Evidence for Endocyclic Cleavage of Conformationally Restricted Glycopyranosides
Evidence for Endocyclic Cleavage of Conformationally Restricted Glycopyranosides
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DOI：
10.1002/chem.200900064
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发表时间：
2009-01-01
影响因子：
4.3
通讯作者：
Ito, Yukishige
中科院分区：
文献类型：
--
作者：
Manabe, Shino;Ishii, Kazuyuki;Ito, Yukishige
与其它吡喃糖苷相比，在刘易斯酸存在下，携带2，3-反式-氨基甲酸酯-和-碳酸酯-的吡喃糖苷非常容易从β向α方向进行端基异构化。该反应由吡喃糖苷的内环裂解引起。内环裂解的构象限制的吡喃糖苷在椅子形式的证据是通过内和分子间的Friedel-Crafts反应，氯化物加成，并减少所产生的阳离子。另一方面，具有扭曲构象的吡喃糖苷从未以内环方式裂解。
2,3-trans-carbamate- and -carbonate-carrying pyranosides were very easily anomerised from the beta to the alpha direction in the presence of a Lewis acid compared to other pyranosides. This reaction is caused by endocyclic cleavage of the pyranosides. Evidence for endocyclic cleavage of conformationally restricted pyranosides in the chair form was obtained by intra- and intermolecular Friedel-Crafts reactions, chloride addition, and reduction of the generated cation. On the other hand, pyranosides with the distorted conformation were never cleaved in an endocyclic manner.