Abstract
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.
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