Synthesis of beta-D-Galf-(1-3)-D-GlcNAc by the trichloroacetamidate method and of beta-D-Galf-(1-6)-D-GlcNAc by SnCl4-promoted glycosylation.

In a continuation of our studies on the characterization of the glycoproteins of T. cruzi new galactofuranosyl disaccharides were synthesized. Beta-D-Galf-(1-3)-D-GlcNAc was prepared by employing the trichloroacetamidate procedure for the glycosylation step. The mild conditions of this reaction are appropriate for condensation of 2,3,5,6-tetra-O-benzoyl-beta-D-galactofuranosyl trichloroacetamidate with acid-labile benzyl 2-acetamido-4,6-O-benzylidene-2-deoxy-alpha-D-glucopyranoside. On the other hand, tin(IV) chloride promoted condensation of benzyl 2-acetamido-3-O-benzoyl-2-deoxy-alpha-D-glucopyranoside with penta-O-benzoyl-alpha-beta-D-galactofuranose gave the derivative of beta-D-Galf-(1-6)-D-GlcNAc in 78% yield.