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Two new ditopic metalloporphyrin receptors constructed by combining metalloporphyrin with crown ethers have been prepared and characterized. 1H NMR and MS spectra confirmed the complexation of receptor with peptide driven by coordination interaction and hydrogen bonding. UV/vis experiments revealed that the receptors exhibited high binding affinity to histidine-containing peptides. These receptors could differentiate short peptides of C-terminal histidine and N-terminal histidine and formed the most stable complexes with tripeptide.
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The pollution characteristics of ambient fine particulate matter (PM2.5) containing polycyclic aromatic hydrocarbons (PAHs) and nitrated PAHs (NPAHs) in samples collected during a typical winter time period in Taiyuan of China were investigated. The obtained results revealed that the mean mass concentrations of PM2.5, ΣPAHs (sum of 16 PAHs) and ΣNPAHs (sum of 3 NPAHs) on PM2.5 were 161.4 μg/m3, 119.8 ng/m3 and 0.446 ng/m3, respectively. Diagnostic ratios of PAHs and NPAHs implied that coal consumption might be the main source of the PM2.5 pollution. The measured PM2.5 mass concentrations, BaP equivalent toxicity (28.632 ng/m3) and individual carcinogenicity index (3.14×10-5) were much higher than those of the recommended safety standards.
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(6-Amino-2-chloro-3-fluorophenyl)methanol is prepared through both traditional methods and palladium catalyzed iterative C-H halogenation reactions. In comparison to traditional approach, the C-H functionalization strategy demonstrated a few advantages including milder reaction conditions, higher yields, better selectivity and practicality, and high chemical diversity.
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The tumbling dynamics of individual absorbed polymer chains in shear flow is studied by employing multi-particle collision dynamics simulation techniques combined with molecular dynamics simulations. We find that the dependence of tumbling frequencies on shear rate is independent of both adsorption strength and surface corrugate.
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Dipeptidyl peptidase IV (DPP4) inhibitors are proven in the treatment of type 2 diabetes. We designed and synthesized a series of novel indole compounds that selectively inhibit the activity of DPP4 over dipeptidyl peptidase 9 (DPP9) (>200 fold). We further co-crystallized DPP4 with indole sulfonamide (compound 1) to confirm a proposed binding mode. Good metabolic stability of the indole compounds represents another positive attribute for further development.
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Phytochemical investigation of the aerial parts of Leonurus japonicus led to the isolation of one unusual clerodane diterpenoid, leojaponin A (1), characterized by a C4-C7 oxa-bridge, and two new labdane diterpenoids, leojaponins B (2) and C (3). The structures of these new compounds were determined based on extensive 1D and 2D NMR spectroscopic data. To the best of our knowledge, compound 1 is the first clerodane diterpenoid obtained from Leonurus. japonicus. All of them were evaluated for their cytotoxicity.
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A series of fluorescent siloxane-polyurethanes (HPMS-PUs) containing an amino-functionalized, 1,8-naphthalimide, fluorescent monomer (AABD) as a chain extender were synthesized. The properties of the HPMS-PUs were investigated by UV-vis and fluorescence spectroscopies, thermogravimetric analysis and thermal migration behavior. The maximum absorption and emission wavelengths of HPMS-PUs showed a red shift of about 4 nmand a blue shift of about 9 nm, respectively, compared to those of AABD. The Stokes shifts of AABD and HPMS-PU2 were 3514 and 2931 cm-1, respectively. The quantum yield of HPMS-PU2 was 0.79, which was six times higher than that of AABD. Concentration self-quenching was observed in both AABD and HPMS-PUs. The fluorescence of HPMS-PUs was quite stable with respect to both temperature and fluorescence quencher effects. The thermal stability of HPMS-PUs increased with AABD content. The fluorophore units in the HPMS-PUs did not readily migrate.
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The imaging mass spectrometry (IMS) technology has experienced a rapid development in recent years. A new IMS technology which is based on air flowassisted ionization (AFAI) was reported. It allows for the convenient pretreatment of the samples and can image a large area of sample in a single measurement with high sensitivity. The AFAI in DESI mode was used as the ion source in this paper. The new IMS method is named AFADESI-IMS. The adoption of assisted air flow makes the sample pretreatment easy and convenient. An optimization of the distance between the ion transport tube and MS orifice increases the sensitivity of the system. For data processing, a program based on MATLAB with the function of numerical analysis was developed. A theoretical imaging resolution of a few hundred microns can be achieved. The composite AFAI-IMS images of different target analytes were imaged with high sensitivity. A typical AFAI-IMS image of the whole-body section of a rat was obtained in a single analytical measurement. The ability to image a large area for relevant samples in a single measurement with high sensitivity and repeatability is a significant advantage. The method has enormous potentials in the MS imaging of large and complicated samples.
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The structure-activity relationship (SAR) study of a 1,2,3,4,4a,9a-hexahydro-1H-xanthene series of selective, human glucocorticoid receptor α (hGRα) antagonists is reported. Compounds were screened using hydroxyapatite-based GR binding and MMTV-Luc co-transfection reporter gene assays. Four different regions of the scaffold were modified to assess the effects on hGRα antagonism and related potency. Compound 8d exhibits an 8-fold better bioactivity than the original hit 1a, as well as an improved chemical stability, which make it a promising lead for the subsequent optimization.
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A solid complex, readily prepared from commercially available sodium triphenylphosphine-m-sulfonate (TPPMS) and carbon tetrabromide, can be used as an easily recoverable and reusable catalyst system for one-pot condensation of 2-naphthol with aldehydes to construct 14-aryl(alkyl)-14H-dibenzo[a,j]- xanthene derivatives and one-pot condensation of 2-naphthol with aldehydes and cyclic 1,3-dicarbonyl compounds to construct 12-aryl(alkyl)-8,9,10,12-tetrahydrobenzo[a]xanthen-11-one derivatives.
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A series of novel sorafenib derivatives have been designed and synthesized. The cytotoxic activities of these compounds were tested in three tumor cell lines. Most of the compounds showed potent antiproliferative activity against the tested cell lines with IC50 = 0-20 μmol/L. Some compounds demonstrated competitive antiproliferative activities to sorafenib against all three cancer cell lines. Among them, compound 5g demonstrated significant inhibitory activity against A549, ACHN and MDAMB- 231 cell lines with IC50 values of 1.29, 1.99, 3.11 μmol/L, respectively.
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Pyrazoles and their derivatives are important heterocycles found in nature and present in numerous bioactive compounds. In contrast to 3 or 5-aryl pyrazole, the preparation of 4-aryl pyrazole is fairly rare. Utilizing microwave irradiation, the synthesis of 4-substituted-arylpyrazole via Suzuki cross-coupling has been developed with a wide range of substrates. The remarkable advantages of this method are mild reaction conditions, simple operation, high yield, and short reaction time. Product structures were identified by MS, 1H NMR, 13C NMR, and elemental analysis.
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A direct asymmetric tandem reaction of α-nitro ketones with β,γ-unsaturated α-ketoesters was found to be catalyzed by a bifunctional rosin-derived thiourea and gave 5-nitro-2-actoxyl-2-pentenates in excellent ee values and yields, a much better result than previously reported. Furthermore, through theoretical analysis, literature research and experimental verifications, a new mechanism involving an inverse-electron-demand Diels-Alder (IEDDAR) and a retro-Henry reaction was proposed.
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A convenient, efficient and practical metal-free method for the synthesis of substituted phenols from arylboronic acids has been developed. The protocol uses hydrogen peroxide as a hydroxylating agent, ammonium bicarbonate as an additive, and the reactions were conveniently performed in water at room temperature. Themethod shows an excellent tolerance of functional groups, so it will find a wide variety of applications in academic and industrial research.
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A novel electrochemical sensor based on the immobilization of tyrosinase (tyr) onto gold nanoparticles (nano-Au) and thioctic acid amide (T-NH2) self-assembled monolayers (SAMs)-modified gold electrode has been developed for the determination of bisphenol A (BPA). It was found that the nano-Au could significantly enhance the electrochemical response of tyr/nano-Au/T-NH2/Au electrode to BPA, and the enhancement effect of nano-Au on the current response was also related to the enzyme. The results indicated that the biosensor could be used as a detector for BPA determination with a linear range from 3.99 ×10-7 mol/L to 2.34×10-4 mol/L and a detection limit of 1.33×10-7 mol/L. In addition, this biosensor showed good reproducibility.
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A new phase transition compound, 2-methoxyanilinium perchlorate-18-crown-6 (1) {(o- CH3OC6H4NH3)+(18-crown-6)·ClO4-}, has been synthesized and separated as crystals. Differential scanning calorimetry (DSC) measurements show a pair of sharp peaks at 225 K (heating) and 210 K (cooling), indicating the phase transition is first-order. Dielectric anomalies observed at 225 K (heating) and 210 K (cooling) further confirm the phase transition. The crystal structures determined at 298 K and 123 K are both triclinic in P-1. The most distinct difference between room-temperature and lowtemperature structures is the order-disorder transition of the host 18-crown-6 molecule, which is the driving force of the phase transition.
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The photochromic ring-opening reaction of spiropyran (SP) has been investigated by a realistic semiclassical dynamics simulation, accompanied by SA3-CASSCF(12,10)/MS-CASPT2 potential energy curves (PECs) of S0-S2. The main simulation results show the dominate pathway corresponds to the ringopening process of trans-SP to form the most stable merocyanine (MC) product. These findings provide more important complementarity for interpreting experimental observations.
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A simple and practical method for the synthesis of N-substituted-2-aminobenzothiazoles via a crosscoupling reaction of 2-iodo anilines with isothiocyanates is envisaged using nano copper oxide as a recyclable catalyst and Cs2CO3 as a base in PEG-400, as a bio-degradable, reusable, inexpensive and nontoxic reaction medium, under ligand-free conditions. The present tandem process underlines environmental acceptability to access a wide range of N-substituted-2-aminobenzothiazoles in good to excellent yields.
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A series of novel calix[4]arene derivatives incorporating two triazolyl 1,3-diketo subunits in alternate positions at the lower rim were synthesized and screened for HIV integrase inhibition activity. The chemical structures of these compounds were confirmed by means of 1H NMR, 13C NMR, and ESI-MS. Preliminary bioassays indicated that calix[4]arene derivatives proved to be more active than p-tert-butylcalix[4]arene derivatives. In particular, compound 4g presented the most potent integrase strand transfer inhibitory activity with an IC50 value of 6.1 μmol/L.
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A new series of quinazolin-4(3H)-one derivatives containing a (1,3-diphenyl-1H-pyrazol-4-yl) core with substituents at the 2-position and aromatic or heteroaromatic substituents at the 3-position were synthesized using an L-proline catalyzed one-pot multi-component reaction approach. All the synthesized compounds were characterized and screened for their antimicrobial, antifungal and anti-tubercular activities.
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A temperature-controlled ionic liquid dispersive liquid-phasemicroextraction in combination with high performance liquid chromatography was developed for the enrichment and determination of triazine herbicides such as cyanazine, simazine, and atrazine in water samples. 1-Octyl-3-methylimidazolium hexafluorophosphate ([C8MIM][PF6]) was selected as the extraction solvent. Several experimental parameters were optimized. Under the optimal conditions, the linear range for cyanazine was in the concentration range of 0.5-80 μg/L and the linear range for simazine and atrazine was in the range of 1.0-100 mg/L. The limit of detection (LOD, S/N = 3) was in the ranges of 0.05-0.06 μg/L, and the intra day and inter day precision (RSDs, n = 6)was in the ranges of 3.2%-6.6% and 4.8%-8.9%, respectively. Four real water samples were analyzed with the developedmethod, and the experimental results showed that the spiked recoveries were satisfactory. All these exhibited that the developed method was a valuable tool for monitoring such pollutants.
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First total synthesis of cajanolactone A and cajanonic acid A has been achieved through steps of anion-anion condensations, cyclization, Williams etherification, selective demethylation, 1,3-sigmatropic rearrangement and hydrolysis. This work provides an efficient method for future cajanonic acid A derivatives synthesis.
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meso-Tetrakis(4-aminophenyl)porphyrin (TAPP) can self-assemble into nanostructures with different morphologies by a phase-transfer method. The morphologies (nanospheres, nanorods and nanothorns) of porphyrin nanoaggregates could be easily tuned just by changing the concentration of porphyrin in a proper solvent at room temperature. HRTEM images revealed the formation of highly ordered supramolecular arrays of TAPP, i.e., superlattice of TAPP molecules in nanoaggregates, which agreed well with the size of one molecule of TAPP. UV-vis absorption spectra showed an obvious red shift of the Soret band of TAPP, indicating the formation of J-aggregates of TAPP in nanoaggregates.
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The continuous dehydration of D-glucose into 5-hydroxymethylfurfural (HMF) was carried out under mild conditions, using SO3H-functionalized acidic ionic liquids as catalysts and H2O-4-methyl-2- pentanone (MIBK) biphasic system as solvent. High glucose conversion of 97.4% with HMF yield of 75.1% was obtained at 120 ℃ for 360 min, also, small amounts of levulinic acid (LA) and formic acid were generated. Generally, the dosage of catalyst and the initial content of glucose influenced the reaction significantly; the HMF selectivity decreased with the excessive elevation of temperature and prolonging of time; and water content in the system had a negative effect on the reaction. The ionic liquid catalyst could be recycled and exhibited constant activity for five successful runs. This paper provided a new strategy for HMF production from glucose.
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A series of bisthienylethenes containing imidazole and imidazolium derivatives have been prepared and the products have been characterized by means of NMR and MS. Their photochromic and fluorescent switch properties have been investigated by UV-vis absorption spectra and fluorescence spectra. The fluorescent emissions of these kinds of photochromic compounds can be simply modulated by varying the imidazole groups, which shows that these compounds may have potential application in the design of fluorescent photochromic materials.
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A dabco-based basic ionic liquid, 1-butyl-4-aza-1-azaniabicyclo[2.2.2]octane hydroxide, has been developed as a catalyst for a convenient and rapid method for the Michael addition of active methylene compounds to α,β-unsaturated carboxylic esters and nitriles. The method is very simple, and the yields are very high. The catalyst can be recycled several times without much loss of activity.
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Maxacalcitol, the 22-oxa-derivative of 1α, 25-dihydroxyvitamin D3, has been used as an antihyperparathyroidism and antipsoriatic drug. In this paper, an alternative synthetic route has been developed using commercially available vitamin D2 as the starting material. In addition, as a key intermediate, the asymmetric synthesis of 20(S)-alcohol 14 with the chiral auxiliary (R-CBS) was described for the first time. This new synthetic route afforded Maxacalcitol with improved overall yield (13.9%) in eleven steps.
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3-(Diphenylphosphino)propanoic acid (L2) has proved to be an efficient ligand for the copper-catalyzed C-N coupling reactions. N-arylation of imidazoles with aryl iodides catalyzed by CuCl/L2 was smoothly carried out in DMSO at 100 ℃ with a yield up to 98%. N-arylation of 1H-pyrazole with aryl iodides and bromides catalyzed by Cu(OAc)2/L2 in 1,4-dioxane also gave the corresponding products with yields of 40%-98%.
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A facile, one-pot synthesis of N-aryl propargylamine from aromatic boronic acid, aqueous ammonia, and propargyl bromide has been achieved under microwave-assisted conditions. The reactions can be smoothly completed within a total 10 min through a two-step procedure, including copper-catalyzed coupling of aromatic boronic acids with aqueous ammonia and following propargylation by propargyl bromide.
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The selected 18 energetic compounds were theoretically investigated by using the density functional theory (DFT) quantum mechanical code, DMol3, and the Hansen solubility parameters (HSPs) analyses. The results showed that 4-nitrotoluene, 4-nitrophenol, N,N'-dimethyl-N,N'-diphenylurea and N,N'- diethyl-N,N'-diphenylurea contain relatively electron-rich aromatic rings. Four satisfactory energetic precursors with electron-rich rings were quickly and effectively found by electrostatic potential (ESP) surfaces and HSPs analyses. The results also indicated that the absolute value of the lowest unoccupied molecular orbital (LUMO) of the energetic precursors with electron-rich rings often was less than 3.00 eV, and the absolute value of LUMO of the energetic precursors with electron deficient rings was oftenmore than 3.00 eV. Additionally, we found that with at least two eutectic points was a prerequisite for two precursors to form a cocrystal.
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Novel liver-specific nitric oxide (NO) releasing drugs with bile acid as both the NO carrier and targeting ligand were designed and synthesized by direct nitration of the hydroxyl group in bile acids or the 3-O-hydroxyl alkyl derivatives, with the intact 24-COOH being preserved for hepatocyte specific recognition. Preliminary biological evaluation revealed that oral administrated targeted conjugates could protect mice against acute liver damage induced by acetaminophen or carbon tetrachloride. The nitrate level in the liver significantly increased after oral administration of 1e while nitrate level in the blood did not significantly change. Co-administration of ursodeoxycholic acid (UDCA) significantly antagonized the increase of nitrate in the liver resulted by administration of 1e.
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A simple and selective method using a column packed with graphene oxide (GO) as a solid phase extractant has been developed for the multi-element preconcentration of Fe(Ⅲ), Ni(Ⅱ), Cu(Ⅱ) and Zn(Ⅱ) ions prior to flame atomic absorption spectrometric determinations. The method is based on the sorption of mentioned ions on synthesized GO using 2-(tert-butoxy)-N-(3-carbamothioylphenyl)acetamide as a chelating agent. Several parameters on the extraction and complex formation were optimized. Under the optimized conditions (pH 6, flow rate 9 mL/min), metal ions were retained on the column, then quantitatively eluted by HNO3 solution (5 mL, 3.0 mol/L). The preconcentration factor was calculated as 250. The detection limits for the analyte ions of interest were found in the range of 0.11 ng/mL (Ni2+) to 0.63 ng/mL (Cu2+). The column packed with GO was adequate for metal ions separation in matrixes containing alkali, alkaline earth, transition and heavy metal ions.
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Electrochemical oxidation of hydroquinone (1a) has been studied in the presence of 6-methyl-2- thiouracil (3a) and 6-propyl-2-thiouracil (3b) as nucleophiles in a DMF/buffer mixture, using cyclic voltammetry and controlled-potential coulometry. The results indicated that the p-quinone (2a) derived from 1a participates in a 1,4-Michael addition reaction with the thiouracil derivatives (3a-b) to form the corresponding hydroquinonethioether derivatives (6a-6b). The electrosynthesis of these compounds (6a-b) has been successfully performed on carbon rod electrodes in an undivided cell in good yield and purity.
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A simple and efficient Knoevenagel condensation between α,β-unsaturated aldehydes and active methylene compounds is reported. Notably, this condensation can be catalyzed by PPL (lipase from porcine pancreas) with satisfied yields (49%-92%). Moreover, PPL induces moderate Z/E selectivity in the Knoevenagel condensation.
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Two new compounds named as 3β,12,16-trihydroxy-6,8,11,13-abietatrien (1), (8R,8'S)-4,4',8-trihy-droxyl- 3,3'-dimethoxyl-9'-lignanolide (2) and a new natural product 4,4'-dihydroxyl-3,3',5,5'- dimethoxyldiphenyl diketone (3) were isolated from the whole herbs of Selaginella involven Spring. The structures were elucidated by spectroscopic analyses including UV, IR, 1D, 2DNMR and MS methods. Additionally, these three compounds exhibited potent protective effect against the injury of PC-12 cells induced by hypoxia/reoxygenation.
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The macrocyclic ligand, 15-crown-5, was used as an ionophore for fabrication of a polyvinyl chloride (PVC) based membrane sensor for Ag(I) cation. For construction of the Ag(I) cation selective electrode, the best response characteristics were obtained using the composition: 15-crown-5/PVC/o-nitrophenyloctylether (NPOE)/sodium tetraphenyl borate (NaTPB) in the percentage ratio of 5.6/30/60.5/3.9 (w/w/w/w). The electrochemical sensor shows a linear dynamic range 1.0×10-7-1.0×10-1 mol/L and a Nernstian slope of 58.9±0.5 mV/decade with a detection limit of 8.09×10-8 mol/L for Ag(I) cation. It has a fast response time of <10 s and can be used for at least 8 weeks without any considerable divergences in its potential response. It was successfully used as an indicator electrode in potentiometric titration of Ag(I) cation with I- and Cl- anions and also for the determination of this metal cation in radiology waste water.
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Low generational (G0-G2, G for generation) polyamidoamine (PAMAM) dendrimers were investigated as enhancers to improve the aqueous solubility of folic acid at pH 11 and pH 5. In these two cases, the solubility of folic acid increases with both the dendrimer concentration and generation. However, the solubilization mechanism is different. The electrostatic interaction between the primary amines of dendrimers and the ionized carboxylic groups of folic acid dominates the dissolution process at pH 11, while the increase of the solubility of folic acid at pH 5 is attributed to the hydrophobic encapsulation inside the dendrimer molecules. In addition, for comparison ethylenediamine was used as a small molecule control to examine the "dendritic effect" in the dendrimer-related solubilization process. Interestingly, PAMAM dendrimers exhibit, at pH 5, a significant superiority over ethylenediamine in enhancing solubility, whereas this "dendritic effect" cannot be observed under the basic condition.
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We have prepared silica, SiO2 coated NiO and NiO coated SiO2 by sol-gel method. The physicochemical properties of the desired materials were investigated by surface charge properties, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy, surface area measurements and X-ray diffraction (XRD) analyses. The point of zero charge (PZC) of the solid was determined by the salt addition method. In coated materials, two PZC values were noted representing the surface charge of their counterparts. The SEM image of SiO2 coated NiO displays a uniform coating of silica on the surface of NiO, whereas in case of NiO coated SiO2, a honeycomb like appearance was observed with highly porous structures. In the diffractograms of NiO, the characteristic peaks were suppressed in NiO coated silica, however, no diffraction peak could be seen in SiO2 coated NiO. Batch adsorption technique was applied for the removal of Pb2+ ions from aqueous solution. The sorption trend for Pb2+ ions was observed in the order of NiO coated SiO2 > SiO2 coated NiO > NiO > SiO2. This trend confirms that the coated materials have more sorption capacities than their parent counterparts.
