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.