VLA-4 is implicated in several inflammatory and autoimmune disease states. A series of cyclic β-amino acids (β-aa) was studied as VLA-4 antagonists. Binding affinity was highly dependent on the dihedral angle (ϕ) between the amino and the carboxyl termini of the β- aa. Compound 5m where the β-aa is embedded in a bicycle possesses the most preferred ϕ (120°). It is a potent and bioavailable VLA-4 antagonist (VCAM-Ig α4β1 IC50= 54nM, rat ...