Six-Step Synthesis of Alcyopterosin A, a Bioactive Illudalane Sesquiterpene with a <i>gem</i>-Dimethyl­cyclopentane Ring

Strategic pairing of ring openings and cycloisomerization provides rapid and efficient “open and shut” entry into sparsely functionalized illudalanes, as exemplified here in the context of a six-step synthesis of alcyopterosin A. Key steps include a tandem ring-opening fragmentation/olefination process for preparing a neopentyl-tethered 1,6-enyne, ring-opening olefination telescoped with alkyne homologation, and Rh-catalyzed oxidative cycloisomerization