The efficient entry into the tricyclic core of halichlorine

An efficient and diastereoselective synthesis of the tricyclic core structure 3 found in the marine alkaloid halichlorine 1 has been accomplished starting from Grigg’s tricyclic isoxazolidine 5, which was prepared by the tandem intramolecular Michael addition–[3+2] cycloaddition of the corresponding oxime of 4.