Organic Synthesis Using Oxiranyl Anions

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Oxiranyl anions are nucleophilic and their reaction with a variety of electrophiles provides a new methodology for introducing an oxiranyl group directly into organic molecules. The generation and reaction of oxiranyl anions and their applications to natural product synthesis were carried out in this project.1. Alkylation of oxiranyl anionsSulfonyl-stabilized oxiranyl anions, gerenated by deprotonation of the corresponding epoxy sulfones with n-BuLi in THF at -100℃, reacted with trifluoromethanesulfonate esters (triflate) to give the coupled products in high yield.2. Synthesis of polytetrahydropyrans by 6-endo cyclizationThe new method for the synthesis of trans-fused polytetrahydropyrans was developed. The approach involves two key reactions : (i) alkylation of a sulfonyl-stabilized oxiranyl anion with a triflate, (ii) acid-promoted 6-endo cyclization of the resulting hydroxy epoxy sulfone assisted by the electron-withdrawing sulfonyl group.3. Synthesis of methyl-substituted 6 membered cyclic ethers.A general procedure for the synthesis of tetrahydropyrans having methyl groups adjacent to the ring oxygen was developed based on the 6-endo cyclization of methyl-substituted hydroxy epoxy sulfones.4. Synthesis of Hemibrevetoxin BHemibrevetoxin B is one of polycyclic ether marine toxins isolated from the cultured cells of the red tide organism Gymnodinium breve and has the unique 6,6,7,7-tetracyclic ether ring system. The formal total synthesis of hemibrevetoxin B was accomplished by using oxiranyl anion strategy.