Leiden Institute of Chemistry, Leiden University, P.O. Box 9502, 2300 RA Leiden (The Netherlands).
Angew Chem Int Ed Engl. 2015 Jun 22;54(26):7670-3. doi: 10.1002/anie.201502581. Epub 2015 May 8.
The total synthesis of mixed-sequence alginate oligosaccharides, featuring both β-D-mannuronic acid (M) and α-L-guluronic acid (G), is reported for the first time. A set of GM, GMG, GMGM, GMGMG, GMGMGM, GMGMGMG, and GMGGMG alginates was assembled using GM building blocks, having a guluronic acid acceptor part and a mannuronic acid donor side to allow the fully stereoselective construction of the cis-glycosidic linkages. It was found that the nature of the reducing-end anomeric center, which is ten atoms away from the reacting alcohol group in the key disaccharide acceptor, had a tremendous effect on the efficiency with which the building blocks were united. This chiral center determines the overall shape of the acceptor and it is revealed that the conformational flexibility of the acceptor is an all-important factor in determining the outcome of a glycosylation reaction.
首次报道了具有β-D-甘露糖醛酸（M）和α-L-古洛糖醛酸（G）的混合序列褐藻酸盐寡糖的全合成。一组 GM、GMG、GMGM、GMGMG、GMGMGM、GMGMGMG 和 GMGGMG 褐藻酸盐使用 GM 构建块组装，这些构建块具有古洛糖醛酸受体部分和甘露糖醛酸供体侧，以允许顺式糖苷键的完全立体选择性构建。结果发现，与反应醇基团相隔十个原子的还原端非端中心的性质对构建块结合的效率有巨大影响。这个手性中心决定了受体的整体形状，揭示了受体的构象灵活性是决定糖苷化反应结果的一个至关重要的因素。
