The first synthesis of (−)-isoambreinolide, (+)-vitexifolin D and (+)-vitedoin B

A very efficient method for synthesizing spirolactones is reported. Treatment of δ,e-unsaturated carboxylic acids with iodine and triphenylphosphine under mild conditions leads to the corresponding spiro γ-lactones in high yield and with complete stereoselectivity. Utilizing this, the first synthesis of the terpene spirolactones (−)-isoambreinolide, (+)-vitexifolin D and (+)-vitedoin B has been achieved.