Based on a preactivation protocol with (p-Tol)2SO/Tf2O, a practical, straightforward, and high-yielding synthesis of α-sialyl C-glycosides was accomplished by coupling N-acetyl-5-N,4-O-oxazolidione protected thiosialoside with various trimethylsilyl enol ethers and allyltrimethylsilanes. High yields and excellent α-selectivities were obtained for the strong Ï-nucleophiles with large nucleophilicity values (N = 4.4â9.0), irrespective of whether silyl enol ethers, silyl ketene acetals or allyltrimethylsilanes were used for the electrophilic C-sialylation.
基于(p-Tol)2SO/Tf2O预活化策略,通过N-乙酰基-5-N,4-O-
恶唑烷酮保护的
硫代
唾液酸与各种三甲基
硅基烯醇醚及烯丙基三甲基
硅烷的偶联反应,实现了α-
唾液酸型C-糖苷的实用、简便及高产率合成。对于具有大亲核性值(N = 4.4–9.0)的强π-亲核试剂,无论是
硅醚烯醇、
硅醚
乙缩醛还是烯丙基三甲基
硅烷作为亲电C-
唾液酸化试剂,均能获得高产率和极佳的α-选择性。