Stereocontrolled Synthesis of Heterocyclic C-Nucleosides. Protecting Group Effect and Molecular Modeling Studies
作者:Dominique Guianvarc'h、Jean-Louis Fourrey、Marie-Elise Tran Huu Dau、Vincent Guérineau、Rachid Benhida
DOI:10.1021/jo016345x
日期:2002.5.1
We report herein a short stereocontrolled synthesis of heterocyclic C-nucleosides (indole, imidazole, benzimidazole, and 6-iodobenzimidazole). First, condensation of 2-lithiated heterocycles 2-5 with 5-(tert-butyldiphenylsilyl)-2,3-O-isopropylidene-D-gamma-ribonolactone (1) afforded the hemiacetals 6-9 in good yields. Then, borohydride reduction (NaBH(4)) of the protected hemiacetals proceeded stereoselectively
我们在此报告了杂环C-核苷(吲哚,咪唑,苯并咪唑和6-碘代苯并咪唑)的短立体控制合成。首先,2-锂化的杂环2-5与5-(叔丁基二苯基甲硅烷基)-2,3-O-异亚丙基-D-γ-核糖内酯(1)的缩合以高收率得到半缩醛6-9。然后,将受保护的半缩醛的硼氢化物还原反应(NaBH(4))立体选择性地进行,主要得到S二醇10-13,经Mitsunobu环化,得到的α-C-核苷14-17。相反,相同的PPh(3)/ DEAD处理游离杂环二醇10d和11d的1:1非对映混合物,分别通过立体控制过程分别获得了β-端基异构体14dbeta和15dbeta。在分子模型研究的支持下,讨论了这些立体控制步骤的机理。