Synthesis and Antimicrobial Evaluation of γ-Borono Phosphonate Compounds in Escherichia coli and Mycobacterium smegmatis

Design and synthesis of fosmidomycin analogs containing aza-linkers and their biological activity evaluation

BACKGROUND

The enzymes involved in the 2-C-methyl-d-erythritol 4-phosphate (MEP) pathway are attractive targets of a new mode of action for developing anti-infective drugs and herbicides, and inhibitors against 1-deoxy-d-xylulose 5-phosphate reductoisomerase (IspC), the second key enzyme in the pathway, have been intensively investigated; however, few works are reported regarding IspC inhibitors designed for new herbicide discovery.

RESULTS

A series of fosmidomycin (FOS) analogs were designed with nitrogen-containing linkers replacing the trimethylene linker between the two active substructures of FOS, phosphonic acid and hydroxamic acid. Synthesis followed a facile three-step route of sequential aza-Michael addition of α-amino acids to dibenzyl vinylphosphonate, amidation of the amino acid carboxyl with O-benzyl hydroxylamine, and simultaneous removal of the benzyl protective groups. Biological activity evaluation of IspC and model plants revealed that some compounds had moderate enzyme and model plant growth inhibition effects. In particular, compound 10g, which has a N-(4-fluorophenylethyl) nitrogen-containing linker, exhibited the best plant inhibition activities, superior to the control FOS against the model plants Arabidopsis thaliana, Brassica napus L., Amaranthus retroflexus and Echinochloa crus-galli. A dimethylallyl pyrophosphate rescue assay on A. thaliana confirmed that both 10g and FOS exert their herbicidal activity by blocking the MEP pathway. This result consistent with molecular docking, which confirmed 10g and FOS binding to the IspC active site in a similar way.

CONCLUSION

Compound 10g has excellent herbicidal activity and represents the first herbicide lead structure of a new mode of action that targets IspC enzyme in the MEP pathway. © 2023 Society of Chemical Industry.

Over 40 Years of Fosmidomycin Drug Research: A Comprehensive Review and Future Opportunities

To address the continued rise of multi-drug-resistant microorganisms, the development of novel drugs with new modes of action is urgently required. While humans biosynthesize the essential isoprenoid precursors isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) via the established mevalonate pathway, pathogenic protozoa and certain pathogenic eubacteria use the less well-known methylerythritol phosphate pathway for this purpose. Important pathogens using the MEP pathway are, for example, Plasmodium falciparum, Mycobacterium tuberculosis, Pseudomonas aeruginosa and Escherichia coli. The enzymes of that pathway are targets for antiinfective drugs that are exempt from target-related toxicity. 2C-Methyl-D-erythritol 4-phosphate (MEP), the second enzyme of the non-mevalonate pathway, has been established as the molecular target of fosmidomycin, an antibiotic that has so far failed to be approved as an anti-infective drug. This review describes the development and anti-infective properties of a wide range of fosmidomycin derivatives synthesized over the last four decades. Here we discuss the DXR inhibitor pharmacophore, which comprises a metal-binding group, a phosphate or phosphonate moiety and a connecting linker. Furthermore, non-fosmidomycin-based DXRi, bisubstrate inhibitors and several prodrug concepts are described. A comprehensive structure-activity relationship (SAR) of nearly all inhibitor types is presented and some novel opportunities for further drug development of DXR inhibitors are discussed.

Structure-activity relationship of 2-aminodibenzothiophene pharmacophore and the discovery of aminobenzothiophenes as potent inhibitors of Mycobacterium smegmatis

Tuberculosis (TB) is one of the deadliest infectious diseases worldwide and its current treatments have been complicated with the emergence of multi-drug resistant (MDR-TB) and extensively drug-resistant (XDR-TB) strains. Therefore, the discovery of new antitubercular agents is in need to overcome this problem. In our efforts to discover novel candidates for the treatment of tuberculosis, we describe in this work in vitro activityagainstM. smegmatis for a series of aminated benzo-fused heterocycles, particularly, dibenzothiophene to explore the structure-activity relationship of 2-aminodibenzothiophene 3aa. From these studies, three compounds 5-aminobenzothiophene 3ia, 6-aminobenzothiophene 3ma (MIC: 0.78 µg/mL) and 5-aminobenzofuran 3ja (MIC: 1.56 µg/mL) were identified as potent inhibitors of M. smegmatis with low cytotoxicity. These results suggested the significance of these compounds 3ia, 3ja and 3ma for the future development of candidate agents to treat tuberculosis.

Non-hydroxamate inhibitors of 1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR): A critical review and future perspective

1-deoxy-d-xylulose 5-phosphate reductoisomerase (DXR) catalyzes the second step of the non-mevalonate (or MEP) pathway that functions in several organisms and plants for the synthesis of isoprenoids. DXR is essential for the survival of multiple pathogenic bacteria/parasites, including those that cause tuberculosis and malaria in humans. DXR function is inhibited by fosmidomycin (1), a natural product, which forms a chelate with the active site divalent metal (Mg²⁺/Mn²⁺) through its hydroxamate metal-binding group (MBG). Most of the potent DXR inhibitors are structurally similar to 1 and retain hydroxamate despite the unfavourable pharmacokinetic and toxicity profile of the latter. We provide our perspective on the lack of non-hydroxamate DXR inhibitors. We also highlight the fundamental flaws in the design of MBG in these molecules, primarily responsible for their failure to inhibit DXR. We also suggest that for designing next-generation non-hydroxamate DXR inhibitors, approaches followed for other metalloenzymes targets may be exploited.