4-Butyl-3-methylphthalic acid was recognized as a metallo-β-lactamase inhibitor. The structure–activity relationship study of substituted phthalicacids afforded 3-phenylphthalic acidderivatives as potent IMP-1 inhibitors. On the other hand, 3-substituted with 4-hydroxyphenyl phthalicacidderivative displayed a potent combination effect with biapenem (BIPM) against Pseudomonas aeruginosa that produce