-sp2 coupling is followed, in the same pot, by an sp2-sp coupling.; The synthetic route is developed from a 'first-generation' 13-step pathway, to a 'second-generation' 6-step pathway. |
