## Abstract

Screening of bacteria for the production of β -lactam antibiotics has resulted in the discovery of a family of structurally similar monocyclic β -lactam-containing molecules. These compounds, referred to as monobactams, are produced by a range of bacterial species. Although relatively weak antibacterial agents, the naturally occurring monobactams are highly stable to the action of β -lactamases. Structure activity relationships among a range of chemically synthesized monobactams have led to the identification and progression of SQ 26,776. SQ 26,776 shows a high degree of activity against β -lactamase-producing aerobic Gramnegative rods and is stable to the majority of β -lactamases produced by these organisms.