A straightforward access to the C10âC20 skeleton of gymnodimine, incorporating a tetrahydrofuran fragment, is described. The elaboration of the THF moiety is based on a stereocontrolled UenoâStork cyclization. A Lewis-acid mediated allylation of the resulting acetal at C13 and a HornerâWadsworthâEmmons olefination on the ketone at C17 complete the synthesis.