O-sialylation with N-acetyl-5-N,4-O-carbonyl-protected thiosialoside donors in dichloromethane:: Facile and selective cleavage of the oxazolidinone ring
O-sialylation with N-acetyl-5-N,4-O-carbonyl-protected thiosialoside donors in dichloromethane:: Facile and selective cleavage of the oxazolidinone ring
复制标题
DOI：
10.1021/jo062431r
复制
发表时间：
2007-03-30
影响因子：
3.6
通讯作者：
Li, Wenju
中科院分区：
文献类型：
--
作者：
Crich, David;Li, Wenju
制备了N-乙酰基-5-N，4-O-羰基保护的硫代唾液酸苷供体，其结构已通过X射线晶体学确定，并在与各种受体的偶联中进行了测试。该供体在与各种伯烷基和碳水化合物受体的连接中在N-碘代琥珀酰亚胺和三氟甲磺酸原位活化方法下在-40 ℃在二氯甲烷中给出优异的产率和α-选择性。恶唑烷酮亚结构对α-唾液酸化的有利影响通过与N，N-二乙酰基唾液酸供体的比较研究来说明，该供体表现出较差的产率和α-选择性。在NIS/TfOH活化方法下，唾液酸化选择性与供体的异头构型无关，但与反应温度高度相关。与NIS/TfOH方法相反，Ph 2SO/Tf 2 O促进在二氯甲烷中产生β-选择性偶联。N-乙酰基-5-N，4-O-羰基保护的唾液酸糖苷（α-和β-端基异构体）的恶唑烷酮可以通过在温和条件下用甲醇钠处理而干净地裂解，而不除去乙酰胺。
An N-acetyl-5-N,4-O-carbonyl-protected thiosialoside donor, the structure of which has been defined through X-ray crystallography, was prepared and tested in couplings to a wide range of acceptors. This donor gives excellent yields and alpha-selectivities in linking with various primary alkyl and carbohydrate acceptors under the N-iodosuccinimide and trifluoromethanesulfonic acid in situ activation method at -40 degrees C in dichloromethane. The favorable affect of the oxazolidinone substructure for alpha-sialylation is illustrated by a comparison study with a N,N-diacetylsialyl donor, which exhibited inferior yields and alpha-selectivities. The sialylation selectivity is independent of the anomeric configuration of the donor, but is highly related to the reaction temperature under the NIS/TfOH activation method. In contrast to the NIS/TfOH method, the Ph2SO/Tf2O promotion gives beta-selective couplings in dichloromethane. The oxazolidinone of the N-acetyl-5-N,4-O-carbonyl protected sialosides, both alpha- and beta-anomers, could be cleaved cleanly by treatment with sodium methoxide under mild conditions without removal of the acetamide.