Stereoselective Synthesis of Donor-Acceptor Cyclopropapyranone by Intramolecular Cyclopropanation of Vinylogous Carbonates: Application to the Total Synthesis of (+/-)-Diospongin B

An intramolecular, stereoselective cyclopropanation of vinylogous carbonates with carbenes using copper catalyst is developed for the synthesis of donor-acceptor substituted cyclopropapyranones. Completely regioselective ring cleavage of each of the cyclopropane bonds was achieved under suitable reaction conditions, leading to a diverse array of cyclic ethers. The developed method is utilized in the total synthesis of (+/-)-diospongin B