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Keywords:

  • Total synthesis;
  • Carbohydrates;
  • Glycosylation;
  • Oligosaccharides;
  • Regio­selectivity;
  • Diastereoselectivity

Abstract

The total synthesis of 2d-deoxy Lewisx pentasaccharide is described. Ethyl 2-O-acetyl-3,4,6-tri-O-benzyl-1-thio-α,β-D-galactopyranoside was condensed with a diol of glucosamine to regio- and stereoselectively give the disaccharide, the C-2′ position was then reduced after stereoselective fucosylation to afford a Lewisx trisaccharide analogue. Regioselective glycosylation of a known lactoside diol with this trisaccharide provided a pentasaccharide that, after deprotection, gave the target pentasaccharide.