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Self-assembly of spin-labeled antimicrobial peptides magainin 2 and PGLa in lipid bilayers. Biophys Chem 2024; 310:107251. [PMID: 38678820 DOI: 10.1016/j.bpc.2024.107251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 04/15/2024] [Accepted: 04/21/2024] [Indexed: 05/01/2024]
Abstract
The cationic antimicrobial peptides PGLa and magainin 2 (Mag2) are known for their antimicrobial activity and synergistic enhancement in antimicrobial and membrane leakage assays. Further use of peptides in combinatory therapy requires knowledge of the mechanisms of action of both individual peptides and their mixtures. Here, electron paramagnetic resonance (EPR), double electron-electron resonance (DEER, also known as PELDOR) and electron spin echo envelope modulation (ESEEM) spectroscopies were applied to study self-assembly and localization of spin-labeled PGLa and Mag2 in POPE/POPG membranes with a wide range of peptide/lipid ratios (P/L) from ∼1/1500 to 1/50. EPR and DEER data showed that both peptides tend to organize in clusters, which occurs already at the lowest peptide/lipid molar ratio of 1/1500 (0.067 mol%). For individual peptides, these clusters are quite dense with intermolecular distances of the order of ∼2 nm. In the presence of a synergistic peptide partner, these homo-clusters are transformed into lipid-diluted hetero-clusters. These clusters are characterized by a local surface density that is several times higher than expected from a random distribution. ESEEM data indicate a slightly different insertion depth of peptides in hetero-clusters when compared to homo-clusters.
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2
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Design of Triazolium-Grafted Peptidomimetic Macrocycles with Facial Amphipathicity to Target Pathogenic Bacteria. Org Lett 2024; 26:4088-4092. [PMID: 38709636 DOI: 10.1021/acs.orglett.4c01149] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/08/2024]
Abstract
Access to 1,2,3-triazolium-grafted peptoid macrocycles was developed by macrocyclization and multivalent postmodification of linear peptoid oligomers carrying an alternance of benzylic and propargyl groups as side chains. X-ray analysis and NMR studies revealed a conformational preference for constrained hairpin-shaped structures leading to the facial amphipathic character of these macrocycles. A preliminary evaluation showed the antimicrobial activities of these new cationic amphipathic architectures.
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3
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Unnatural helical peptidic foldamers as protein segment mimics. Chem Soc Rev 2023; 52:4843-4877. [PMID: 37401344 PMCID: PMC10389297 DOI: 10.1039/d2cs00395c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2022] [Indexed: 07/05/2023]
Abstract
Unnatural helical peptidic foldamers have attracted considerable attention owing to their unique folding behaviours, diverse artificial protein binding mechanisms, and promising applications in chemical, biological, medical, and material fields. Unlike the conventional α-helix consisting of molecular entities of native α-amino acids, unnatural helical peptidic foldamers are generally comprised of well-defined backbone conformers with unique and unnatural structural parameters. Their folded structures usually arise from unnatural amino acids such as N-substituted glycine, N-substituted-β-alanine, β-amino acid, urea, thiourea, α-aminoxy acid, α-aminoisobutyric acid, aza-amino acid, aromatic amide, γ-amino acid, as well as sulfono-γ-AA amino acid. They can exhibit intriguing and predictable three-dimensional helical structures, generally featuring superior resistance to proteolytic degradation, enhanced bioavailability, and improved chemodiversity, and are promising in mimicking helical segments of various proteins. Although it is impossible to include every piece of research work, we attempt to highlight the research progress in the past 10 years in exploring unnatural peptidic foldamers as protein helical segment mimics, by giving some representative examples and discussing the current challenges and future perspectives. We expect that this review will help elucidate the principles of structural design and applications of existing unnatural helical peptidic foldamers in protein segment mimicry, thereby attracting more researchers to explore and generate novel unnatural peptidic foldamers with unique structural and functional properties, leading to more unprecedented and practical applications.
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4
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Research Advances on the Bioactivity of 1,2,3-Triazolium Salts. Int J Mol Sci 2023; 24:10694. [PMID: 37445872 DOI: 10.3390/ijms241310694] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2023] [Revised: 06/21/2023] [Accepted: 06/25/2023] [Indexed: 07/15/2023] Open
Abstract
1,2,3-Triazolium salts have demonstrated significant potential in the fields of medicine and agriculture, exhibiting exceptional antibacterial, antifungal, anticancer, and antileishmanial properties. Moreover, these salts can be utilized as additives or components to produce nano- and fiber-based materials with antibacterial properties. In this review, we summarize several synthetic strategies to obtain 1,2,3-triazolium salts and the structures of 1,2,3-triazolium derivatives with biological activities in the domains of pharmaceuticals, pesticides, and functional materials. Additionally, the structure-activity relationship (SAR) of 1,2,3-triazolium salts with different biological activities has been analyzed. Finally, this review presents the potential applications and prospects of 1,2,3-triazolium salts in the fields of agriculture, medicine, and industrial synthesis.
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5
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Multi-Component Sequential Synthesis of Dihydroorotic Acid-Based Amphiphilic Molecules. SYNTHESIS-STUTTGART 2022. [DOI: 10.1055/a-1913-3105] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/16/2022]
Abstract
AbstractAn efficient multicomponent sequential process, which occurs in mild condition has been exploited for the synthesis of systematically modified amphiphilic molecules where the cationic head is tethered to a lipophilic tail through a dihydroorotic acid linker. The process is operatively simple, high yielding, and flexible. Such a strategy could impact combinatorial synthesis of wide libraries of amphiphilic molecules to be tested as transfection agents and/or as antimicrobials.
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6
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First series of N-alkylamino peptoid homooligomers: solution phase synthesis and conformational investigation. Beilstein J Org Chem 2022; 18:845-854. [PMID: 35923157 PMCID: PMC9296984 DOI: 10.3762/bjoc.18.85] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 06/29/2022] [Indexed: 11/26/2022] Open
Abstract
The synthesis and conformational analysis of the first series of peptoid oligomers composed of consecutive N-(alkylamino)glycine units is investigated. We demonstrate that N-(methylamino)glycine homooligomers can be readily synthesized in solution using N-Boc-N-methylhydrazine as a peptoid submonomer and stepwise or segment coupling methodologies. Their structures were analyzed in solution by 1D and 2D NMR, in the solid state by X-ray crystallography (dimer 2), and implicit solvent QM geometry optimizations. N-(Methylamino)peptoids were found to preferentially adopt trans amide bonds with the side chain N–H bonds oriented approximately perpendicular to the amide plane. This orientation is conducive to local backbone stabilization through intra-residue hydrogen bonds but also to intermolecular associations. The high capacity of N-(methylamino)peptoids to establish intermolecular hydrogen bonds was notably deduced from pronounced concentration-dependent N–H chemical shift variation in 1H NMR and the antiparallel arrangement of mirror image molecules held together via two hydrogen bonds in the crystal lattice of dimer 2.
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7
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Helical Foldamers and Stapled Peptides as New Modalities in Drug Discovery: Modulators of Protein-Protein Interactions. Processes (Basel) 2022. [DOI: 10.3390/pr10050924] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
A “foldamer” is an artificial oligomeric molecule with a regular secondary or tertiary structure consisting of various building blocks. A “stapled peptide” is a peptide with stabilized secondary structures, in particular, helical structures by intramolecular covalent side-chain cross-linking. Helical foldamers and stapled peptides are potential drug candidates that can target protein-protein interactions because they enable multipoint molecular recognition, which is difficult to achieve with low-molecular-weight compounds. This mini-review describes a variety of peptide-based foldamers and stapled peptides with a view to their applications in drug discovery, including our recent progress.
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8
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Design of Oligourea-Based Foldamers with Antibacterial and Antifungal Activities. Molecules 2022; 27:molecules27051749. [PMID: 35268850 PMCID: PMC8911826 DOI: 10.3390/molecules27051749] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 02/24/2022] [Accepted: 03/01/2022] [Indexed: 02/05/2023] Open
Abstract
There is an urgent need to develop new therapeutic strategies to fight the emergence of multidrug resistant bacteria. Many antimicrobial peptides (AMPs) have been identified and characterized, but clinical translation has been limited partly due to their structural instability and degradability in physiological environments. The use of unnatural backbones leading to foldamers can generate peptidomimetics with improved properties and conformational stability. We recently reported the successful design of urea-based eukaryotic cell-penetrating foldamers (CPFs). Since cell-penetrating peptides and AMPs generally share many common features, we prepared new sequences derived from CPFs by varying the distribution of histidine- and arginine-type residues at the surface of the oligourea helix, and evaluated their activity on both Gram-positive and Gram-negative bacteria as well as on fungi. In addition, we prepared and tested new amphiphilic block cofoldamers consisting of an oligourea and a peptide segment whereby polar and charged residues are located in the peptide segment and more hydrophobic residues in the oligourea segment. Several foldamer sequences were found to display potent antibacterial activities even in the presence of 50% serum. Importantly, we show that these urea-based foldamers also possess promising antifungal properties.
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9
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Nitrobenzoxadiazole derivatives of the rat selective toxicant norbormide as fluorescent probes for live cell imaging. Bioorg Med Chem 2022; 59:116670. [DOI: 10.1016/j.bmc.2022.116670] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Revised: 02/10/2022] [Accepted: 02/11/2022] [Indexed: 11/23/2022]
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10
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Solution‐Phase Synthesis of Backbone‐Constrained Cationic Peptoid Hexamers with Antibacterial and Anti‐Biofilm Activities. European J Org Chem 2021. [DOI: 10.1002/ejoc.202101155] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
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11
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Peptoids with Antibiofilm Activity against the Gram Negative Obligate Anaerobe, Fusobacterium nucleatum. Molecules 2021; 26:molecules26164741. [PMID: 34443332 PMCID: PMC8398059 DOI: 10.3390/molecules26164741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Revised: 07/29/2021] [Accepted: 08/03/2021] [Indexed: 11/16/2022] Open
Abstract
Peptoids (oligo N-substituted glycines) are peptide analogues, which can be designed to mimic host antimicrobial peptides, with the advantage that they are resistant to proteolytic degradation. Few studies on the antimicrobial efficacy of peptoids have focused on Gram negative anaerobic microbes associated with clinical infections, which are commonly recalcitrant to antibiotic treatment. We therefore studied the cytotoxicity and antibiofilm activity of a family of peptoids against the Gram negative obligate anaerobe Fusobacterium nucleatum, which is associated with infections in the oral cavity. Two peptoids, peptoid 4 (NaeNpheNphe)4 and peptoid 9 (NahNspeNspe)3 were shown to be efficacious against F. nucleatum biofilms at a concentration of 1 μM. At this concentration, peptoids 4 and 9 were not cytotoxic to human erythrocytes or primary human gingival fibroblast cells. Peptoids 4 and 9 therefore have merit as future therapeutics for the treatment of oral infections.
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Photosensitizer-peptoid conjugates for photoinactivation of Gram-negative bacteria: structure-activity relationship and mechanistic studies. Org Biomol Chem 2021; 19:6546-6557. [PMID: 34259297 DOI: 10.1039/d1ob00926e] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Multitarget engagement is considered an effective strategy to overcome the threat of bacterial infection, and antimicrobials with multiple mechanisms of action have been successful as natural chemical weaponry. Here, we synthesized a library of photosensitizer-peptoid conjugates (PsPCs) as novel antimicrobial photodynamic therapy (aPDT) agents. The peptoids, linkers, and photosensitizers were varied, and their structure-antimicrobial activity relationships against Escherichia coli were evaluated; PsPC 9 was indicated to be the most promising photoresponsive antimicrobial agent among the synthesized PsPCs. Spectroscopic analyses indicated that 9 generated singlet oxygen upon absorption of visible light (420 nm) while maintaining the weakly helical conformation of the peptoid. Mechanistic studies suggested that damage to the bacterial membrane and cleavage of DNA upon light irradiation were the main causes of bactericidal activity, which was supported by flow cytometry and DNA gel electrophoresis experiments. We demonstrated that the optimal combination of membrane-active peptoids and photosensitizers can generate an efficient aPDT agent that targets multiple sites of bacterial components and kills bacteria by membrane disruption and reactive oxygen species generation.
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Synthesis, Characterization, and Evaluation of Antibacterial Activity of Ferrocenyl‐1,2,3‐Triazoles, Triazolium Salts, and Triazolylidene Complexes of Gold(
i
) and Silver(
i
). Eur J Inorg Chem 2021. [DOI: 10.1002/ejic.202100024] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
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14
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Helical Antimicrobial Peptide Foldamers Containing Non-proteinogenic Amino Acids. ChemMedChem 2021; 16:1226-1233. [PMID: 33565721 DOI: 10.1002/cmdc.202000940] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Indexed: 12/18/2022]
Abstract
Antimicrobial peptides (AMPs) are potential novel therapeutic drugs against microbial infections. Most AMPs function by disrupting microbial membranes because of their amphipathic properties and ordered secondary structures. In this minireview, we describe recent efforts to develop helical AMP foldamers containing non-proteinogenic amino acids, such as α,α-disubstituted α-amino acids, β-amino acids, γ-amino acids, side-chain stapling and N-alkyl glycines.
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15
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Gramicidin-S-Inspired Cyclopeptidomimetics as Potent Membrane-Active Bactericidal Agents with Therapeutic Potential. ChemMedChem 2020; 16:368-376. [PMID: 33026182 DOI: 10.1002/cmdc.202000568] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2020] [Revised: 09/22/2020] [Indexed: 12/27/2022]
Abstract
Antimicrobial peptides (AMPs) are promising antibacterial agents often hindered by their undesired hemolytic activity. Inspired by gramicidin S (GS), a well-known cyclodecapeptide, we synthesized a panel of antibacterial cyclopeptidomimetics using β,γ-diamino acids (β,γ-DiAAs). We observed that peptidomimetic CP-2 displays a bactericidal activity similar to that of GS while possessing lower side-effects. Moreover, extensive studies revealed that CP-2 likely kills bacteria through membrane disruption. Altogether, CP-2 is a promising membrane-active antibiotic with therapeutic potential.
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16
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The Best Peptidomimetic Strategies to Undercover Antibacterial Peptides. Int J Mol Sci 2020; 21:E7349. [PMID: 33027928 PMCID: PMC7583890 DOI: 10.3390/ijms21197349] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2020] [Revised: 09/23/2020] [Accepted: 09/25/2020] [Indexed: 02/05/2023] Open
Abstract
Health-care systems that develop rapidly and efficiently may increase the lifespan of humans. Nevertheless, the older population is more fragile, and is at an increased risk of disease development. A concurrently growing number of surgeries and transplantations have caused antibiotics to be used much more frequently, and for much longer periods of time, which in turn increases microbial resistance. In 1945, Fleming warned against the abuse of antibiotics in his Nobel lecture: "The time may come when penicillin can be bought by anyone in the shops. Then there is the danger that the ignorant man may easily underdose himself and by exposing his microbes to non-lethal quantities of the drug make them resistant". After 70 years, we are witnessing the fulfilment of Fleming's prophecy, as more than 700,000 people die each year due to drug-resistant diseases. Naturally occurring antimicrobial peptides protect all living matter against bacteria, and now different peptidomimetic strategies to engineer innovative antibiotics are being developed to defend humans against bacterial infections.
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17
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Abstract
This feature article highlights the progress that has been made towards the development of novel anti-infective peptoids and the key areas for future development within this field.
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18
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Synthesis of PEGylated Salicylaldehyde Azine via Metal-free Click Chemistry for Cellular Imaging Applications. Chem Res Chin Univ 2019. [DOI: 10.1007/s40242-019-9077-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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19
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Comprehensive review on the anti-bacterial activity of 1,2,3-triazole hybrids. Eur J Med Chem 2019; 168:357-372. [DOI: 10.1016/j.ejmech.2019.02.055] [Citation(s) in RCA: 98] [Impact Index Per Article: 19.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2019] [Revised: 02/17/2019] [Accepted: 02/17/2019] [Indexed: 01/07/2023]
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20
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NCα-gem-dimethylated peptoid side chains: A novel approach for structural control and peptide sequence mimetics. Biopolymers 2019; 110:e23273. [PMID: 30897209 DOI: 10.1002/bip.23273] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2018] [Revised: 02/28/2019] [Accepted: 03/01/2019] [Indexed: 01/05/2023]
Abstract
The design of linear peptoid oligomers adopting well-defined secondary structures while mimicking defined peptide primary sequences is a major challenge in the context of drug discovery. To this end, chemists have developed cis-inducing peptoid side chains to build robust polyproline type I helices. However, the number of efficient examples remains scarce and chemical diversity accessible through the use of these side chains is limited. Herein, we introduce an array of NCα-gem-dimethylated peptoid residues mimicking proteinogenic amino acids. Submonomer synthesis and block-coupling approaches were explored to access heterooligomers incorporating these novel types of side chains. NMR studies of monomer and trimer models showed that the NCα-gem-dimethylated groups exert complete cis control on the backbone amide conformation. Lastly, a preliminary molecular modeling study gave an insight into the preferred orientation of the substituents of the NCα-gem-dimethyl side chains relative to the peptoid backbone.
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21
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22
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Oxopiperazine capping: Formation of oxopiperazine-containing peptoids via C-terminal cyclization. Tetrahedron Lett 2018. [DOI: 10.1016/j.tetlet.2018.09.047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
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23
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Antimicrobial 1,3,4-trisubstituted-1,2,3-triazolium salts. Bioorg Med Chem Lett 2018; 28:3320-3323. [PMID: 30219525 DOI: 10.1016/j.bmcl.2018.09.011] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2018] [Revised: 09/06/2018] [Accepted: 09/09/2018] [Indexed: 11/18/2022]
Abstract
A series of 1,3,4-trisubstituted-1,2,3-triazolium bromide salts were prepared by efficient two-step sequences of azide-alkyne cycloaddition and benzylic substitution. The antimicrobial activity of each triazolium salt and correlating triazole precursor was evaluated using a minimum inhibitory concentration (MIC) assay. MIC activities as low as 1 µM against Gram-positive bacteria, 8 µM against Gram-negative bacteria and 4 µM against fungi were observed for salt analogs, while neutral triazoles were inactive. Analogs representing selective and broad-spectrum antimicrobial activity were each identified. MIC structure-activity relationships observed within this motif indicate that the presence of cationic charge and balance of overall hydrophobicity are strongly impactful, while benzyl vs. aryl substituent identity and variation of substituent regiochemistry are not.
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