title: Solid-phase synthesis of a glycosylated hexapeptide of human sialophorin, using the trichloroacetimidate method.
abstract: A hexapeptide containing a beta-D-Gal p-(1-->3)-alpha-D-Gal pNAc-(1-->O)-L-threonine unit was synthesized using glycosylated pentafluorophenyl esters in an Fmoc-based strategy. In all of the glycosylation reactions, trichloroacetimidates were successfully employed. The disaccharide moiety was prepared from tetra-O-acetyl-alpha-D-galactopyranosyl trichloroacetimidate and tert-butyldimethylsilyl 2-azido-6-O-benzoyl-2-deoxy-beta-E-galactopyranoside with boron trifluoride etherate as a catalyst. The glycosylated active esters were obtained in the reaction of alpha and beta 2,3,4,6-tetra-O-acetyl-beta-D-galactopyranosyl-(1-->3)-4-O-acetyl-2-azid o-6- O-benzoyl-2-deoxy-D-galactopyranosyl trichloroacetimidates with Fmoc-protected pentafluorophenyl esters of L-serine and L-threonine in the presence of trimethylsilyl trifluoromethanesulfonate as Lewis acid. The glycosylated pentafluorophenyl ester of L-threonine was transformed into glycopeptides via a solid-phase synthesis. Azide reduction and N-acetylation were performed on the solid phase with a thioacetic acid-pyridine mixture. The glycopeptide was then cleaved from the resin with strong acid, also removing the acid-labile protecting groups of the peptide chain. Finally, the acyl groups used for sugar protection were cleaved with sodium methoxide, affording the completely deprotected N-acetyl-L-leucyl-L-glutamyl-O-[beta-D-galactopyranosyl-(1-->3)-2- acetamido-2-deoxy-alpha-D-galactopyranosyl]-L-threonyl-L-seryl-L-threony l- glycinamide (1) in high purity.
authors.affiliation: Fakultät für Chemie, Universität Konstanz, Germany.
authors.forename: J
authors.initials: J
authors.lastname: Rademann
authors.forename: R R
authors.initials: RR
authors.lastname: Schmidt
mesh_terms: D000081:Acetamides; D000116:Acetylgalactosamine / Q000737:chemistry; D000595:Amino Acid Sequence; D015703:Antigens, CD; D002240:Carbohydrate Sequence; D062845:Chloroacetates; D004952:Esters / Q000138:chemical synthesis / Q000737:chemistry; D005690:Galactose / Q000737:chemistry; D006020:Glycopeptides / Q000138:chemical synthesis* / Q000737:chemistry; D006031:Glycosylation; D006801:Humans; D051917:Leukosialin; D008969:Molecular Sequence Data; D009842:Oligopeptides / Q000138:chemical synthesis* / Q000737:chemistry; D012795:Sialoglycoproteins / Q000737:chemistry*; D013912:Threonine / Q000737:chemistry; D014238:Trichloroacetic Acid / Q000737:chemistry
chemical_list: D000081:Acetamides; D015703:Antigens, CD; D062845:Chloroacetates; D004952:Esters; D006020:Glycopeptides; D051917:Leukosialin; D009842:Oligopeptides; C465014:SPN protein, human; D012795:Sialoglycoproteins; D013912:Threonine; D014238:Trichloroacetic Acid; C009528:trichloroacetamide; D000116:Acetylgalactosamine; D005690:Galactose