Highly α- and β-Selective Radical<i> C</i>-Glycosylation Reactions Using a Controlling Anomeric Effect Based on the Conformational Restriction Strategy. A Study on the Conformation−Anomeric Effect− Stereoselectivity Relationship in Anomeric Radical Reactions
作者:Hiroshi Abe、Satoshi Shuto、Akira Matsuda
DOI:10.1021/ja011321t
日期:2001.12.1
stereoselectivity of anomeric radical reactions was significantly influenced by the 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. Thus, the conformationally restricted 1-phenylseleno-D-xylose
我们假设,由于异头自由基反应的立体选择性受到异头效应的显着影响,这可以通过限制自由基中间体的构象来控制,因此对底物吡喃糖环的适当构象限制将使高度α-和β-立体选择性异头自由基反应是可能的。因此,设计了构象受限的 1-苯基硒-D-木糖衍生物 9 和 10,受限于 (4)C(1)-构象,以及受限于 (1)C(4)-构象的 11 和 12并通过在吡喃糖环上的羟基上引入适当的保护基团作为异头自由基反应的模型底物合成。Bu(3)SnD 的自由基氘化和 Bu(3)SnCH(2)CH [双键] CH(2) 或 CH(2) [双键] CHCN 的 C-糖基化,使用 (4)C( 1)-限制性底物 9 和 10,高度立体选择性地提供相应的 α-产物 (α/β = 97:3-85:15),而 (1)C(4)-限制性底物 11 和 12 选择性地产生β - 产品(alpha/beta = 1:99-0:100)。