Efficient conjugation and preferential DNA binding of oligonucleotides containing 2′-O-(2-oxoethyl)arabinouridine

Oligodeoxyribonucleotides were synthesized that contain a novel nucleoside, 2′-O-(2-oxoethyl)arabinouridine. Whereas such oligonucleotides showed only a slight reduction in the T_M values of their complexes with complementary DNA, a significant destabilization was observed in the case of duplexes formed with RNA. This may be explained by the C_2′-endo conformation of 2′-O-(2,3-dihydroxypropyl)arabinouridine as demonstrated by NMR experiments in D₂O. The modified oligonucleotides were used to synthesize a number of conjugates with dyes, biotin and a N-modified laminin peptide, by hydrazone and oxime formation. We suggest that the 2′-arabinoaldehyde-containing DNA duplexes may be valuable tools for affinity modification of DNA-binding proteins.     

9,10-双-三甲基硅乙炔基蒽的合成及其光谱性质研究

<正>苯乙炔类化合物是一类π-共轭化合物,具有重要的理论研究价值,在分子导线、分子传感器、液晶显示中的偏振器、发光二极管和能量传输材料等光电领域有着广泛的应用[1-6]。目前对苯乙炔类聚合物和齐聚物的研究很多,而对苯乙炔类小分子研究得很少。我们采用对二溴蒽和三甲基     

2′,3′,4′,5′-Tetraacetyl-N(3)-carboxymethylriboflavin derivatives: synthesis and fluorescence studies

The hitherto not described 2′,3′,4′,5′-tetraacetyl-N(3)-carboxymethylriboflavin (1) could be prepared starting from 2′,3′,4′,5′-tetraacetylriboflavin by alkylation with tert-butyl α-bromoacetate and benzyl α-bromoacetate, followed by deprotection reaction. The results of fluorescence studies are described.     

Oligonucleotides containing 7-propynyl-7-deazaguanine: synthesis and base pair stability

Oligonucleotides incorporating the propynyl derivative of 7-deaza-2′-deoxyguanosine (1) were synthesized by solid-phase oligonucleotide synthesis. As building blocks the phosphoramidites 7a,b were prepared. The incorporation of 1 into oligonucleotides exerts a positive effect on the DNA duplex stability. The duplex stabilization by 1 was higher than that of 7-iodo-7-deaza-2′-deoxyguanosine (2b). The stabilizing effect of the 7-propynyl group introduced in the 7-deazapurines is similar to that reported for 8-aza-7-deazapurines. From CD spectra it was deduced that the B-DNA structure is not significantly altered by compound 1.     

Fluorescent 2-(2′-hydroxybenzofuran)benzoxazole (HBBO) borate complexes: synthesis,optical properties,and theoretical calculations

The multi-step synthesis, structural and optical properties of original luminescent borate complexes derived from 2-(2′-hydroxybenzofuran)benzoxazole (HBBO) are reported. Functionalization at position 3 of the benzofuran ring was readily achieved through an electrophilic cyclization key step followed by a Sonogashira cross-coupling reaction. The optical properties of the resulting boron difluoride dyes highlight different photophysical behaviors depending on the nature of the substitution at position 3 of the benzofuran core (^tBu-phenylacetylene or NⁿBu₂-phenylacetylene). The NⁿBu₂-phenylacetylene moiety favors a sizeable intramolecular charge transfer as evidenced by a strong solvatochromism; a feature further confirmed by ab initio calculations.     

Synthesis of reversible fluorescent organogel containing 2-(2′-hydroxyphenyl)benzoxazole: fluorescence enhancement upon gelation and detecting property for nerve gas simulant

A new low molecular mass organogelator 1 containing 2-(2′-hydroxyphenyl)benzoxazole (HPB) group with long alkyl chain was synthesized by the reaction with 5-amino-2-(2′-hydroxy-4′-methylphenyl)benzoxazole and dodecyl isocyanate in THF at room temperature. The reversible gelation ability of 1 was investigated using a heating-cooling method in various organic solvents. The stable organogel was formed from carbon tetrachloride or from cyclohexane at the concentration as low as 0.9%. The self-assembled supramolecular gel structure formed by non-covalent bonding was confirmed with field emission-scanning electron microscope (FE-SEM) exhibiting fibril- or ribbon-shaped structure depending on the solvent used. Regarding the aggregation-induced emission enhancement (AIEE) phenomenon, the optical properties were investigated in its solution and gelled state. The detecting properties of resulting organogel toward nerve gas simulant were monitored by UV-vis and fluorescence spectroscopy. Both color change from colorless to greenish yellow and disruption of gel structure resulting from alteration in intermolecular forces were observed upon the exposure to nerve gas simulant.     

9,10-二(苯亚甲基-硫亚甲基)蒽的合成及其对Cu2+的识别

荧光分子开关和分子识别是超分子化学的重要组成部分。蒽环作为一个优良的荧光基团被广泛应用于分子开关的设计及分子识别中。Resorci-narenes母体衍生物的合成研究中采用蒽环作为荧光基团已被报道多次[1-4],Luigi Fabbrizzi合成的多氨基蒽衍生物[5]对Zn2 具有良好的PET效应。蒽系荧光分子在分子逻辑门系统中日益受到了研究者的重视,de Silva等在研究中发现一蒽环化合物[6]在Mg2 作用存在OR逻辑行为。在后续研究中发现两类蒽环化合物在一定条件下分别存在AND[7]和NOR[8]逻辑行为。在分子识别的研究中,Shin-ichi Sasaki合成的含穴状…     

Utilization of an ionic liquid in situ preconcentration method for the determination of the 15 + 1 European Union polycyclic aromatic hydrocarbons in drinking water and fruit‐tea infusions

An ionic liquid (IL) in situ preconcentration method was optimized and applied to the monitoring of the 15 + 1 European Union polycyclic aromatic hydrocarbons in water and fruit‐tea infusions. The optimized method utilizes 10 mL of water (or infusion) containing 38 μL of the IL 1‐butyl‐3‐methylimidazolium chloride and a content of 36.1 g/L NaCl, which are mixed with Li‐NTf₂ (340 μL, 0.2 g/mL), followed by vortex (4 min) and centrifugation (5 min). The obtained microdroplet containing hydrocarbons is diluted with acetonitrile and injected into an HPLC with UV/Vis and fluorescence detection. The method presented average enrichment factors of 127 for water (tap water and bottled water) and 27 for two fruit‐tea infusions; with average relative recoveries of 86.7 and 106% for water and fruit‐tea infusions, respectively. The method was sensitive, with detection limits ranging from 0.001 to 0.050 ng/mL in water, and from 0.010 to 0.600 ng/mL in fruit‐tea infusions, for the fluorescent hydrocarbons. Real extraction efficiencies ranged from 12.7 to 58.7% for water, and from 20.2 to 117% for the infusions. The method was also fast (～12 min) and free of organic solvents in the extraction step.     

Synthesis and properties of 4′,5′-bis(methylthio)-4,5-bis(2-pyridylethynyl)tetrathiafulvalene and its copper complexes

Synthesis of redox-active bis-pyridine ligand, 4′,5′-bis(methylthio)-4,5-bis(2-pyridylethynyl)tetrathiafulvalene (1) has been carried out in moderate yield starting from the corresponding diiodide. Bis(pyridylethynyl)-TTF 1 forms 1:1 complexes with Cu(I) and Cu(II) salts. Occurrence of the charge transfer from the TTF moiety to the copper atom was found to depend on the environment of copper atom.     

Syntheses of 2′-C-amidoalkyl and 2′-C-cyanoalkyl containing oligodeoxyribonucleotides and assessment of their hybridisation affinity for complementary DNA and RNA

Oligodeoxynucleotides containing 2′-C-branched nucleosides with an amide or nitrile appended to either a one or two carbon alkyl chain have been synthesised. The phosphoramidites of the 2′-C-modified nucleosides were prepared and incorporated into the oligonucleotides using automated DNA synthesis. The duplex stability with complementary RNA and DNA was measured by UV melting experiments, in order to assess whether the amide/nitrile function could induce any duplex stability without the presence of the 2′-oxygen. The duplex stabilities of the oligonucleotides containing the 2′-C-modifications were decreased in the absence of the 2′-oxygen.     

Intense Dyes through Chromophore–Chromophore Interactions: Bi- and Trichromophoric Perylene-3,4:9,10-bis(dicarboximide)s

Simple perylene dyes , which are known for their high extinction coefficients, are converted into intense and highly fluorescent (at ca. 540 nm) dyes such as 1 by a directed chromophore–chromophore coupling. Molar extinction coefficients of more than 400 000 L mol⁻¹ cm⁻¹ are attained. R = CH(C₆H₁₃)₂, CH(C₇H₁₅)₂, CH(C₉H₁₉)₂.     

Synthesis of new fluorescent 2-(2′,2″-bithienyl)-1,3-benzothiazoles

Bithienyl-1,3-benzothiazole derivatives were synthesised by reacting various 5-formyl-5′-alkoxy- or 5-formyl-5′-N,N-dialkylamino-2,2′-bithiophenes with ortho-aminobenzenethiol in good to excellent yields. Evaluation of the fluorescence properties of these compounds was carried out. They show strong fluorescence in the 450-600 nm region, as well as high quantum yields and large Stokes’ shifts.     

Magnetic metal–organic framework MIL‐100(Fe) microspheres for the magnetic solid‐phase extraction of trace polycyclic aromatic hydrocarbons from water samples

In this work, a magnetic metal–organic framework designated as MIL‐100(Fe) was prepared and applied as a magnetic solid‐phase extraction sorbent for the determination of trace polycyclic aromatic hydrocarbons in environmental water samples by coupling with high‐performance liquid chromatography and fluorescence detection. The magnetic microspheres exhibited large surface areas and high extraction ability, making them excellent candidates as sorbents for enrichment of trace polycyclic aromatic hydrocarbons. Under the optimized experimental conditions, good sensitivity levels were achieved with low detection limits ranging from 32 to 2110 pg/mL and good linearities with correlation coefficients higher than 0.9990 for the investigated 13 polycyclic aromatic hydrocarbons. The proposed method has been validated in the analysis of real water samples with mean recoveries in the range of 81.4–126.9% at four spiked levels and the relative standard deviations in the range of 1.3–17.0%. The magnetic MIL‐100(Fe) microspheres were stable enough for 150 extractions without a significant loss of extraction performance.     

Reactions of (η6-Arene)tricarbonylchromium Complexes: Hydrogenation,Nitration, and Bromination

In this study, we explore the reactions of coordinated arenes, e.g., hydrogenation, nitration, and bromination, to prepare compounds which are not accessible from conventional organic synthesis. The reaction products formed from reactions with the coordinated and the uncoordinated arenes are compared. The polycyclic aromatic hydrocarbons (PAHs) employed for this study include phenanthrene, methyl- and acetyl-phenanthrene, and benz[a]anthracene (BA), The tricarbonylchromium group demonstrated various characteristics which influence the reactions in this work, such as an electronic effect to deactivate hydrogenation, a steric effect to exhibit, highly positional selective nitration, and a free radical mechanism to direct bromine to attack at the ring coordinated to tricarbonylchromium.     

Two‐Photon Absorption Properties of Dehydrobenzo[12]annulenes and Hexakis(phenylethynyl)benzenes: Effect of Edge‐Linkage

Two‐photon absorption (TPA) properties of two trefoil‐shaped compounds with different edge linkages—tris(hexadehydrotribenzo[12]annulene) and tris(tetradehydrotribenzo[12]annulene)—and three asterisk‐shaped compounds having no edge‐linkage—hexakis(phenylethynyl)benzenes—are investigated experimentally by the open‐aperture Z‐scan and TPA‐induced fluorescence methods with wavelength tuneable femtosecond pulses. The compound with ethynylene edge‐linkage exhibits the most intense TPA (the maximal TPA cross section is 1300±170 GM at 572 nm where 1 GM=10^?50 cm⁴ s molecule^?1 photon^?1). The TPA activity of the compounds is primarily explained in terms of the planarity of the molecules in relation with the type of edge‐linkage.     

Synthesis of conjugated 2 and 2,5-(ethenyl) and (ethynyl)phenylethynyl thiophenes: fluorescence properties

Nano conjugated thienylethenyl and thienylethynyl compounds with controlled structure and dimensions have been efficiently prepared, by heterocoupling reaction between 1,4-(thienylethynyl)phenylacetylene (or thienylethenyl)phenylacetylene and 2- or 2,5-dihalothiophene. Conjugated 1,4-di(2-thienylethynylphenyl)- (or 2-thienylethenylphenyl)-1,3-butadiyne were obtained by the homocoupling of the terminal acetylenes in excellent yield. The end-capped (N,N-dimethylaminophenyl)- and [3,5-di(trimethylsilylethynyl)-1-ethynyl]-2,5-di(phenylethynyl)_nthiophene were obtained by the heterocoupling between the corresponding terminal acetylene and 2,5-di(iodo)thiophene, catalyzed by the bis(triphenylphosphine)palladium and cuprous iodide system in excellent yield.     

Synthesis and self-assembly of oligomers containing cruciform 9,10-bis(arylethynyl)anthracene unit: formation of supramolecular nanostructures based on rod-length-dependent organization

Conjugated rod-coil molecules, incorporating flexible and rigid blocks, have a strong affinity to self-organize into various supramolecular nanostructures in the bulk state.In this study, we report synthesized oligomers containing cruciform 9,10-bis(arylethynyl)anthracene units and characterized their self-assembly behavior. The molecular structures were characterized with ¹H, ¹³C NMR, and matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) mass spectroscopy. An investigation of the supramolecular nanostructures of these molecules using differential scanning calorimetry, thermal polarized optical microscopy, and small-angle X-ray scattering revealed that the rod length of coil-rod-coil molecules with identical rod to coil volume ratios dramatically influences self-assembly behavior in the bulk state. Molecules 2 and 3 with relatively longer rod lengths self-assemble into lamellar structures in the solid state, whereas, molecules 1 and 4 self-assemble into two-dimensional (2-D) oblique columnar structures in the liquid crystalline phase, in addition, on heating, molecule 1 transforms from the oblique columnar phase to the nematic phase.     

Syntheses and properties of complexes with bis(2,2′-bipyridyl)ruthenium(II) moieties coordinated to 4,4′:2′,2′′:4′′,4′′′-quaterpyridinium ligands

Eleven new complexes of the form cis-[Ru^II(bpy)₂(L^A)]⁴⁺ (bpy = 2,2′-bipyridyl; L^A = a pyridinium-substituted bpy derivative) have been prepared and isolated as their PF₆⁻ salts. Characterisation involved various techniques including ¹H NMR spectroscopy and MALDI mass spectrometry. The UV-Vis spectra show intense intraligand π → π^∗ absorptions and metal-to-ligand charge-transfer (MLCT) bands with two distinct maxima in the visible region. Small shifts in the MLCT bands correlate with the electron-withdrawing strength of the ligand L^A. Cyclic voltammograms show quasi-reversible or reversible Ru^III/II oxidation waves, and two or more ligand-based reductions with varying degrees of reversibility. The variations in the redox potentials correlate with changes in the structure of L^A, and also with the MLCT energies. Differential pulse voltammetry allows the first reduction process for two of the complex salts to be resolved into two peaks. Single-crystal X-ray structures have been solved for three of the new complex salts and also for a pro-ligand salt. Two carboxylate-functionalised compounds have been tested as photosensitizers on TiO₂-coated electrodes, but show only negligible efficiencies, in accord with expectations.     

1-(Imidazol-1-yl)-indolizines—two-step synthesis and optical properties

A one-pot process leading to complex aromatic heterocyclic compounds has been designed. Kröhnke methodology has been used to synthesize indolizines bearing an aldimino-substituent at position 1. Further reaction of these compounds with 1,2-diketones and ammonium acetate led to tetra-substituted imidazoles in 5–28% overall yield. The resulting compounds display strong absorption of UV radiation and emission of a blue light accompanied with large Stokes shifts. Replacing the aryl substituents with thiophene at position 3 of the indolizine and position 2 of the imidazole produce a further red shift of the absorption (vs products with substituted benzene rings) as a result of a more planar conformation in the ground state.     

Cyclization versus oligomerization of SP- and RP-5′-OH-N-benzoyl-2′-deoxycytidine-3′-O-(2-thio-4,4-pentamethylene-1,3,2-oxathiaphospholane)s

The S_P-isomer of 5′-OH-N⁴-benzoyl-2′-deoxycytidine-3′-O-(2-thio-4,4-pentamethylene-1,3,2-oxathiaphospholane) undergoes DBU-promoted intramolecular cyclization providing as a sole product S_P-deoxycytidine cyclic 3′,5′-O,O-phosphorothioate. Unexpectedly, the R_P-counterpart yields a mixture of products consisting of R_P-deoxycytidine cyclic 3′,5′-O,O-phosphorothioate and macrocyclic oligo(deoxycytidine phosphorothioate)s. The results of molecular modeling indicate that the dychotomy observed for the R_P substrate may result from remarkably higher energy of the corresponding transition states, caused by the presence of bulky ‘spiro’ pentamethylene substituent at the position C4 in the oxathiaphospholane ring.