The acquisition of drug resistance by human pathogens is of grave concern to healthcare community, and therefore various novel approaches are being actively pursued worldwide to overcome this threatening problem. The siderophore-antibiotic conjugate (SAC) strategy is a Trojan horse approach, in which the bacterial iron assimilation mechanism based on the utilization of siderophores, small molecule iron chelators, is exploited for intracellular delivery of antibiotic molecules into specific pathogens. The concept of this approach has been well proven by the mode of action of a number of natural product antibiotics possessing the SAC structure, i.e., albomycins and salmycins. However, despite the excellent in vitro, in vivo activity, delivery of those SAC molecules into clinical applications has yet to be limited. In this regard, our laboratory has been interested in addressing a number of pending issues for the design of effective SAC molecules, particularly, in treating drug-resistant Gram-negative pathogens such as Acinetobacter baumannii. This presentation will entail our recent progresses in understanding chemistry and biology of acinetobactin, a major siderophore of A. baumannii, as well as albomycin δ₂, a prototypical SAC natural product.