Abstract

NOKWEQU, Mbulelo G.; NKAMBULE, Comfort M.  and  GAMMON, David W.. A Serendipitous Formation of a Cysteine-bridged Disaccharide. S.Afr.j.chem. (Online) [online]. 2014, vol.67. ISSN 1996-840X.

N-acetyl-L-cysteine bearing free carboxylic acid and sulfhydryl groups was glycosylated with 1,2,3,4,6-Penta-O-acetyl-ß-D-glucopyranoside in the presence of SnCl₄ as a promoter to give the S-glycosylated cysteine in 64 % yield. However, when excess donor was used, a previously unreported cysteine-bridged disaccharide was isolated in 54 % yield. The acetamido group on cysteine, which lowers the pK_a of the carboxylic acid group of the amino acid, plays no role in the formation of the bridged disaccharide since 3-mercaptopropionic acid reacts in a similar manner to give the 3-mercaptopropionic acid-bridged disaccharide in 52 % yield.

Keywords : Glycopeptides; glycosylation; bridged-disaccharides.

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