We describe here a rational design and synthesis of (3-O-carboxymethyl)-beta-D-galactopyranosyl alpha-D-mannopyranoside which is 5 times as active as sialyl Lewis X in binding to E-selectin and also effective against P- and L-selectin. A new method for the 1,1-glycosidic bond formation via coupling of protected trimethylsilyl beta-D-galactoside and alpha-mannosyl fluoride in the presence of BF3 . Et(2)O is described.