Synthesis and antibacterial activities of 5-hydroxy-4-amino-2(5H)-furanones

Effects of Synthetic Tetronamides and Methylated Denigrins on Bacterial Quorum Sensing and Biofilm Formation

Detrimental biofilms of bacterial pathogens cause chronic infections with a high-level tolerance to antibiotics. To identify new control agents, we synthesized and tested a total of 14 tetronamides (including 5 new compounds) and 6 denigrin intermediates on the model species Escherichia coli. At a concentration of 50 μg/mL, two tetronamides and two methylated denigrins exhibited significant inhibitory effects against biofilm formation of E. coli RP437, e.g., by 60 and 94%, respectively. Structural analysis of the tested compounds revealed that p-methoxybenzylidene and p-methoxyphenethyl moieties of denigrins are important for biofilm inhibition, while the former group is also essential to the activity against quorum sensing (QS) via AI-2. Specifically, tetramethyldenigrin B has strong inhibitory effects against both E. coli biofilm formation and AI-2-mediated QS and thus provides a promising lead structure for designing better control agents. Consistently, tetramethyldenigrin B also showed inhibitory activity against biofilm formation of uropathogenic E. coli. Together, these findings provide new insights for the rational design of novel biofilm and QS inhibitors.

Synthesis and medicinal chemistry of tetronamides: Promising agrochemicals and antitumoral compounds

Butenolides and tetronic acids occupy a prominent position in synthetic chemistry due to their ubiquitous distribution in nature. This has stimulated investigations firstly in the synthesis of such systems and, laterly, the interest has turned to the understanding of the quantum structure of such systems, allowing a deeper understanding of the mechanism and reactivity of this cyclic scaffold. In contrast, tetronamides, which consist of compounds bearing a 4-aminofuran-2(5H)-one backbone, are relatively rare in nature and synthetic routes to such compounds are poorly explored. This review highlights both the importance of the tetronamide scaffold in medicinal chemistry and the most relevant recondite synthetic strategies for obtaining compounds of this class.

Synthesis, antibacterial activity and mechanism of new butenolides derivatives containing an amide moiety

A series of novel butenolide derivatives containing an amide were designed and synthesized with flupyradifurone as the lead compound. The biological activities test found that this series of compounds did not exhibit insecticidal activity, but had good antibacterial activities. Among all target compounds, compound 19 showed good antibacterial activity in vitro against Xanthomonas oryzae pv. oryzae (Xoo), with an EC₅₀ value of 35.8 mg/L, which was superior to that of bismerthiazol (73.5 mg/L). Under greenhouse conditions, the curative and protective activities of compound 19 against bacterial leaf blight were 40.9% and 48.9% at 100 mg/L, respectively, which were superior to those of bismerthiazol (31.2% and 31.4%). In addition, compound 19 can not only cause changes in the cell surface morphology of Xoo, but also increase the activity of rice defense enzymes. The mechanism of action studies showed that the protective activity of compound 19 against rice bacterial leaf blight is closely related to the improvement of defense-related enzyme activities and the upregulation of proteins involved in oxidative phosphorylation.

Alkynoates as Versatile and Powerful Chemical Tools for the Rapid Assembly of Diverse Heterocycles under Transition-Metal Catalysis: Recent Developments and Challenges

Heterocycles, heteroaromatics and spirocyclic entities are ubiquitous components of a wide plethora of synthetic drugs, biologically active natural products, marketed pharmaceuticals and agrochemical targets. Recognizing their high proportion in drugs and rich pharmacological potential, these invaluable structural motifs have garnered significant interest, thus enabling the development of efficient catalytic methodologies providing access to architecturally complex and diverse molecules with high atom-economy and low cost. These chemical processes not only allow the formation of diverse heterocycles but also utilize a range of flexible and easily accessible building units in a single operation to discover diversity-oriented synthetic approaches. Alkynoates are significantly important, diverse and powerful building blocks in organic chemistry due to their unique and inherent properties such as the electronic bias on carbon-carbon triple bonds posed by electron-withdrawing groups or the metallic coordination site provided by carbonyl groups. The present review highlights the comprehensive picture of the utility of alkynoates (2007-2019) for the synthesis of various heterocycles (> 50 types) using transition-metal catalysts (Ru, Rh, Pd, Ir, Ag, Au, Pt, Cu, Mn, Fe) in various forms. The valuable function of versatile alkynoates (bearing multifunctional groups) as simple and useful starting materials is explored, thus cyclizing with an array of coupling partners to deliver a broad range of oxygen-, nitrogen-, sulfur-containing heterocycles alongside fused-, and spiro-heterocyclic compounds. In addition, these examples will also focus the scope and reaction limitations, as well as mechanistic investigations into the synthesis of these heterocycles. The biological significance will also be discussed, citing relevant examples of drug molecules highlighting each class of heterocycles. This review summarizes the recent developments in the synthetic methods for the synthesis of various heterocycles using alkynoates as readily available starting materials under transition-metal catalysis.

Synthesis of N-2(5H)-furanonyl sulfonyl hydrazone derivatives and their biological evaluation in vitro and in vivo activity against MCF-7 breast cancer cells

A series of (E)-N-2(5H)-furanonyl sulfonyl hydrazone derivatives have been rationally designed and efficiently synthesized by one-pot reaction with good yields for the first time. This green approach with wide substrate range and good selectivity can be achieved at room temperature in a short time in the presence of metal-free catalyst. The cytotoxic activities against three human cancer cell lines of all newly obtained compounds have been evaluated by MTT assay. Among them, compound 5 k exhibits high cytotoxic activity against MCF-7 human breast cancer cells with an IC₅₀ value of 14.35 μM. The cytotoxic mechanism may involve G2/M phase arrest pathway, which is probably caused by activating DNA damage. Comet test and immunofluorescence results show that compound 5 k can induce DNA damage in time- and dose-dependent manner. Importantly, 5 k also can effectively inhibit the proliferation of MCF-7 cells and angiogenesis in the zebrafish xenograft model. It is potential to further develop N-2(5H)-furanonyl sulfonyl hydrazone derivatives as potent drugs for breast cancer treatment with higher cytotoxic activity by modifying the structure of the compound.

An antibacterial dental light-cured glass-ionomer cement with improved hardness

An antibacterial dental light-cured glass-ionomer cement has been developed and evaluated. An antibacterial furanone derivative was synthesized and covalently attached onto the surface of alumina filler particles. The formed antibacterial fillers were then mixed into a light-curable glass-ionomer cement formulation. Surface hardness and bacterial viability were used to evaluate the modified cements. Effects of coated furanone moiety content on the modified fillers, modified alumina filler particle size and loading, and total glass filler content were investigated. Results showed that increasing antibacterial furanone content, modified particle size and loading, and total glass filler content generally increased surface hardness. Increasing furanone moiety, filler loading and total filler content increased antibacterial activity. On the other hand, increasing particle size decreased antibacterial activity. The leaching tests indicate that the modified experimental cement showed no leachable antibacterial component to bacteria and cells.

Synthesis of new tetronamides displaying inhibitory activity against bloom-forming cyanobacteria

BACKGROUND

The increasing frequency and intensity of cyanobacterial blooms pose a serious threat to aquatic ecosystems. These blooms produce potent toxins that can contaminate drinking water and endanger the life of wild and domestic animals as well as humans. Consequently, the development of effective methods for their control is a matter of high priority. We have previously shown that some γ-benzylidenebutenolides, related to the rubrolide family of natural products, are capable of inhibiting the photosynthetic electron transport chain (Hill reaction), a target of commercial herbicides. Here we report the synthesis and biological properties of a new class of rubrolide-inspired molecules featuring a tetronamide motif.

RESULTS

A total of 47 N-aryl tetronamides, including 38 aldol adducts, were prepared bearing phenyl, biphenyl, naphthyl, aliphatic and heteroaromatic groups. Some of the aldol adducts were dehydrated to the corresponding γ-benzylidenetetronamides, although satisfactory yields were obtained in only three cases (52-97%). None of the synthesized compounds were capable of blocking the Hill reaction. This notwithstanding, several aldol adducts equipped with a biphenyl substituent displayed excellent inhibitory activity against Synechococcus elongatus and other cyanobacterial strains (IC₅₀  = 1-5 μM). Further, these tetronamides were found to be essentially inactive against eukaryotic microorganisms.

CONCLUSION

Several newly synthesized biphenyl-containing tetronamides were shown to display potent and selective inhibitory activity against cyanobacteria. These compounds appear to exert their biological effects without interfering with the Hill reaction. As such, they represent novel leads in the search of environmentally benign agents for controlling cyanobacterial blooms. © 2019 Society of Chemical Industry.

An improved dental composite with potent antibacterial function

A new BisGMA-based antibacterial dental composite has been formulated and evaluated. Compressive strength and bacterial viability were utilized to evaluate the formed composites. It was found that the new composite exhibited a significantly enhanced antibacterial function along with improved mechanical and physical properties. The bromine-containing derivative-modified composite was more potent in antibacterial activity than the chlorine-containing composite. The modified composites also exhibited an increase of 30-53% in compressive yield strength, 15-30% in compressive modulus, 15-33% in diametral tensile strength and 6-20% in flexural strength, and a decrease of 57-76% in bacterial viability, 23-37% in water sorption, 8-15% in shrinkage, 8-13% in compressive strength, and similar degree of conversion, than unmodified composite. It appears that this experimental composite may possibly be introduced to dental clinics as an attractive dental restorative due to its improved properties as well as enhanced antibacterial function.

Polyvinylchloride surface with enhanced cell/bacterial adhesion-resistant and antibacterial functions

This study reports synthesis and attachment of a novel antibacterial and hydrophilic polymer onto a polyvinylchloride surface via a simple and mild surface coating technique. The compound 3,4-dichloro-5-hydroxy-2(5H)-furanone was derivatized and copolymerized with N-vinylpyrrolidone. The copolymer was then covalently coated onto polyvinylchloride surface. 3T3 mouse fibroblast cells and bacterium Pseudomonas aeruginosa were used to evaluate surface adhesion and antibacterial activity. Results showed that the polymer-modified polyvinylchloride surface not only exhibited significantly decreased 3T3 fibroblast cell adhesion with a 64–84% reduction but also demonstrated significantly decreased P. aeruginosa adhesion with a 65–84% reduction, as compared to unmodified polyvinylchloride. Furthermore, the modified polyvinylchloride surfaces exhibited significant antibacterial functions by inhibiting P. aeruginosa growth with a 58–80% reduction and killing bacteria, as compared to unmodified polyvinylchloride. These results demonstrate that covalent polymer attachment conferred cell/bacterial adhesion-resistant and antibacterial properties to the polyvinylchloride surface.

Surface modification of polyurethane with a hydrophilic, antibacterial polymer for improved antifouling and antibacterial function

Antimicrobial surface is important for the inhibition of bacteria or biofilm formation on biomaterials. The objective of this study was to immobilize a novel hydrophilic polymer containing the antibacterial moiety onto polyurethane surface via a simple surface coating technology to make the surface not only antibacterial but also antifouling. The compound 3,4-dichloro-5-hydroxy-2(5H)-furanone was derivatized, characterized and incorporated onto polyvinylpyrrolidone containing succinimidyl functional groups, followed by coating onto the polyurethane surface. Contact angle, antibacterial function and protein adsorption of the modified surface were evaluated. The result shows that the modified surface exhibited significantly enhanced hydrophilicity with a 54-65% decrease in contact angle, increased antibacterial activity to Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa with a 24-57% decrease in viability, and reduced human serum albumin adsorption with a 64-70% decrease in adsorption, as compared to the original polyurethane.

Androgen Receptor Is Inactivated and Degraded in Bladder Cancer Cells by Phenyl Glucosamine via miR-449a Restoration

Background

Bladder cancer caused by exposure to aniline dyes, chronic cystitis, and smoking is detected in approximately 70 000 new cases annually. In the USA alone, it leads to 15 000 deaths every year. In the present study, we investigated the role of 3-((4′-amino-[1,1′-biphenyl]-4-yl)amino)-4-bromo-5-oxo-2,5-dihydrofuran-2-yl acetate (ABDHFA) in the inhibition of bladder cancer cell viability.

Material/Methods

Viability of cells was examined using MTT assay and distribution of cell cycle was assessed by flow cytometry. Expression of cyclin D1, androgen, prostate-specific antigen (PSA), and miR-449a was analyzed using Western blot and quantitative real-time polymerase chain reaction assays.

Results

The results demonstrated that ABDHFA treatment inhibited viability of UMUC3 and TCCSUP AR-positive bladder cancer cells. ABDHFA treatment led to break-down of AR in UMUC3 and TCCSUP cells after 48 h in a dose-dependent manner. Up-regulation of miR-449a by lentivirus transfection down-regulated the AR signalling pathway. In UMUC3 and TCCSUP cells, ABDHFA treatment led to inhibition of mRNA and protein expression corresponding to AR.

Conclusions

In summary, the present study demonstrates that proliferation of AR-positive bladder carcinoma cells is markedly reduced by ABDHFA treatment through arrest of cell cycle and degradation of AR protein. Thus, ABDHFA, a novel compound, can be used for the treatment of bladder cancer.

Antimicrobial Effects of Sulfonyl Derivative of 2(5H)-Furanone against Planktonic and Biofilm Associated Methicillin-Resistant and -Susceptible Staphylococcus aureus

The gram-positive opportunistic bacterium Staphylococcus aureus is one of the most common causatives of a variety of diseases including skin and skin structure infection or nosocomial catheter-associated infections. The biofilm formation that is an important virulence factor of this microorganism renders the antibiotic therapy ineffective, because biofilm-embedded bacteria exhibit strongly increased tolerance to antimicrobials. Here, we describe a novel 3-chloro-5(S)-[(1R,2S,5R)-2-isopropyl-5-methylcyclohexyloxy]-4-[4-methylphenylsulfonyl]-2(5H)-furanone (F105), possessing a sulfonyl group and l-menthol moiety. Minimal inhibitory and bactericidal concentration values (MIC and MBC) of F105 were 10 and 40 mg/L, respectively, suggesting F105 biocidal properties. F105 exhibits pronounced activity against biofilm-embedded S. aureus and increases the efficacy of aminoglycosides (amikacin, gentamicin, and kanamycin) and benzalkonium chloride with fractional inhibitory concentration index values of 0.33–0.44 and 0.29, respectively, suggesting an alternative external treatment option, e.g., for wound infections. Moreover, low concentrations (0.5–1.3 mg/L) of F105 reduced the MICs of these antimicrobials twofold. By using confocal laser scanning microscopy and CFU counting, we show explicitly that F105 also restores the antimicrobial activity of gentamicin and ampicillin against S. aureus biofilms by several orders of magnitude. Biofilm structures were not destroyed but sterilized, with embedded cells being almost completely killed at twofold MBC. While F105 is quite toxic (CC₅₀/MBC ratio 0.2), our data suggest that the F105 chemotype might be a promising starting point for the development of complex topical agents for combined anti-staphylococcal biofilm-therapies restoring the efficacy of some antibiotics against difficult to treat S. aureus biofilm.

Prediction of the Regioselectivity of 1,3-Dipolar Cycloaddition Reactions of Nitrile Oxides with 2(5H)-Furanones Using Recent Theoretical Reactivity Indices

The regioselectivity of a series of 16 1,3-dipolar cycloaddition reactions of nitrile oxides with 2(5 H)-furanones has been analysed by means of global and local electrophilic and nucleophilic reactivity indices using density functional theory at the B3LYP level together with the 6-31G(d) basis set. The local electrophilicity and nucleophilicity indices, based on Fukui and Parr functions, have been calculated for the terminal sites, namely the C1 and O3 atoms of the 1,3-dipole and the C4 and C5 atoms of the dipolarophile. These local indices were calculated using both Mulliken and natural charges and spin densities. The results obtained show that the C5 atom of the 2(5 H)-furanones is the most electrophilic site whereas the O3 atom of the nitrile oxides is the most nucleophilic centre. It turns out that the experimental regioselectivity is correctly reproduced, indicating that both Fukui- and Parr-based indices are efficient tools for the prediction of the regiochemistry of the studied reactions and could be used for the prediction of new designed reactions of the same kind.

Thermodynamically driven, syn-selective vinylogous aldol reaction of tetronamides

A stereoselective vinylogous aldol reaction of N-monosubstituted tetronamides with aldehydes is described.

Quinoline based furanones and their nitrogen analogues: Docking, synthesis and biological evaluation

A small library of twenty-four quinoline based butenolides also known as furanones and their nitrogen analogues was prepared by using two different aroylpropionic acids, viz. 3-(2-naphthoyl)propionic acid (3) and 3-(biphenyl-4-yl)propionic acid (4), as starting materials. The 3-aroylpropionic acids were reacted with different 6-substituted-2-chloroquinolin-3-carbaldehydes (2a–d) to obtain the corresponding furan-2(3H)-ones (5a–h). The purified and characterized furanones were then converted into their corresponding 2(3H)-pyrrolones (6a–h) and N-benzyl-pyrrol-2(3H)-ones (7a–h). The antimicrobial activities of the title compounds were evaluated against two strains of each Gram +ve (Staphylococcus aureus and Bacillus subtilis), Gram −ve bacteria (Escherichia coli and Pseudomonas aeruginosa) and against fungal strains of Aspergillus niger and Aspergillus flavus. In vivo anti-inflammatory potential of the title compounds was investigated by standard method. Majority of the compounds showed significant antibacterial activity against both the Gram +ve strains. Eight most potent anti-inflammatory compounds (5b, 5d, 5h, 6b, 7b, 7d, 7f, 7h) which exhibited >53% inhibition in edema, were also screened for their in vivo analgesic activity. All the tested compounds were found to have significant reduction in ulcerogenic action but only three compounds (5d, 5h and 7h) showed comparable analgesic activity to standard drug, diclofenac. The results were also validated using in silico approach and maximum mol doc score was obtained for compounds 7a–h. On comparing the in vivo and in silico anti-inflammatory results of synthesized compounds, N-benzyl pyrrolones (7a–h) emerged as the potent anti-inflammatory agents. It was also observed that compounds that possess electron withdrawing group such as —Cl or NO₂ are more biologically active.

An efficient and facile synthesis of 3-amino-5-chromenyl-butenolides from 3-formyl chromone, dialkyl acetylenedicarboxylate, and primary amines

A three-component reaction of 3-formyl chromones, dialkyl acetylenedicarboxylate, and isocyanides in the presence of POCl(3) was used as a highly efficient and practical approach for the synthesis of 3-amino-5-chromenyl-butenolides. High yields and high bond forming efficiency, and simple operations are the advantages of this method. Graphical abstract.

A novel furanone-modified antibacterial dental glass ionomer cement

A novel furanone derivative and a polyacid constructed from it were synthesized, characterized and formulated into experimental high strength cements. The compressive strength (CS) and Streptococcus mutans viability were used to evaluate the mechanical strength and antibacterial activity of the cements. The effect of human saliva and aging were investigated. The antibacterial activity against Lactobacillus sp. and cytotoxicity to human pulp cells were also evaluated. The results show that all the formulated furanone-containing cements showed antibacterial activity, with an initial reduction in CS. The effect of the furanone derivative loading was significant. Increasing loading enhanced the antibacterial activity but reduced the initial CS of the formed cements. The derivative showed antibacterial activity against both S. mutans and Lactobacillus sp. Human saliva did not affect the antibacterial activity of the cement. The cytotoxicity study with human dental pulp cells shows that the furanone-modified cement was biocompatible. A 30 day aging study indicated that the cements may have long-lasting antibacterial activity. Within the limitations of this study it appears that the experimental cement could be a clinically attractive dental restorative due to its high mechanical strength and antibacterial function.

A novel antibacterial resin composite for improved dental restoratives

A novel furanone-containing antibacterial resin composite has been prepared and evaluated. compressive strength (CS) and Streptococcus mutans viability were used to evaluate the mechanical strength and antibacterial activity of the composites. The modified resin composites showed a significant antibacterial activity without substantially decreasing the mechanical strengths. With 5-30 % addition of the furanone derivative, the composite kept its original CS unchanged but showed a significant antibacterial activity with a 16-68 % reduction in the S. mutans viability. Further, the antibacterial function of the new composite was not affected by human saliva. The aging study indicates that the composite may have a long-lasting antibacterial function. Within the limitations of this study, it appears that the experimental antibacterial resin composite may potentially be developed into a clinically attractive dental restorative due to its high mechanical strength and antibacterial function.

Synthesis of a new class of antimicrobial agents incorporating the indolin-2-one moiety

New furanone derivatives incorporating the indolin-2-one moiety 3 were prepared via the Perkin reaction of isatins 1 with aroylpropionic acids 2 under conventional conditions or microwave irradiation. A series of functionally heterocyclic derivatives (e.g., pyridazines, pyrroles, and sulfonamides) incorporating the indolin-2-one moiety was achieved via reaction of 3 with different reagents under microwave irradiation conditions. The newly synthesized compounds were characterized on the basis of FTIR, (1)H, (13)C NMR and mass spectral studies. Some of the new synthesized compounds were screened for antibacterial activity against Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus), Gram-negative bacteria (Escherichia coli and Shigilla flexneri) and antifungal activity against Aspergillus flavus and Candida albicans. Compound 8 j was equipotent to chloramphenicol in inhibiting the growth of E. coli minimum inhibitory concentration (MIC 2.5 μg/mL). Compound 8j may possibly be used as a lead compound for developing a new antibacterial agents. The antibacterial activity is expressed as the corresponding MIC (μg/mL) values.

(E)-Methyl 2-chloro-4-dicyclo-hexyl-amino-4-oxobut-2-enoate

In the title compound, C(17)H(26)ClNO(3), both cyclo-hexyl rings have chair conformations. In the crystal, mol-ecules are linked by weak inter-molecular C-H⋯O hydrogen bonds.

3-Bromo-5-meth-oxy-4-(4-methyl-piperidin-1-yl)furan-2(5H)-one

There are two molecules in the asymmetric unit of title compound, C(11)H(16)BrNO(3), which was obtained via the tandem Michael addition-elimination reaction of 3,4-dibromo-5-meth-oxy-furan-2(5H)-one and 4-methyl-piperidine in the presence of potassium fluoride. The furan-one rings are approximately planar [maximum atomic deviations of 0.026 (2) and 0.015 (2) Å, respectively]. The packing is stabilized by weak inter-molecular C-H⋯O and C-H⋯Br inter-actions.

(5S)-3-Chloro-5-[(1R,2S,5R)-2-isopropyl-5-methyl-cyclo-hex-yloxy]-4-(4-methyl-piperidin-1-yl)furan-2(5H)-one

The title compound, C₂₀H₃₂ClNO₃, was obtained via a tandem asymmetric Michael addition–elimination reaction of (5S)-3,4-dichloro-5-(l-menth­yloxy)furan-2(5H)-one and 4-methyl­piperidine in the presence of potassium fluoride. The furan­one ring is approximately planar [maximum atomic deviation = 0.022 (2) Å] while the cyclo­hexane ring adopts a chair conformation. Weak inter­molecular C—H⋯O hydrogen bonding is present in the crystal structure.

Convenient synthesis of 3,4-dichloro-5-hydroxy-2(5H)-furanone glycoconjugates

3,4-Dichloro-5-hydroxy-2(5H)-furanone treated with methyl chloroformate in the presence of diisopropylethylamine (Hünig’s base) gave the corresponding carbonate. The labile methoxycarbonyloxy group smoothly undergoes substitution by amino alcohols. The obtained 5-(ω-hydroxyalkylamino) mucochloric acid derivatives reacted with peracetylated glucals using triphenylphosphine hydrobromide as a catalyst to give the title muchloric acid glycoconjugates.

(5S)-3-Chloro-4-(2,5-dihydro-1H-pyrrol-1-yl)-5-[(1R,2S,5R)-2-isopropyl-5-methyl-cyclo-hex-yloxy]furan-2(5H)-one

The title compound, C(18)H(26)ClNO(3), was obtained via a tandem asymmetric Michael addition-elimination reaction of 3,4-dichloro-5-(S)-(l-menth-yloxy)furan-2(5H)-one and 2,5-di-hydro-1H-pyrrole in the presence of potassium fluoride. In the mol-ecule, the nearly planar dihydro-pyrrole ring [maximum atomic deviation = 0.019 (3) Å] is oriented at a dihedral angle of 10.73 (8)° to the the nearly planar furan-one ring [maximum atomic deviation = 0.011 (2) Å]; the cyclo-hexane ring adopts a chair conformation. In the crystal, mol-ecules are linked via weak inter-molecular C-H⋯O hydrogen bonds, forming supra-molecular chains running along the b axis.

Monohalogenated maleimides as potential agents for the inhibition of Pseudomonas aeruginosa biofilm

New monohalogenated maleimide derivatives (with bromine, chlorine or iodine) were synthesized to test the effect of halogen atoms in inhibiting the formation of Pseudomonas aeruginosa biofilm. The evaluation of their biological activities clearly defines a structure-activity relationship. In this study, the bactericidal action of the three compounds was observed at the concentration range 0.3-5.0 mM on Luria-Bertani agar plates. The halogen atom of these molecules was critical in modulating the antibacterial activity, with a slightly higher effectiveness for chlorine. Confocal laser scanning microscopy was used to examine P. aeruginosa biofilms cultivated in flow cells. At concentration as low as 40 microM, the bromine and iodine compounds displayed a total inhibition towards the formation of bacterial biofilm. At this concentration, the bacterial attachment to glass surfaces was strongly affected by the presence of bromine and iodine whereas the chlorine derivative behaved as a bactericidal compound. A bioluminescent reporter strain was then used to detect the effect of the chemically synthesized maleimides on quorum sensing (QS) in P. aeruginosa. At the concentration range 10-100 microM, bioluminescence assays reveal that halogenated maleimides were able to interfere with the QS of the bacterium. Although the relationship between the weak inhibition of cell-to-cell communication (15-55% of the signal) and the high inhibition of biofilm formation has not been elucidated clearly, the results demonstrate that bromo- and iodo-N-substituted maleimides bromine and iodine may be used as new potent inhibitors that control bacterial biofilms.

Solid-phase synthesis of optically active substituted 2 aminofuranones using an activated carbonate linker

An efficient three-step solid-phase synthesis of diverse 3,5-disubstituted-2-aminofuranones has been developed. alpha-Hydroxy acids loaded on a nitrophenyl carbonate derivative of Wang resin are used as acylating agents for the C-acylation of active methylene compounds and the resulting intermediates provided, through a cyclative cleavage reaction, the desired product.