A privileged Glycon! A radical‐addition Meerwein–Ponndorf–Verley (MPV) reduction sequence provides access to functionalizedα‐CF2‐galactosides (see scheme). Introduction of a CF2Br group in the pseudo‐anomeric position aided the transfer of an aglycon chain from O‐2 to C‐1′ through an intramolecular addition–reduction sequence, which involved a Br–Li exchange. This methodology gives access to a wide
Addition of Electrophilic Radicals to 2-Benzyloxyglycals: Synthesis and Functionalization of Fluorinated α-<i>C</i>-Glycosides and Derivatives
作者:Sophie Colombel、Nathalie Van Hijfte、Thomas Poisson、Eric Leclerc、Xavier Pannecoucke
DOI:10.1002/chem.201302070
日期:2013.9.16
A new method for the synthesis of fluorinated α‐C‐glycosides is described. The reactions between highly electrophilicradicals (fluorinated or unfluorinated) and a 2‐benzyloxyglucal or galactal provide 2‐keto‐D‐arabino‐ or 2‐keto‐D‐lyxo‐hexopyranosides through an addition/fragmentation process. Sodium borohydride mediated or Meerwein–Ponndorf–Verley (MPV) reduction of these compounds provides α‐C‐glycosides
描述了一种合成氟化α- C-糖苷的新方法。高亲电子基团(氟化或未氟化)与2-苄氧基葡萄糖或半乳糖之间的反应通过加成/分解过程提供了2-酮基-D-阿拉伯糖基或2-酮基-D-己基-吡喃吡喃糖苷。这些化合物的硼氢化钠介导的或Meerwein-Ponndorf-Verley(MPV)还原可提供具有适当锚定基团的α- C-糖苷,以进行进一步的合成修饰。CF 2 CO 2 i Pr或CF 2的存在假异头位置的Br基团可实现有效的还原/烯化或Br / Li交换/亲核加成序列。这些转变为糖缀合物的氟化C糖苷类似物的合成开辟了道路。
Synthesis of 2′,3′-Dideoxy-2′-Fluoro-4′-Thionucleosides from a Fluoroxanthate
The synthesis of a thiobutyrolactone as precursor of modified nucleosides is reported from a fluoroxanthate and a protected allylic alcohol. This approach opens a new and straightforward route for the synthesis of 2',3'-dideoxy-2'-fluoro-4'-thiothymidine derivatives in few steps, including the formation of a fluorothiolactone and a Vorbruggen thymine base alkylation reaction.
Inexpensive Radical Methylation and Related Alkylations of Heteroarenes
作者:Qi Huang、Samir Z. Zard
DOI:10.1021/acs.orglett.8b00190
日期:2018.3.2
A simple method for the introduction of a methyl and higher aliphatic group to various heteroarenes using very inexpensive reagents is described. It is based on the radical addition of a carboxylic xanthate followed by decarboxylation. Depending on the heteroarene structure, the decarboxylation can be spontaneous or induced by heating in N,N-dimethylacetamide or N-methyl pyrrolidone in a microwave
tetrahydrofuran derivatives is reported from S-alkyl dithiocarbonates. The study of the group transfer reaction fromxanthates and alkenes afforded intermediate S-alkyl dithiocarbonates. From 2,3-dihydrofuran derivatives, the displacement of the resulting anomeric xanthates with various nucleophiles in the presence of Lewis acid allowed the formation of new carbon−carbon and carbon−heteroatom bonds