Platensimycin

In modern drug discovery, antibodies or libraries of simple synthetic organic compounds, mostly of heterocyclic origin, are favored. Natural products play an increasingly inferior role as they are considered structurally too complex, limited in quantity, and difficult to synthesize, manipulate, and derivatize. Thus it was a sensation when a Merck research group reported that classical screening of metabolites from Streptomyces platensis has unearthed a low-molecular-weight organic compound with remarkable antibiotic properties.

Platensimycin, an active metabolite of Streptomyces platensis, was initially discovered by a combination of RNA interferin induced gene-silencing and library screening to microbial extracts. Platensimycin selectively inhibits beta - ketoacyl-acyl carrier protein (ACP) synthase II (FabF) that is recognized as an effective broad-spectrum antibiotic against drug-resistant microorganism strains. Its novel scaffold and extraordinary antibacterial activity have drawn great attentions in recent years. So far, a number of synthetic strategies have been explored for the total synthesis of platensimycin. Moreover, many analogues have been investigated in terms of structure-activity relationships (SAR). This review provides a detailed overview of updated studies on platensimycin, focusing on various total and formal synthetic strategies, development of analogues, and the structure-activity relationships.

Platensimycin and platencin are novel antibiotics produced by Streptomyces platensis. They are potent and non-toxic natural products active against Gram-positive pathogens, including antibiotic-resistant strains and Mycobacterium tuberculosis. They were isolated using an intriguing target-based whole-cell antisense differential sensitivity assay as inhibitors of fatty acid biosynthesis of type II. This type of biosynthesis is not present in humans. Platensimycin inhibits the elongation-condensing enzyme FabF, whereas platencin inhibits both FabF and FabH. For these antibiotics to become successful drugs, their pharmacokinetics must be improved. They have too high a rate of clearance in the body, yielding a low degree of systematic exposure. They work well when administered by continuous infusion, but this is not a useful method of delivery to patients. The two antibiotics and many analogs have been prepared by chemical synthesis. Natural congeners have also been obtained from the producing actinomycete. However, none of these molecules are as active as platensimycin and platencin. Using tools of rational metabolic engineering, superior strains have been produced making hundreds of times more antibiotic than the natural strains.