Organic Synthesis Using Oxiranyl Anions

氧基阴离子是亲核的，它们与多种亲电试剂的反应为氧基直接引入有机分子提供了一种新的方法。本课题主要研究了氧基阴离子的生成、反应及其在天然产物合成中的应用。环氧砜与n- bui在THF中-100℃脱质子反应生成磺酰基稳定的氧基阴离子，与三氟甲烷磺酸酯（三氟酸酯）反应，得到高收率的偶联产物。6-内环化法合成多四氢吡喃化合物建立了一种合成多四氢吡喃的新方法。该方法涉及两个关键反应：(i)磺酰基稳定的氧酰阴离子与三酸酯的烷基化；（ii）在吸电子磺酰基的帮助下，酸促进羟基环氧砜的6-内环化。甲基取代6元环醚的合成。基于甲基取代羟基环氧砜的6-内环环化，提出了一种合成甲基与环氧相邻的四氢吡喃的一般方法。Hemibrevetoxin B是从赤潮生物裸子藻（Gymnodinium breve）培养细胞中分离得到的一种多环醚海洋毒素，具有独特的6,6,7,7-四环醚体系。采用氧基阴离子策略完成了半毒毒素B的正式全合成。

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.