Synthesis of novel siderophores for the investigation of the pore size of transmembrane siderophore-receptors and development of siderophore conjugates for the diagnosis of infections with Gram-negative bacteria

鉴于致病性革兰氏阴性菌对现有抗生素的耐药性日益增强，开发新的抗微生物药物和概念来对抗和检测致病性细菌是非常重要的。开发针对革兰氏阴性菌的新型抗生素的创新策略是基于将抗菌药物与铁载体结合，铁载体是小分子铁结合剂，已知通过特定铁载体受体的识别，主动运输穿过革兰氏阴性菌的细胞壁屏障。这种特洛伊木马偶联物可以主动将药物或报告分子传递给细菌，并在细菌内部积累。特别是Enterobactin和Salmochelins，它们是高亲和力的铁结合物，在人类宿主感染过程中对铁积累起重要作用，是新型铁载体缀合物的开发重点。然而，迄今为止，关于铁载体识别后跨膜受体打开的瞬时孔的实际大小的信息有限。本项目旨在开发肠obactin和Salmochelin衍生物，在重要识别区域外的铁载体骨干中为效应分子提供新的附着点。基于这些铁载体，计划合成用于检测细菌的新型刺激反应性铁载体报告偶联物。因此，应该开发新的基于罗丹明的潜在荧光报告分子，这些报告分子具有偶氮还原酶响应的氨基三甲基锁定触发机制，当铁载体被细胞内偶氮还原酶摄取到细菌中时，这些报告分子被激活。此外，nir荧光吲哚庚花青素报告分子与对硝基苯触发器计划被创建，它应该显示荧光转移到红色，可见波长在细胞内的硝基还原酶还原。此外，基于所提出的铁载体，设想了具有尺寸定义的虚拟有效载荷的偶联物以及刺激敏感的[2]-轮烷-铁载体-报告偶联物的发展，这将首次允许研究铁载体受体FepA和铁的孔有关潜在共轭有效载荷的尺寸，刚性和极性。有关结构-活性-关系的结果数据计划用于设计和开发基于所提出的铁载体的抗菌药物偶联物，用于治疗革兰氏阴性细菌感染。

In the view of growing resistance of pathogenic, Gram-negative bacteria against established antibiotics, the development of novel antimicrobials and concepts to fight and detect pathogenic bacteria is of enormous importance. An innovative strategy for the development of novel antibiotics against Gram-negative bacteria is based on the conjugation of antimicrobial drugs to siderophores, small molecule iron-binders, known to be actively transported across the cell wall barrier of Gram-negative bacteria through recognition by specific siderophore receptors. Such Trojan Horse conjugates can actively deliver drugs or reporter molecules to bacteria and accumulate them inside. Especially, Enterobactin and Salmochelins, which are high affinity iron binders, playing an important role for iron accumulation during infection in human hosts, are in the focus of the development of novel siderophore conjugates. However, to date there is only limited information on the actual size of the transient pore of the transmembrane siderophore receptors opened after siderophore recognition. The present project aims of developing Enterobactin and Salmochelin derivatives bearing a novel attachment point for effector molecules in the backbone of the siderophores outside of the area important for recognition. Based on these siderophores novel stimuli-responsive siderophore-reporter conjugates for the detection of bacteria are planned to be synthesized. Therefore, novel latent fluorescent Rhodamin-based reporter molecules bearing an azo-reductase-responsive amino-trimethyl-lock-trigger should be developed, which are supposed to be activated upon siderophore-mediated uptake into bacteria by intracellular azo-reductases. Additionally, NIR-fluorescent indoheptacyanin-based reporter molecules with a para-nitrobenzyl-trigger are planned to be created, which are supposed to show a fluorescence shift to the red, visible wavelength upon reduction by intracellular nitro-reductases. Furthermore, based on the presented siderophores the development of conjugates with size-defined dummy payloads as well as stimuli-sensitive [2]-rotaxane-siderophore-reporter conjugates are envisaged, which for the first time should allow the investigation of the pores of siderophore receptors FepA and IroN concerning size, rigidity and polarity of potential conjugate payloads. The resulting data on structure-activity-relationships are planned to enable the design and development of antimicrobial siderophore-drug conjugates based on the presented siderophores for the treatment of infections with Gram-negative bacteria within a follow up grant application.