o-Bromobenzoyl l-tryptophan 1 inhibits the association of LFA-1 with ICAM-1 with an IC50 of 1.7 μM. Evaluation of the structure–activity relationship of the benzoyl moiety shows that 2, 6- di-substitutions greatly enhance potency of this class of inhibitors. Electronegative substitutions that favor a 90° angle between the benzoyl ring and the amide bond yield the most potent compounds. There is a strong correlation between the potency of the ...