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Background: Enterococcus faecium is an important nosocomial pathogen. It has a high propensity for horizontal gene transfer, which has resulted in the emergence of MDR strains that are difficult to treat. The most notorious of these, vancomycin-resistant E. faecium, are usually treated with linezolid or daptomycin. Resistance has, however, been reported, meaning that new therapeutics are urgently needed. The 1,2,4-oxadiazoles are a recently discovered family of antimicrobials that are active against Gram-positive pathogens and therefore have therapeutic potential for treating E. faecium. However, only limited data are available on the activity of these antimicrobials against E. faecium.Objectives: To determine whether the 1,2,4-oxadiazole antimicrobials are active against MDR and daptomycin-non-susceptible E. faecium.Methods: The activity of the 1,2,4-oxadiazole antimicrobials against vancomycin-susceptible, vancomycin-resistant and daptomycin-non-susceptible E. faecium was determined using susceptibility testing, time-kill assays and synergy assays. Toxicity was also evaluated against human cells by XTT and haemolysis assays.Results: The 1,2,4-oxadiazoles are active against a range of MDR E. faecium, including isolates that display non-susceptibility to vancomycin and daptomycin. This class of antimicrobial displays rapid bactericidal activity and demonstrates superior killing of E. faecium compared with daptomycin. Finally, the 1,2,4-oxadiazoles act synergistically with daptomycin against E. faecium, with subinhibitory concentrations reducing the MIC of daptomycin for non-susceptible isolates to a level below the clinical breakpoint.Conclusions: The 1,2,4-oxadiazoles are active against MDR and daptomycin-non-susceptible E. faecium and hold great promise as future therapeutics for treating infections caused by these difficult-to-treat isolates. [ABSTRACT FROM AUTHOR]

SPRY domain-containing suppressor of cytokine signaling box protein (SPSB) 2-deficient macrophages have been found to exhibit prolonged expression of inducible nitric oxide synthase (iNOS) and enhanced killing of persistent pathogens, suggesting that inhibitors of the SPSB2−iNOS interaction have potential as novel anti-infectives. In this study, we describe the design, synthesis, and characterization of cyclic peptidomimetic inhibitors of the SPSB2-iNOS interaction constrained by organic linkers to improve stability and druggability. SPR, ITC, and 19F NMR analyses revealed that the most potent cyclic peptidomimetic bound to the iNOS binding site of SPSB2 with low nanomolar affinity (KD 29 nM), a 10-fold improvement over that of the linear peptide DINNN (KD 318 nM), and showed strong inhibition of SPSB2-iNOS interaction in macrophage cell lysates. This study exemplifies a novel approach to cyclize a Type II β-turn linear peptide and provides a foundation for future development of this group of inhibitors as new anti-infectives. [ABSTRACT FROM AUTHOR]

A new method for the synthesis of cystathionine containing cyclic peptides has been developed. Conventionally such systems are typically made with relatively late-stage on-resin cyclisation involving reaction between a chlorohomoalanine and cysteine residue. We offer a different approach involving early incorporation of a cystathionine residue through on-resin reaction between a cysteine residue and an N -Alloc iodohomoalanine cumyl ester. Subsequent cyclisation then involves amide bond formation. The success of this method was demonstrated by applying it to the synthesis of a cystathionine analogue of the disulfide bridge cyclic peptide, N -acetylated cyclic peptide c[CVDINNNC]-NH 2 , a biologically active iNOS binding epitope mimetic that binds tightly to the protein, SPSB2. Our method expands the repertoire of synthetic options towards the construction of cystathionine containing cyclic peptides. [ABSTRACT FROM AUTHOR]

In our attempts to synthesize 3-(alkylthio)- and 3-(alkoxy)-1,2,4-triazines without substituents at the 5- or 6-position, the synthesis of their anticipated precursor 3-(methylsulfonyl)-1,2,4 triazine was also optimized. The reactivity of 3-(methylsulfonyl)-1,2,4-triazine towards alkyl and aryl thiols, primary and secondary alkylamines, phenols, and alcohols was explored, and the reactions were optimized to maximize the isolation of the corresponding 3-substituted 1,2,4-triazine. Good yields were obtained for the products of the reactions with all of the aforementioned nucleophiles, with the exception of alcohols, by using alkali metal carbonates. Higher yields of 3-(alkoxy)-1,2,4-triazines were obtained by using the appropriate magnesium alkoxide as the nucleophile. [ABSTRACT FROM AUTHOR]

SPSB2 mediates the proteasomal degradation of iNOS. Inhibitors of SPSB2-iNOS interaction are expected to prolong iNOS lifetime and thereby enhance killing of persistent pathogens. Here, we describe the synthesis and characterization of two redox-stable cyclized peptides containing the DINNN motif required for SPSB2 binding. Both analogues bind with low nanomolar affinity to the iNOS binding site on SPSB, as determined by SPR and 19F NMR, and efficiently displace full-length iNOS from binding to SPSB2 in macrophage cell lysates. These peptides provide a foundation for future development of redox-stable, potent ligands for SPSB proteins as a potential novel class of anti-infectives. [ABSTRACT FROM AUTHOR]

A series of naphthyridinol analogs of α-tocopherol (α-TOH, right) with varying sidechain substitution was synthesized to determine how systematic changes in the lipophilicity of these potent antioxidants impact their radical-trapping activities in lipid bilayers, regenerability by water-soluble reductants, and binding to human tocopherol transport protein (TTP). The activities of the naphthyridinols were assayed in phosphatidylcholine unilamellar liposomes using a recently developed high-throughput assay that employs a boron dipyrromethene conjugate of α-TOH (H2B-PMHC) that undergoes fluorescence enhancement upon oxidation. The naphthyridinols afforded a dose-dependent protection of H2B-PMHC consistent with unprecedented peroxyl radical-trapping activity in lipid bilayers. While sidechain length and/or branching had no effect on their apparent reactivity, it dramatically impacted reaction stoichiometry, with more lipophilic compounds trapping two peroxyl radicals and more hydrophilic compounds trapping significantly less than one. It is suggested that the less lipophilic compounds autoxidize rapidly in the aqueous phase and that preferential partitioning of the more lipophilic compounds to the bilayer protects them from autoxidation. The cooperativity of a lipophilic naphthyridinol with water-soluble reducing agents was also studied in liposomes using H2B-PMHC and revealed superior regenerability by each of ascorbate, N-acetylcysteine, and urate when compared to α-TOH. Binding assays with human TTP, a key determinant of the bioavailability of the tocopherols, reveal that the naphthyiridinols can be very good ligands for the protein. In fact, naphthyridinols with sidechains of eight or more carbons had affinities for TTP which were similar to, and in one case 10-fold better than, α-TOH. [ABSTRACT FROM AUTHOR]

For both environmental protection and improved energy efficiency, CO2-triggered switchable surfactants have been developed to change surface activity and solubility upon command. Surfactant activity is turned on by introduction of one atmosphere of CO2 and reversed by purging with air or nitrogen. These surfactants have numerous potential industrial applications related to their ability to stabilize and destabilize emulsions upon command. To assess their potential environmental impacts, we tested the acute toxicity of nine switchable surfactants to rainbow trout (Oncorhyncus mykiss) at pH ∼8.0, typical of natural surface waters. The surfactants were synthesized in several variations, differing in the structure of the hydrophobic tail group, the hydrophilic head group, or both. A strong correlation between the log of the estimated octanol/water partition coefficients (log P) and the toxicity of eight switchable surfactants formed the basis of a structure–activity relationship that was used to design a ninth compound. That new compound had the lowest toxicity of all of the switchable surfactants tested. The effect of log P on acute toxicity was similar to that reported in the literature for other organic compounds. This model shows that despite the addition of varying functional groups, switchable surfactant toxicity remains largely dependent on log P and differs little from traditional non-switchable surfactants. The log P relationship developed provides a very useful tool for screening new compounds for acute toxicity. [ABSTRACT FROM AUTHOR]

The condensation of primary amine with N,N-dimethylacetamide dimethyl acetal yields a mixture of acetamidine and imidate ester. The product distribution in this reaction depends on the temperature, solvent, and structure of the primary amine. It is possible to suppress the formation of imidate ester by performing the reaction in the presence of excess dimethyl amine, yielding acetamidine as the exclusive product. For acetamidines that cannot be purified either by crystallization or distillation, this new method is necessary for the generation of pure acetamidines in good yields. [ABSTRACT FROM AUTHOR]

A range of ionic liquids (ILs) containing a pyridinium cation were synthesised and their biodegradability was evaluated using the CO2headspace test (ISO 14593). ILs bearing a 1-(2-hydroxyethyl) side chain were prepared from either pyridine or nicotinic acid derivatives. These ILs showed high levels of biodegradation under aerobic conditions and can be classified as ‘readily biodegradable’. In contrast, pyridinium ILs with methyl or ethyl ether side chains showed significantly lower levels of biodegradability in the same test. Biodegradation studies on a range of novel ILs with acetal and carbamate functionalities, as well as thiazolium-based salts, also showed low levels of mineralization. [ABSTRACT FROM AUTHOR]

Ionic liquid mediated deprotection of tert -butyldimethyl silyl (TBDMS) ethers derived from various primary and secondary alcohols have been studied and the reaction conditions optimized. Deprotection of the silyl ethers in FeCl 3 based ionic liquids in presence of acetic anhydride yielded the acetate esters of the corresponding alcohols in good yields. The transprotection methodology was extended to the silyl ethers of nucleosides to yield the corresponding acetylated products. [ABSTRACT FROM AUTHOR]

The ionic liquid, 1-butyl-3-methylimidazolium chloroaluminate, [bmim]Cl·AlCl3, N=0.67 mediated syntheses of aromatic sulfonamides via electrophilic substitution of arenes is reported. The protocol serves as a distinctly expeditious and ambient route towards the syntheses of these pharmaceutically useful compounds, yielding quantitative conversions at room temperature within 5–30 min in most of the cases. The Lewis acidity and molar stoichiometry of the ionic liquid influences the extent of conversion. The method has been used for the syntheses of a diverse range of sulfonamides by variation of arenes and sulfamoyl chlorides. With monosubstituted benzenes, the protocol offers an added advantage of exclusive selectivity towards the formation of para substituted sulfonamides over the ortho products. [Copyright &y& Elsevier]

The oxalic acid salt of 2-aminomethyl-3-oxyl-2,4,4-trimethyl-1,3-oxazolidine has been synthesised from 1-chloroacetone. Being water soluble, the salt is a promising candidate for varied applications. It has been functionalised with electrophilic groups generating novel spin labelling reagents. [Copyright &y& Elsevier]

The lipase-catalysed transesterifications of 2-hydroxymethyl-1,4-benzodioxane in two different ionic liquids, 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim]PF6 and 1-butyl-3-methylimidazolium tetrafluoroborate, [bmim]BF4 and different organic solvents was studied. The hydrophobic and hydrophilic properties of ionic liquids and organic solvents do influence the lipase activity as illustrated from the results. The influence of the ionic liquid as an additive in an organic solvent on this reaction has been demonstrated. The enzymes in ionic liquids in combination can be recycled for several runs without substantial diminution in the lipase activity. [Copyright &y& Elsevier]

1-Butyl-3-methylimidazolium chloroaluminate, [bmim]Cl·AlCl3, N=0.67 and 1-butylpyridinium chloroaluminate, [bpy]Cl·AlCl3, N=0.67 ionic liquids were found to work well as the Lewis acid catalyst and solvent in the Knoevenagel condensations of benzaldehyde and substituted benzaldehydes with diethyl malonate to give benzylidene malonates. The benzylidene malonates subsequently underwent Michael additions with diethyl malonate. The extent of Michael product formed during the reaction was found to vary with the Lewis acidity and the molar proportion of ionic liquid. The influence of Lewis acidity of the ionic liquid on the Knoevenagel and Michael products is demonstrated. In the case of 2-hydroxyarylaldehydes, the reactions led to the formation of 3-ethoxycarbonyl coumarins under ambient conditions. [Copyright &y& Elsevier]

Reports on the Friedel-Crafts sulfonylation in 1-butyl-3-methylimidazolium chloroaluminate ionic liquids. Effect of Lewis acidity of the ionic liquid on the initial extent of the conversion; Use of the nuclear magnetic resonance to investigate the mechanistic details of the reaction; Factors attributed to the change in speciation of aluminum.

1-Butyl-3-methylimidazolium hexafluorophosphate ionic liquid was employed as a reaction medium for lipase-catalysed aliphatic polyester synthesis. Lipase PS-C exhibited excellent catalysis in polycondensation of diethyl octane-1,8-dicarboxylate and 1,4-butanediol at room temperature and at 60°C. A relatively high molecular weight polymer was obtained at 60°C. [Copyright &y& Elsevier]

The diagrams of the chemical equation for the synthesis of the 3-(Arylthio)-1,2,4-triazines, 3-(Alkoxy), 3-(Aryloxy), and 3-(Alkylamino) is presented, with the methods of applying 3-(Methylsulfonyl)- -1,2,4-triazine.

A diagram for a new methodology for the synthesis of 3-amino-1H-indole-2-carboxylates is presented.

Abstract: Dihydropteroate synthase (DHPS) is an enzyme of the folate biosynthesis pathway, which catalyzes the formation of 7,8‐dihydropteroate (DHPt) from 6‐hydroxymethyl‐7,8‐dihydropterin pyrophosphate (DHPPP) and para‐aminobenzoic acid (pABA). DHPS is the long‐standing target of the sulfonamide class of antibiotics that compete with pABA. In the wake of sulfa drug resistance, targeting the structurally rigid (and more conserved) pterin site has been proposed as an alternate strategy to inhibit DHPS in wild‐type and sulfa drug resistant strains. Following the work on developing pterin‐site inhibitors of the adjacent enzyme 6‐hydroxymethyl‐7,8‐dihydropterin pyrophosphokinase (HPPK), we now present derivatives of 8‐mercaptoguanine, a fragment that binds weakly within both enzymes, and quantify sub‐μ m binding using surface plasmon resonance (SPR) to Escherichia coli DHPS (EcDHPS). Eleven ligand‐bound EcDHPS crystal structures delineate the structure–activity relationship observed providing a structural framework for the rational development of novel, substrate‐envelope‐compliant DHPS inhibitors. [ABSTRACT FROM AUTHOR]

SPRY domain-containing SOCS box protein 2 (SPSB2) regulates inducible nitric oxide synthase ( iNOS) by targeting it for proteasomal degradation. Inhibiting this interaction prolongs the intracellular lifetime of iNOS, leading in turn to enhanced killing of infectious pathogens such as bacteria and parasites. SPSB2 recognizes a linear motif (DINNN) in the disordered N-terminus of iNOS, and ligands that target the DINNN binding site on SPSB2 are potentially novel anti-infective agents. We have explored 19F NMR as a means of probing ligand binding to SPSB2. All six Trp residues in SPSB2 were replaced with 5-fluorotryptophan (5-F-Trp) by utilizing a Trp auxotroph strain of Escherichia coli. The labeled protein was well folded and bound a DINNN-containing peptide with similar affinity to native SPSB2. Six well-resolved 5-F-Trp resonances were observed in the 19F NMR spectrum and were assigned using site-directed mutagenesis. The 19F resonance of W207 was significantly perturbed upon binding to DINNN-containing peptides. Other resonances were perturbed to a lesser extent although in a way that was sensitive to the composition of the peptide. Analogues of compounds identified in a fragment screen also perturbed the W207 resonance, confirming their binding to the iNOS peptide-binding site on SPSB2. 19F NMR promises to be a valuable approach in developing inhibitors that bind to the DINNN binding site. [ABSTRACT FROM AUTHOR]

Abstract: A hydroxyl group appended task specific ionic liquid was designed and synthesised. The ionic liquid was used as a vehicle for the substrate of our interest for lipase catalysed kinetic resolution. The ionic liquid anchored ibuprofen underwent Candida antarctica lipase catalysed hydrolysis yielding the S-enantiomer. The strategy facilitated easy post-resolution isolation of the enantiomers and also carries the prospect of recyclability. [Copyright &y& Elsevier]

Abstract: The Ferrier glucosylation of alcohols with 3,4,6-tri-O-acetyl-d-glucal has been investigated with several metal nitrates and the optimal catalyst is bismuth nitrate pentahydrate (BNP). Good yields of pseudoglycals were also obtained with ferric nitrate nonahydrate (FNN), heightening the catalyst dosage (50mol%) being required however. The BNP-mediated reactions showed remarkable solvent dependency and in the optimal protocol, the amount of BNP as low as 10mol% was effective, furnishing excellent yields of O-glucosides with good anomeric selectivity in acetonitrile. A comparison of BNP and FNN in terms of yields and selectivity of the product has been made. In comparison to the reactions in acetonitrile, the catalytic ability of BNP was found to enhance drastically in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate [bmim][PF6]. [Copyright &y& Elsevier]

The Candida rugosa lipase-catalysed enantioselective hydrolysis of butyl 2-(4-chlorophenoxy)propionate 1 has been carried out in aqueous buffer with ionic liquid as co-solvent. The influence of ionic liquid on the catalytic efficiency and selectivity has been studied, using both hydrophobic and hydrophilic ionic liquids. The markedly enhanced enantioselectivity towards the R enantiomer of substrate 1 is observed under optimum additive conditions (1:1 composition of ionic liquid and buffer). Hydrophobic ionic liquids offered almost quantitative conversions with ee ≥ 99%. [Copyright &y& Elsevier]

Lipase-mediated regioselective biotransformations such as hydrolysis and alcoholysis of 3,4,6-tri-O-acetyl-d-glucal, 1 have been studied in organic solvent, tetrahydrofuran (THF) and two different ionic liquids, namely 1-butyl-3-methylimidazolium hexafluorophosphate, [bmim]PF6 and 1-butyl-3-methylimidazolium tetrafluoroborate, [bmim]BF4. The influence of different reaction media on the rates and regioselectivity of enzyme catalysis has been demonstrated. A marked regioselectivity towards the formation of 4,6-di-O-acetyl-d-glucal, 2 was observed in [bmim]PF6 with 84% product formation after 6 h with 98% selectivity in hydrolysis and 48% after 8 h with 98% selectivity in alcoholysis. [Copyright &y& Elsevier]

A new protocol is developed for the synthesis of N-substituted thioamides, employing arenes and isothiocyanates in 1-butyl-3-methylimidazolium chloroaluminate ionic liquid, [bmim]Cl·2AlCl3, as a homogenous Lewis acid catalyst and solvent. The effect of Lewis acidity and the stoichiometry of the ionic liquid on the extent of product formation is studied. Studies reveal that a progressive increase in yields was observed with increasing Lewis acidity, and two equivalents of [bmim]Cl·2AlCl3 was the optimal amount for the reaction. A distinct para selectivity for the incoming thioamido group on activated arenes was observed under ambient conditions. [ABSTRACT FROM AUTHOR]

Abstract: A new series of 2‐phenylthiazole derivatives were designed, synthesized, characterized and evaluated as potential candidates to treat Alzheimer's disease. Most of these compounds exhibited significant acetylcholinesterase inhibitory activities. Among them, compound ethyl 2‐[4‐(4‐{[2‐(pyrrolidin‐1‐yl)ethyl]amino}butoxy)phenyl]thiazole‐4‐carboxylate (5 b–8) exhibited the best acetylcholinesterase inhibition activity with IC50 values of 4.8 μM. Moreover, the compound ethyl 2‐(4‐{[5‐(cyclohexylamino)pentyl]oxy}phenyl)thiazole‐4‐carboxylate (5 c–6) had the best butyrylcholinesterase inhibitory activity, with an IC50 value of 0.16 μM. The docking studies demonstrated that compound 5 b–8 could interact with both the catalytic active site (CAS) and the peripheral anionic site (PAS) of acetylcholinesterase. Compound 5 b–8 also showed biometal chelating abilities. These attributes highlight 5 b–8 as a promising candidate for further studies directed to the development of novel drugs against Alzheimer's disease. [ABSTRACT FROM AUTHOR]

6-Hydroxymethyl-7,8-dihydropterin pyrophosphokinase (HPPK) is a member of the folate biosynthesis pathway found in prokaryotes and lower eukaryotes that catalyzes the pyrophosphoryl transfer from the ATP cofactor to a 6-hydroxymethyl-7,8-dihydropterin substrate. We report the chemical synthesis of a series of S-functionalized 8-mercaptoguanine (8MG) analogues as substrate site inhibitors of HPPK and quantify binding against the E. coli and S. aureus enzymes (EcHPPK and SaHPPK). The results demonstrate that analogues incorporating acetophenone-based substituents have comparable affinities for both enzymes. Preferential binding of benzyl-substituted 8MG derivatives to SaHPPK was reconciled when a cryptic pocket unique to SaHPPK was revealed by X-ray crystallography. Differential chemical shift perturbation analysis confirmed this to be a common mode of binding for this series to SaHPPK. One compound (41) displayed binding affinities of 120 nM and 1.76 μM for SaHPPK and EcHPPK, respectively, and represents a lead for the development of more potent and selective inhibitors of SaHPPK. [ABSTRACT FROM AUTHOR]

The interaction between carbon dioxide (CO2) and amidines such as 1,8-diazabicyclo[5.4.0]undecane (DBU) has been extensively studied, but the reaction of isovalent CS2 with such bases has been largely ignored, apart from a single crystallography report. Acyclic acetamidines are cleaved by CS2 at room temperature to give an isothiocyanate and a thioacetamide. Because the pathway to that cleavage involves a rotation that is difficult for cyclic amidines, the reaction of CS2 with cyclic amidines produces an entirely different product: a cyclic carbamic carboxylic trithioanhydride structure. The path to that product involves sp3 C-H activation leading to the formation of a new C-C bond at a carbon α to the central carbon of the amidine group. Alkylation and ring-opening of the cyclic carbamic carboxylic trithioanhydride has also been demonstrated under ambient conditions. [ABSTRACT FROM AUTHOR]

The practice of adding salt to water to induce salting out of contaminants or to break emulsions and suspensions is generally avoided industrially because of the expense of the necessary treatment of the salty water afterwards. However, the use of switchable water, an aqueous solvent with switchable ionic strength, allows for reversible generation and elimination of salts in aqueous solution, through the introduction and removal of CO2. In the effort to improve the efficiency of these switchable salts, a physical study modeling their reactivity and solution behaviour has been performed, resulting in a set of design principles for future switchable water additives. The resulting polyamines synthesized using this template show the highest efficiency recorded for a switchable water additive. [ABSTRACT FROM AUTHOR]

A new kind of switchable solvent, a switchable-hydrophilicity solvent, is hydrophobic and has very low miscibility with water when in air but is hydrophilic and has complete miscibility with water when under an atmosphere of CO2. We report here the first example of such a solvent, N,N,N′-tributylpentanamidine. Solvents such as these could be used for the extraction of low-polarity organic products, such as vegetable oils, followed by the removal of the solvent from the product by carbonated water. Carbonated water is able to extract the solvent from the product because the CO2converts the solvent to its hydrophilic form. The solvent can then be separated from the carbonated water upon removal of the CO2, because this removal triggers the conversion of the solvent back to its hydrophobic, water-immiscible form. Importantly, distillation is not required for removal of the solvent from the product. [ABSTRACT FROM AUTHOR]

The title reactions are investigated in detail. [ABSTRACT FROM AUTHOR]