Structure-based design and synthesis of a number of potent and selective memapsin 2 inhibitors are described. These inhibitors were designed based upon the X-ray structure of memapsin 2-bound inhibitor 3 that incorporates methylsulfonyl alanine as the P2-ligand and a substituted pyrazole as the P3-ligand. Of particular importance, we examined the ability of the substituted isophthalic acid amide derivative to mimic the key interactions in the S2-S3 ...