Synthese der trissaccharid-determinanten des entero-bacterial common antigens

In the presence of silver silicate, the reaction of 3,4,6-tri-O-acetyl-2-azido-2-deoxy-α-d-acetyl-2-azido-2-deoxy-α-d-mannopyranosyl bromide with 1,6-anhydro-2-azido-3-O-benzyl-2-deoxy-β-d-glucopyranose gave β-glycosidically linked 1,6-anhydro-2-azido-3-O-benzyl-2-deoxy-4-O-(3,4,6-O-(3,4,6-tri-O-acetyl-2-azido-2-deoxy-β-d- mannopyranosyl)-β-dd- glucopyranose. After deacetylation and catalytic oxidation with oxygen and platinum, 1,6-anhydro-2-azido-4-O-[(3-azido-2-deoxy-β-d-mannopyranosyl)uronic acid]-3-O-benzyl-2-deoxy-β-d-glucopyranose was obtained. A series of intermediate steps led to the glycosyl donor 6-O-acetyl-2-azido-3-O-benzyl-4-O-[benzyl (3,4-di-O-acetyl-2-azido-2-deoxy-β-d-mannopyranosyl)uronate]-2-deoxy-α,β-glucopyranosyl chloride which was coupled with 8-methoxycarbonyloctyl 4-azido-2-O-benzyl-4,6-dideoxy-α-d-galactopyranoside to give 8-methoxycarbonyloctyl O-[benzyl (3,4-di-O-acetyl-2-azido-2-deoxy-β-d-mannopyranosyl)uronate]-(1→4)-O (6-O-acetyl-2-azido-3-O-benzyl-2-deoxy-α-d-glucopyranosyl)-(1→3)-4-azido-2-O-benzyl-4,6-dideoxy-α-d-s galactopyranoside. Deblocking gave the spacer-linked repeating unit of the enterobacterial common antigen, β-d-ManpNAcA-(1→4)-α-d-GlcpNAc-(1→3)-α-d-Fucp4NAcO(CH₂)₈CO₂CH₃.