Latest ArticlesFour new seco-dibenzocyclooctadiene lignans, kadlongilignans A-D (1-4), consisting of a rare 6, 7-seco-(1), two 15, 16-seco-(2 and 3) and a 9, 10-seco-dibenzocyclooctadiene (4) lignans, were isolated from the roots of Kadsura longipedunculata. Their structures were elucidated by spectroscopic analysis, including extensive NMR, MS and ECD (electronic circular dichroism) spectra. Compounds 3 and 4 exhibited potent inhibitory activities against NO (nitric oxide) production of LPS (lipopolysaccharide)-induced murine macrophages with the inhibition rates of 36.3% and 26.9%, respectively.
A heteropore covalent organic framework (COF) integrating tetraphenylethene skeleton and catechol segment is designed and synthesized. It exhibits extremely high stability in water under different pH conditions, which makes it an excellent material for adsorptive removal of Cd(Ⅱ) from aqueous solutions with very fast adsorption kinetics, high uptake capacity, and good recyclability.
A new silver mediated aminophosphinoylation of propargyl alcohols with aromatic amines and Hphosphine oxides for the construction of α-aminophosphine oxides has been developed. The C-N and C-P bond could be efficiently formed in one pot operation via sequential C-C and C-O bond cleavage of propargylic alcohols. This present methodology, which not only provides a simple and alternative strategy for the synthesis of α-aminophosphine oxides, but also opens a new window for the cleavage reactions of propargyl alcohols via dealkynalation coupling.
A quinine-derived thiourea-catalyzed inter-/intramolecular Michael cycloaddition of chromoneoxindole/benzofuranone synthons with 3-substituted methylenebenzofuranones has been established, which constructed enantiomerically pure bispiro[benzofuran-oxindole/benzofuran-chromanone]s bearing five consecutive stereocenters including two spiro quaternary carton centers in good yields (up to 93%) with high diastereoselectivities (up to >20:1 dr) and good enantioselectivities (up to >99% ee). Moreover, this is the first example of bifunctional chromone-benzofuranone synthon directed organocatalytic tandem reaction, and also the first example of the bispiro[benzofuran-oxindole] and bispirobenzofuranone, potentially useful in medicinal chemistry.
The toxic organic dye contaminants in wastewater are extremely harmful to the ecosystem. Surface enhanced Raman scattering (SERS) is a technique with high sensitivity and chemical specificity which fulfills the requirements for monitoring dye contaminants in wastewater. However, as one of the common dye contaminants, methyl orange (MO) has very weak affinity to metallic surfaces and is difficult to be detected by SERS at low concentrations. Therefore, a new type of SERS substrate with Ag nanoparticle monolayer functionalized by mono-6-deoxy-6-thio-β-cyclodextrin (β-CD-SH) was prepared to efficiently capture and detect MO in wastewater with a limit of detection of 5×10-7 mol/L. The hydrophobic cavity of β-CD is responsible for the efficient trap and enrichment of MO on the Ag NPs surface, achieving a strong SERS signal of MO at low concentrations and at different pH values. This study provides new insight into designing a well-performed adsorbent for the capture and detection of organic contaminants.
A new star-shaped molecule StOF-Br3 containing oligofluorenes and halogen atoms (Bromine) has been synthesized and studied by Scanning Tunneling Microscopy (STM) at the highly oriented pyrolytic graphite (HOPG) surface. We have obtained the high-resolution self-assembled STM images, from which the highly ordered and closely packed non-porous arrangements of the StOF-Br3 molecular selfassemblies at the heptanoic acid/HOPG surface could be observed. The molecular models and selfassembled StOF-Br3 architectures have been given in the following text. Besides, we have also figured out the surface free energy by the density functional theory (DFT) calculation, which proved that the halogen···halogen interaction was strong enough to stabilize the ordered molecular self-assemblies. This work verifies the existence of bromine···bromine interactions, and meanwhile provides a kind of effective approach for quickly building ordered molecular nanoarchitectures with large areas and different geometries.
Two-dimensional mesoporous materials combing ultrathin nanosheet morphology with well-defined mesoporous structures, are now emerging and becoming increasingly important for their promising applications in energy storage, electronic devices, electrocatalysts and so on. Here, we synthesized a kind of polypyrrole-based two-dimensional mesoporous materials with uniform pore size, ultrathin thickness and high surface area. Serving for electrochemical NH3 sensor, they exhibited a fast response and high sensitivity. Therefore, our study would promote much interest in design of new materials for gas sensor applications.
A seven-step total synthesis of α-cyclopiazonic acid is reported from a commercially available 4-bromoindole. Salient feature of the work is the rapid formation of tetracyclic skeleton via a bioinspired [3+2] annulation to form the C/D rings.
Surface chemical properties of supports have an important influence on active sites and their catalytic behavior. Here, we fabricated a series of cobalt-based catalysts supported by carbon layer-coated ordered mesoporous silica (OMS) composites for higher alcohol synthesis (HAS). The carbon layers were derived from different sources and uniformly coated on the porous surface of OMS. Combined with the characterization results of carbonized catalysts, it is demonstrated that the carbon layer-coated supports significantly enhanced the metal dispersion and increased the ratio of Co2+ to Co0 sites, which further increased the CO conversion and alcohols selectivity. Moreover, it is found that the catalytic activity changed in line with the amount of defects and surface oxygenic groups of carbon layers, which resulted from the different carbon sources. The highest space time yield of C2+OH was 27.5 mmol gcat-1 h-1) obtained by the catalyst coated with glucose-derived carbon layer. But the carbon source is not the key factor influencing the distribution of Co-Co2+ dual sites and shows little effect on selectivity in HAS. These results may guide for further design of carbon supported catalysts.
The acetyl ester plays an important role for protection of the hydroxyl groups in carbohydrates synthesis. In the present study, we described an efficient deprotection of acetyl group of pentacyclic triterpenoid by using methanolic ammonia in THF solution. Good selectivity for cleaving gal-C2-OAc group of 3β-hydroxy-olean-12-en-28-oic acid 28-N-2, 3, 4, 6-tetra-O-acetyl-β-D-galactopyranoside (3) was achieved in the presence of methanolic ammonia within 4 h at low temperature (-60℃) in a yield of 56%. The reaction disclosed here provides a new method for the synthesis of C2 selective modified carbohydrates, which is more useful than conventional synthesis procedure that usually requires many steps including temporary regioselective protection and deprotection. When the reaction temperature was increased from -60℃ to room temperature, the cleavage of the other three acetyl groups of galactose in an order of C4-OAc > C3-OAc > C6-OAc was observed. Based on this study, a plausible route for the deacetylation reaction has been proposed.
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