Solid-phase synthesis of glycopeptide carrying a tetra-N-acetyllactosamine-containing core 2 decasaccharide |
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Authors: | Akiharu Ueki Yoshiaki Nakahara |
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Institution: | Department of Applied Biochemistry, Institute of Glycoscience, Tokai University, 1117 Kitakaname, Hiratsuka-shi, Kanagawa 259-1292, Japan |
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Abstract: | A novel synthesis of tetralactosaminyl O-glycoamino acid is described. The stereoselective assemblage of a lactosaminyl unit was performed by 2-trichloroacetamido group-assisted β-glycosylation. Initial investigation into the synthesis of decasaccharyl threonine 2 showed limited success because of the low yield in the step concerning the removal of 4-O-chloroacetyl groups. In contrast, 4-O-benzylated decasaccharyl threonine 50 was efficiently synthesized from key LacNAc derivative 35 carrying a 3-O-allyl protecting group at the Gal residue by reiterative glycosylation using the (N-phenyl)trifluoroacetimidate method. Decasaccharide 50 was used as a building block in the solid-phase synthesis of a MUC1-related glycopeptide. Synthetic glycopeptide was obtained through two acidic processes: cleavage from resin with reagent K at a lowered temperature and debenzylation with a diluted cocktail of low-acidity TfOH. Desired glycopeptide 54 was isolated as the major product, while a series of the saccharide-shortened minor products were generated due to the acid-labile property of the β-GlcNAc glycosidic linkages. |
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