Department of Chemistry and Biochemistry, University of Colorado Boulder, Boulder, CO, 80309, USA.
Nat Commun. 2018 Sep 7;9(1):3650. doi: 10.1038/s41467-018-06016-4.
Oligosaccharides, one of the most abundant biopolymers, are involved in numerous biological processes. Although many efforts have been put in preparative carbohydrate chemistry, achieving optimal anomeric and regioselectivities remains challenging. Herein we describe an oxidative glycosylation method between anomeric stannanes and oxygen nucleophiles resulting in the formation of a C-O bond with consistently high anomeric control for glycosyl donors bearing a free C2-hydroxyl group. These reactions are promoted by hypervalent iodine reagents with catalytic or stoichiometric amounts of Cu or Zn salts. The generality of this transformation is demonstrated in 42 examples. Mechanistic studies indicate that the oxidative glycosylation is initiated by the hydroxyl-guided delivery of the hypervalent iodine and tosylate into the anomeric position, and results in excellent 1,2-trans selectivity. The unique mechanistic paradigm, high selectivities, and mild reaction conditions make this method suitable for the synthesis of oligosaccharides and for integration with other methodologies such as automated synthesis.
寡糖是最丰富的生物聚合物之一，参与许多生物过程。尽管在制备碳水化合物化学方面已经做出了许多努力，但实现最佳的端基和区域选择性仍然具有挑战性。在此，我们描述了一种在端基锡烷和氧亲核试剂之间的氧化糖基化方法，该方法导致具有游离 C2-羟基的糖基供体形成 C-O 键，具有一致的高端基控制。这些反应由高价碘试剂在催化或化学计量量的 Cu 或 Zn 盐的促进下进行。该转化的通用性在 42 个实例中得到了证明。机理研究表明，氧化糖基化是由高价碘和亲核试剂在羟基引导下进入端基位置引发的，导致优异的 1,2-反式选择性。这种独特的机理范例、高选择性和温和的反应条件使该方法适用于寡糖的合成，并可与其他方法（如自动化合成）集成。
