Structural optimization and photopharmacological studies of the cystobactamids class of natural products

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Testolin, Giambattista: Structural optimization and photopharmacological studies of the cystobactamids class of natural products. Hannover : Gottfried Wilhelm Leibniz Universität, Diss., 2018, 237 S. DOI: https://doi.org/10.15488/4547

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Abstract: 
There is an urgent need to discover novel antibiotics, particularly with activity against Gram-negative bacteria that are the most threatening for public health. In the past, nature has been the main source of antibiotic scaffolds and can still provide novel chemical architectures. Cystobactamids are novel natural products isolated from Myxobacteria that possess an intriguing oligomeric scaffold composed of para-aminobenzoic acid derived moieties and show remarkable activity against clinically relevant Gram-negative bacteria. This thesis details a medicinal chemistry investigation of this novel natural product class based around cystobactamid 861-2. Multiple synthetic routes to the cystobactamids were established in order to prepare analogues with variations at different sites of the molecular scaffold. In sum more than 50 derivatives were synthesized and extensive structure-activity relationships were established. Cystobactamids with clearly improved antibacterial properties were identified from this study. Notably, the spectrum coverage of the class was extended to highly relevant Gram-negative bacteria such as K. pneumoniae and E. cloacae. Furthermore, several analogs active against P. aeruginosa were synthesized and the antimicrobial potency was enhanced against selected pathogens such as A. baumannii. Additionally, two possible bacterial resistance mechanisms were investigated. It was demonstrated that the protein Tsx does not affect the uptake of the cystobactamids and that the hydrolytic instability determined by the endopeptidase AlbD can potentially be overcome with a structural innovation, replacing the critical amide bond with a triazole. Finally, photoswitchable cystobactamids were synthesized with either the N- or C-terminal side of the molecule modified. These photoresponsive antibiotics suggested intriguing information regarding the binding mode of the cystobactamids with their target enzyme. To sum up, the chemical scaffold of the cystobactamids natural product was optimized and the activity against Gram-negative bacteria was enhanced. Essential structure activity relationships have been defined. This confirmed and highlighted the great potential of this class of natural products to yield novel antibiotics for the future.
License of this version: Es gilt deutsches Urheberrecht. Das Dokument darf zum eigenen Gebrauch kostenfrei genutzt, aber nicht im Internet bereitgestellt oder an Außenstehende weitergegeben werden.
Document Type: doctoralThesis
Publishing status: publishedVersion
Issue Date: 2019
Appears in Collections:Naturwissenschaftliche Fakultät
Dissertationen

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1 image of flag of Germany Germany 397 67.06%
2 image of flag of United States United States 44 7.43%
3 image of flag of Russian Federation Russian Federation 41 6.93%
4 image of flag of Czech Republic Czech Republic 29 4.90%
5 image of flag of No geo information available No geo information available 14 2.36%
6 image of flag of United Kingdom United Kingdom 10 1.69%
7 image of flag of Italy Italy 9 1.52%
8 image of flag of France France 9 1.52%
9 image of flag of India India 5 0.84%
10 image of flag of China China 3 0.51%
    other countries 31 5.24%

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