Radical-mediated transformations have emerged as powerful methods for the synthesis of rare and unnatural branched, deoxygenated, and isomeric sugars. Here, we describe a radical-mediated axial-to-equatorial alcohol epimerization method to transform abundant glycans into rare isomers. The method delivers highly predictable and selective reaction outcomes that are complementary to other sugar isomerization methods. The synthetic utility of isomer interconversion is showcased through expedient glycan synthesis, including one-step glycodiversification. Mechanistic studies reveal that both site- and diastereoselectivities are achieved by highly selective H atom abstraction of equatorially disposed α-hydroxy C–H bonds.

中文翻译：

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碳水化合物的选择性轴向到赤道差向异构化

自由基介导的转化已成为合成稀有和非天然支链、脱氧和异构糖的有效方法。在这里，我们描述了一种自由基介导的轴向到赤道醇差向异构化方法，可将丰富的聚糖转化为稀有异构体。该方法提供高度可预测和选择性的反应结果，与其他糖异构化方法互补。异构体相互转化的合成效用通过方便的聚糖合成展示，包括一步糖多样化。机理研究表明，位点选择性和非对映选择性都是通过赤道位置的 α-羟基 C-H 键的高选择性 H 原子提取来实现的。