Leiden University, Leiden Institute of Chemistry, Einsteinweg 55, 2333 CC, Leiden, The Netherlands.
Radboud University Institute for Molecules and Materials, Heyendaalseweg 135, 6525 AJ, Nijmegen, The Netherlands.
Nat Commun. 2020 May 29;11(1):2664. doi: 10.1038/s41467-020-16362-x.
Controlling the chemical glycosylation reaction remains the major challenge in the synthesis of oligosaccharides. Though 1,2-trans glycosidic linkages can be installed using neighboring group participation, the construction of 1,2-cis linkages is difficult and has no general solution. Long-range participation (LRP) by distal acyl groups may steer the stereoselectivity, but contradictory results have been reported on the role and strength of this stereoelectronic effect. It has been exceedingly difficult to study the bridging dioxolenium ion intermediates because of their high reactivity and fleeting nature. Here we report an integrated approach, using infrared ion spectroscopy, DFT computations, and a systematic series of glycosylation reactions to probe these ions in detail. Our study reveals how distal acyl groups can play a decisive role in shaping the stereochemical outcome of a glycosylation reaction, and opens new avenues to exploit these species in the assembly of oligosaccharides and glycoconjugates to fuel biological research.
控制糖化学的糖苷化反应仍然是寡糖合成的主要挑战。尽管可以使用邻基参与来引入 1,2-反式糖苷键，但 1,2-顺式键的构建很困难，且尚无通用解决方案。远程参与（LRP）通过远端酰基可能会控制立体选择性，但关于这种立体电子效应的作用和强度已有相互矛盾的报道。由于 bridging dioxolenium 离子中间体的高反应性和短暂性质，研究它们极其困难。在这里，我们报告了一种综合方法，使用红外离子光谱、DFT 计算和一系列糖苷化反应来详细研究这些离子。我们的研究揭示了远端酰基如何在糖基化反应的立体化学结果中发挥决定性作用，并为在寡糖和糖缀合物的组装中利用这些物质以推动生物研究开辟了新途径。
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