Reagent peak-free liquid chromatography–fluorescence analysis of carboxylic acids using a fluorous scavenging–derivatization method

We developed a fluorous scavenging–derivatization method for reagent peak-free liquid chromatography (LC)–fluorescence analysis of carboxylic acids. In this method, carboxylic acids were fluorescently derivatized with 1-pyrenemethylamine in the presence of 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide and 1-hydroxy-1H-benzotriazole. Residual excess unreacted reagent was tagged with 2-(perfluorooctyl)ethyl isocyanate and could be selectively removed by microfluorous solid-phase extraction before LC analysis. With use of this method, eight fluorescent derivatives of linear aliphatic carboxylic acids (C₁–C₈) can be separated within 30 min by reversed-phase LC with gradient elution. In the chromatogram obtained, the fluorous-tagged unreacted reagent peak is greatly decreased after microfluorous solid-phase extraction and does not interfere with the quantification of each acid. With use of microfluorous solid-phase extraction with 80% (v/v) aqueous methanol elution, over 99.9% of the unreacted fluorescent reagent was removed. The detection limits (signal-to-noise ratio of 3) for the carboxylic acids examined are 2.3–8.0 fmol per 10-μL injection. We also applied this method successfully to the analysis of highly polar carboxylic acids such as α-keto acids and tricarboxylic acid cycle metabolites.     

Concentration dependences of the physicochemical properties of a water–acetone system

Concentration dependences of the UV spectrum, refractive index, specific electrical conductivity, boiling point, pH, surface tension, and heats of dissolution of a water–acetone system on the amount of acetone in the water are studied. It is found that the reversible protolytic interaction of the components occurs in all such solutions, resulting in the formation of hydroxyl and acetonium ions. It is shown that shifts of the equilibrium between the molecules and ions in the solution leads to extreme changes in their electrical properties. It is concluded that the formation of acetone solutions of water is accompanied by heat absorption, while the formation of aqueous solutions of acetone is accompanied by heat release.     

Synthesis of Multifluoromethylated γ-Sultines by a Photoinduced Radical Addition–Polar Cyclization

Despite the significance of sultines in synthesis, medicine, and materials science, the chemistry of sultines has remained unexplored due to their inaccessibility. Herein, we demonstrate the development of a photoredox-catalyzed multifluoromethyl radical addition/SO₂ incorporation/polar cyclization cascade approach to multifluoromethylated γ-sultines. The reactions proceed by single electron transfer induced multifluoromethyl radical addition to an alkene followed by SO₂ incorporation, and single-electron reduction for polar 5-exo-tet cyclization. Key to the success of the protocol is the use of easily oxidizable multifluoroalkanesulfinates as bifunctional reagents. The reactions proceed with excellent functional-group tolerance to deliver γ-sultines in moderate to excellent yields.     

Effect of a novel charring agent on thermal degradation and flame retardancy of acrylonitrile–butadiene–styrene

A novel charring agent poly(p-propane terephthalamide) (PPTA) was synthesized by using terephthaloyl chloride and 1,3-propanediamine through solution polycondensation and it was used together with ammonium polyphosphate (APP) to prepare a novel intumescent flame retardant (IFR) for ABS. The thermal degradation behaviour and flame retardancy were investigated, the results showed that PPTA could be effective as a charring agent, the flame retardancy of ABS and the mass of residues improved greatly with the addition of IFR. When the content of APP was 22.5 mass% and PPTA was 7.5 mass%, the limiting oxygen index (LOI) value of IFR-ABS system was found to be 32.4, and class V-0 of UL-94 test was passed. Moreover, the synergistic effects of two different adjuvants AlPi and MnO₂ in IFR-ABS system have been studied.     

Free Radical–Mediated Chemoselective Reduction of Enones

A novel methodology has been devised for the chemoselective reduction of enones involving the use of ⁿ Bu₃SnH and azobisisobutyronitrile. The 1,4-reduction of variously substituted α,β-unsaturated cyclic and acyclic enones has been successfully carried out under free radical reaction conditions. The reaction has been determined to proceed via single-electron transfer.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications^® for the following free supplemental resource(s): Full experimental and spectral details.]     

Development of radiogallium–ethylenecysteamine cysteine complex as a possible renal imaging agent

[⁶⁷Ga]-ethylenecysteamine cysteine ([⁶⁷Ga]ECC) was prepared using freshly prepared [⁶⁷Ga]GaCl₃ and ethylenecysteamine cysteine (ECC) for 30 min at 90 °C (radiochemical purity ≈97 ± 0.88% ITLC, specific activity: 210 ± 5 GBq/mM). Stability of the complex was checked in human serum for 24 h at 37 °C. Partition co-efficient of the tracer in octanol:saline mixture was determined (log P; 0.8). The biodistribution of the radiolabeled compound in vital organs of wild-type rats were compared with that of free Ga³⁺ cation up to 48 h. Initial biodistribution results showed significant kidney excretion of the tracer comparable to that of homologous ^99mTc compound.     

Preparation and properties of waterborne polyurethane–urea anionomers—influences of the type of neutralizing agent and chain extender

Waterborne polyurethane–urea anionomers were prepared by polyaddition reaction using isophorone diisocyanate (IPDI), poly(tetramethylene ether) glycol (PTMG, Mn=1000), dimethylolbutanoic acid (DMBA), and hydrazine monohydrate (HD), ethylene diamine (EDA), 1,4-butane diamine (BDA) as a chain extender, followed by neutralization of pendant COOH groups by NH₄OH/Cu(OH)₂ or triethylamine (TEA) as a neutralizing agent. The effects of the types of neutralizing agent such as NH₄OH/Cu(OH)₂ and TEA with various chain extenders on the properties of waterborne polyurethane–urea ionomers were investigated. Two loss modulus peaks for all samples are observed owing to the glass transition temperature of soft segments (Tg_s) and the glass transition temperature of hard segments (Tg_h). The conductivity, Tg_h, Tg, and tensile strength/modulus of TEA-based samples increased in the order of BDA>EDA>HD; however, those of NH₄OH/Cu(OH)₂-based samples increased in the order of HD>EDA>BDA. TEA-based film samples were found to have higher thermal stability, Tg_h, Tg, tensile strength/modulus, and storage modulus than NH₄OH/Cu(OH)₂-based ones at the same chain extender. On the other hand NH₄OH/Cu(OH)₂-based samples had higher conductivity and stronger antibacterial halo than TEA-based samples.     

Synthesis and properties of a functionalized heterobimetallic Re(I)–Gd(III) complex as a potential dual-contrast agent for molecular imaging

In the design of dual-imaging probes, the first functionalized and neutral heterobimetallic Re(I)–Gd(III) complex, highly soluble in aqueous solutions, has been prepared. This system exhibits interesting photophysical properties (λ_em = 578 nm, ? = 1.4%) for optical imaging and substantial higher relaxivity (r₁ = 6.6 mM⁻¹ s⁻¹ at 0.47 T and 37 °C) than the clinically used MRI contrast agents. Moreover, this system incorporates an aromatic ester functionality suitable for bioconjugation.     

Radical cyclization–fragmentation of ω-haloalkyl cyclobutanones: a modular approach to medium-sized carbocycles

A facile radical cyclization–fragmentation sequence of ω-haloalkyl-tethered spirocyclobutanones, which are readily available by the Kulinkovich cyclopropanation of cycloalkene carboxylates and subsequent electrophilic addition to haloalkyl acetals, provides a convenient method for appending seven- and eight-membered rings onto cycloalkene carboxylates. An enantioselective preparation of a medium-sized carbocycle is possible by the use of a non-racemic, C₂-symmetric acetal.     

Synthesis and preclinical pharmacological evaluation of a novel 99mTc–shikonin as a potential tumor imaging agent

Shikonin was isolated from Ratanjot pigment then the obtained shikonin was well characterized. This study is aimed to optimize radiolabeling yield of shikonin with ^99mTc with respect to factors that affect the reaction conditions such as shikonin amount, SnCl₂·2H₂O amount, reaction time and pH of the reaction mixture. In vitro stability of the radiolabeled complex was checked and it was found to be stable for up to 6?h. Biodistribution studies showed that, ^99mTc?Cshikonin accumulate in tumor sites with higher T/NT than other currently available ^99mTc(CO)₃-VIP, ^99mTc?Cnitroimidazole analogues and ^99mTc?Cpolyamine analogues indicating that shikonin deliver ^99mTc to the tumor sites with a percentage sufficient for imaging and can overcome many drawbacks of other radiopharmaceuticals used for tumor imaging.     

The effect of pomegranate seed powder addition on radical scavenging activity determined by TLC–DPPH test and selected properties of gluten-free pasta

The aim of the present work was to study the effect of pomegranate seeds powder (PSP) supplementation to gluten-free (GF) sheeted pasta on cooking properties, sensory characteristics and antioxidants properties using TLC-DPPH test. Five levels of pomegranate seed powder were used (2.5, 5.0, 7.5, 10.0 and 12.5%) on formula replacement basis. Antioxidant potential of GF pasta increased with the addition of pomegranate seeds powder. The GF pasta without additives and with 2.5% concentration of PSP did not reveal ability to scavenge free radicals. The highest aforementioned activity was observed for crude pomegranate seed extract followed by GF pasta with 12.5, 10.0, 7.5 and 5.0% addition of PSP. The total dietary fibers content of pasta increased from 5.68 to 14.80?g/100?g with the increase in the incorporation of PSP from 0 to 12.5%. The results revealed that cooking loss of gluten-free pasta increased from 9.09 to 10.18%, whereas pasta firmness decreased from 381.43 to 366.30?N, upon incorporation of PSP. Pomegranate seeds powder decreased the lightness of the pasta from 82.26 to 57.27. Sensory analysis suggested that control pasta (without PSP) and pasta supplemented with low levels of PSP have the most acceptable quality. In conclusion, incorporating PSP at low levels enhanced the nutritional quality of pasta without a significant adverse effect on its cooking, textural and sensory properties.     

Investigation of the transformations of a novel anti-cancer agent combining HPLC, HPLC–MS and direct ESI–HRMS analyses

One of the main problems of anti-cancer therapy is an insufficient differentiation between normal and malignant cells by the known anti-proliferant agents. The antibody-directed enzyme prodrug therapy is a promising approach for a selective treatment of cancer, in which a non-toxic prodrug is enzymatically converted into a highly cytotoxic drug at the surface of malignant cells by a targeted antibody–enzyme conjugate. The transformations and the stability of a very promising novel prodrug and its corresponding cytotoxic derivative were now investigated in detail by high-performance liquid chromatography (HPLC)–mass spectrometry (MS). In order to determine the time-dependent DNA alkylation efficiency and the sequence selectivity of the novel compounds, DNA binding studies using direct electrospray–Fourier transform ion cyclotron resonance–MS (ESI–FTICR–MS) have been performed. These measurements were accompanied by HPLC analyses followed by MS of the separated species to confirm the results of the direct ESI–FTICR–MS measurements. The sites of DNA alkylation could be identified unambiguously by the mass spectrometric fragmentation pattern of the alkylated oligodeoxynucleotides as well as by the results of HPLC followed by MS. A combination of all techniques applied led to a better understanding of the mode of action of the new therapeutics and might be used for an estimation of the cytotoxicity of different prodrugs and drugs since the alkylation efficiency correlates with the bioactivity of the compounds in cell culture investigations. After enzymatic cleavage of the sugar moiety, the untoxic prodrug is converted rapidly into the corresponding highly cytotoxic drug that alkylates DNA with high efficiency Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.

Sulfonimidamide as a directing agent for Pd-catalyzed regioselective oxidative C–H acyloxylation of arenes

In this report, we describe the utilization of sulfonimidamide (SIA) as a novel directing group for a Pd-catalyzed regioselective oxidative C–H acyloxylation of aryl group of N-aroyl part of SIA in moderate to good yields in the presence of (Diacetoxyiodo)benzene (PhI(OAc)₂) as an oxidizing agent and alkanoic acid as solvent. The solvent alkanoic acid is found to be the source of acyloxylation.     

The photocatalytic properties of Ti–Mo oxides prepared by a simple sol–gel route

Powders containing mixtures of titania and molybdite in different ratios were prepared by sol–gel processing. The sols were dried and subsequently calcined at 300, 500 and 700 °C. Depending on the ratio of Ti and Mo in the initial sol and the calcination temperature, Ti-doped MoO₃, TiO₂/MoO₃ or Mo-doped TiO₂ have been formed. The as prepared samples were characterised by scanning electron microscopy with attached X-ray dispersive energy analysis, X-ray diffractometry, Raman spectroscopy, gas adsorption and optical characterisation by ultraviolet/visible spectroscopy. The latter was used for the analysis of the photocatalytic properties on the decolourisation of methylene blue solutions under visible light irradiation. The phase composition, the specific surface and the photocatalytic activity were influenced by the molybdenum content and the calcination temperature. The final molybdenum content in the samples additionally depends on the calcination temperature. The optimum photocatalytic properties were observed or Ti-doped MoO₃.     

Rheological properties of chiral liquid crystals possessing a cholesteric–smectic A transition

We have measured the rheological properties of two cholesterol derivatives (cholesteryl myristate and cholesteryl nonanoate) in the vicinity of their cholesteric–smecticA transitions. The results for the two compounds differ qualitatively, and are in agreement with results based on optical observations of new defects in cholesteryl nonanoate showing that this material, traditionally considered as a typical cholesteric, in fact exhibits a TGBA phase between the cholesteric and smectic A phases.     

Preparation and properties of a novel waterborne fluorinated polyurethane–acrylate hybrid emulsion

The waterborne fluorinated polyurethane–acrylate hybrid emulsion (WFPUA) was prepared by two steps, including the preparation of the fluorinated alcohol blocked polyurethanes (FBPU) in the mixtures of vinyl monomers and fluorinated monomers and then the free radical polymerization after the pre-emulsification of the said system. The effects of hydrophilic monomer (MDEA) on the surfactivity and the emulsifiability of the FBPU were firstly reported. Then, the particle size (d), zeta potential (ζ), and viscosity (η) of the WFPUA hybrid emulsion were characterized, respectively. At the same time, the surface properties and the mechanical properties of the films were investigated. The results show that the increase of MDEA is good for the emulsifiability and the lower surface tension of the FBPU. This increase improves the stability, the ζ and η, yet decreases the d of the WFPUA emulsion. However, it has disadvantages to the hydrophobic performance of the WFPUA films. When the content of the MDEA in the WFPUA is increased from 4.67 to 14.89 %, the surface free energies are increased from 22.22 to 27.28 mJ m^?2 and the attenuation rate of the contact angle–time curve is increased from 0.3051° to 0.6290°/min. Also, with the increase of MDEA, the tensile strength and the shore hardness of the film are increased, but its elongation at break is decreased. The storage moduli of the film are enhanced remarkably. Meanwhile, the glass transition temperature of the soft segment [T_g(s)] is reduced and that of the hard segment [T_g(h)] is raised.