Search results
Search for "resistance" in Full Text gives 316 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Molecular-level architectural design using benzothiadiazole-based polymers for photovoltaic applications
Beilstein J. Org. Chem. 2017, 13, 863–873, doi:10.3762/bjoc.13.87
- orbitals of polymer P2. Both the HOMO and LUMO levels of the polymer have decreased energy as compared to polymer P1 (from −5.48 eV to −5.53 eV and from −3.58 eV to −3.75 eV, respectively). This reduction of the HOMO energy level improves the resistance towards oxidative degradation of the material. Also
Continuous-flow processes for the catalytic partial hydrogenation reaction of alkynes
Beilstein J. Org. Chem. 2017, 13, 734–754, doi:10.3762/bjoc.13.73
- issues owing to many potential side reactions, particularly in relation to chemoselectivity, i.e., over-hydrogenation of alkenes to alkanes [44][45], resistance of other functional groups (ketones [46][47], amines [48][49], azides [50]), regioselectivity [51][52] , isomerization [53][54] and
- ]; the strong metal–support interactions, particularly for inorganic oxide materials, e.g., TiO2 [94][95]. Besides contributing to catalyst resistance by hampering the loss and the size increase of active sites, MNP stabilization is a key factor to limit the amount of metal leached in solution, an issue
- selectivity issues, need of toxic additives, high metal loadings and limited catalyst resistance. Ever increasing environmental and economic constraints have boosted the development of innovative catalytic materials and processes with improved performance and lower environmental impact. Great advancements
Novel β-cyclodextrin–eosin conjugates
Beilstein J. Org. Chem. 2017, 13, 543–551, doi:10.3762/bjoc.13.52
- ]. Singlet oxygen offers important advantages over conventional drugs as it: i) potentially attacks biological substrates of different nature (i.e., lipids, proteins, and DNA), ii) does not suffer from multidrug resistance (MDR) problems, and iii) due to its short half-life (<0.1 ms) and lack of charge, it
NMR reaction monitoring in flow synthesis
Beilstein J. Org. Chem. 2017, 13, 285–300, doi:10.3762/bjoc.13.31
- : Excellent B1-field uniformity and B1/i field efficiency resulting in a high signal-to-noise ratio (SNR). In comparison to planar coils, the solenoid have lower resistance, better nutation curves (reaching the ideal sinusoidal behaviour) representing a much more uniform B1 field than planar coils, however
- planar coils are: Planar coils suffer of a high series resistance resulting in a low SNR as the latter is dominated by the thermal noise of the coil. The SNR depends on the geometrical features of the coil. For instance, the number of turns is crucial since a large number of turns can increase the
- unitary field produced by the coil but will also lead to higher resistance [21]. It is believed that the nearby windings of the coil induce static field distortions resulting in lower resolution and sensitivity in the NMR spectrum [22]. The optimum dimensions for a planar microcoil were presented by van
Enduracididine, a rare amino acid component of peptide antibiotics: Natural products and synthesis
Beilstein J. Org. Chem. 2016, 12, 2325–2342, doi:10.3762/bjoc.12.226
- 10.3762/bjoc.12.226 Abstract Rising resistance to current clinical antibacterial agents is an imminent threat to global public health and highlights the demand for new lead compounds for drug discovery. One such potential lead compound, the peptide antibiotic teixobactin, was recently isolated from an
- uncultured bacterial source, and demonstrates remarkably high potency against a wide range of resistant pathogens without apparent development of resistance. A rare amino acid residue component of teixobactin, enduracididine, is only known to occur in a small number of natural products that also possess
- encountered to date in the development of efficient synthetic routes to facilitate drug discovery efforts inspired by the discovery of teixobactin. Keywords: amino acid; bacterial resistance; enduracididine; natural products; peptide antibiotics; Review Introduction The enduracididines The enduracididines
Evidence for an iterative module in chain elongation on the azalomycin polyketide synthase
Beilstein J. Org. Chem. 2016, 12, 2164–2172, doi:10.3762/bjoc.12.206
- from a BAC library of S. malaysiensis DSM4137 genomic DNA as described in Supporting Information File 1, and named pYJ2. To allow the introduction of the cloned azl cluster into actinomycete host strains that are intrinsically resistant to thiostrepton (tsr), the tsr resistance cassette of pYJ2 was
- replaced by the apramycin resistance cassette aac(3)IV [57] using RedET recombineering of pYJ2 in E. coli to generate BAC clone pML1. Tri-parental mating was used [58] to introduce pML1 into E. coli ET12567, a triply methylation-deficient strain that provides higher efficiency of conjugation into many
- strain was used for conjugation with S. lividans. Selection for apramycin resistance led to the isolation of exconjugants, four of which were analysed using PCR with two flanking and twelve internal PCR primer pairs. Two colonies were found which appeared to contain the full azl gene cluster while the
Diastereoselective synthesis of 3,4-dihydro-2H-pyran-4-carboxamides through an unusual regiospecific quasi-hydrolysis of a cyano group
Beilstein J. Org. Chem. 2016, 12, 2093–2098, doi:10.3762/bjoc.12.198
- the path of transformations without the participation of water (Scheme 3, path II) as actual. Such an abnormal resistance of the imine moiety to be simply hydrolyzed in aqueous acidic media is very exciting. Therefore we attempted to use other acids to investigate the behavior of the imine moiety in
- exceptional diastereoselectivity based on the reaction of available 4-oxoalkane-1,1,2,2-tetracarbonitriles (adducts of TCNE and ketones) with aldehydes in acidic media. Unusual processes of regiospecific quasi-hydrolysis of a cyano group and abnormal resistance of the imine moiety to be hydrolyzed in aqueous
A flow reactor setup for photochemistry of biphasic gas/liquid reactions
Beilstein J. Org. Chem. 2016, 12, 1798–1811, doi:10.3762/bjoc.12.170
- are suitable for most applications. A low dead volume and a high pressure resistance are key characteristics of T mixers. However, careful optimization of the internal size, shape, and dead volume of the T-mixer directly affects the local concentrations of the reagents and thus can have dramatic
Rearrangements of organic peroxides and related processes
Beilstein J. Org. Chem. 2016, 12, 1647–1748, doi:10.3762/bjoc.12.162
- rearrangement of aliphatic hydroperoxides proceeds quite readily in concentrated H2SO4 [318] or superacids [319] (Scheme 52). This is associated with higher resistance of these compounds toward acid-catalyzed rearrangements compared with benzylic or allylic hydroperoxides. For example, aliphatic hydroperoxides
Beta-hydroxyphosphonate ribonucleoside analogues derived from 4-substituted-1,2,3-triazoles as IMP/GMP mimics: synthesis and biological evaluation
Beilstein J. Org. Chem. 2016, 12, 1476–1486, doi:10.3762/bjoc.12.144
- their corresponding nucleosides [2][3]. Recent studies on patients affected by haematological malignancies, such as acute myeloid leukaemia (AML) and myelodysplasic syndrome (MS), have demonstrated the involvement of cN-II in the resistance to cytotoxic drugs such as mercaptopurines and suggested the
Mutagenic activity of quaternary ammonium salt derivatives of carbohydrates
Beilstein J. Org. Chem. 2016, 12, 1434–1439, doi:10.3762/bjoc.12.138
- properties, QASs have many drawbacks. Their rapid spread in society and the increasing resistance of pathogenic microorganisms [16] require new chemicals, including QASs, posing new risks for the environment and the living organisms. However, the long-term effects of these new compounds with regard to their
Discovery of an inhibitor of the production of the Pseudomonas aeruginosa virulence factor pyocyanin in wild-type cells
Beilstein J. Org. Chem. 2016, 12, 1428–1433, doi:10.3762/bjoc.12.137
- important opportunistic human pathogen [1]. This opportunistic pathogen is well known to be a challenging infection to completely eradicate in infected patients due to high levels of intrinsic resistance to a wide variety of antibiotics [1][2][3][4][5][6] and the tendency of P. aeruginosa cells to form
3,6-Carbazole vs 2,7-carbazole: A comparative study of hole-transporting polymeric materials for inorganic–organic hybrid perovskite solar cells
Beilstein J. Org. Chem. 2016, 12, 1401–1409, doi:10.3762/bjoc.12.134
- to P3HT. Dynamic impedance spectroscopy Dynamic impedance spectroscopy was used to determine the charge-transporting parameters in the PSCs, such as the chemical capacitance, recombination resistance, and charge conductivity [45]. It is known that the performance metrics of the HTMs in the PSCs can
- be partially explained by these parameters. For example, it was suggested that FF is associated with the series resistance (Rs), and a low Rs is required to construct high performance photovoltaic devices [46]. The dynamic impedance spectra of the PSCs with different HTMs over the frequency range of
On the mechanism of imine elimination from Fischer tungsten carbene complexes
Beilstein J. Org. Chem. 2016, 12, 1322–1333, doi:10.3762/bjoc.12.125
- /reductive elimination pathway shuttling the hydrogen atom from the nitrogen atom via the W atom to the carbene carbon atom. This pathway is unfeasible for homologous chromium complexes and explains the resistance of Cr(CO)5(E-2) towards thermal E-3 formation. A base-assisted pathway for imine formation is
Artificial Diels–Alderase based on the transmembrane protein FhuA
Beilstein J. Org. Chem. 2016, 12, 1314–1321, doi:10.3762/bjoc.12.124
- respect to both activity and endo selectivity were observed. The cavity of FhuA appears to enhance the reaction as reported by Hayashi et al. for nitrobindin [26], Reetz et al. for serum albumin [22][23], and Roelfes et al. for Lactococcal multidrug resistance Regulator (LmrR) [25]. Furthermore, the
The role of alkyl substituents in deazaadenine-based diarylethene photoswitches
Beilstein J. Org. Chem. 2016, 12, 1103–1110, doi:10.3762/bjoc.12.106
- substitution pattern, diarylethenes with one alkyl group can exhibit significant photochromism, but they generally show poor stability towards extended UV irradiation, low thermal stability, and decreased fatigue resistance. The results obtained provide an important direction for the design of new efficient
- cyclopentenyl bridge, which may also be perfluorinated. Substituents on the aryl rings tune the photophysical and chemical properties, such as absorption and isomerization wavelengths, thermal stability, and fatigue resistance. In 2010 our group reported the first diarylethene-based photoswitchable nucleosides
- hybridization upon switching [43][44]. This new class of diarylethenes showed promising photophysical and photochemical properties, such as the location of the photostationary states, reversibility of switching, thermal stability, and fatigue resistance. In 2013 we developed a 2nd generation of diarylethene
Antibacterial structure–activity relationship studies of several tricyclic sulfur-containing flavonoids
Beilstein J. Org. Chem. 2016, 12, 1065–1071, doi:10.3762/bjoc.12.100
- of one of the greatest problems faced by modern medicine: multidrug-resistant bacteria. Resistance may arise via various mechanisms including changes in cell-wall permeability, target site mutation, antibiotic inactivation and the development of efflux pumps that transport the drugs out of the cell
A cross-metathesis approach to novel pantothenamide derivatives
Beilstein J. Org. Chem. 2016, 12, 963–968, doi:10.3762/bjoc.12.95
- larger groups via cross-metathesis. The method was applied in the synthesis of a new pantothenamide with improved stability in human blood. Keywords: antibiotic; antiplasmodial; coenzyme A; metathesis; pantothenate; Introduction Bacteria, fungi, and parasites are all rapidly acquiring resistance to
- currently applied antimicrobials and as a result, our ability to treat infections effectively is diminishing. Efforts to control infections in this resistance era have taken a variety of paths from a renewed push for novel antimicrobial agents to a fresh understanding of antibiotic resistance mechanisms [1
Muraymycin nucleoside-peptide antibiotics: uridine-derived natural products as lead structures for the development of novel antibacterial agents
Beilstein J. Org. Chem. 2016, 12, 769–795, doi:10.3762/bjoc.12.77
- protein E from bacteriophage X174, Bugg et al. reported a different site of inhibition in pronounced distance to the proposed active site. It has been demonstrated before that mutation of phenylalanine 288 (F288L) in helix 9 of MraY caused resistance against lysis protein E [72][73]. An interaction
- reflect several effects such as target interaction, cellular uptake and potential resistance mechanisms of the microorganism. MIC values are therefore widely used, also in studies on muraymycin analogues (e.g., [22][76][77][78]) and have been the basis of many structure–activity relationship studies (see
Three new trixane glycosides obtained from the leaves of Jungia sellowii Less. using centrifugal partition chromatography
Beilstein J. Org. Chem. 2016, 12, 674–683, doi:10.3762/bjoc.12.68
- for the prevention of Leishmania diseases exist, whereas current chemotherapy is ineffective due to the high toxicity, the emergence of drug resistance, and the high cost of treatment, among others [15][16][17]. Consequently, infected people betake of medicinal plants as an alternative to provide
Unconventional application of the Mitsunobu reaction: Selective flavonolignan dehydration yielding hydnocarpins
Beilstein J. Org. Chem. 2016, 12, 662–669, doi:10.3762/bjoc.12.66
- being efficient inhibitors of the multidrug resistance (MDR) efflux pump (e.g., of Staphylococcus aureus): this activity had been serendipiously employed in traditional medicine (without knowledge of the mechanism) in the treatment of leprosy with chaulmoogra oil. This oil, which is obtained from fruits
- -methoxyhydnocarpin has been described to enhance the antimicrobial activity of berberine [19]. In the light of steadily growing antibiotic resistance any potent and nontoxic MDR inhibitor is of utmost importance. Hydnocarpin has also antineoplastic activity due to sensitizing multidrug-resistant cancer cell lines
Elucidation of a masked repeating structure of the O-specific polysaccharide of the halotolerant soil bacteria Azospirillum halopraeferens Au4
Beilstein J. Org. Chem. 2016, 12, 636–642, doi:10.3762/bjoc.12.62
- deleterious salt stress effects by producing osmoprotectants and enzymes and inducing plant systemic resistance. Additionally, they enhance plant growth by the synthesis of phytohormones and vitamins, fixation of atmospheric nitrogen, and solubilization of soil phosphates [2][3][4]. Strains of the species
- polysaccharide backbone diversifies enormously their O-unit structures [25]. In addition, side-chain glucosylation of the OPS of these bacteria contributes to acid resistance [27] and is crucial for their permeation into the host cell [28]. Plant-associated bacteria are no exception, and the presence of non
Antibiotics from predatory bacteria
Beilstein J. Org. Chem. 2016, 12, 594–607, doi:10.3762/bjoc.12.58
- possess antioxidative properties and might thus confer resistance towards oxidative stress [63]. Structurally, the DKxanthenes harbor a hydrophilic asparagine moiety attached to a hydrophobic polyene chain bearing an additional oxazoline and pyrrol ring system. Their production seems to be universal among
- active-center cleft. After binding to the switch region, myxopyronins and corallopyronins prevent the opening of the clamp [104][105]. Prey bacteria that develop resistance against corallopyronin, e.g., due to a rpoB mutation, also become resistant towards predation by C. coralloides [82]. It is thus
- ) hybrid were found to be involved in the assembly of the core structure. Furthermore, the cluster included four additional ORFs that have specific roles in tailoring reactions and drug resistance [111]. Unlike the ubiquitous DKxanthenes or myxochelins, althiomycin is only produced by a few members of the
Effective in silico prediction of new oxazolidinone antibiotics: force field simulations of the antibiotic–ribosome complex supervised by experiment and electronic structure methods
Beilstein J. Org. Chem. 2016, 12, 415–428, doi:10.3762/bjoc.12.45
- : compliance constants; computational chemistry; drug design; molecular recognition; relaxed force constants; Introduction Antibiotic resistance is one of the major health problems in modern societies, causing millions of deaths per year [1][2][3]. Although Alexander Fleming recognized the importance of the
- resistance phenomena as early as 1940 [4], in the 1970s the problem of bacterial infection seemed to be solved, because a wide range of potent antibiotics were available. During the last two decades the situation nevertheless changed dramatically: the logarithmic rise in the prevalence of penicillin
- growth of bacterial resistance. To date, only two crystal structures of linezolid bound to its ribosomal target are available: a) linezolid bound to the 50S subunit of Deinococcus radiodurans (DR) with a resolution of 3.5 Å [20] and linezolid bound to 50S of Haloarcula marismortui (HM) (resolution: 2.7 Å
Versatile synthesis and biological evaluation of novel 3’-fluorinated purine nucleosides
Beilstein J. Org. Chem. 2015, 11, 2509–2520, doi:10.3762/bjoc.11.272
- for specific reasons. The fluorine atom possesses unique characteristics; it enhances the lipophilicity of organic compounds and C–F bonds have low chemical reactivity imparting high enzymatic stability and resistance to metabolic processes. The high electronegativity of fluorine and the lipophilicity
Other Beilstein-Institut Open Science Activities
