Total nucleotide analysis of Hydra DNA and RNA by MEKC with LIF detection and 32P‐postlabeling

The model organism Hydra has been used for molecular studies for more than 20 years, however, its DNA base composition has not been determined yet. We have analyzed DNA and total RNA of the freshwater polyp Hydra magnipapillata with two independent procedures of high accuracy and sensitivity – fluorescence labeling of nucleotides followed by CE‐LIF detection and ³²P‐postlabeling. DNA of Hydra was digested either to deoxyribonucleoside‐5′‐monophosphates or deoxyribonucleoside‐3′‐monophosphates selectively conjugated with the fluorescent dye 4,4‐difluoro‐5,7‐dimethyl‐4‐bora‐3a,4a‐diaza‐s‐indacene‐3‐propionyl ethylene diamine hydrochloride (BODIPY FL EDA) separated and detected using CE‐LIF. Both versions of the assay revealed a high A+T composition of 78 and 71%, whereas total DNA methylation (5‐methyldeoxycytidine) was 2.6 and 3.1%. Total Hydra RNA showed highest base levels for guanine (33%) and a level of 1.4% for pseudouracil. All values were in good agreement with those determined by the ³²P‐postlabeling method.     

Synthesis and Structures of N‐Alkyl‐1,13‐dimethoxychromeno‐ [2,3,4‐kl]acridinium Salts: The Missing Azaoxa[4]helicenium

Helical structures are interesting due to their inherent chirality. Helicenium ions are triarylmethylium structures twisted into configurationally stable helicenes through the introduction of two heteroatom bridges between the three aryl substituents. Of the configurationally stable [4]helicenium ions, derivatives with sulfur, oxygen and nitrogen bridges have already been synthesised. However, one [4]helicenium ion has proven elusive, until now. We present herein the first synthesis of the 1,13‐dimethoxychromeno[2,3,4‐kl]acridinium (DMCA⁺) [4]helicenium ion. A series of six differently N‐substituted DMCA⁺ ions as their hexafluorophosphate salts are reported. Their cation stability was evaluated and it was found that DMCA⁺ is ideally suited as a phase‐transfer catalyst with a pK_R+ of 13.0. The selectivity of nucleophilic addition to the central carbon atom of DMCA⁺ has been demonstrated with diastereotopic ratios of up to 1:10. The single‐crystal structures of several of the DMCA⁺ salts were determined, and structural differences between N‐aryl‐ and N‐alkyl‐substituted cations were observed. The results of a comparative study of the photophysics of the [4]helicenium ions are presented. DMCA⁺ is found to be a potent red‐emitting dye with a fluorescence quantum yield of 20 % in apolar solvents and a fluorescence lifetime of 12 ns. [4]Helicenium ions, including DMCA⁺, all suffer from solvent‐induced quenching, which reduces the fluorescence quantum yields significantly (?_fl<5 %) in polar solvents. A difference in photophysical properties is observed between N‐aryl‐ and N‐alkyl‐substituted DMCA⁺, which has tentatively been attributed to a difference in molecular conformation.     

Asymmetric Ring Opening/Cyclization/Retro‐Mannich Reaction of Cyclopropyl Ketones with Aryl 1,2‐Diamines for the Synthesis of Benzimidazole Derivatives

A highly efficient asymmetric ring‐opening/cyclization/retro‐Mannich reaction of cyclopropyl ketones with aryl 1,2‐diamines has been realized using a chiral N,N′‐dioxide/Sc^III catalyst. Benzimidazoles containing chiral side chains were generated under mild reaction conditions in excellent outcomes (up to 99 % yield and 97 % ee). This method also provides efficient access to chiral benzimidazole‐substituted amide and cycloheptene derivatives.     

Highly Stereoselective [3+2] Cycloadditions of Chiral Palladium‐Containing N1‐1,3‐Dipoles: A Divergent Approach to Enantioenriched Spirooxindoles

A catalytic asymmetric [3+2] cycloaddition reaction of chiral palladium‐containing N¹‐1,3‐dipoles with methyleneindolinones has been successfully developed. The reaction allows an efficient construction of 3,3′‐pyrrolinyl spirooxindoles with high yields and excellent stereoselectivities (up to 93 % yield, 19:1 d.r. and >99 % ee). A synthetic application of this methodology is demonstrated and a stereocontrol mechanism is proposed.     

Asymmetric Hetero‐Diels–Alder Reaction of Danishefsky’s Diene with α‐Ketoesters and Isatins Catalyzed by a Chiral N,N′‐Dioxide/Magnesium(II) Complex

A highly enantioselective hetero‐Diels–Alder reaction of Danishefsky’s diene with α‐ketoesters and isatins has been realized by using a chiral N,N′‐dioxide/Mg^II complex. In the presence of only 0.1–0.5 mol % catalyst, a series of substrates were transformed into the corresponding tetrasubstituted 2,3‐dihydropyran‐4‐ones in up to 99 % yield and more than 99 % ee in two hours.     

Determination of Copper and Zinc Ions by Flame-AAS After Preconcentraction Using Sodium Dodecyl Sulfate Coated Alumina Modified with 3-((1H-Indol-3-yl)-3,4,5-trimethyl)-1H-indole

A sensitive and simple method for the simultaneous preconcentration of trace amount Cu²⁺ and Zn²⁺ ions in some real samples has been established, which is based on the sorption of Cu²⁺ and Zn²⁺ on 3‐((1H‐indol‐3‐yl)‐3,4,5‐trimethyl)‐1H‐indole (ITMI) loaded on sodium dodecyl sulfate (SDS) coated alumina. The metal absorbed on the complexes was eluted using 3 mol/L nitric acid. The influences of the analytical parameters including pH and sample volume were investigated. The effects of matrix ions on the retentions of the analytes were also examined. The recoveries of analytes were generally higher than 95% with a low RSD. The method has been successfully applied to content evaluation of these metals in real samples.     

Synthesis of Doubly Ethyl‐Bridged Bis(p‐sulfonatocalix[4]arene) and Its Supramolecular Polymerization with Viologen Dimer

A water‐soluble supramolecular polymer with a high degree of polymerization and viscosity has been constructed based on the strong host–guest interaction between p‐sulfonatocalix[4]arenes (SC4As) and viologen. A homoditopic doubly ethyl‐bridged bis(p‐sulfonatocalix[4]arene) (d‐SC4A) was prepared and its binding behavior towards methyl viologen compared with the singly ethyl‐bridged bis(p‐sulfonatocalix[4]arene) (s‐SC4A) by NMR spectroscopy and isothermal titration calorimetry. By employing a viologen dimer (bisMV⁴⁺) as the homoditopic guest, two linear AA/BB‐type supramolecular polymers, d‐SC4A?bisMV⁴⁺ and s‐SC4A?bisMV⁴⁺, were successfully constructed. Compared with s‐SC4A?bisMV⁴⁺, d‐SC4A?bisMV⁴⁺ shows much higher solubility and viscosity, and has also been characterized by viscosity, diffusion‐ordered NMR spectroscopy, dynamic light scattering, and atomic force microscopy measurements. Furthermore, the polymer is responsive to electrostimulus as viologen is electroactive, which was studied by cyclic voltammetry. This study represents a proof‐of‐principle as the polymer can potentially be applied as a self‐healing and degradable polymeric material.     

Electrosynthesis and electrochromic properties of free‐standing copolymer based on oligo(oxyethylene) cross‐linked 2,2’‐bithiophene and 3,4‐ethylenedioxythiophene

Oligo(oxyethylene) chains cross‐linked 2,2’‐bithiophene (BT‐E5‐BT) has been synthesized successfully. A free‐standing copolymer film based on BT‐E5‐BT and 3,4‐ethylenedioxythiophene (P(BT‐E5‐BT‐co‐EDOT)) has been synthesized by electrochemical polymerization. The electrical conductivity of P(BT‐E5‐BT‐co‐EDOT) copolymer (16 S m^?1) has improved by four orders of magnitude compared to the homopolymer of BT‐E5‐BT (P(BT‐E5‐BT), 5 × 10^?3 S m^?1) at room temperature. Both homopolymer and copolymer films exhibit well‐defined redox and satisfied coloration efficiency. Spectroelectrochemistry studies indicate that the P(BT‐E5‐BT‐co‐EDOT) has a lower band gap in the range of 1.83–1.90 eV and shows more plentiful electrochromic colours (green, blue, purple and salmon pink) compared with the homopolymer P(BT‐E5‐BT). The Copolymer P(BT‐E5‐BT‐co‐EDOT) shows the moderate optical contrast (26% of 480 nm) and coloration efficiency (205.41 cm^?1 C^?2). The copolymer method provides a novel way to fabricate a free‐standing organic electrochromic device. © 2015 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016 , 54, 1583–1592     

Copper(I)-anilide complex [Na(phen)3][Cu(NPh2)2]: an intermediate in the copper-catalyzed N-arylation of N-phenylaniline

Complex [Na(phen)₃][Cu(NPh₂)₂] ( 2 ), containing a linear bis(N‐phenylanilide)copper(I) anion and a distorted octahedral tris(1,10‐phenanthroline)sodium counter cation, has been isolated from the catalytic C? N cross‐coupling reaction with the CuI/phen/tBuONa (phen=1,10‐phenanthroline) catalytic system. Complex 2 can react with 4‐iodotoluene to produce 4‐methyl‐N,N‐diphenylaniline ( 3 a ) with 70.6 % yield. In addition, 2 can work as an effective catalyst for C? N coupling under the same reaction conditions, thus indicating that 2 is the intermediate of the catalytic system. Both [Cu(NPh₂)₂]^? and [Cu(NPh₂)I]^? have been observed by in situ electron ionization mass spectrometry (ESI‐MS) under catalytic reaction conditions, thus confirming that they are intermediates in the reaction. A catalytic cycle has been proposed based on these observations. The molecular structure of 2 has been determined by single‐crystal X‐ray diffraction analysis.     

Effect of pH on the Metabolism of Aconitine under Rat Intestinal Bacteria and Analysis of Metabolites Using HPLC/MS-MSn Technique

A semi‐quantitative method of mass spectrometry (MS) has been described for the analysis of metabolites of aconitine by rat intestinal bacteria at different pH. At pH 7.0, the rat intestinal bacteria exhibit optimal activity for the metabolism of aconitine. A high‐performance liquid chromatography‐electrospray ionization multiple‐stage mass spectrometry (HPLC/ESI‐MSⁿ) method has been applied to investigate the characteristic product ions of metabolites. Then, the logical fragmentation pathways of metabolites have been proposed. By comparing the retention time (t_R) of HPLC and the ESI‐MSⁿ data with the data of standard compounds and reports from literature, ten metabolites have been identified and a distinctive metabolite (15‐deoxyaconitine) has been deduced first time. The experimental results demonstrate that HPLC/ESI‐MSⁿ is a specific and useful method for the identification of metabolites of aconitine. Also, in the present paper, the HPLC‐MS method was introduced to determine the synthetical metabolite prior to the study of the toxicity by the method of Bliss.     

Solid Phase Extraction of Thallium(III) on Micro Crystalline Naphthalene Modified with N,N’-Bis(3-methylsalicylidene)- ortho-phenylenediamine and Determination by Spectrophotometry

A novel, simple, sensitive and effective method has been developed for preconcentration of thallium on N,N’-bis(3-methylsalicylidene)-ortho-phenylenediamine (MSOPD) adsorbent in a pH range 5.0—10.0, prior to its spectrophotometric determination, based on the oxidation of bromopyrogallol red at λ＝520 nm. This method makes it possible to quantitize thallium in a range of 3.6×10－9 to 2.0×10－5 mol/L, with a detection limit (S/N＝3) of 1.42×10－9 mol/L. This procedure has been successfully applied to determine the ultra trace levels of thallium in the environmental samples, free from the interference of some diverse ions. The precision, expressed as relative standard deviation of three measurements, is better than 2.9%.     

Stripping Analysis of As(III) by Means of Screen‐Printed Electrodes Modified with Gold Nanoparticles and Carbon Black Nanocomposite

A novel sensor based on carbon black‐gold nanoparticle nanocomposite modified screen‐printed electrode (CB‐AuNPs/SPE) for the detection of As(III) has been developed. The sensor was prepared modifying the SPE with CB and AuNPs by a drop casting automatable deposition. The As(III) was detected by CB‐AuNPs/SPE using anodic stripping voltammetry, with a high sensitivity (673±6 µA µM^?1 cm^?2) and reaching a LOD of 0.4 ppb. Finally, CB‐AuNPs/SPE has been applied to As(III) trace analysis in drinking water, obtaining satisfactory recovery values (99±9 %).     

An Agostic Iridium Pincer Complex as a Highly Efficient and Selective Catalyst for Monoisomerization of 1‐Alkenes to trans‐2‐Alkenes

A unique Ir complex (^tBuNC^CP)Ir with the pyridine–phosphine pincer as the sole ligand, featuring a dual agostic interaction between the Ir and two σ C−H bonds from a t Bu substituent, has been prepared. This complex exhibits exceptionally high activity and excellent regio‐ and stereoselectivity for monoisomerization of 1‐alkenes to trans ‐2‐alkenes with wide functional‐group tolerance. Reactions can be performed in neat reactant on a more than 100 gram scale using 0.005 mol % catalyst loadings with turnover numbers up to 19000.     

Efficient Preparation of Alkaloids Polycarpine and Polycarpaurines A and C

An efficient method for the preparation of alkaloids polycarpine and polycarpaurines A and C via microwave‐assisted three‐step one‐pot reaction as the key step has been developed. This is the first report about the synthesis of polycarpaurines A and C. Starting from commercially available p‐methoxybenzaldehyde, polycarpine and polycarpaurine A were obtained over seven steps with 40 and 24 % overall yield, respectively. Polycarpine could convert to polycarpaurine C in 72% yield in the presence of NaHSO₃. The structure of polycarpine and polycarpaurines A and C was confirmed by ¹H NMR, ¹³C NMR, and HRMS.     

Full four‐component relativistic calculations of the one‐bond 77Se–13C spin‐spin coupling constants in the series of selenium heterocycles and their parent open‐chain selenides

Four‐component relativistic calculations of ⁷⁷Se–¹³C spin–spin coupling constants have been performed in the series of selenium heterocycles and their parent open‐chain selenides. It has been found that relativistic effects play an essential role in the selenium–carbon coupling mechanism and could result in a contribution of as much as 15–25% of the total values of the one‐bond selenium–carbon spin‐spin coupling constants. In the overall contribution of the relativistic effects to the total values of ¹J(Se,C), the scalar relativistic corrections (negative in sign) by far dominate over the spin‐orbit ones (positive in sign), the latter being of less than 5%, as compared to the former (ca 20%). A combination of nonrelativistic second‐order polarization propagator approach (CC2) with the four‐component relativistic density functional theory scheme is recommended as a versatile tool for the calculation of ¹J(Se,C). Solvent effects in the values of ¹J(Se,C) calculated within the polarizable continuum model for the solvents with different dielectric constants (ε 2.2–78.4) are next to negligible decreasing negative ¹J(Se,C) in absolute value by only about 1 Hz. The use of the locally dense basis set approach applied herewith for the calculation of ⁷⁷Se–¹³C spin‐spin coupling constants is fully justified resulting in a dramatic decrease in computational cost with only 0.1–0.2‐Hz loss of accuracy. Copyright © 2014 John Wiley & Sons, Ltd.     

Synthesis and characterization of a novel electroluminescent polymer based on a phenoxazine derivative

We report the preparation of a new electroluminescent polymer by the oxidative coupling copolymerization of N‐(4‐n‐butylphenyl)phenoxazine and 9,9‐di‐n‐butylfluorene with ferric(III) chloride. The reaction yields soluble polymers with a weight‐average molecular weight as high as 9000. The reactivity has been studied with respect to the reaction time, temperature, and feed ratio of the comonomers. Under optimum conditions, a copolymer with a 50% comonomer incorporation ratio can be obtained in a 75% yield. The polymers have been characterized with differential scanning calorimetry, cyclic voltammetry, and optical spectroscopy. A simple single‐layer light‐emitting‐diode device of an indium tin oxide/polymer/Mg–Ag structure shows a luminance of 200 cd/m² at an 18‐V operating voltage. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 4338–4345, 2006     

Synthesis of Davankov‐type hypercrosslinked resins using different isomer compositions of vinylbenzyl chloride monomer,and application in the solid‐phase extraction of polar compounds

Two different gel‐type resins have been prepared by suspension polymerization using 2 wt % divinylbenzene (DVB) with either p‐vinylbenzyl chloride (pVBC) or a mixture of VBC isomers (～ 70% m‐; ～ 30% p‐). Significant difference in the chlorine content was observed, which was attributed to a more favored hydrolysis process when p‐VBC was used. The presence of hydroxyl groups has been confirmed by elemental microanalytical data and solid‐state ¹³C cross‐polarization/magic angle spinning (CP‐MAS) nuclear magnetic resonance (NMR) spectra. Hypercrosslinked resins were prepared from both gel‐type precursors by treatment with FeCl₃ in 1,2‐dichloroethane (DCE) at 80 °C. The resultant resins showed differences in specific surface area and degree of hydrophilicity. The performance of the hypercrosslinked resins was evaluated in solid‐phase extraction (SPE) of polar compounds, and better results were obtained for the hypercrosslinked resin prepared from p‐VBC that combines a relatively high specific surface area (908 m² g^?1) and somewhat higher oxygen content (3.96 wt % O). © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1718–1728, 2005     

A New Benzotriazole‐Mediated Stereoflexible Gateway to Hetero‐2,5‐diketopiperazines

Open chain Cbz‐L ‐aa¹‐L ‐Pro‐Bt (Bt=benzotriazole) sequences were converted into either the corresponding trans‐ or cis‐fused 2,5‐diketopiperazines (DKPs) depending on the reaction conditions. Thermodynamic tandem cyclization/epimerization afforded selectively the corresponding trans‐DKPs (69–75 %). Complementarily, tandem deprotection/cyclization led to the cis‐DKPs (65–72 %). A representative set of proline‐containing cis‐ and trans‐DKPs has been prepared. A mechanistic investigation, based on chiral HPLC, kinetics, and computational studies enabled a rationalization of the results.     

Kinetics and mechanism of oxidation of the drug mephenesin by bis(hydrogenperiodato)argentate(III) complex anion

Mephenesin is being used as a central‐acting skeletal muscle relaxant. Oxidation of mephenesin by bis(hydrogenperiodato)argentate(III) complex anion, [Ag(HIO₆)₂]^5?, has been studied in aqueous alkaline medium. The major oxidation product of mephenesin has been identified as 3‐(2‐methylphenoxy)‐2‐ketone‐1‐propanol by mass spectrometry. An overall second‐order kinetics has been observed with first order in [Ag(III)] and [mephenesin]. The effects of [OH^?] and periodate concentration on the observed second‐order rate constants k′ have been analyzed, and accordingly an empirical expression has been deduced: k′ = (k_a + k_b[OH^?])K₁/{f([OH^?])[IO^?₄]_tot + K₁}, where [IO^?₄]_tot denotes the total concentration of periodate, k_a = (1.35 ± 0.14) × 10^?2M^?1s^?1 and k_b = 1.06 ± 0.01 M^?2s^?1 at 25.0°C, and ionic strength 0.30 M. Activation parameters associated with k_a and k_b have been calculated. A mechanism has been proposed to involve two pre‐equilibria, leading to formation of a periodato‐Ag(III)‐mephenesin complex. In the subsequent rate‐determining steps, this complex undergoes inner‐sphere electron transfer from the coordinated drug to the metal center by two paths: one path is independent of OH^? whereas the other is facilitated by a hydroxide ion. In the appendix, detailed discussion on the structure of the Ag(III) complex, reactive species, as well as pre‐equilibrium regarding the oxidant is provided. © 2007 Wiley Periodicals, Inc. Int J Chem Kinet 39: 440–446, 2007     

Triazine‐Cored Lanthanide‐Based Metal–Organic Frameworks Featuring Unique Water Chains and Strong Characteristic Emissions

A new triazine‐cored tricarboxylic acid, N,N′,N“‐1,3,5‐triazine‐2,4,6‐triyltris(cis‐4‐aminocyclohexane‐carboxylic acid) (H₃L), has been prepared by replacing the chlorine atoms of cyanuric chloride with cis‐4‐aminocyclohexane‐carboxylic acid, which has been used for the construction of a series of triazine‐cored lanthanide‐based metal–organic frameworks (MOFs). All these MOFs were structurally authenticated, revealing that they are isostructural and exist as two‐dimensional (2D) coordination networks with the general formula [Ln(L)(H₂O)₂]?5.5 H₂O (Ln= 1?Gd , 2?Tb , 3?Eu ). A unique one‐dimensional water chain, composed of primary tetrameric cyclic rings and dodecameric cyclic rings, has been found entrapped in the lattice. Moreover, all these compounds display bright characteristic photoluminescence. Particularly, for 1 , apart from the strong blue emission peak (Φ_f=20.6 %) corresponding to the intraligand transition under near‐UV excitation, the characteristic emissions of Gd³⁺ cation (Φ_f=5.0 %) were unexpectedly observed upon excitation at 273 nm.