Expedient Synthesis of SMAMPs via Click Chemistry

Synthesis of novel 1,2,3-triazole-substituted tomentosins

A series of 1,2,3-triazole-containing tomentosin scaffolds was obtained from tomentosin 1. The synthesis involved a Michael addition of trimethylsilylazide on the α-methylene-γ-lactone function of the natural sesquiterpene lactone 1 to give the diastereoisomers 2 and 3, which were readily separated by column chromatography. These compounds underwent copper-catalyzed Huisgen 1,3-dipolar cycloaddition with various terminal alkynes to provide compounds 4a–h and 5a–h in good yields.

Arylhydrazone ligands as Cu-protectors and -catalysis promoters in the azide-alkyne cycloaddition reaction

A series of water soluble copper(ii) complexes, [Cu(κO¹O²N-H₂L¹)(H₂O)₂]·2H₂O (2), [Cu(κO-H₃L¹)₂(H₂O)₄] (3), [Cu(κO-H₄L²)₂(H₂O)₄] (5) and [Cu(H₂O)₆]·2H₂L³·2(CH₃)₂NCHO (7), were prepared by the reaction of Cu(NO₃)₂·3H₂O with sodium (Z)-2-(2-(1-amino-1,3-dioxobutan-2-ylidene)hydrazineyl)benzenesulfonate, [Na(μ₄-1:2κO¹,2κO²,3κO³,4κO⁴-H₃L¹)]_n (1; for 2 and 3), sodium (Z)-3-(2-(1-amino-1,3-dioxobutan-2-ylidene)hydrazineyl)-4-hydroxybenzene-sulfonate, [Na(μ-1κO¹,2κO²-H₄L²)]₂ (4; for 5) or sodium (Z)-2-(2-(1,3-dioxo-1-(phenylamino)butan-2-ylidene)hydrazineyl)naphthalene-1-sulfonate, [Na(μ-1κO¹O²,2κO³-H₂L³)(CH₃OH)₂]₂ (6; for 7). Compounds 1-7 were fully characterized, also by single-crystal X-ray diffraction analysis, and applied as homogeneous catalysts for the azide-alkyne cycloaddition (AAC) reaction to afford 1,4-disubstituted 1,2,3-triazoles. A structure-catalytic activity relationship has been recognized for the first time on the basis of the occurrence of resonance- and charge-assisted hydrogen bond interactions (RAHB and CAHB), in charge and ligand binding modes, enabling the catalytic activity of the compounds to be ordered as follows: Cu(NO₃)₂≪7 (complex salt with RAHB and CAHB) < 3 (with RAHB and CAHB) < 5 (with RAHB) < 2 (neither RAHB nor CAHB). Complex 2, without such non-covalent interactions, was found to be the most efficient catalyst for the AAC reaction, affording up to 98% product yield after being placed for 15 min, at 125 °C, in a water/acetonitrile mixture under low power (10 W) MW irradiation.

Design, synthesis and biological evaluation of novel 7-amino-[1,2,4]triazolo[4,3-f]pteridinone, and 7-aminotetrazolo[1,5-f]pteridinone derivative as potent antitumor agents

To develop novel therapeutic agents with anticancer activities, two series of novel 7-amino-[1,2,4]triazolo[4,3-f]pteridinone, and 7-aminotetrazolo[1,5-f]pteridinone derivatives were designed and synthesized. All compounds were tested for anti-proliferative activities against five cancer cell lines. The structure-activity relationships (SARs) studies were conducted through the variation in two regions, the moiety of A ring and the terminal aniline B on pteridinone core. 1-Methyl-1,2,4-triazole derivative L₇ with 2,6-dimethylpiperazine showed the most potent antiproliferative activity against A549, PC-3, HCT116, MCF-7 and MDA-MB-231 cell lines with IC₅₀ values of 0.16 μM, 0.30 μM, 0.51 μM, 0.30 μM, and 0.70 μM, respectively. Combined with the results of the molecular docking and enzymatic studies, the PLK1 was very likely to be one of the drug targets of compound L₇. Furthermore, to clarify the anticancer mechanism of compound L₇, further explorations in the bioactivity were conducted. The results showed that compound L₇ obviously inhibited proliferation of A549 cell lines, induced a great decrease in mitochondrial membrane potential leading to apoptosis of cancer cells, suppressed the migration of tumor cells, and arrested G1 phase of A549 cells.

Recent Advances in Antimicrobial Polymers: A Mini-Review

Human safety and well-being is threatened by microbes causing numerous infectious diseases resulting in a large number of deaths every year. Despite substantial progress in antimicrobial drugs, many infectious diseases remain difficult to treat. Antimicrobial polymers offer a promising antimicrobial strategy for fighting pathogens and have received considerable attention in both academic and industrial research. This mini-review presents the advances made in antimicrobial polymers since 2013. Antimicrobial mechanisms exhibiting either passive or active action and polymer material types containing bound or leaching antimicrobials are introduced. This article also addresses the applications of these antimicrobial polymers in the medical, food, and textile industries.

Modulating Antimicrobial Activity and Mammalian Cell Biocompatibility with Glucosamine-Functionalized Star Polymers

The development of novel reagents and antibiotics for combating multidrug resistance bacteria has received significant attention in recent years. In this study, new antimicrobial star polymers (14-26 nm in diameter) that consist of mixtures of polylysine and glycopolymer arms were developed and were shown to possess antimicrobial efficacy toward Gram positive bacteria including methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE) (with MIC values as low as 16 μg mL(-1)) while being non-hemolytic (HC50 > 10,000 μg mL(-1)) and exhibit excellent mammalian cell biocompatibility. Structure function analysis indicated that the antimicrobial activity and mammalian cell biocompatibility of the star nanoparticles could be optimized by modifying the molar ratio of polylysine to glycopolymers arms. The technology described herein thus represents an innovative approach that could be used to fight deadly infectious diseases.

Synthesis of energy transfer cassettes via click and Suzuki–Miyaura cross coupling reactions

Novel cassettes capable of energy transfer involving simple synthetic methodsviz., click reaction at C-8 position and palladium catalyzed Suzuki–Miyaura cross coupling at C-6 position of imidazo[1,2-a]pyrazine, have been represented.

Membrane-Active Small Molecules: Designs Inspired by Antimicrobial Peptides

Infectious diseases continue to be one of the major contributors to human morbidity. The rapid rate at which pathogenic microorganisms have developed resistance against frontline antimicrobials has compelled scientists to look for new alternatives. Given their vast antimicrobial repertoire, substantial research effort has been dedicated toward the development of antimicrobial peptides (AMPs) as alternative drugs. However, inherent limitations of AMPs have driven substantial efforts worldwide to develop synthetic mimics of AMPs. This review focuses on the progress that has been made toward the development of small molecules that emulate the properties of AMPs, both in terms of design and biological activity. Herein we provide an extensive discussion of the structural features of various designs and we examine biological properties that have been exploited. Furthermore, we raise a number of questions for which the field has yet to provide solutions and discuss possible future research directions that remain either unexploited or underexploited.

Cell penetrating synthetic antimicrobial peptides (SAMPs) exhibiting potent and selective killing of mycobacterium by targeting its DNA

Naturally occurring antimicrobial peptides (AMPs) are powerful defence tools to tackle pathogenic microbes. However, limited natural production and high synthetic costs in addition to poor selectivity limit large-scale use of AMPs in clinical settings. Here, we present a series of synthetic AMPs (SAMPs) that exhibit highly selective and potent killing of Mycobacterium (minimum inhibitory concentration <20 μg mL(-1)) over E. coli or mammalian cells. These SAMPs are active against rapidly multiplying as well as growth saturated Mycobacterium cultures. These SAMPs are not membrane-lytic in nature, and are readily internalized by Mycobacterium and mammalian cells; whereas in E. coli, the lipopolysaccharide layer inhibits their cellular uptake, and hence, their antibacterial action. Upon internalization, these SAMPs interact with the unprotected genomic DNA of mycobacteria, and impede DNA-dependent processes, leading to bacterial cell death.

One-pot sequential alkynylation and cycloaddition: regioselective construction and biological evaluation of novel benzoxazole-triazole derivatives

Individually, benzoxazole and triazole moieties are of significant biological interest owing to their importance in drugs and pharmaceuticals. To assess their combined biological impact when woven into one molecule, we designed a novel, regioselective, multicomponent, one-pot (MCOP) approach for the construction of benzoxazole-linked triazoles. The synthesis has been achieved in two sequential steps involving copper-catalyzed alkynylation of benzoxazole followed by a 1,3-dipolar cycloaddition reaction. By combination of these two bioactive units into one core, a series of new benzoxazole-triazole scaffolds has been synthesized and subjected to in vitro antibacterial and anticancer evaluation. Tests against clinical isolates of Staphylococcus aureus and Escherichia coli showed potent Gram-negative activity for compounds 4{1,1,1}, 4{1,1,4}, and 4{1,2,1}. The cytotoxicity of the synthesized library was determined against three cancer cell lines: HeLa, SKBr3, and Hep G2. Compound 4{2,2,2} showed significant cytotoxicity against all the cell lines. These preliminary bioassay evaluations strongly suggest the promise and scope of these novel molecules as therapeutic agents in medical science.

TMEDA-derived biscationic amphiphiles: An economical preparation of potent antibacterial agents

Bis-alkylated derivatives of N,N,N',N'-tetramethylethylenediamine (TMEDA) represent a well-known class of versatile biscationic amphiphiles, owing to their low cost and ease of preparation. Asymmetric TMEDA derivatives, however, have been studied significantly less, particularly in regards to their antimicrobial properties. We have thus prepared a series of 36 mono- and bis-alkylated TMEDA derivatives to evaluate their inhibition of bacterial growth. This series of compounds showed low micromolar activity against a panel of four bacteria. Optimal inhibition was observed when the biscationic amphiphiles possessed modest asymmetry and were composed of between 20 and 24 total carbon atoms in the side chains. These amphiphiles were prepared in a simple two-step procedure, utilizing inexpensive materials and atom-economical reactions, making them practical for further development.