Stereocontrolled Total Synthesis of (−)-Isocelorbicol and Its Elaboration to Natural Dihydro-β-agarofuran Esters

The first total synthesis of four naturally occurring dihydro-β-agarofuran esters has been accomplished via a highly stereocontrolled 14-step access to their common core triol, (−)-isocelorbicol. A semipinacol rearrangement of an epoxy alcohol to install a quaternary carbon, diastereoselective conjugate reduction of a spirocyclic butenolide for the establishment of a methyl-bearing chiral center, and ring-closing metathesis to construct the decalin ring system were exploited as the key steps for the high-yielding synthesis of (−)-isocelorbicol.