Synthetic studies towards the O-specific polysaccharide of Shigella sonnei

Synthetic routes are described to zwitter-ionic disaccharides that are dias tereoisomerically related to frame-shifted repeating units of the title pol ysaccharide that contains 2-acetamido-4-amino-2,4,6-trideoxy-D-galactose an d 2-acetamido-2-deoxy-L-altruronic acid. The intermediates corresponding to the trideoxygalactose residue feature acylamino functions at C-2 and an az ido group at C-4. Best results were obtained with N-phthaloyl- and N-trichl oroacetyl-protected derivatives. The intermediates corresponding to the uro nic acid residue were either a D-altruronic acid-derived acceptor or a D-al trose-derived donor in which C-6 was oxidized after disaccharide formation.