Scheme 1.

(A) The A and B histo blood group antigens and their possible peripheral disaccharide core structures (the core types studied herein are in bold). X stands for the linked atom at the reducing-end residue (X = 3 for types-1 and -4; X = 4 for types-2 and -6). (B) Tetra- and pentasaccharide representative structures of the A and B blood group antigens of type-1, -2, -4, and -6 studied herein. The difference between A and B antigens is the substituent at C2 of the terminal residue (highlighted in blue): -OH (Gal) for the B antigen, and NHAc (GalNAc) for the A antigen. The type depends on the peripheral disaccharide core structure whose structural differences are highlighted in orange.