Intramolecular 1,8-Hydrogen-Atom Transfer Reactions in (1→4)-<i>O</i>-Disaccharide Systems: Conformational and Stereochemical Requirements
作者:Cosme G. Francisco、Antonio J. Herrera、Alan R. Kennedy、Angeles Martín、Daniel Melián、Inés Pérez-Martín、Luis M. Quintanal、Ernesto Suárez
DOI:10.1002/chem.200801414
日期:2008.11.17
stereochemical and conformational factors controlling the intramolecular hydrogen-atom transfer (HAT) reaction between the two pyranose units in a (1-->4)-O-disaccharide when promoted by a primary 6-O-yl radical are studied. Models with alpha-D-Glcp-(1-->4)-beta-D-Glcp, alpha-L-Rhamp-(1-->4)-alpha-D-Galp or alpha-D-Manp-(1-->4)-beta-L-Gulp skeletons led exclusively to the abstraction of the hydrogen from H--C-5'
研究了由伯6-O-基团促进时控制(1-> 4)-O-二糖中两个吡喃糖单元之间分子内氢原子转移(HAT)反应的立体化学和构象因素。具有alpha-D-Glcp-(1-> 4)-beta-D-Glcp,alpha-L-Rhamp-(1-> 4)-alpha-D-Galp或alpha-D-Manp-(1的模型-> 4)-β-L-Gulp骨架仅导致从H--C-5'提取氢并通过九元过渡态形成1,3,5-三氧杂环丁烷环系统以稳定的船椅构造为基础。尽管如此,α-L-Rhamp-(1-> 4)-alpha-D-Glcp或alpha-D-Manp-(1-> 4)-alpha-D-Galp的衍生物专门从H- -C-1'通过七元过渡态产生糖苷间螺原酸酯。