Abstract
Since ampicillin, one of the important semi-synthetic derivatives of penicillins, is restricted in use because of its unfavorable physico-chemical and pharmacological properties, the author synthesized a new derivative, methampicillin lysinate and its physical and characteristics were determined. The antibacterial activity of this compound against ten species of Gram positive and negative bacteria in vitro showed that it was more active to Gram negative bactria than the positive and that was three times more potent than ampicillin trihydrate.