The Isothiocyanato Moiety: An Ideal Protecting Group for the Stereoselective Synthesis of Sialic Acid Glycosides and Subsequent Diversification
作者:Appi Reddy Mandhapati、Salla Rajender、Jonathan Shaw、David Crich
DOI:10.1002/anie.201409797
日期:2015.1.19
preparation of a crystalline, peracetyl adamantanyl thiosialoside donor protected by an isothiocyanate group is described. On activation at −78 °C in the presence of typical carbohydrate acceptors, this donor gives high yields of the corresponding sialosides with exquisite α‐selectivity. The high selectivity extends to the 4‐O‐benzyl‐protected 3‐OH acceptors, which are typically less reactive and selective
描述了受异硫氰酸酯基团保护的结晶过乙酰基金刚烷基硫唾液酸苷供体的制备。在典型碳水化合物受体存在的情况下在 -78 °C 下激活时,该供体可产生高产率的相应唾液酸苷,并具有精致的 α-选择性。高选择性延伸至 4-O-苄基保护的 3-OH 受体,其反应性和选择性通常低于半乳糖 3,4-二醇。用三(三甲基甲硅烷基)硅烷或烯丙基三(三甲基甲硅烷基)硅烷处理α-唾液酸苷导致C5 → N5键被C → H或C → C键取代。异硫氰酸酯保护的唾液酸与硫代酸反应生成酰胺,而与胺反应生成硫脲,硫脲可以转化为胍。新供体观察到的非常高的 α 选择性和异硫氰酸酯功能的丰富化学性质大大扩展了唾液酸苷 5 位的优化范围。