The use of discharge lamps as directly modulated atom reservoirs for selective line modulation in atomic emission spectrometry

A simple method is described for selectively modulating the atomic or ionic resonance lines emitted by an excitation source. A modified discharge lamp with a cylindrical hollow cathode is used to generate a modulated atom cloud. The emission from the excitation source is then imaged through the modulated atom cloud within the cylindrical cathode lamp, to yield a selectively modulated signal. The ability of the system to reduce spectral interferences in inductively-coupled plasma emission spectrometry is assessed and discussed.     

Selective oxidation of benzylic or allylic hydroxyl group of sec-1,2-diols

A mild and efficient method to selectively oxidize chiral sec-1,2-diols has been developed, which demonstrates that 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) can selectively oxidize benzylic or allylic hydroxyl group of sec-1,2-diols under ultrasound wave promotion. The configuration of the adjacent chiral center is retained.     

Dioxygen-Triggered β-Hydroxysulfonylation of Terminal Olefins Controlled by DABCO

A dioxygen-triggered selectively difunctionalization of olefins to achieve β-hydroxysulfones has been developed. Particularly, the mechanism of this reaction can be controlled by DABCO, which act as a single electron transfer reagent, to selectively obtain ketosulfone or hydroxysulfone. The reaction was conducted in a clean, safe, mild, and catalyst-free conditions. Moreover, as a proof-of-concept, two bioactive molecules were synthesized easily using this method.     

Euphohelioscopin A Is a PKC Activator Capable of Inducing Macrophage Differentiation

To identify small molecules that selectively control hematopoietic stem cell differentiation, we performed an unbiased screen using primary human CD34(+) cells. We identified a plant-derived natural product, euphohelioscopin A, capable of selectively differentiating CD34(+) cells down the granulocyte/monocytic lineage. Euphohelioscopin A also inhibits proliferation and induces differentiation of the myeloid leukemia cell lines THP-1 and HL-60. Mechanistic studies revealed that euphohelioscopin A is an activator of protein kinase C (PKC), and that the promonocytic effects of this natural product are mediated by PKC activation. In addition to shedding insights into normal hematopoiesis, this work may ultimately facilitate the application of stem cell therapies to a host of myeloid dysfunctions.     

Phosphine ligand triggered oxidative decarbonylative homocoupling of aromatic aldehydes: selectively generating biaryls and diarylketones

A novel rhodium-catalyzed oxidative decarbonylative homocoupling of aromatic aldehydes to generate biaryls and diarylketones selectively and efficiently, triggered by the choice of different phosphine ligands.     

An efficient preparation of 1-phenylsulfonylindolyl methyl sulfoxides using KF/m-CPBA

A variety of 1-phenylsulfonylindolylmethyl sulfides are selectively oxidized to the corresponding sulfoxides using a hitherto unexplored KF/m-CPBA system. A major advantage is the absence of over-oxidation.     

ATP recognition and sensing with a phenanthroline-containing polyammonium receptor

A new polyammonium receptor is able to selectively recognise and sense ATP among triphosphate nucleotides, thanks to ATP-induced quantitative quenching of its fluorescence emission.     

Charge transfer through DNA triggered by site selective charge injection into adenine

A positive charge, which was injected site selectively into adenine (A) of a DNA double strand, migrates along (A:T)n sequences in a distance independent way.     

Selective,one-pot synthesis of 2,3,6-trisubstituted pyridine and 2-cyclohexen-1-one derivatives from bicyclic ketals

Boron difluoromethanesulfonate, prepared from 5 equivalents of trimethylsilyl methanesulfonate and 1 equivalent of boron trifluoride etherate, has proved to be an active Lewis acid catalyst for the one-pot transformation reaction of bicyclic ketals in the 6,8-dioxabicyclo[3.2.1]octane series to 2,3,6-trisubstituted pyridine or 2-cyclohexen-1-one selectively, depending on conditions. A 1,5-diketone was the reaction intermediate for both products. Pyridine was formed selectively by using a nitrile as a solvent or a reagent, but cyclohexenone was prepared in methylene chloride instead of a nitrile.     

Three-dimensional metallized features on polymeric substrates by microcontact printing

We demonstrate the formation of 3-D metallized features on a polymeric substrate by microcontact printing. A patterned silicon stamp was "inked" with catalytic particles. Thereafter, particles were selectively removed from the raised regions of the stamp. A molten polymer was embossed against the stamp. Upon cooling and separation, the catalytic particles that were within the recessed areas of the stamp were transferred to the polymer. The polymer was then immersed in an electroless plating bath, and metallization occurred selectively on the areas where the catalytic particles were present. We have achieved 3-D metallized columns as small as 500 nm in diameter and about 1 mum tall.     

A new synthetic route to chloride selective [2]catenanes

A novel anion templation route has been developed to synthesise two new catenanes, which are observed to selectively complex chloride in protic solvent media.     

Methyltrioxorhenium catalyzed oxidation of 1,2-diols to 1,2-diketones using hydrogen peroxide as oxidant

A variety of 1,2-diols were oxidized selectively to the corresponding 1,2-diketones by the dropwise addition of 30% aqueous hydrogen peroxide using methyltrioxorhenium as catalyst.     

Detection of cerebrospinal fluid leakage by specific measurement of transferrin glycoforms

A simple and rapid detection of cerebrospinal fluid (CSF) leakage would benefit spine surgeons making critical postoperative decisions on patient care. We have assessed novel approaches to selectively determine CSF β2‐transferrin (β2TF), an asialo‐transferrin (aTF) biomarker, without interference from serum sialo‐transferrin (sTF) in test samples. First, we performed mild periodate oxidation to selectively generate aldehyde groups in sTF for capture with magnetic hydrazide microparticles, and selective removal with a magnetic separator. Using this protocol sTF was selectively removed from mixtures of CSF and serum containing CSF aTF (β2TF) and serum sTF, respectively. Second, a two‐step enzymatic method was developed with neuraminidase and galactose oxidase for generating aldehyde groups in sTF present in CSF and serum mixtures for magnetic hydrazide microparticle capture. After selectively removing sTF from mixtures of CSF and serum, ELISA could detect significant TF signal only in CSF, while the TF signal in serum was negligible. The new approach for selective removal of only sTF in test samples will be promising for the required intervention by a spine surgeon.     

Substrate-Controlled Hydrogenation of Flavanones: Selective Synthesis of 2′-Hydroxy-1,3-Diarylpropanes and Flavans

A new substrate-controlled hydrogenation of flavanones to selectively obtain different hydrogenation products is herein reported. Thus, hydrogenation of flavanones bearing different electron-donating and electron withdrawing substituents (Cl, Br, Me, OMe, OH) provided the corresponding 1,3-diarylpropanes in excellent yields. This procedure offers a straightforward, simple, and cost-effective method for the preparation of glycosylated 2′-hydroxy-1,3-diarylpropanes derived from natural flavanones such as Naringin and Hesperedin. On the contrary, when the hydrogenation was performed over fluorinated flavanones, the corresponding flavans were selectively obtained in excellent yields.     

The Os/Cu-Al-hydrotalcite catalysed hydroxylation of alkenes

A new Os/Cu-Al-hydrotalcite-like catalyst is described which, with N-methylmorpholine oxide as co-oxidant, heterogeneously catalyses the hydroxylation of olefins to give diols selectively and in high yield.     

Rotaxanes capable of recognising chloride in aqueous media

A new, versatile chloride-anion-templating synthetic pathway is exploited for the preparation of a series of eight new [2]rotaxane host molecules, including the first sulfonamide interlocked system. (1)H NMR spectroscopic titration investigations demonstrate the rotaxanes' capability to selectively recognise the chloride anion in competitive aqueous solvent media. The interlocked host's halide binding affinity can be further enhanced and tuned through the attachment of electron-withdrawing substituents and by increasing its positive charge. A dicationic rotaxane selectively binds chloride in 35% water, wherein no evidence of oxoanion binding is observed. NMR spectroscopy, X-ray structural analysis and computational molecular dynamics simulations are used to account for rotaxane formation yields, anion binding strengths and selectivity trends.     

Direct aromatization of chlorohydroazulenones with triflic anhydride: access to chloroazulenyl triflates

A direct and efficient aromatization of chlorohydroazulenones has been achieved by using triflic anhydride and then lutidine or tropylium cation to afford selectively chloroazulenes and chloroazulenyl triflates, respectively.     

Fluorescence response of 3-trifluoroacetylaminophthalimide to a Li(+)-I(-) ion pair induced by 254 nm photolysis in acetonitrile

A 3-trifluoroacetylaminophthalimide selectively distinguished LiI from other alkaline-metal iodides and lithium halides by a marked fluorescence colour change, from orange-yellow to sky-blue, subsequent to 254 nm photolysis.     

Lewis Acid catalyzed reactions of vinylidenecyclopropanes with activated carbon-oxygen double bond: a facile synthetic protocol for functionalized tetrahydrofuran and 3,6-dihydropyran derivatives

A number of functionalized tetrahydrofuran and 3,6-dihydropyran derivatives are prepared selectively in moderate to good yields by the reactions of vinylidenecyclopropanes with activated carbonyl compounds in the presence of Lewis acid.     

Ligand-free Ag(I)-catalyzed carboxylation of terminal alkynes with CO2

A convenient approach to selectively prepare a wide range of functionalized propiolic acids was developed by AgI-catalyzed carboxylation of terminal alkynes using carbon dioxide as carboxylative agent under ligand-free conditions.