Synthesis of mono- and di-α-l-fucosylated 2-acetamido-2-deoxy-N-glycyl-β-d-glucopyranosylamines modeling N-glycoprotein carbohydrate-peptide bond region based on 2-acetamido-N-(N-tert-butyloxycarbonylglycyl)-2-deoxy-β-d-glucopyranosylamine

Abstract

A synthesis of glycyl-spacered N-β-glycosides of diand trisaccharides such as α-l-Fucp-(1→3)-β-d-GlcNAcp-NHCOCH₂NH₂ (1), α-l-Fucp-(1→6)-[α-{asl}-Fucp-(1→3)]-β-d-GlcNAcp-NHCOCH₂NH₂ (2), α-l-Fucp-(1→6)-β-d-GlcNAcp-NHCOCH₂NH₂ ({sn3}), which model the carbohydrate-peptide bond region of fucosylated N-glycoproteins of animals and plants, was accomplished. The synthesis was carried out by the fucosylation of unprotected N-glycoside β-{}scd-GlcNAcp-NHCOCH₂NHBoc (Boc is the tert-butyloxycarbonyl) (4), 4,6-O-benzylidene derivative of compound 4, and protected disaccharide 1 (α-l-FucpBn₃-(1→3)-β-d-GlcNAcp-NHCOCH₂NHBoc (Bn is the benzyl)) with ethyl 2,3,4-tri-O-benzyl-1-thio-β-l-fucoside (in the presence of CuBr₂ and an excess of Et₄NBr). A possibility of the selective ?-fucosylation of N-glycoside 4 at the primary hydroxy group in the presence of secondary hydroxy groups (in 34% yield) was demonstrated. Amino spacered N-glycosides 1–3 were obtained after the removal of protecting groups.