Synthesis of the O-linked pentasaccharide in glycoproteins of Trypanosoma cruzi and selective sialylation by recombinant trans-sialidase
摘要:
The mucin-like glycoproteins of Trypanosoma cruzi have novel O-linked oligosaccharides that are acceptors of sialic acid in the trans-sialidase (TcTS) reaction. The transference of sialic acid from host glycoconjugates to the mucins is involved in infection and pathogenesis. The synthesis of the pentasaccharide, beta-D-Galp-(1 -> 2)-[beta-D-Galp-(1 -> 43)]-beta-D-Galp-(1 -> 6)-[beta-D-Galf-(1 -> 4)]-D-GlcpNAc and the corresponding alditol, previously isolated by reductive beta-elimination of the mucins, is described. The key step was the 6-O-glycosylation of a easily accessible derivative of beta-D-Galf-(1 -> 4)-D-GlcpNAc with a beta-D-Galp-(1 -> 2)-[beta-D-Galp-(1 -> 3)]-D-Galp donor using the trichloroacetimidate method. The P-linkage was diastereoselectively obtained by the nitrile effect. The pentasaccharide is the major oligosaccharide in the mucins of T. cruzi, G strain and presents two terminal beta-D-Galp residues for possible sialylation by TcTS. A preparative sialylation reaction was performed with its benzyl glycoside and the sialylated product was isolated and characterized. NMR spectroscopic analysis showed that selective monosialylation occurred at the terminal (1 -> 3) linked galactopyranose. (c) 2006 Elsevier Ltd. All rights reserved.
Synthesis of the O-linked pentasaccharide in glycoproteins of Trypanosoma cruzi and selective sialylation by recombinant trans-sialidase
摘要:
The mucin-like glycoproteins of Trypanosoma cruzi have novel O-linked oligosaccharides that are acceptors of sialic acid in the trans-sialidase (TcTS) reaction. The transference of sialic acid from host glycoconjugates to the mucins is involved in infection and pathogenesis. The synthesis of the pentasaccharide, beta-D-Galp-(1 -> 2)-[beta-D-Galp-(1 -> 43)]-beta-D-Galp-(1 -> 6)-[beta-D-Galf-(1 -> 4)]-D-GlcpNAc and the corresponding alditol, previously isolated by reductive beta-elimination of the mucins, is described. The key step was the 6-O-glycosylation of a easily accessible derivative of beta-D-Galf-(1 -> 4)-D-GlcpNAc with a beta-D-Galp-(1 -> 2)-[beta-D-Galp-(1 -> 3)]-D-Galp donor using the trichloroacetimidate method. The P-linkage was diastereoselectively obtained by the nitrile effect. The pentasaccharide is the major oligosaccharide in the mucins of T. cruzi, G strain and presents two terminal beta-D-Galp residues for possible sialylation by TcTS. A preparative sialylation reaction was performed with its benzyl glycoside and the sialylated product was isolated and characterized. NMR spectroscopic analysis showed that selective monosialylation occurred at the terminal (1 -> 3) linked galactopyranose. (c) 2006 Elsevier Ltd. All rights reserved.