Synthesis of (.+-.)-costunolide, an antitumor germacranolide, from E,E-farnesol by use of a low-valent chromium reagent.
E,E-Farnesol was transformed into ω-bromo-farnesal, which cyclized to afford a racemic germacrane-type compound (5) with a low-valent chromium reagent 5 was then converted to (±)-dihydrocostunolide and (±)-costunolide.