A β-lactamase inhibitor (Kis = 29-110 nM for class A and class C enzymes); selective for bacterial β-lactamases over a panel of mammalian serine proteases (IC50s = ≥1,000 μM); potentiates the activity of biapenem against K. pneumonia expressing KPC-2 at 0.02 μg/ml; potentiates the activity of carbapenem antibiotics against clinical isolates of various bacteria (MICs = ≤0.06-4 and 4-64 μg/ml in the presence and absence of compound, respectively); reduces the number of CFUs in the lung in a neutropenic mouse lung infection model when used in combination with biapenem or meropenem at 50 mg/kg