Preparation of spacer-containing di-, tri-, and tetrasaccharide fragments of the circulating anodic antigen of Schistosoma mansoni for diagnostic purposes

Abstract

The chemical synthesis of beta-d-GlcpA-(1->3)-beta-d-GalpNAc-(1->O)CH2CH-H2, beta-d-Galp- NAc-(1->6)-[beta-d-GlcpA-(1->3)]-beta-d-GalpNAc-(1->O)CH2CH-CH2, and beta-d-GlcpA-(1->3)-beta-d- GalpNAc-(1->6)-[beta-d-GlcpA-(1->3)]-beta-d-GalpNAc-(1->O)CH2CH-CH2 is described. These oli- gosaccharides represent fragments of the circulating anodic antigen, secreted by the parasite Schistosoma mansoni in the circulatory system of the host. The applied synthesis strategy includes the preparation of a non-oxidised backbone oligosaccharide, with a levulinoyl group at O-6 of the -d-glucose residue. After the selective removal of the levulinoyl group, the obtained hydroxyl functions were converted into carboxyl groups, using pyridinium dichromate and acetic anhydride in dichloromethane, to a€ord the desired glucuronic-acid-containing oligosaccharides. Subse- quently, the allyl glycosides have been elongated with cysteamine to give the corresponding amine- spacer-containing oligosaccharides.