Dicitrinones E and F,citrinin dimers from the marine derived fungus Penicillium citrinum HDN-152-088

Two new citrinin dimers named dicitrinones E and F (1 and 2), together with one biogenetically related known citrinin monomer (3), were isolated from the marine derived fungus Penicillium citrinum HDN-152-088. All structures including the absolute configurations were elucidated on the basis of comprehensive spectroscopic data, and assisted by ECD calculations. Among them, compounds 1 and 2 belong to the class of citrinin dimers with a rare carbon-bridged C-7/C-7′ linkage. Compound 1 displayed antioxidant activity with IC₅₀ value of 23.73 μM.     

Biomimetically inspired total synthesis of (12S)-12-hydroxymonocerin and (12R)-12-hydroxymonocerin

A concise asymmetric total synthesis of (12S)-12-hydroxymonocerin (1) and (12R)-12-hydroxymonocerin (2) were efficiently achieved from the known 4-bromo-2,6-dimethoxyphenol. The synthetic approach was inspired by our biomimetic synthesis of (+)-monocerin (3) and 7-O-demethylmonocerin (4). The cis-fused furobenzopyranones of 1 and 2 was efficiently constructed via an intramolecular nucleophilic trapping of a quinonemethide intermediate, which was obtained by benzylic oxidation of compound 10 using 2,3-Dichloro-5,6-dicyano-1,4-benzoquinone (DDQ).     

Cytotoxic Diterpenoids from the Stem Bark of Annona squamosa L.

Three new ent‐kaurane diterpenoids, (4α)‐19‐nor‐ent‐kaurane‐4,16,17‐triol ( 1 ), (4α,16α)‐17‐(acetyloxy)‐19‐nor‐ent‐kaurane‐4,16‐diol ( 2 ), and 17‐hydroxy‐ent‐kaur‐15‐en‐19‐al ( 3 ), together with 11 known compounds, were isolated from the stem bark of Annona squamosa L. The structures of 1 – 3 were identified by analysis of their spectroscopic data. All compounds were evaluated for cytotoxic activity against human lung cancer (95‐D) and ovarian cancer (A2780) cell lines, and compounds 3, 5, 7, 11 – 14 exhibited promising antiproliferative activities with IC₅₀ values ranging from 0.38 to 34.66 μM .     

Preparation of fluorescent polyvinyl alcohol keto-derivatives nanoparticles and selective determination of chromium(VI)

A novel fluorescent polyvinyl alcohol keto-derivatives nanoparticle (PVAK) has been prepared in one-step method. The nanoparticles has excitation and emission maxima at 349 and 462 nm, respectively. Based on the fluorescence quenching of PVAK by Cr(VI), we established a simple and selective fluorimetric method for the determination of Cr(VI) without separation of Cr(III) in water. The reaction conditions between Cr(VI) and PVAK were investigated in detail. Furthermore, the reaction mechanism between PVAK and Cr(VI) was also discussed. Under optimal experimental conditions, a limit of detection of 0.02 microg mL(-1) was achieved. The calibration curve was linear over the concentration range 0.1-13.2 microg mL(-1) with a correlation coefficient of 0.9987. The proposed method has been applied to the selective quantification of Cr(VI) in synthetic samples and waste-water samples with the satisfactory results.     

Practical synthesis of 3-aryl anthranils via an electrophilic aromatic substitution strategy

We report a practical route for the synthesis of valuable 3-aryl anthranils from readily available anthranils and simple arenes by using the classical electrophilic aromatic substitution (EAS) strategy. This transformation goes through an electrophilic substitution and rearomatisation sequence by employing Tf₂O as an effective activator. A wide range of arenes were compatible in this transformation, delivering various structurally diversified 3-aryl anthranils in good yields and high regioselectivity. In addition, a variety of readily available feedstocks such as olefins, alkenyl triflates, silyl enolethers, carbonyl compounds, thiophenols and thiols could also participate in the reaction to achieve the C3 alkenylation, alkylation and thioetherification of anthranils. Of note, the synthesized 3-aryl anthranils proved to be a highly robust platform to access a series of biologically active compounds, drug derivatives and organic optoelectronic materials.

A practical route for the synthesis of valuable 3-aryl anthranils from readily available anthranils and simple arenes has been achieved through an electrophilic substitution and rearomatization sequence by employing Tf₂O as an effective activator.     

Synthesis and application of highly sensitive fluorescent probe for Hg2+ regulated by sulfur

Rhodamine-based fluorescent probe is widely used in chemical analysis, environmental analysis and life sciences area due to their excellent optical properties. Based on the thiophilic property of Hg~(2+), using C = S structural motif as the core segment, our group have designed and synthesized three novel probes containing cinnamyl aldehyde with different substituents, exhibiting high selectivity and excellent sensitivity. The structure-property relationships of these probes have been investigated that the optical change caused by electron withdrawing effect and heavy atom effect. Furthermore, these Hg~(2+) probes could be applied in living mice imaging, which provide a promising tool for quantitative mercury(Ⅱ) ion imaging in living organism.     

Initial Decomposition Mechanism of 3-Nitro-1,2,4-triazol-5-one (NTO) under Shock Loading: ReaxFF Parameterization and Molecular Dynamic Study

We report a reactive molecular dynamic (ReaxFF-MD) study using the newly parameterized ReaxFF-lg reactive force field to explore the initial decomposition mechanism of 3-Nitro-1,2,4-triazol-5-one (NTO) under shock loading (shock velocity >6 km/s). The new ReaxFF-lg parameters were trained from massive quantum mechanics data and experimental values, especially including the bond dissociation curves, valence angle bending curves, dihedral angle torsion curves, and unimolecular decomposition paths of 3-Nitro-1,2,4-triazol-5-one (NTO), 1,3,5-Trinitro-1,3,5-triazine (RDX), and 1,1-Diamino-2,2-dinitroethylene (FOX-7). The simulation results were obtained by analyzing the ReaxFF dynamic trajectories, which predicted the most frequent chain reactions that occurred before NTO decomposition was the unimolecular NTO merged into clusters ((C₂H₂O₃N₄)_n). Then, the NTO dissociated from (C₂H₂O₃N₄)_n and started to decompose. In addition, the paths of NO₂ elimination and skeleton heterocycle cleavage were considered as the dominant initial decomposition mechanisms of NTO. A small amount of NTO dissociation was triggered by the intermolecular hydrogen transfer, instead of the intramolecular one. For α-NTO, the calculated equation of state was in excellent agreement with the experimental data. Moreover, the discontinuity slope of the shock-particle velocity equation was presented at a shock velocity of 4 km/s. However, the slope of the shock-particle velocity equation for β-NTO showed no discontinuity in the shock wave velocity range of 3–11 km/s. These studies showed that MD by using a suitable ReaxFF-lg parameter set, could provided detailed atomistic information to explain the shock-induced complex reaction mechanisms of energetic materials. With the ReaxFF-MD coupling MSST method and a cheap computational cost, one could also obtain the deformation behaviors and equation of states for energetic materials under conditions of extreme pressure.     

Analysis of thermal property in hollow-core polarization maintaining photonic crystal fibers

We study the thermal-induced variance of effective refractive indices (ERIs) and birefringence in several kinds of polarization maintaining fibers (PMF) and carry out numerical simulations by utilizing the finite element method (FEM). Responses under varying temperatures in these fibers are analyzed thoroughly. According to our computational results, hollow-core photonic crystal fibers (HC-PCFs) exhibit much more stable temperature-dependent ERIs and birefringence among these PMFs.     

可获得高衬比干涉条纹的实时全息记录方法

本文提出了一种可以获得高衬比的实时全息记录方法,它通过分析所记录的第一张实时全息图来获得拍摄最佳衬比实时全息图的拍摄参数,文中指出了拍摄最佳衬比实时全息图需要满足的条件,给出了理论分析和实验验证,实验结果与理论相符甚好,对于透明物体的实时法全息图.条纹衬比可接近最佳值1.     

太阳辐射与温室效应

人类活动引起大气中温室气体增加，导致大气中温室效应增强，这一点已引起世界各国的普遍关注。目前，世界各国都在积极采取有效措施，大力控制人为因素所导致的温室效应，不断改善日益恶劣的气候条件。文章简要阐述了温室效应产生的原因，对生态环境的影响，并提出了减缓温室效应的途径。