E-Selectin is a vascular endothelial cell surface protein which mediates leukocyte rolling on the blood vessel wallsan early stage of the inflammatory response. 1 Excessive leukocyte recruitment can cause acute and chronic inflammatory disorders such as reperfusion injuries, psoriasis, rheumatoid arthritis, or respiratory diseases. 2 A possible therapy is to inhibit the interactions of E-selectin with its physiological glycoprotein ligand, the structure of which has not been fully elucidated. 3 The tetrasaccharide sialyl Lewis X (sLex, Chart 1) is the minimum epitope recognized by E-selectin. 4 The concentration of sLex to achieve 50% inhibition (IC50) was determined to be 1100 μM in a static, cell-free E-selectin binding assay using immobilized E-selectin and a biotinylated sLea-polylysine conjugate as multivalent ligand. 5 By modifying sLex we discovered the simplified analogue 1 (Chart 1) which showed 30-fold improved potency (IC50) 36μM) compared with sLex. 6