A β-lactamase inhibitor; inhibits type Ib penicillinase, P. vulgaris cephalosporinase, and C. freundii cephalosporinase (Kis = 15, 0.27, and 0.027 μM, respectively); inhibits B. megaterium growth (0.50 μg/ml); inhibits S. aureus and S. epidermidis growth (MICs = 0.2 and 0.2 μg/ml, respectively)