Organisch Chemisches Institut, Westfälische Wilhelms-Universität Münster, Correnstraße 40, 48149, Münster, Germany.
Chemistry. 2018 Nov 2;24(61):16266-16270. doi: 10.1002/chem.201804416. Epub 2018 Oct 12.
To sustain innovation in glycobiology, effective routes to well-defined carbohydrate probes must be developed. For over a century, glycosylation has been dominated by the formation of the anomeric Csp -O acetal junction in glycostructures. A dissociative mechanistic spectrum spanning S 1 and S 2 is frequently operational thereby reducing the efficiency. By reengineering this fundamental process, an orthogonal disconnection allows the acetal to be formed directly from the reducing sugar without the need for substrate pre-functionalisation. The use of stable aryliodonium salts facilitates a formal O-H functionalisation reaction. This allows lactols to undergo mild, metal-free O-arylation at ambient temperature. The efficiency of the transformation has been validated using a variety of pyranoside and furanoside monosaccharides in addition to biologically relevant di- and trisaccharides (up to 85 %). Fluorinated mechanistic probes that augment the anomeric effect were employed. It is envisaged that this strategy will prove expansive for the construction of complex acetals under substrate-based stereocontrol.
为了维持糖生物学的创新，必须开发出有效的方法来制备具有明确结构的碳水化合物探针。一个多世纪以来，糖基化一直由糖结构中形成的端基 Csp-O 缩醛键来主导。因此经常会出现跨越 S1 和 S2 的离解机理谱，从而降低了效率。通过对这个基本过程进行重新设计，正交断开允许缩醛直接从还原糖形成，而不需要对底物进行预官能化。使用稳定的芳基碘鎓盐促进了形式上的 O-H 官能化反应。这使得内脂可以在温和条件下，在金属自由条件下在室温下进行 O-芳基化。该转化的效率已通过各种吡喃糖苷和呋喃糖苷单糖以及生物相关的二糖和三糖（高达 85%）进行了验证。还使用了增强端基效应的氟化机理探针。预计这种策略将在基于底物的立体控制下构建复杂的缩醛方面具有广阔的应用前景。
