Tetramic acids with unsaturated acyl chains are widely found in natural products possessing a range of biological activities, and bicyclic tetramates represent a suitable scaffold to prepare simple mimics of such complex molecules. An efficient route to functionalize the C(6)-acyl group of a bicyclic tetramate was developed and utilized to prepare a small chemical library with a range of saturated and unsaturated side-chains. The analogues with lipophilic residues possessed highly potent antibacterial activity, which was selective for Gram-positive bacteria, and the best compound was 37-fold more potent than the cephalosporin C control and with an appropriate therapeutic window.