The Unique Reactivity of Conformationally Restricted Pyranosides

在温和的酸性条件下，含2，3-反式氨基甲酸酯基团的吡喃糖苷发生β-向α-方向的端基异构反应。异头碳和内部氧之间的键断裂并再环化。所产生的线性阳离子被捕获，以显示裂解模式的证据。通过对取代基效应的考察，发现氨基甲酸酯基中氮原子上的乙酰基对反应有显著的影响。此外，与吡喃糖苷2，3-反式氨基甲酸酯基团实现了高度的1，2-顺式自由基C-糖基化反应。

The pyranosides with 2, 3-trans carbamate group anomerized from theβ-to theα-direction under mild acidic conditions. The bond between anomeric carbon and internal oxygen is cleaved and re-cyclized. The generated linear cation is trapped in order to show the evidence of the cleavage pattern. After investigation of the substitutent effect, acetyl group on nitrogen of the carbamate group show the significant effect on the anomerization reaction. Furthermore, the high 1, 2-cis radical C-glycosylation reaction was achieved with pyranosides 2, 3-trans carbamate group.