Oligosaccharides related to tumor‐associate antigens. Part 3. Synthesis of the propyl glycosides of the trisaccharide β‐ D ‐Galp‐(1→3)‐β‐ D ‐Gal p NAc‐(1→3)‐α‐ D ‐Gal p and of the Tetrasaccharide α‐ L ‐Fuc p ‐(1→2)‐β‐ D ‐Gal p ‐(1→3)‐β‐ D ‐Gal p NAc‐(1→3)‐α‐ D ‐Gal p , components of a tumor antigen recognized by the antibody MBr1

The synthesis of the trisaccharide β‐ D ‐Gal p ‐(1→3)‐β‐ D ‐Gal p NAc‐(1→3)‐α‐ D ‐Gal p ‐1‐OPr ( 2 ) and of the tetrasaccharide α‐ L ‐Fuc p ‐(1→2)‐β‐ D ‐Gal p NAc‐(1→3)‐β‐ D ‐Gal p ‐1‐OPr ( 3 ), starting from the disaccharidic dihydrooxazole donor 5 , is described. Glycosylation of 5 with 6 in the presence of Me 3 SiOTf gave the trisaccharide 7 which was deprotected with standard methods to give, via 8 , compound 2 ( Scheme 1 ). Alternatively, protection of 8 as the 4′,6′‐ O ‐benzylidene derivative 9 followed by glycosylation with 10 and by standard deprotection afforded the tetrasaccharide 3 ( Scheme 2 ). Biological testing showed that trisaccharide 2 is unable to inhibit the binding of the monoclonal antibody MBr1 to the target tumor cells MCF7, while tetrasaccharide 3 inhibits the binding in ca . 7‐fold extent with respect to the previously tested trisaccharide α‐ L ‐Fuc p ‐(1→2)‐β‐ D ‐Gal p ‐(1→3)‐β‐ D ‐Gal p NAc‐1‐OPr. These results indicate that the galactose corresponding to the unit D of compound 1 plays an important role in defining the MBr1‐recognized epitope and confirm the essential role of fucose for MAb recognition.