Recently, bacterial resistance to antibiotics has become a serious problem in the community. Among drug-resistant pathogens, Acinetobacter baumannii, a gram-negative bacterium, has recently emerged as one of the most threatening pathogens particularly in the nosocomial settings due to its rapid acquisition of the resistance. One of the strategies to treat this A. baumannii infection is the “Trojan Horse” approach using a siderophore as an antibiotic delivery vehicle. The siderophore is a natural product capable of forming the corresponding Fe(III)-chelate, and bacteria utilizes this for the iron assimilation from the environment. A. baumannii uses acinetobactin as the major siderophore, and this molecule features three potential Fe(III) binding moieties; catechol, hydroxamate, and imidazole groups. While two different isomeric structures (1 and 2) of acinetobactin were proposed, our previous studies established the originally reported structure of acinetobactin possessing the oxazoline (1) would be the physiologically relevant form. This finding has suggested that a Trojan horse approach targeting A. baumannii should be based on this acinetobactin structure, but its facile isomerization to the isoxazolidinone congener (2) has posed a technical problem. To resolve this issue, in this study, we have focused on discovery of a chemically stable acinetobactin analogue. Specifically, four different analogues (3 ~ 6) were synthesized and tested for their functions, revealing that the thiazoline analogues (5 and 6) indeed can function as a faithful surrogate for acinetobactin. Based on this result, our laboratory is currently working on developing potent siderophore-antibiotic conjugates against drug-resistant A. baumannii.