Synthetic Studies on Perophoramidine and the Communesins: Construction of the Vicinal Quaternary Stereocenters

An efficient synthetic strategy for installation of the two vicinal quaternary carbon centers of the
communesins 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 effects
on the stereochemical outcome of the Claisen rearrangements have been examined. The stereochemical
assignment of the allyl spirolactone previously reported as 17 has now been revised to 31, which has the
communesin relative configuration at the quaternary carbons. Key C-allyl spirolactone 59 bearing functional
handles required for the communesin core has been constructed with a 9.8:1 diastereomer ratio.