Synthesis of Isopulo'upone.

Abstract Two routes are reported for the synthesis of the title marine metabolite 1. The routes converge at the trienoic aldehyde 4, and are completed by chain extension to the tetraenoic ketone 5 and intramolecular Diels-Alder cyclization. - Daylight lamp irradiation offers a convenient means for converting a cis/trans mixture from a Wittig reaction into the pure trans isomer.