A Serendipitous Formation of a Cysteine-bridged Disaccharide

  • MG Nokwequ
  • CM Nkambule
  • DW Gammon
Keywords: Glycopeptides, glycosylation, bridged-disaccharides.


N-acetyl-L-cysteine bearing free carboxylic acid and sulfhydryl groups was glycosylated with 1,2,3,4,6-Penta-O-acetyl-β- 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 pKa 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.


Journal Identifiers

eISSN: 0379-4350