D(-)-α-[4-Substituted 1-piperazinecarboxamido] benzylpenicillin (I), D(-)-α-[4-substituted 2-oxo-1-piperazinecarboxamido] benzylpenicillin (II), and D(-)-α-[4-substituted 3-oxo-1-piperazinecarboxamido] benzylpenicillin (III) were prepared. In vitro antibacterial activity of these compounds against S. aureus, E. coli, P. aeruginosa, P. vulgaris, and K. pneumoniae was examined and the activity decreased in the order of II, I, and III. These compounds were found to have a stronger antibacterial activity against P. aeruginosa and K. pneumoniae than aminobenzylpenicillin or carbenicillin.
