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Synthetic oligosaccharides related to Group B streptococcal polysaccharides. The rhamnotriose moiety of the common antigen

 

作者: Vince Pozsgay,   Jean-Robert Brisson,   Harold J. Jennings,  

 

期刊: Canadian Journal of Chemistry  (NRC Available online 1987)
卷期: Volume 65, issue 12  

页码: 2764-2769

 

ISSN:0008-4042

 

年代: 1987

 

DOI:10.1139/v87-459

 

出版商: NRC Research Press

 

数据来源: NRC

 

摘要:

The methyl glycoside (1) of the α-L-Rhap-(1 → 2)-α-L-Rhap-(1 → 2)-α-L-Rhap-(1 → portion of the group-specific, common antigen polysaccharide of Group B Streptococci has been synthesized. The key compound of the synthesis was methyl 3,4-di-O-benzyl-α-L-rhamnopyranoside (4). Controlled acetolysis of4gave 1,2-di-O-acetyl-3,4-di-O-benzyl-α-L-rhamnopyranose (10), which upon reaction with4under catalysis by trimethylsilyl trifluoromethanesulfonate (TMS-Tf) yielded the α-(1 → 2)-linked dirhamnoside. Subsequent rhamnosylation followed by deprotection gave1. TMS-Tf was also used in rhamnosylation reactions with tetra-O-acetyl-α-L-rhamnopyranose. Acetylation of acceptor alcohols was found to be a major side reaction in the TMS-Tf assisted glycosylations. One-dimensional nuclear Overhauser enhancement differential spectroscopy indicated that, in solution,1takes up a bent instead of an extended conformation.

 

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