Glycal Glycosylation and 2-Nitroglycal Concatenation, a Powerful Combination for Mucin Core Structure Synthesis
作者:Jürgen Geiger、B. Gopal Reddy、Gottfried A. Winterfeld、R. Weber、M. Przybylski、R. R. Schmidt
DOI:10.1021/jo061670b
日期:2007.6.1
3-O-glycosylated with O-(galactopyranosyl) trichloroacetimidates; depending on the protecting group pattern stereoselectively α- and β-linked disaccharides were obtained. With O-(2-azido-2-deoxyglucopyransyl) trichloroacetimidate as donor (compound 10A), glycosylation of 2 and of a 6-O-unprotected galactal derivative led in acetonitrile as solvent exclusively to a β(1−3)- and a β(1−6)-linked disaccharide, respectively
具有大的6- O- TIPS保护作用的3,4- O-未保护的半乳糖衍生物(化合物2)可以被O-(吡喃半乳糖基)三氯乙酰亚氨酸盐区域选择性地3- O-糖基化。根据保护基的模式,立体选择性地获得α-和β-连接的二糖。以O-(2-叠氮基-2-脱氧葡萄糖吡喃基)三氯乙酰亚氨酸酯为供体(化合物10A),对2和6- O进行糖基化-未保护的半乳糖衍生物在乙腈中仅作为溶剂分别引至β(1-3)-和β(1-6)连接的二糖。糖的半乳糖部分硝化,然后通过迈克尔型添加丝氨酸和苏氨酸衍生物(7a,b)安装了α-半乳糖构型,因此很容易提供O-糖基氨基酸结构单元,用于将核1,核2,核3,核6和核8结构掺入糖肽中。2-硝基半乳糖和2-硝基葡糖衍生物也可以成功地通过迈克尔型加成以重复方式成功地用于糖苷键的形成,从而提供了相应的核心5,核心7和核心6构件。在这种方法中,高度立体选择性的糖苷键的形成仅基于2-型硝基糖的硝基-烯醇