A Study on the Conformation−Anomeric Effect−Stereoselectivity Relationship in Anomeric Radical Reactions, Using Conformationally Restricted Glucose Derivatives as Substrates
作者:Hiroshi Abe、Masaru Terauchi、Akira Matsuda、Satoshi Shuto
DOI:10.1021/jo030128+
日期:2003.9.1
that, since the stereoselectivity of anomeric radical reactions is significantly influenced by the kinetic anomeric effect, which can be controlled by restricting the conformation of the radical intermediate, the proper conformational restriction of the pyranose ring of the substrates would therefore make highly alpha- and beta-stereoselective anomeric radical reactions possible. This theory was based
我们先前的理论认为,由于异头自由基反应的立体选择性受到动力学异头作用的显着影响,可以通过限制自由基中间体的构象来控制,因此底物吡喃糖环的适当构象限制将使α -和β-立体选择性异头自由基反应是可能的。该理论基于我们先前以d-木糖衍生物为底物的端基自由基反应的结果。我们在本文中报道了构象受限的1-苯基硒代d-葡萄糖衍生物2g和3g(受O环双缩酮部分限制在(4)C(1)-构象中)和4g,5g的异头自由基氘化反应。 6g,7g和8g受庞大的O-甲硅烷基保护基团限制在(1)C(4)构象中。使用(4)C(1)限制的底物2g和3g,用Bu(3)SnD进行的自由基氘化可高度立体选择性地提供相应的alpha产物(alpha / beta = 98:2),而(1)C (4)-限制的底物6g具有在5位上的三角形(sp(2))碳取代基,即-CHO,选择性地产生β-产物(α/β= 0:100)。因此,立体选择性由于