Stereocontrolled Nucleophilic Addition to Five-Membered Oxocarbenium Ions Directed by the Protecting Groups. Application to the Total Synthesis of (+)-Varitriol and of Two Diastereoisomers Thereof
作者:Alma Sánchez-Eleuterio、William H. García-Santos、Howard Díaz-Salazar、Marcos Hernández-Rodríguez、Alejandro Cordero-Vargas
DOI:10.1021/acs.joc.7b01211
日期:2017.8.18
stereodivergent C-glycosidation of carbohydrate-derived lactones can be mediated by the protecting groups and applied to the total synthesis of (+)-varitriol and of two diastereoisomers thereof, which represent an unprecedent use of the protecting groups in the synthesis of a naturally occurring compound. In particular, the stereoselective nucleophile attack for 2,3-trans-substituted five-membered ring
碳水化合物衍生的内酯的立体发散的C-糖基化可以由保护基团介导,并应用于(+)-varitriol及其两个非对映异构体的总合成,这代表了保护基团在天然合成中的前所未有的用途。发生的化合物。特别地,保护基团中芳环的存在强烈影响对2,3-反式取代的五元环氧碳鎓离子的立体选择性亲核体攻击。根据量子化学计算,立体选择性取决于带有环外三键的C-2保护基的芳环与氧碳鎓离子之间的π-π相互作用。这些相互作用说明了其中C-2和C-3取代基采用伪轴向取向的构象异构体的稳定性。当保护基不包含芳环时,立体化学结果取决于Woerpel模型建立的立体电子因素。基于这些发现,完成了天然产物(+)-水三酚和两种非对映异构体的简明全合成。