Preparation of Sialyl Donors Carrying Functionalized Ester Substituents: Effects on the Selectivity of Glycosylation
Preparation of Sialyl Donors Carrying Functionalized Ester Substituents: Effects on the Selectivity of Glycosylation
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DOI：
10.1055/s-2003-40332
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发表时间：
2003-06
期刊：
影响因子：
2
通讯作者：
A. Ishiwata;Yukishige Ito
中科院分区：
文献类型：
--
作者：
A. Ishiwata;Yukishige Ito
系统地制备了具有各种酯取代基的甲硫基唾液酸供体。用Ph 3SiSH和CS2 CO 3对甲酯进行亲核取代，然后与RX进行原位烷基化或与R-OH/DCC进行酯化反应，以较好的产率得到这些化合物。研究了由NIS-TfOH促进的糖基化，以检查酯部分的取代基的影响。当在乙腈中进行时，观察到氰基甲基酯、2-氰基乙基酯、2-氰基苄基酯和2-硝基苄基酯的α-选择性增强，这意味着这些取代基有效地增强乙腈的溶剂效应，这可能是通过稳定β-取向的亚硝酸根离子。
Methylthio sialyl donors having various ester substituents were prepared systematically. Nucleophilic displacement of methyl ester with Ph 3 SiSH and CS 2 CO 3 followed by in situ alkylation with RX or esterification with R-OH/DCC afforded these compounds in good yields. Glycosylations promoted by NIS-TfOH were examined in order to examine the effect of substituent of the ester portion. When conducted in CH 3 CN, enhanced α-selectivities were observed for cyanomethyl, 2-cyanoethyl, 2-cyanobenzyl, and 2-nitrobenzyl esters, implying that these substituents are effective enhancing the solvent effect of acetonitrile, possibly by stabilizing the β-oriented nitrilium ion.