Stability of N-formimidoylthienamycin in aqueous solution

The stability of N-formimidoylthienamycin in aqueous solution at 25 and 40 degrees was determined. In pH 5-8 nonnucleophilic inert buffers, pseudo-first-order ring opening was observed with dilute solutions (1 or 2 mg/ml initially). At higher initial concentrations, a second-order reaction also was evident. The rate data were compared with literature data for various cephalosporins and penicillins.