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2014 Volume 25 Issue 9
2014, 25(9): 1211-1214
doi: 10.1016/j.cclet.2014.05.039
Abstract:
Combining the inhibited aptazyme and molecular beacon (MB), we developed a versatile sensing strategy for amplified detection of adenosine. In this strategy, the adenosine aptamer links to the 8-17 DNAzyme to form an aptazyme. A short sequence, denoted as inhibitor, is designed to form a duplex spanning the aptamer-DNAzyme junction, which blocks the catalytic function of the DNAzyme. Only in the presence of target adenosine, the aptamer binds to adenosine, thus the inhibitor dissociates from the aptamer portion of the aptazyme and can no longer form the stable duplex required to inhibit the catalytic activity of the aptazyme. The released DNAzyme domain will hybridize to the MB and catalyze the cleavage in the presence of Zn2+, making the fluorophore separate from the quencher and resulting in fluorescence signal. The results showed that the detection method has a dynamic range from 10 nmol/L to 1 nmol/L, with a detection limit of 10 nmol/L.
Combining the inhibited aptazyme and molecular beacon (MB), we developed a versatile sensing strategy for amplified detection of adenosine. In this strategy, the adenosine aptamer links to the 8-17 DNAzyme to form an aptazyme. A short sequence, denoted as inhibitor, is designed to form a duplex spanning the aptamer-DNAzyme junction, which blocks the catalytic function of the DNAzyme. Only in the presence of target adenosine, the aptamer binds to adenosine, thus the inhibitor dissociates from the aptamer portion of the aptazyme and can no longer form the stable duplex required to inhibit the catalytic activity of the aptazyme. The released DNAzyme domain will hybridize to the MB and catalyze the cleavage in the presence of Zn2+, making the fluorophore separate from the quencher and resulting in fluorescence signal. The results showed that the detection method has a dynamic range from 10 nmol/L to 1 nmol/L, with a detection limit of 10 nmol/L.
2014, 25(9): 1215-1219
doi: 10.1016/j.cclet.2014.05.037
Abstract:
Two new β-hydroxy amino acid-coupled secoiridoids, named serinosecologanin (1) and threoninosecologanin (2), were isolated from an aqueous extract of the flower buds of Lonicera japonica. Their uncommon structures including absolute configurations were determined by spectroscopic data analysis, and confirmed by semisynthesis from the co-occurring secologanin (3) and secologanic acid (4). Compounds 1 and 2 exhibited resistant activity against β-glucosidase from almonds and hesperidinase from Aspergillus niger, they also showed activity against the release of glucuronidase in rat polymorphonuclear leukocytes induced by the platelet-activating factor with inhibition rates of (34.9±3.1)% and (53.6±2.6)%, respectively.
Two new β-hydroxy amino acid-coupled secoiridoids, named serinosecologanin (1) and threoninosecologanin (2), were isolated from an aqueous extract of the flower buds of Lonicera japonica. Their uncommon structures including absolute configurations were determined by spectroscopic data analysis, and confirmed by semisynthesis from the co-occurring secologanin (3) and secologanic acid (4). Compounds 1 and 2 exhibited resistant activity against β-glucosidase from almonds and hesperidinase from Aspergillus niger, they also showed activity against the release of glucuronidase in rat polymorphonuclear leukocytes induced by the platelet-activating factor with inhibition rates of (34.9±3.1)% and (53.6±2.6)%, respectively.
2014, 25(9): 1220-1224
doi: 10.1016/j.cclet.2014.06.007
Abstract:
An efficient route to prepare L-glucose and L-galactose is described. The L-sugars are achieved by using the strategy of switching the functional groups at C1 and C5 of D-glucose and D-mannose. The oxidation and reduction of the silyl enol ether at C1 and the lead(IV) tetraacetate mediated oxidative decarboxylation at C5 are the key steps. L-Glucose and L-galactose are prepared in a convenient and inexpensive way.
An efficient route to prepare L-glucose and L-galactose is described. The L-sugars are achieved by using the strategy of switching the functional groups at C1 and C5 of D-glucose and D-mannose. The oxidation and reduction of the silyl enol ether at C1 and the lead(IV) tetraacetate mediated oxidative decarboxylation at C5 are the key steps. L-Glucose and L-galactose are prepared in a convenient and inexpensive way.
2014, 25(9): 1225-1229
doi: 10.1016/j.cclet.2014.04.014
Abstract:
In this work, a reliable and sensitive method for detecting polybrominated diphenyl ethers (PBDEs) has been developed by the combination of liquid-liquid extraction and gas chromatography-mass spectrometry. PBDEs were extracted from a large volume of water by liquid-liquid extraction and purified by silica gel chromatography. In order to reduce the deviation, dibromobiphenyl was exploited as the internal standard to minimize differences among the injections. The quantification was performed using an external standard. Good linear correlation coefficients (>0.991) and a wide linearity range (1.0-500.0 ng/L) indicated the steadiness of the proposed method. Moreover, the satisfactory recovery (>75%) suggested that successful determination of PBDEs in river water had been achieved. Furthermore, the deduction behavior of PBDEs in river water could be inferred according to the results.
In this work, a reliable and sensitive method for detecting polybrominated diphenyl ethers (PBDEs) has been developed by the combination of liquid-liquid extraction and gas chromatography-mass spectrometry. PBDEs were extracted from a large volume of water by liquid-liquid extraction and purified by silica gel chromatography. In order to reduce the deviation, dibromobiphenyl was exploited as the internal standard to minimize differences among the injections. The quantification was performed using an external standard. Good linear correlation coefficients (>0.991) and a wide linearity range (1.0-500.0 ng/L) indicated the steadiness of the proposed method. Moreover, the satisfactory recovery (>75%) suggested that successful determination of PBDEs in river water had been achieved. Furthermore, the deduction behavior of PBDEs in river water could be inferred according to the results.
2014, 25(9): 1230-1234
doi: 10.1016/j.cclet.2014.06.017
Abstract:
A pyridoxal-based chemosensor was synthesized by reacting hydrazine hydrate and pyridoxal hydrochloride in ethanol and characterized by NMR and ESI-MS. The optical properties of the compound were investigated in a methanol: HEPES solution. The compound displayed selectivity for Cu2+, as evidenced by a colorless to yellow color change, which was characterized using UV-vis spectroscopy. The fluorescence of the compound can be quenched only by Cu2+, accompanying by a color change from blue to colorless. Furthermore, it can be used in bioimaging.
A pyridoxal-based chemosensor was synthesized by reacting hydrazine hydrate and pyridoxal hydrochloride in ethanol and characterized by NMR and ESI-MS. The optical properties of the compound were investigated in a methanol: HEPES solution. The compound displayed selectivity for Cu2+, as evidenced by a colorless to yellow color change, which was characterized using UV-vis spectroscopy. The fluorescence of the compound can be quenched only by Cu2+, accompanying by a color change from blue to colorless. Furthermore, it can be used in bioimaging.
2014, 25(9): 1235-1239
doi: 10.1016/j.cclet.2014.05.023
Abstract:
An efficient synthesis of functionalized 4H-chromenes by the tandem reaction of β,γ-unsaturated α-ketoesters with 2-naphthols, 1-naphthols, and 1,3-dihydroxynaphthalenes has been accomplished with high selectivity and excellent yields in the presence of a catalytic amount of bismuth triflate [Bi(OTf)3, 5 mol%] under mild conditions. The functionalized 4H-chromene synthesis and our previous 2H-chromene hemiacetal synthesis could complement each other to enrich reaction diversity.
An efficient synthesis of functionalized 4H-chromenes by the tandem reaction of β,γ-unsaturated α-ketoesters with 2-naphthols, 1-naphthols, and 1,3-dihydroxynaphthalenes has been accomplished with high selectivity and excellent yields in the presence of a catalytic amount of bismuth triflate [Bi(OTf)3, 5 mol%] under mild conditions. The functionalized 4H-chromene synthesis and our previous 2H-chromene hemiacetal synthesis could complement each other to enrich reaction diversity.
2014, 25(9): 1240-1243
doi: 10.1016/j.cclet.2014.04.021
Abstract:
10 mol% CuI combined with the DMEDA ligand can efficiently catalyze the N-arylation of 2-arylindoles with aryl iodides and aryl bromides in good to excellent yields. The aryl halides bearing electron-rich or electron-deficient functional groups can be well tolerated under this mild reaction conditions.
10 mol% CuI combined with the DMEDA ligand can efficiently catalyze the N-arylation of 2-arylindoles with aryl iodides and aryl bromides in good to excellent yields. The aryl halides bearing electron-rich or electron-deficient functional groups can be well tolerated under this mild reaction conditions.
2014, 25(9): 1244-1246
doi: 10.1016/j.cclet.2014.05.018
Abstract:
A sensitive electrochemical sensor for the determination of cysteamine (CA) was developed using a modified multiwall carbon nanotube paste electrode (MWCNTPE) with isoproterenol (ISPT) as a mediator. This modified electrode showed very high electrocatalytic activity for the anodic oxidation of CA. Under the optimized conditions, the electrocatalytic peak current showed a linear relationship with CA concentration in the range of 0.3-450.0 μmol/L with a detection limit of 0.09 μmol/L CA. The modified electrode was used for the determination of CA in real samples such as urine and drug samples.
A sensitive electrochemical sensor for the determination of cysteamine (CA) was developed using a modified multiwall carbon nanotube paste electrode (MWCNTPE) with isoproterenol (ISPT) as a mediator. This modified electrode showed very high electrocatalytic activity for the anodic oxidation of CA. Under the optimized conditions, the electrocatalytic peak current showed a linear relationship with CA concentration in the range of 0.3-450.0 μmol/L with a detection limit of 0.09 μmol/L CA. The modified electrode was used for the determination of CA in real samples such as urine and drug samples.
2014, 25(9): 1247-1251
doi: 10.1016/j.cclet.2014.05.017
Abstract:
Graphitic carbon nitride (g-C3N4) with high photocatalytic activity toward degradation of 4-nitrophenol under visible light irradiation was prepared by HCl etching followed by ammonia neutralization. The structure, morphology, surface area, and photocatalytic properties of the prepared samples were studied. After treatment, the size of the γ-C3N4 decreased from several micrometers to several hundred nanometers, and the specific area of the γ-C3N4 increased from 11.5 m2/g to 115 m2/g. Meanwhile, the photocatalytic activity of γ-C3N4 was significantly improved after treatment toward degradation of 4-nitrophenol under visible light irradiation. The degradation rate constant of the small particle γ-C3N4 is 5.7 times of that of bulk γ-C3N4, which makes it a promising visible light photocatalyst for future applications for water treatment and environmental remediation.
Graphitic carbon nitride (g-C3N4) with high photocatalytic activity toward degradation of 4-nitrophenol under visible light irradiation was prepared by HCl etching followed by ammonia neutralization. The structure, morphology, surface area, and photocatalytic properties of the prepared samples were studied. After treatment, the size of the γ-C3N4 decreased from several micrometers to several hundred nanometers, and the specific area of the γ-C3N4 increased from 11.5 m2/g to 115 m2/g. Meanwhile, the photocatalytic activity of γ-C3N4 was significantly improved after treatment toward degradation of 4-nitrophenol under visible light irradiation. The degradation rate constant of the small particle γ-C3N4 is 5.7 times of that of bulk γ-C3N4, which makes it a promising visible light photocatalyst for future applications for water treatment and environmental remediation.
2014, 25(9): 1252-1255
doi: 10.1016/j.cclet.2014.03.051
Abstract:
One new stenine-type alkaloid, tuberostemonine D (1), together with five known stenine-type alkaloids (2-6) and two known stemoninine-type alkaloids (7 and 8), were isolated from the roots of Stemona tuberosa. Their structureswere elucidated by extensive spectroscopic methods (IR,UV,MS, 1D and 2D NMR), and the structure of 1 was further confirmed by X-ray diffraction analysis. First simultaneous isolation of stenine-and stemoninine-type alkaloids not only added a newchemical type and increased the chemical diversity of Stemona tuberosa, but also provided chemotaxonomic clues for the close relationship between genera Stemona and Stichoneuron, and favored retaining them in the same family.
One new stenine-type alkaloid, tuberostemonine D (1), together with five known stenine-type alkaloids (2-6) and two known stemoninine-type alkaloids (7 and 8), were isolated from the roots of Stemona tuberosa. Their structureswere elucidated by extensive spectroscopic methods (IR,UV,MS, 1D and 2D NMR), and the structure of 1 was further confirmed by X-ray diffraction analysis. First simultaneous isolation of stenine-and stemoninine-type alkaloids not only added a newchemical type and increased the chemical diversity of Stemona tuberosa, but also provided chemotaxonomic clues for the close relationship between genera Stemona and Stichoneuron, and favored retaining them in the same family.
2014, 25(9): 1256-1258
doi: 10.1016/j.cclet.2014.04.004
Abstract:
Two novel 27-norergostanol steroids, panthogenins A (1) and B (2), possessing unusual rings E and F featuring a ketal moiety at C-25 were isolated from rhizomes of Dioscorea panthaica. Their structures and relative configurations were elucidated by extensive spectroscopic methods including 1D and 2D NMR techniques, and the structure of panthogenin A was further confirmed by X-ray crystallography. Both compounds showed potent in vitro insulin sensitizing activity.
Two novel 27-norergostanol steroids, panthogenins A (1) and B (2), possessing unusual rings E and F featuring a ketal moiety at C-25 were isolated from rhizomes of Dioscorea panthaica. Their structures and relative configurations were elucidated by extensive spectroscopic methods including 1D and 2D NMR techniques, and the structure of panthogenin A was further confirmed by X-ray crystallography. Both compounds showed potent in vitro insulin sensitizing activity.
2014, 25(9): 1259-1264
doi: 10.1016/j.cclet.2014.04.012
Abstract:
Aspartame is a widely used sweetener, the long-term safety of which has been controversial ever since it was accepted for human consumption. It is unstable and can produce some harmful degradation products under certain storage conditions. A high-performance liquid chromatography/tandem mass spectrometry method was developed for the simultaneous analysis of aspartame and its four degradation products, including aspartic acid, phenylalanine, aspartyl-phenylalanine and 5-benzyl-3,6-dioxo-2-piperazieacetic acid in water and in diet soft drinks. Aspartame and its four degradation products were quantified by a matrix matched external standard calibration curve with excellent correlation coefficients. The limits of detection were 0.16-5.8 μg/L, which exhibited higher sensitivity than common methods. This method was rapid, sensitive, specific and capable of eliminating matrix interferences. It was also applied to the study of the degradation of aspartame at various pH and temperatures. The results indicated that aspartame was partly degraded under strong acidic or basic conditions and the extent of degradation increased with increasing temperature.
Aspartame is a widely used sweetener, the long-term safety of which has been controversial ever since it was accepted for human consumption. It is unstable and can produce some harmful degradation products under certain storage conditions. A high-performance liquid chromatography/tandem mass spectrometry method was developed for the simultaneous analysis of aspartame and its four degradation products, including aspartic acid, phenylalanine, aspartyl-phenylalanine and 5-benzyl-3,6-dioxo-2-piperazieacetic acid in water and in diet soft drinks. Aspartame and its four degradation products were quantified by a matrix matched external standard calibration curve with excellent correlation coefficients. The limits of detection were 0.16-5.8 μg/L, which exhibited higher sensitivity than common methods. This method was rapid, sensitive, specific and capable of eliminating matrix interferences. It was also applied to the study of the degradation of aspartame at various pH and temperatures. The results indicated that aspartame was partly degraded under strong acidic or basic conditions and the extent of degradation increased with increasing temperature.
2014, 25(9): 1265-1270
doi: 10.1016/j.cclet.2014.05.003
Abstract:
A series of magnetically recyclable Pd/Fe3O4@γ-Al2O3 catalysts were synthesized using the superparamagnetic Fe3O4@γ-Al2O3 core-shell microspheres as the supporter and nano-Pd particles assembled on γ-Al2O3 shell as the active catalytic component. The structure of the catalysts was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption-desorption and vibrating sample magnetometer (VSM). The catalytic activity and the recyclability properties of the catalysts for the Heck coupling reaction with aryl bromides and the olefins were investigated. The results show that the microspheres of the magnetic Pd/Fe3O4@γ-Al2O3 catalysts were about 400 nm and the nano-Pd particles assembled on γ-Al2O3 shell were about 3-4 nm in size. The saturation magnetization (MS) of the magnetic catalysts was sufficiently high to allow magnetic separations. In the Heck coupling reactions, the magnetic Pd/Fe3O4@γ-Al2O3 catalysts exhibited good catalytic activity and recyclability. With Pd/Fe3O4@γ-Al2O3 (0.021 mol%) catalyst, the bromobenzene conversion and product yield reached about 96.8% and 91.2%, respectively, at 120℃ and in 14 h. After being recycled for six times, the conversion of bromobenzene and the recovery of the catalyst were about 80% and 90%, respectively. The nano-Pd particles were kept well dispersed in the used Pd/Fe3O4@γ-Al2O3 catalysts.
A series of magnetically recyclable Pd/Fe3O4@γ-Al2O3 catalysts were synthesized using the superparamagnetic Fe3O4@γ-Al2O3 core-shell microspheres as the supporter and nano-Pd particles assembled on γ-Al2O3 shell as the active catalytic component. The structure of the catalysts was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption-desorption and vibrating sample magnetometer (VSM). The catalytic activity and the recyclability properties of the catalysts for the Heck coupling reaction with aryl bromides and the olefins were investigated. The results show that the microspheres of the magnetic Pd/Fe3O4@γ-Al2O3 catalysts were about 400 nm and the nano-Pd particles assembled on γ-Al2O3 shell were about 3-4 nm in size. The saturation magnetization (MS) of the magnetic catalysts was sufficiently high to allow magnetic separations. In the Heck coupling reactions, the magnetic Pd/Fe3O4@γ-Al2O3 catalysts exhibited good catalytic activity and recyclability. With Pd/Fe3O4@γ-Al2O3 (0.021 mol%) catalyst, the bromobenzene conversion and product yield reached about 96.8% and 91.2%, respectively, at 120℃ and in 14 h. After being recycled for six times, the conversion of bromobenzene and the recovery of the catalyst were about 80% and 90%, respectively. The nano-Pd particles were kept well dispersed in the used Pd/Fe3O4@γ-Al2O3 catalysts.
2014, 25(9): 1271-1274
doi: 10.1016/j.cclet.2014.03.008
Abstract:
Gold nanoparticles (Au NPs) can serve as visualized colorimetric probes for various targets and modification-free sensing strategies are preferred. The donor-acceptor interaction between the electron-rich melamine (MA) and the electron-deficient trinitrotoluene (TNT) allows formation of a supramolecule in aqueous solution. Melamine alone makes the initially individual reddish Au NPs aggregate into gray/blue Au NP assemblies due tomelamine forming multiple ligand sites toward the Au NPs. Interestingly, the preformed supramolecule of MA-TNT disenables aggregation of the Au NPs. Therefore the unmodified Au NPs provide facile colorimetric probes for TNT detection in aqueous solution. Rapid identification of TNT is established by naked eye inspection. By using spectrophotometer tools, quantification of TNT is accomplished with a linear range of 80 μmol L-1 to 1.2 μmol L-1 and a limit of detection (LOD) of 27 μmol L-1. In contrast to previous strategy with surface-modified Au NPs, here a modification-free sensing strategy for TNT assay has been developed with greater convenience, rapidity, and cost-effectiveness.
Gold nanoparticles (Au NPs) can serve as visualized colorimetric probes for various targets and modification-free sensing strategies are preferred. The donor-acceptor interaction between the electron-rich melamine (MA) and the electron-deficient trinitrotoluene (TNT) allows formation of a supramolecule in aqueous solution. Melamine alone makes the initially individual reddish Au NPs aggregate into gray/blue Au NP assemblies due tomelamine forming multiple ligand sites toward the Au NPs. Interestingly, the preformed supramolecule of MA-TNT disenables aggregation of the Au NPs. Therefore the unmodified Au NPs provide facile colorimetric probes for TNT detection in aqueous solution. Rapid identification of TNT is established by naked eye inspection. By using spectrophotometer tools, quantification of TNT is accomplished with a linear range of 80 μmol L-1 to 1.2 μmol L-1 and a limit of detection (LOD) of 27 μmol L-1. In contrast to previous strategy with surface-modified Au NPs, here a modification-free sensing strategy for TNT assay has been developed with greater convenience, rapidity, and cost-effectiveness.
2014, 25(9): 1275-1278
doi: 10.1016/j.cclet.2014.03.009
Abstract:
In order to improve the stabilization and spinnability of polyacrylonitrile, a bifunctional comonomer containing both ester and amide groups was synthesized to prepare poly(acrylonitrile-co-3-aminocarbonyl-3-butenoic acid methyl ester) [P(AN-co-ABM)] copolymers used as the carbon fiber precursor instead of poly(acrylonitrile-acrylamide-methyl acrylate) [P(AN-AM-MA)] terpolymer. The differential scanning calorimetry and thermogravimetry results show that the stabilization of P(AN-co-ABM) have been remarkably improved by ABM compared with P(AN-AM-MA) terpolymer, such as lower initiation temperature, broadened exothermic peak and smaller activation energy. Moreover, the spinnability of P(AN-co-ABM) is also improved by ABM due to the lubrication of ester groups in ABM. This study clearly shows that P(AN-co-ABM) copolymer is a better material for use as a carbon fiber precursor than P(AN-AM-MA) terpolymer.
In order to improve the stabilization and spinnability of polyacrylonitrile, a bifunctional comonomer containing both ester and amide groups was synthesized to prepare poly(acrylonitrile-co-3-aminocarbonyl-3-butenoic acid methyl ester) [P(AN-co-ABM)] copolymers used as the carbon fiber precursor instead of poly(acrylonitrile-acrylamide-methyl acrylate) [P(AN-AM-MA)] terpolymer. The differential scanning calorimetry and thermogravimetry results show that the stabilization of P(AN-co-ABM) have been remarkably improved by ABM compared with P(AN-AM-MA) terpolymer, such as lower initiation temperature, broadened exothermic peak and smaller activation energy. Moreover, the spinnability of P(AN-co-ABM) is also improved by ABM due to the lubrication of ester groups in ABM. This study clearly shows that P(AN-co-ABM) copolymer is a better material for use as a carbon fiber precursor than P(AN-AM-MA) terpolymer.
2014, 25(9): 1279-1281
doi: 10.1016/j.cclet.2014.04.011
Abstract:
In this paper, thermoexpandable polymeric microspheres were prepared by suspension polymerization with acrylonitrile (AN) and methyl methacrylate (MMA) as monomers and i-butane as a blowing agent. The micromorphology and thermal stability were researched by polarized microscopy and TGA. The diameter of the expandable microspheres increased from about 20 μm (unexpanded) to 40-80 μm (expanded) upon heating. The maximum expansion volume was higher than 22 times of the original volume and the density of the expanded microspheres was about 16.7 kg/m3. The blowing agent content in microspheres was about 20 wt% and To.e., Tm.e. and To.s. were 80 ℃, 120-130℃ and 140-145 ℃, respectively.
In this paper, thermoexpandable polymeric microspheres were prepared by suspension polymerization with acrylonitrile (AN) and methyl methacrylate (MMA) as monomers and i-butane as a blowing agent. The micromorphology and thermal stability were researched by polarized microscopy and TGA. The diameter of the expandable microspheres increased from about 20 μm (unexpanded) to 40-80 μm (expanded) upon heating. The maximum expansion volume was higher than 22 times of the original volume and the density of the expanded microspheres was about 16.7 kg/m3. The blowing agent content in microspheres was about 20 wt% and To.e., Tm.e. and To.s. were 80 ℃, 120-130℃ and 140-145 ℃, respectively.
2014, 25(9): 1282-1286
doi: 10.1016/j.cclet.2014.03.022
Abstract:
A novel fused isocoumarin skeleton has been synthesized through selective domino multicyclizations by mixing homothallic acid and 2,3-diphenylacryloyl chloride at 200℃ under catalyst and solvent free reaction conditions. Six fused rings with two stereogenic centers were assembled in a convenient onepot operation in good yield. The resulting hexacyclic fused isocoumarin skeleton and its stereochemistry was fully characterized and unambiguously confirmed by X-ray diffraction analysis.
A novel fused isocoumarin skeleton has been synthesized through selective domino multicyclizations by mixing homothallic acid and 2,3-diphenylacryloyl chloride at 200℃ under catalyst and solvent free reaction conditions. Six fused rings with two stereogenic centers were assembled in a convenient onepot operation in good yield. The resulting hexacyclic fused isocoumarin skeleton and its stereochemistry was fully characterized and unambiguously confirmed by X-ray diffraction analysis.
2014, 25(9): 1287-1290
doi: 10.1016/j.cclet.2014.04.008
Abstract:
A polyvinylpolypyrrolidone supported triflic acid was shown to be useful as a recyclable heterogeneous catalyst for the rapid and efficient synthesis of quinoxaline derivatives in good-to-excellent yields. The catalyst is easily prepared, air-stable, reusable, and easily removed from the reaction mixtures.
A polyvinylpolypyrrolidone supported triflic acid was shown to be useful as a recyclable heterogeneous catalyst for the rapid and efficient synthesis of quinoxaline derivatives in good-to-excellent yields. The catalyst is easily prepared, air-stable, reusable, and easily removed from the reaction mixtures.
2014, 25(9): 1291-1295
doi: 10.1016/j.cclet.2014.04.027
Abstract:
Due to the high affinity between dithiocarbamate (DTC) and Hg2+, a fluorescent probe based on squaraine chromophore with DTC side arm for Hg2+ via coordination induced deaggregation signaling has been designed and synthesized. Squaraine has a high tendency to aggregate in aqueous solution, and such self-aggregation usually results in a dramatic absorption spectral broadening with fluorescence emission quenching. The combination of the DTC side arm of the probe with Hg2+ induces steric hindrance, leading to the deaggregation of the dye complex, companying with a fluorescence emission restoration. In EtOH-H2O (20:80, v/v) solution, this "turn on" fluorescent probe has high selectivity and sensitivity toward Hg2+ over other metal ions, and the limit of detection for Hg2+ was estimated as 2.19×10-8mol/L by 3σ/k.
Due to the high affinity between dithiocarbamate (DTC) and Hg2+, a fluorescent probe based on squaraine chromophore with DTC side arm for Hg2+ via coordination induced deaggregation signaling has been designed and synthesized. Squaraine has a high tendency to aggregate in aqueous solution, and such self-aggregation usually results in a dramatic absorption spectral broadening with fluorescence emission quenching. The combination of the DTC side arm of the probe with Hg2+ induces steric hindrance, leading to the deaggregation of the dye complex, companying with a fluorescence emission restoration. In EtOH-H2O (20:80, v/v) solution, this "turn on" fluorescent probe has high selectivity and sensitivity toward Hg2+ over other metal ions, and the limit of detection for Hg2+ was estimated as 2.19×10-8mol/L by 3σ/k.
2014, 25(9): 1296-1300
doi: 10.1016/j.cclet.2014.04.019
Abstract:
We describe a convenient method for the synthesis of 1,2-disubstituted acetylenes via a cross-coupling reaction of (bromoethynyl)benzene with Grignard reagents. The reaction of (bromoethynyl)benzene (1 mmol) with Grignard reagent (1.3 mmol) mediated by NiCl2 (4 mol%) and (p-CH3Ph)3P (8 mol%) in THF could produce 1,2-disubstituted acetylenes in good yields at room temperature.
We describe a convenient method for the synthesis of 1,2-disubstituted acetylenes via a cross-coupling reaction of (bromoethynyl)benzene with Grignard reagents. The reaction of (bromoethynyl)benzene (1 mmol) with Grignard reagent (1.3 mmol) mediated by NiCl2 (4 mol%) and (p-CH3Ph)3P (8 mol%) in THF could produce 1,2-disubstituted acetylenes in good yields at room temperature.
2014, 25(9): 1301-1304
doi: 10.1016/j.cclet.2014.06.009
Abstract:
A simple synthetic approach for the transformation of (S)-Ugi's amine, another configuration of (R)-Ugi's amine, one of the most widely used intermediate in the preparation of chiral ferrocene-based ligands, has been developed via esterification using anhydride, alkaline hydrolysis and active manganese dioxide oxidation, and the corresponding ferrocenyl ketone was afforded in good yields.
A simple synthetic approach for the transformation of (S)-Ugi's amine, another configuration of (R)-Ugi's amine, one of the most widely used intermediate in the preparation of chiral ferrocene-based ligands, has been developed via esterification using anhydride, alkaline hydrolysis and active manganese dioxide oxidation, and the corresponding ferrocenyl ketone was afforded in good yields.
2014, 25(9): 1305-1307
doi: 10.1016/j.cclet.2014.03.010
Abstract:
The graphene-based semi-solid grease with low friction coefficient was prepared by highly dispersed mixing method. The friction testing result showed that the friction coefficient of the graphene oxidebased semi-solid grease reduced from ca. 0.105 of graphite-based one to ca. 0.075, approximately 30% decreasing. Further, the graphene-based semi-solid grease shows the more outstandingly lubricating property, and the friction coefficient approximately drops to the range of between 0.04 and 0.06. By comparing with the graphite-based grease, the friction coefficient decreases about 40%-60% and the wear reduced over 50%.
The graphene-based semi-solid grease with low friction coefficient was prepared by highly dispersed mixing method. The friction testing result showed that the friction coefficient of the graphene oxidebased semi-solid grease reduced from ca. 0.105 of graphite-based one to ca. 0.075, approximately 30% decreasing. Further, the graphene-based semi-solid grease shows the more outstandingly lubricating property, and the friction coefficient approximately drops to the range of between 0.04 and 0.06. By comparing with the graphite-based grease, the friction coefficient decreases about 40%-60% and the wear reduced over 50%.
2014, 25(9): 1308-1310
doi: 10.1016/j.cclet.2014.03.040
Abstract:
One new nonadride derivative rubratoxin C (1) together with a known compound rubratoxin B (2) were isolated from an endophytic fungus Penicillium sp. F-14. Their structures were elucidated by various spectroscopicmethods. Bioassays showed that 2 had moderate cytotoxic effect against HCT-8, BEL-7402, Ketr3, A2780, MCF-7 and BGC-823 human cancer cell lines, and 1 exhibited weak activity.
One new nonadride derivative rubratoxin C (1) together with a known compound rubratoxin B (2) were isolated from an endophytic fungus Penicillium sp. F-14. Their structures were elucidated by various spectroscopicmethods. Bioassays showed that 2 had moderate cytotoxic effect against HCT-8, BEL-7402, Ketr3, A2780, MCF-7 and BGC-823 human cancer cell lines, and 1 exhibited weak activity.
