Hydrazin-Reaktionen, XIV. Reaktionen von Azido-Zuckern mit Hydrazin

[Synthesis of the pentasaccharide chain of the Forsman antigen]

The pentasaccharide chain of the Forssman antigen, O-(2-acetamido-2-deoxy-alpha-D-galactopyranosyl)-(1 leads to 3)-O-(2-acetamido-2-deoxy-beta-D-galactopyranosyl)-(1 leads to 3)-O-alpha-D-galactopyranosyl-(1 leads to 4)-O-beta-D-galactopyranosyl-(1 leads to 4)-D-glucopyranose (46) was synthesized by a block synthesis in which an alpha-D-glycoside linkage between two D-galactose residues was formed. The trisaccharide O-(6-O-acetyl-2-azido-3,4-di-O-benzoyl-2-deoxy-alpha-D-galactopyranosyl)-(1 leads to 3)-O-(6-O-acetyl-4-O-bebenzyl-2-deoxy-2-phthalimido-beta-D-galactopyranosyl)-(1 leads to 3)-6-O-acetyl-2,4-di-O-benzyl-alpha-D-galactopyranosyl bromide (40) (this was obtained through acetolysis of O-(6-O-acetyl-2-azido-3,4-di-O-benzoyl-2-deoxy-alpha-D-galactopyranosyl)-(1 leads to 3)-O-(6-O-acetyl-4-O-benzyl-2-deoxy-2-phthalimido-beta-D-galactopyranosyl)-(1 leads to 3)-1,6-anhydro-2,4-di-O-benzyl-beta-D-galactopyranose to the acetyl derivative, followed by reaction with titanium tetrabromide under anhydrous conditions) was condensed with benzyl-4-O-)6-O-benzoyl-2,3-di-O-benzyl-beta-D-galactopyranosyl)-2,3,6-tri-O-benzyl-beta-D-glucopyranoside were in the presence of silver carbonate and perchlorate. The resulting pentasaccharide was deprotected to give 46.