The absolute configurations of two natural diterpene butenolides were confirmed through the synthesis of ent-16-hydroxycleroda-4(18),13-dien-15,16-olide (2) and ent-cleroda-4(18),13-dien-15,16-olide (3), enantiomers of the natural products, starting from (+)-hardwickiic acid (1).
(+)-hardwickiic acid; clerodane; butenolide; absolute configuration