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 glycoprotei ns of T. cruzi new galactofuranosyl disaccharides were synthesized. beta-D- Galf-(1-3)-D-GlcNAc (1) 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-galactof uranosyl trichloroacetamidate (6) with acid-labile benzyl 2-acetamido-4,6-O -benzylidene-2-deoxy-alpha-D-glucopyranoside (3). On the other hand, tin(IV ) chloride promoted condensation of benzyl 2-acetamido-3-O-benzoyl-2-deoxy- alpha-D-glucopyranoside (11) with penta-O-benzoyl-alpha,beta-D-galactofuran ose (4) gave the derivative of beta-D-Galf-(1-6)-D-GlcNAc (2) in 78% yield.