title: Active-latent glycosylation strategy toward Lewis X pentasaccharide in a form suitable for neoglycoconjugate syntheses.
abstract: Glycosylation of 4-nitrophenyl 2-acetamido-6-O-tert-butyldiphenylsilyl-2-deoxy-1-thio-beta-D-gluc opyranoside with phenyl 2,3,4,6-tetra-O-benzoyl-1-thio-beta-D-galactopyranoside in the presence of NIS and TfOH as catalyst gave the lactosamine derivative regiospecifically in high yield. Further 3-O-fucosylation with phenyl 2,3,4-tri-O-benzyl-1-thio-beta-L-fucopyranoside using DMTST as promoter afforded the Lex trisaccharide intermediate. The latent glycosyl donor was transformed into its active form (p-acetamidothiophenyl) by reduction with zinc in acetic acid and N-acetylation. Glycosidation with p-nitrothiophenyl lactoside acceptor in the presence of NIS/TfOH as catalyst gave the Lex pentasaccharide in 71% yield.
authors.affiliation: Department of Chemistry, University of Ottawa, ON, Canada.
authors.forename: S
authors.initials: S
authors.lastname: Cao
authors.forename: Z
authors.initials: Z
authors.lastname: Gan
authors.forename: R
authors.initials: R
authors.lastname: Roy
mesh_terms: D002236:Carbohydrate Conformation; D002240:Carbohydrate Sequence; D006001:Glycoconjugates / Q000138:chemical synthesis*; D006031:Glycosylation; D007202:Indicators and Reagents; D016256:Lewis X Antigen / Q000737:chemistry*; D008969:Molecular Sequence Data; D009844:Oligosaccharides / Q000138:chemical synthesis / Q000737:chemistry*; D016339:Spectrometry, Mass, Fast Atom Bombardment
chemical_list: D006001:Glycoconjugates; D007202:Indicators and Reagents; D016256:Lewis X Antigen; D009844:Oligosaccharides