No abstract

Platensimycin (1a) and platencin (2) are inhibitors of FabF and FabF/H bacterial fatty acid synthase. The discovery of natural congeners is an approach that can render a better understanding of the structure-function relationships of complex natural products. The isolation and structure elucidation of nine new congeners (11-20) of platensimycin and platencin are described from a fermentation broth of Streptomyces platensis. These hydroxylated congeners are likely derived by cytochrome P450 oxidation of the terpenoid units post-cyclization. Polar groups in the terpenoid portion of the molecule produce negative interactions with the hydrophobic pocket of FabF, resulting in poor activities. However, the discovery of these compounds serves an important purpose, not only to understand structure-function relationships, which cannot be easily accessed by chemical modification, but also to provide access to compounds that could be used for structural identification/confirmation of the oxidative trace metabolites produced in vivo during animal experiments.

Platensimycin and platencin are novel natural product antibiotics that inhibit bacterial growth by inhibiting condensing enzymes FabF and FabF/FabH of fatty acid biosynthesis pathways, respectively. Continued search for the natural congeners of these compounds led to the isolation of platensic acid, the free C-17 tetracyclic enoic acid, and platensimide A, a 2,4-diaminobutyric acid amide derivative. Isolation, structure, semisynthesis, and activity of these compounds are described.

Thiazolyl peptides are a class of highly rigid trimacrocyclic compounds consisting of varying but large numbers of thiazole rings. The need for new antibacterial agents to treat infections caused by resistant bacteria prompted a reinvestigation of this class, leading to the previous isolation of thiazolyl peptides, namely, thiazomycin (5) and thiazomycin A (6), congeners of nocathiacins (1-4). Continued chemical screening led to the isolation of six new thiazolyl peptide congeners (8-13), of which three had truncated structures lacking an indole residue. From these, compound 8 showed activity similar to thiazomycin. Two compounds (9 and 10) showed intermediate activities, and the three truncated compounds (11-13) were essentially inactive. The discovery of the truncated compounds revealed the minimal structural requirements for activity and suggested probable biosynthetic pathways for more advanced compounds. The isolation, structure elucidation, antibacterial activity, and proposed biogenesis of thiazomycins are herein described.

Platensimycin and platencin are inhibitors of FabF and FabF/H bacterial fatty acid synthesis enzymes, respectively. Discovery of natural congeners provides one of the ways to understand the relationship of chemical structure and biological function. Efforts to discover the natural analogs of platensimycin by chemical screening led to the isolation of platensimycin B 4 , a glucoside congener of platensimycin. This analog showed significantly attenuated activity and critically defined the limited binding space around the aromatic ring and established the importance of the free phenolic and carboxyl group for the activity.