Search results
Search for "concentration" in Full Text gives 1382 result(s) in Beilstein Journal of Organic Chemistry. Showing first 200.
Discrimination of β-cyclodextrin/hazelnut (Corylus avellana L.) oil/flavonoid glycoside and flavonolignan ternary complexes by Fourier-transform infrared spectroscopy coupled with principal component analysis
Beilstein J. Org. Chem. 2023, 19, 380–398, doi:10.3762/bjoc.19.30
- avellana L.) oil is a valuable source of oleic acid bound in various triglyceride combinations. The highest content was observed for triolein, OOO (61–77.5% relative concentration), but also OOL (glyceryl 1,2-dioleate 3-linoleate) and OOP (glyceryl 1,2-dioleate 3-palmitate) were found in high relative
- flavonolignans as impurities) and were purchased from Sigma-Aldrich, St. Louis, MO, USA. Ethanol used for complex synthesis was of 96% concentration (v/v) and was purchased from ChimReactiv (Bucharest, Romania). The analysis of the FA profile of the hazelnut oil required the derivatization (transesterification
Recommendations for performing measurements of apparent equilibrium constants of enzyme-catalyzed reactions and for reporting the results of these measurements
Beilstein J. Org. Chem. 2023, 19, 303–316, doi:10.3762/bjoc.19.26
- equilibrium. The total ATP concentration is the sum of the concentrations of the individual ionic species formed by the protonation or metal ion binding reactions of the ATP species Additional metal ion complexes (e.g., involving Ca2+, K+, and Na+) can also be included in Equation 4. Similar expressions can
- zero. Consequently, the standard molar Gibbs energy change ΔrG° = −RTlogeK, where R is the gas constant and K is the equilibrium constant written in terms of activities a of chemical species. An activity equals the concentration (i.e., molality m, concentration c, or mole fraction x) multiplied by an
- .). In addition to the total concentration of ATP in all of its bound or liganded forms, one should report the unambiguous identifier of the substance that was actually used in the study. The identifiers can be a CAS number, a PubChem CID, ChEBI ID, or any database entry (e.g., adenosine 5′-triphosphate
Continuous flow synthesis of 6-monoamino-6-monodeoxy-β-cyclodextrin
Beilstein J. Org. Chem. 2023, 19, 294–302, doi:10.3762/bjoc.19.25
- sulfonyl chloride reagents are used. 2-Naphthalenesulfonyl chloride in pyridine is one common method. However, the concentration of γ-CD must be lower than 20 mM to favor monosubstitution and to ensure the optimal yield (around 30%) after recrystallization from hot water [9]. Sometimes purification using
Strategies to access the [5-8] bicyclic core encountered in the sesquiterpene, diterpene and sesterterpene series
Beilstein J. Org. Chem. 2023, 19, 245–281, doi:10.3762/bjoc.19.23
- the eight-membered ring by RCM (Scheme 1). Optimization of the reaction parameters (temperature, solvent, concentration, and catalyst amount) was carried out with G-I catalyst. Indeed, the authors noticed that high temperatures improved the reaction conversion, and dichloromethane seemed to furnish
- of the product but with lower yields (25%). The effect of the concentration was also important, since increasing or lowering the concentration from 0.01 M resulted in lower yields. The same trend was observed when the temperature was varied. Finally, the amount of catalyst was explored: increasing
Investigation of cationic ring-opening polymerization of 2-oxazolines in the “green” solvent dihydrolevoglucosenone
Beilstein J. Org. Chem. 2023, 19, 217–230, doi:10.3762/bjoc.19.21
- of 2-ethyl-2-oxazoline and 2-butyl-2-oxazoline using a variety of initiators in the recently commercialized "green" solvent dihydrolevoglucosenone (DLG). Detailed 1H NMR spectroscopic analysis was performed to understand the influence of the temperature and concentration on the polymerization process
- of polymerization rates. Therefore, the apparent rate of polymerization depending on the initiator used was also calculated. The apparent propagation rate () can be calculated according to the equation below, where [M]t is the concentration of the monomer over time, [I]0 is the concentration of the
- initiating group (which equals the concentration of the propagation species [P*] if a fast and quantitative initiation is achieved), [M]0 is the initial concentration of the monomer, and t is the reaction time. Considering that kp is constant and [P*] should be constant and equal to [I]0, a linear plot of
Friedel–Crafts acylation of benzene derivatives in tunable aryl alkyl ionic liquids (TAAILs)
Beilstein J. Org. Chem. 2023, 19, 212–216, doi:10.3762/bjoc.19.20
- diminished yields, but the loss is rather small compared to the reduced catalyst concentration. To further characterize our catalytic system, the acylation was performed on a larger scale to investigate whether upscaling changes the performance of the catalytic system. Table 3 shows the results of the
Total synthesis of insect sex pheromones: recent improvements based on iron-mediated cross-coupling chemistry
Beilstein J. Org. Chem. 2023, 19, 158–166, doi:10.3762/bjoc.19.15
- C6 synthon, by a Hunsdiecker–Borodin bromodecarboxylation, adapting the recent micellar conditions developed by Rajanna for the synthesis of alkenyl halides starting from α,β-unsaturated acids [34]. However, purification and concentration of 1-bromopenta-1,3-diene proved to only promote its
- degradation, likely by polymerization. To circumvent this matter, we developed a workup procedure allowing to directly obtain THF solutions of 1-bromopenta-1,3-diene in the 0.4–0.7 M concentration range, and no further purification was required. Those solutions can be directly used in a subsequent iron
- is slowed down due to the drop of the concentration of coupling reagents. The affinity of ferrous precatalysts for thiolate ligands had also been reported by Cahiez earlier in the cross coupling of alkyl Grignard reagents with alkenyl halides, 2-naphthylthiolates being used as additives [40]. No in
Insight into oral amphiphilic cyclodextrin nanoparticles for colorectal cancer: comprehensive mathematical model of drug release kinetic studies and antitumoral efficacy in 3D spheroid colon tumors
Beilstein J. Org. Chem. 2023, 19, 139–157, doi:10.3762/bjoc.19.14
- combined mechanism which is frequently encountered in release studies. When the power law can adequately represent the whole collection of data in these situations, further confirmation can be gained. The special case of “β” = 1 is compatible with first order release, whereas the concentration gradient in
- cell culture methods have been investigated comparatively. The findings showed that nanoparticles and free drugs less effectively reach the underlying cells in 3D spherical tumors due to multilayered cells, and the concentration of 3D tumor-penetrating drugs is lower than in conventional cell culture
- concentration has been related to cell membrane fluidity and rigidity, treatment resistance in cancer cells, and drug uptake through the cell membrane. Excipients such as methyl-β-CD are widely used to extract cholesterol from cancer cells such as melanoma and MCF7 cells in order to promote cellular uptake of
Nostochopcerol, a new antibacterial monoacylglycerol from the edible cyanobacterium Nostochopsis lobatus
Beilstein J. Org. Chem. 2023, 19, 133–138, doi:10.3762/bjoc.19.13
- MeOH to adjust its concentration to 60% (v/v). This was extracted with CH2Cl2 for three times, and the CH2Cl2-soluble layer was partitioned between aqueous 90% MeOH and n-hexane. The most active aqueous MeOH layer (113.3 mg) was subjected to ODS flash chromatography with a stepwise elution by MeCN/50
- According to a procedure described in [6], the antimicrobial potency of chromatographic fractions was evaluated by a paper disk-agar diffusion method. Fractions at each purification stage were diluted to the same concentration with MeOH, and 10 μL aliquots were impregnated into 6 mm-diameter paper disks
- and the concentration at which the growth of microbes was completely inhibited was defined as the minimum inhibitory concentration (MIC). Structure of nostochopcerol (1) and selected COSY (bold lines) and HMBC (arrows) correlations. Synthesis of 1-linoleoyl-sn-glycerol (3a) and 3-linoleoyl-sn-glycerol
Preparation of β-cyclodextrin/polysaccharide foams using saponin
Beilstein J. Org. Chem. 2023, 19, 78–88, doi:10.3762/bjoc.19.7
- specific area of the matrix is intended to be increased, permitting a greater accessibility to β-cyclodextrin sites. Results and Discussion Production of saponin foams As a first step, the determination of the foamability of saponin aqueous solutions allows us to find the surfactant concentration for which
- a maximum of foam volume will be produced. This value will correspond to the minimum amount of this ingredient required to produce the cyclodextrin/polysaccharide foams. As can be seen in Figure 1 (left), two linear fittings were applied in the foam volume vs concentration plot, where the junction
- of both lines gives us an approximate optimal foamability for a saponin concentration value of ca. 0.3%. These measurements correspond to solutions prepared using deionized water. Other factors such as the viscosity due to the polysaccharides or the ionic strength contributed by the catalyst can
Modern flow chemistry – prospect and advantage
Beilstein J. Org. Chem. 2023, 19, 33–35, doi:10.3762/bjoc.19.3
- disadvantages when moving from batch reactions to a continuous flow regime, dispersion phenomena play a detrimental role. These gradient effects occur when a stream of reagent is introduced into the reactor by pushing it with pure solvent. The reagents with well-defined concentration then leach into the solvent
Inline purification in continuous flow synthesis – opportunities and challenges
Beilstein J. Org. Chem. 2022, 18, 1720–1740, doi:10.3762/bjoc.18.182
- and reversed-phase chromatography (Table 1). Optimization of conditions regarding the purification step is needed such as adjusting the concentration of the crude mixture, or the addition of a drying cartridge with molecular sieves. At the end, products with excellent purity are obtained (97–99% by
- analysis to control the acid concentration. Good extraction efficiency and purification were achieved for an amine as a test substrate that was contaminated with a minor impurity. Remaining challenges such as time-consuming optimization and the need for several pumps can be overcome through careful
- concentration of less than 1% within four hours, and water-soluble monomers. In addition, the integration of this setup into an inline synthesis step starting from block copolymer solutions, and rhodamine encapsulation produced micelles without affecting the particle size is also demonstrated. The growing
Redox-active molecules as organocatalysts for selective oxidative transformations – an unperceived organocatalysis field
Beilstein J. Org. Chem. 2022, 18, 1672–1695, doi:10.3762/bjoc.18.179
- amounts of strong oxidants ((NH4)2Ce(NO3)6 [91], PhI(OAc)2 [92], t-BuOOt-Bu [93], etc.) are needed to generate a sufficient concentration of PINO radicals for the effective trapping of C-centered radicals and excess amounts of a CH-reagent are necessary for high selectivity. The electrochemical oxidative
Preparation of β-cyclodextrin-based dimers with selectively methylated rims and their use for solubilization of tetracene
Beilstein J. Org. Chem. 2022, 18, 1596–1606, doi:10.3762/bjoc.18.170
- . Unfortunately, we did not succeed with solvents, such as water or methanol, where an increase in solubility is most desired. But some success we obtained with DMSO. For our experiments, we used the same mass of a host in every experiment, meaning the molar concentration of a CD in the samples was different
- . Especially it concerned the dimers whose solutions were approximately two times less concentrated than others. However, we decided from the practical point of view that the effectiveness of the solubilization effect should be calculated to the host's mass rather than its molar concentration. The UV
- absorbance spectrum of tetracene in DMSO consists of several regions gradually rising with the concentration. The absorption band at 476 nm is the best choice for building a calibration plot with a sufficient linear region (Figure 4). Exceeding the concentration above 1 mmol/L slowly decreases the linearity
Simple synthesis of multi-halogenated alkenes from 2-bromo-2-chloro-1,1,1-trifluoroethane (halothane)
Beilstein J. Org. Chem. 2022, 18, 1567–1574, doi:10.3762/bjoc.18.167
- ). Decreasing the amount of halothane clearly increased the reaction efficiency to give 2a in 69% yield (Table 1, entry 5). We reasoned that the reaction was largely dependent on the concentration of phenoxide ions, as these would act as both a nucleophile and base in the reaction medium to give formation of 1
Solid-phase total synthesis and structural confirmation of antimicrobial longicatenamide A
Beilstein J. Org. Chem. 2022, 18, 1560–1566, doi:10.3762/bjoc.18.166
- ][27][28][29], such as concentration, pH, and purity. Thus, analyses of the NMR spectra of peptides sometimes lead to incorrect structural determination even though total synthesis of the proposed structures is successful [30]. In this study, synthesized and natural 1 were compared by collecting LC–MS
- product, which could be due to the presence of uncharacterized impurities. To verify the bioactivity of 1, the antimicrobial activity of synthesized 1 was preliminary tested in this study following a previously reported method [8], revealing that chemically synthesized 1 (minimum inhibitory concentration
A study of the DIBAL-promoted selective debenzylation of α-cyclodextrin protected with two different benzyl groups
Beilstein J. Org. Chem. 2022, 18, 1553–1559, doi:10.3762/bjoc.18.165
- in Table 1. Firstly, reaction with DIBAL in toluene at 0.3 M concentration and at 50 °C gave after 24 h almost complete conversion of the starting material to a symmetrical compound 8 that according to MALDI–TOF MS has lost two DCB groups and not any benzyl group. The compound was analyzed with 1H
Using UHPLC–MS profiling for the discovery of new sponge-derived metabolites and anthelmintic screening of the NatureBank bromotyrosine library
Beilstein J. Org. Chem. 2022, 18, 1544–1552, doi:10.3762/bjoc.18.164
- stock solution, which had a final concentration of 1 mg/mL (minimum stock solution volume = 0.5 mL). UHPLC–MS analysis All extracts (1 mg/mL) were subjected to UHPLC–MS profiling using an Thermo Scientific Accucore column with an injection volume of 10 µL. Isocratic conditions of 10% MeOH/90% H2O (0.1
New triazole-substituted triterpene derivatives exhibiting anti-RSV activity: synthesis, biological evaluation, and molecular modeling
Beilstein J. Org. Chem. 2022, 18, 1524–1531, doi:10.3762/bjoc.18.161
- control Ct value from the RSV protein F Ct value. Compound 8 reduced RSV protein F gene expression by approximately 65% at a concentration of 12.5 µM, compared to that of the control (Figure 2B). These results are in accordance with the EC50 value of compound 8, verifying that compound 8 exhibited
Cyclometalated iridium complexes-catalyzed acceptorless dehydrogenative coupling reaction: construction of quinoline derivatives and evaluation of their antimicrobial activities
Beilstein J. Org. Chem. 2022, 18, 1507–1517, doi:10.3762/bjoc.18.159
- compounds was evaluated against Staphylococcus aureus (Gram-positive), Escherichia coli (Gram-negative), and Candida albicans (fungi) mainly by examining the minimum inhibitory concentration (MIC) (Table 4). As shown in Table 4, the compounds 3ab, 3ah, and 3ad showed high antibacterial activities against
Microelectrode arrays, electrosynthesis, and the optimization of signaling on an inert, stable surface
Beilstein J. Org. Chem. 2022, 18, 1488–1498, doi:10.3762/bjoc.18.156
- array because it is the nature of those molecules that defines the biological interactions that can be studied [10][11]. As discussed below, such efforts need to not only control the selectivity of the reactions for specific, predetermined sites on the array, but also control the surface concentration
- above the array, and when it binds one of the molecules fixed to the surface of a set of electrodes in the array it causes a change in the current to be measured at those electrodes. This change in current can be recorded and the binding event monitored. By varying the concentration of the protein in
- used for the subsequent signaling experiment [20]. The hydroquinone/quinone redox couple has superior stability to the iron-based systems used previously [20], and its use leads to more reproducible binding curves. To generate the binding curve shown in Figure 4, the concentration of the integrin
Supramolecular approaches to mediate chemical reactivity
Beilstein J. Org. Chem. 2022, 18, 1463–1465, doi:10.3762/bjoc.18.152
- reactants are confined in the restricted space provided by an enzyme binding pocket, the increase in local concentration, due to the proximity effect, the stabilization of intermediates and transition states cause the acceleration of the reaction. Thus, learning from natural enzymes, novel supramolecular
Sinensiols H–J, three new lignan derivatives from Selaginella sinensis (Desv.) Spring
Beilstein J. Org. Chem. 2022, 18, 1410–1415, doi:10.3762/bjoc.18.146
- control. As a result, compounds 1, 2, 4, and 5 showed mild inhibitory activities with inhibition rates in the range of 9.47–18.75%, compound 3 showed moderate activity with an inhibition rate of 42.06 ± 2.02% at a concentration of 50 μM (ʟ-NMMA, 59.31 ± 2.19%, Table 2). Conclusion In summary, three new
- ]. The cells were seeded in 96-well plates and co-incubated with the test compounds and positive control drug at a concentration of 50 μM or 12.5 μM, followed by stimulation with 1 μg/mL LPS for 18 h. The viability of RAW 264.7 cells was determined by an MTS assay to exclude the interference of the
Preparation of an advanced intermediate for the synthesis of leustroducsins and phoslactomycins by heterocycloaddition
Beilstein J. Org. Chem. 2022, 18, 1385–1395, doi:10.3762/bjoc.18.143
- aqueous CuSO4 solution (4 × 10 mL) and saturated aqueous NH4Cl solution (3 × 10 mL), then dried (MgSO4), filtered and concentred under reduced pressure. The residue was purified by filtration through a short plug of silica gel, eluting with ethyl acetate. Concentration under reduced pressure gave the pure
Cyclodextrin-based Schiff base pro-fragrances: Synthesis and release studies
Beilstein J. Org. Chem. 2022, 18, 1346–1354, doi:10.3762/bjoc.18.140
- group of the compound 3d. Error bars correspond to the regression error; red line corresponds to the polynomial fit of the experimental data. Time evolution of the headspace concentration of heptanal (2h) after successive extractions from the gaseous phase above (A): heptanal (2h) in aqueous phosphate
- buffers and (B): heptanylimino-β-CD (3h) in aqueous phosphate buffers. Sampling intervals in the corresponding regions: I – 4 min (A) or 5 min (B), II – 10 min, III – 60 min. Time evolution of the headspace concentration of benzaldehyde (2d) after successive extractions from the gaseous phase above (A
- ): benzaldehyde (2d) in aqueous phosphate buffers and (B): benzylimino-β-CD (3d) in aqueous phosphate buffers. Sampling intervals in the corresponding regions: I – 4 min, II – 10 min, III – 60 min. Time evolution of the headspace concentration of 5-methylfurfural (2j) after successive extractions from the gaseous
Other Beilstein-Institut Open Science Activities
