A series of olivanic acid/thienamycin analogues have been prepared by total synthesis. Particular attention was given to the effect of the side-chain substituents on the chemical, beta-lactamase and metabolic stability of the final products. All of the compounds possessed a broad and high level of in vitro antibacterial activity against Gram-positive and Gram-negative organisms including beta-lactamase-producing strains. Two derivatives (8c) and (8j) were selected for further evaluation on the basis of in vitro activity, ease of synthesis and stability parameters. The improved metabolic stability of the selected analogues, relative to the naturally-occurring olivanic acid, MM 13902, could be demonstrated in terms of better activity, higher blood levels and improved urinary recovery in in vivo studies in mice.