A general strategy for synthesis of both (6Z)- and (6E)-cladiellin diterpenes: total syntheses of (-)-cladiella-6,11-dien-3-ol, (+)-polyanthellin A, (-)-cladiell-11-ene-3,6,7-triol, and (-)-deacetoxyalcyonin acetate

The first total synthesis of an (E)-cladiellin diterpene, (-)-cladiella-6,11-diene-3-ol (1), was accomplished featuring an intramolecular amide enolate alkylation-intramolecular Diels-Alder strategy. In addition, a highly stereo-, regio-, and chemoselective synthetic strategy for other members of the cladiellin diterpenes such as (+)-polyanthellin A (2), (-)-cladiell-11-ene-3,6,7-triol (3), and (-)-deacetoxyalcyonin acetate (4) was developed utilizing the synthetic (E)-cladiellin 1 as a common intermediate by taking advantage of the unique chemical properties of its C(6)-(E)-oxatricyclic skeleton.