An efficient synthetic strategy for installation of the two vicinal quaternary carbon centers of thecommunesins is reported. Key steps include the O-allylation/Claisen rearrangement of spirolactone systems,which are formed by tandem intramolecular Heck cyclization/carbonylation. Substituent and solvent effectson the stereochemical outcome of the Claisen rearrangements have been examined. The stereochemicalassignment of the allyl spirolactone previously reported as
17 has now been revised to
31, which has thecommunesin relative configuration at the quaternary carbons. Key
C-allyl spirolactone
59 bearing functionalhandles required for the communesin core has been constructed with a 9.8:1 diastereomer ratio.
