8-Acyloxy-1,3-benzoxazine-2,4-diones as siderophore components for antibiotics

8-Acyloxy-1,3-benzoxazine-2,4-diones as masked catechol derivatives represe nt a novel type of siderophore components, whose growth promoting activity is low or not existing if tested alone. But after conjugation with beta-lac tam antibiotics the resulting conjugates show a significantly increased ant ibacterial activity against Gram-negative bacteria compared with their pare nt antibiotics. Investigations using a set of penetration and iron transpor t mutants demonstrated that the conjugates use iron transport systems to pe netrate the bacterial outer membrane. Title compounds were synthesized from (2,3-dimethoxycarbonyloxy)-benzoic acid and different amino compounds. Con jugates with penicillins and cephalosporins were prepared.