"Super Armed" Glycosyl Donors: Conformational Arming of Thioglycosides by Silylation

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• 作者：Christian Marcus Pedersen ; Lars Ulrik Nordstr//pubs.acs.org/images/gifchars/oslash.gif" border="0">m ; Mikael Bols
• 刊名：Journal of the American Chemical Society
• 出版年：2007
• 出版时间：July 25, 2007
• 年：2007
• 卷：129
• 期：29
• 页码：9222 - 9235
• 全文大小：289K
• 年卷期：v.129,no.29(July 25, 2007)
• ISSN：1520-5126

文摘

Glycosyl donors protected with bulky silyl protective groups (tert-butyldimethylsilyl, TBS), on the2-, 3-, and 4-OH groups were found to have superior reactivity compared with benzylated thioglucosides.The enhanced reactivity is explained by the stereoelectronic effects associated with the conformationalchange induced by the silylation. A TBS silylated thioglucoside donor has axial OR groups, whereas abenzylated thioglucoside has equatorial OR groups, leading to much more favorable charge-dipoleinteractions in the transition state. This concept could be used to create "super armed" glucosyl, mannosyl,rhamnosyl, and galactosyl donors, which could cross-couple with the armed acceptors, phenyl 2,3,4-tri-O-benzyl--D-thioglucoside or phenyl 2,3,6-tri-O-benzyl--D-thioglucoside, to give the corresponding armeddisaccharides in good to excellent yields.