Spirocycles; Tetramates; Antibacterial Highly functionalised spirocyclic tetramates were prepared via a sequential Knoevenagel reaction and [1,5]-prototropic shift (Treaction) of bicyclic tetramates. While these compounds isomerise in solution, stable analogues can be prepared via appropriate choice of substituents. Further modification of these compounds allows for introduction of aromatic groups, making them suitable as skeletons suitable for application in medicinal chemistry.