Stereoselective Synthesis of a Dimer Containing an α-Linked 2-Acetamido-4-Amino-2,4,6-Trideoxy-D-Galactopyranose (Sugp) Unit

P. Smid Ethyl 1-thio-α-D-mannopyranoside 5 was convened to properly protected 2-acetamido-4-amino-2,4,6-trideoxy-D-galactopyranose (Sugp) glycosyl donors 1-3, which could be used to glycosylate l,6-anhydro-2-azido-3-O-benzyl-2-deoxy-β-D-galactopyranose 23, leading to the highly stereoselective formation of dimer 24. Complete deblocking of 24 was accomplished in three steps giving the target disaccharide l,6-anhydro-2-acetamido-2-deoxy-4-O-(2-acetamido-4-amino-2.4.6-trideoxv-α-D-galactopyranosyl)-β-D-galactopyranose (4).