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Aldrich - 731374; Tri-n-butylphosphine 99%; CAS No. 998-40-3; NSC 91700 | Tributylphosphine | TBP | P(n-Bu)3; ligand suitable for Buchwald-Hartwig cross coupling, Suzuki-Miyaura coupling, Stille coupling, Sonogashira coupling, Negishi coupling, Heck coupling and Hiyama coupling reaction| Find related products, papers, technical documents, MSDS & more at Sigma-Aldrich

Tri-n-butylphosphine 99 998-40-3

Tri-<I>n</I>-butylphosphine

Substrate-controlled, phosphine-catalyzed domino reactions of activated conjugated dienes: highly diastereoselective synthesis of bicyclic skeletons.

P(n)Bu(3)-catalyzed cyclization reactions of salicylaldimines and salicylaldehydes with ethyl 2,3-butadienoate gave the corresponding functionalized chromans in moderate to good yields in THF under mild conditions. The new reaction provides a new method for the synthesis of biologically active chroman products.

Synthesis of functionalized chromans by PnBu3-catalyzed reactions of salicylaldimines and salicylaldehydes with allenic ester.

Several human diseases, in particular metabolic disorders, often lead to the accumulation of characteristic metabolites in plasma, urine and cells. The selected diseases of this type include cystinuria and homocystinuria. In the typical laboratory diagnosis of these two diseases, a positive nitroprusside test is followed by quantitative analysis of urine cysteine and homocysteine in order to differentiate between cystinuria and homocystinuria. A sensitive and reproducible assay for total urine cysteine and homocysteine has been developed. The essential steps in the assay include conversion of disulphides to free thiols with tributylphosphine, conjugation of the thiols with 2-chloro-1-methyl pyridinium iodide, separation of S-pyridinium derivatives of cysteine and homocysteine from other endogenous urine thiol derivatives by reversed-phase high-performance liquid chromatography, and detection and quantitation by spectrophotometry. The method has a sensitivity of 4 pmol and is reproducible, intra- and inter-day coefficients of variation are from 1.37 to 4.14% and from 2.38 to 5.01%, respectively. The mean concentration of total urine cysteine and homocysteine in healthy donors (7 men and 7 women) were for women. 92.0 +/- 45.8 and 16.4 +/- 4.8 respectively, and for men 120.9 +/- 46.6 and 21.5 +/- 7.4 nmol/ml, respectively. Total urine homocysteine represents approximately 17.7% of cysteine in the urine of normal individuals.

Urinary excretion measurement of cysteine and homocysteine in the form of their S-pyridinium derivatives by high-performance liquid chromatography with ultraviolet detection.

Aziridines underwent cyclization reaction with carbon disulfide and isothiocyanate in the presence of organophosphine to afford thiazolidinone derivatives in good to high yields. The mechanistic study revealed that organophosphine serves as a catalyst in the reaction.

Tributylphosphine-catalyzed cycloaddition of aziridines with carbon disulfide and isothiocyanate.

Aminothiols have been implicated in the pathogenesis of arteriosclerosis, and reliable methods are needed to determine their concentrations in body fluids. We present a comparison of two analytical methods and focus on the reduction of low-molecular weight and protein-mixed disulfides of homocysteine, cysteine, cysteinyl-glycine, and glutathione. The plasma total aminothiol profile was determined by HPLC with fluorescence detection after derivatization with ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulfonate. Disulfides and protein-bound aminothiols were reduced by either tri-n-butylphosphine (the TBP method) or tris(2-carboxyethyl)phosphine (the TCEP method); the effects of temperature, time of reduction, and concentration of reductants were evaluated. The intraassay imprecision (CV) was <3% for all aminothiols using both methods. The interassay CVs for total cysteine (tCys), total cysteinyl-glycine (tCys-Gly), and total homocysteine (tHcy) were <4% and <8% for the TCEP and TBP methods, respectively, whereas for total glutathione (tGSH) the interassay CV was >12% for both methods. Deming regression and Bland-Altman difference plots showed positive biases for total aminothiol concentrations determined by the TCEP method relative to the TBP method. The mean proportional biases were 65%, 27%, 6%, and 60% for tCys, tCys-Gly, tHcy, and tGSH, respectively. The calculated concentrations of total aminothiols by the TCEP method were less influenced by changes in temperature and concentration of reducing agent or by calibrator matrix. The agreement between the TCEP and TBP methods was considerably lower for the determination of tCys, tCys-Gly, and tGSH than for tHcy. For total-aminothiol determination, the TCEP method yields better reproducibility and is more robust than the TBP method.

Measurement of homocysteine and other aminothiols in plasma: advantages of using tris(2-carboxyethyl)phosphine as reductant compared with tri-n-butylphosphine.

Upon exposure of mono-enone mono-allylic carbonates to tributylphosphine and 1 mol % Pd(Ph3P)4, efficient conversion to the corresponding cycloallylated products is achieved. This transformation combines the nucleophilic features of the Morita-Baylis-Hillman reaction with the electrophilic features of the Trost-Tsuji reaction.

Catalytic enone cycloallylation via concomitant activation of latent nucleophilic and electrophilic partners: merging organic and transition metal catalysis.

Solvent effects on hydrogen bonding.

A method was developed for the simultaneous determination of gamma-glutamylglutathione (gamma-GluGSH) and other low-molecular-mass thiol compounds (cysteine, cysteamine, homocysteine, cysteinylglycine, gamma-glutamylcysteine, glutathione and N-acetylcysteine) using high-performance liquid chromatography combined with precolumn fluorescence labeling with ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulphonate (SBD-F). These SBD-labeled thiol compounds were separated within 35 min on a Cosmosil 5C-18AR column with isocratic elution using 75 mM sodium citrate buffer (pH 2.90)-methanol (98:2) and detected fluorimetrically (ex. 386 nm, em. 516 nm). The calibration graphs using 2-mercaptoethanol as an internal standard showed good linearity in the range from 20 pmol to 10 nmol for all thiol compounds examined. The application of this method for the quantitative determination of thiol compounds in the urine from gamma-glutamyl transpeptidase-deficient mice was also demonstrated. This method is sufficiently simple, rapid and sensitive for the determination of gamma-GluGSH and other low-molecular-mass thiol compounds in biological samples.

Determination of gamma-glutamylglutathione and other low-molecular-mass biological thiol compounds by isocratic high-performance liquid chromatography with fluorimetric detection.

A detailed investigation of the factors affecting the determination of total plasma 7-fluorobenzo-2-oxa-1,3-diazole-4-sulfonate (SBD)-thiol derivatives (i.e. cysteine, homocysteine and cysteinylglycine) is described. Essentially, this assay entails extracting specific thiols by plasma disulphide bond reduction, protein precipitation, sulphydryl compound derivatization with the thiol-specific fluorogenic reagent ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulphonate (SBD-F), and subsequent separation with isocratic reversed-phase high-performance liquid chromatography. By improving the reliability of several analytical parameters (composition of the mobile phase, pretreatment of the sample using different reducing and protein precipitation agents, and optimization of the derivatization of thiols with SBD-F), a number of critical issues can be identified and solved.

Study of factors affecting the determination of total plasma 7-fluorobenzo-2-oxa-1,3-diazole-4-sulfonate (SBD)-thiol derivatives by liquid chromatography.

The phosphine-catalyzed [3 + 2]-cycloaddition of 5-methylenehydantoins 4 with the ylides 5, derived from addition of tributylphosphine to the 2-butynoic acid derivatives, 6a-d, gives spiro-heterocyclic products. The camphor sultam derivative 6b gives optically active products. Noteable was that the ylides derived from ethyl 2-butynoate and the 3-(2-butynoyl)-1,3-oxazolidin-2-one derivatives 6c and 6d gave spiro-heterocyclic products with reverse regioselectivities. The N,N-dibenzylprotected cycloadduct has been converted to carbocyclic hydantocidin and 6,7-diepi-carbocyclic hydantocidin.

Synthesis of carbocyclic hydantocidins via regioselective and diastereoselective phosphine-catalyzed [3 + 2]-cycloadditions to 5-methylenehydantoins.

Intracellular recordings in vivo remains the best technique to link single-neuron electrical properties to network function. Yet existing methods are limited in accuracy, throughput, and duration, primarily via washout, membrane damage, and movement-induced failure. Here, we introduce flexible quartz nanopipettes (inner diameters of 10-25 nm and spring constant of ∼0.08 N/m) as nanoscale analogs of traditional glass microelectrodes. Nanopipettes enable stable intracellular recordings (seal resistances of 500 to ∼800 MΩ, 5 to ∼10 cells/nanopipette, and duration of ∼1 hr) in anaesthetized and awake head-restrained mice, exhibit minimal diffusional flux, and facilitate precise recording and stimulation. When combined with quantum-dot labels and microprisms, nanopipettes enable two-photon targeted electrophysiology from both somata and dendrites, and even paired recordings from neighboring neurons, while permitting simultaneous population imaging across cortical layers. We demonstrate the versatility of this method by recording from parvalbumin-positive (Pv) interneurons while imaging seizure propagation, and we find that Pv depolarization block coincides with epileptic spread. Flexible nanopipettes present a simple method to procure stable intracellular recordings in vivo.

Flexible Nanopipettes for Minimally Invasive Intracellular Electrophysiology In Vivo.

We investigate the origins and magnitude of low-frequency noise in high-mobility nanocrystal field-effect transistors and show the noise is of 1/f-type. Sub-band gap states, in particular, those introduced by nanocrystal surfaces, have a significant influence on the 1/f noise. By engineering the device geometry and passivating nanocrystal surfaces, we show that in the linear and saturation regimes the 1/f noise obeys Hooge's model of mobility fluctuations, consistent with transport of a high density of accumulated carriers in extended electronic states of the NC thin films. In the subthreshold regime, the Fermi energy moves deeper into the mobility gap and sub-band gap trap states give rise to a transition to noise dominated by carrier number fluctuations as described in McWhorter's model. CdSe nanocrystal field-effect transistors have a Hooge parameter of 3 × 10(-2), comparable to other solution-deposited, thin-film devices, promising high-performance, low-cost, low-noise integrated circuitry.

Low-frequency (1/f) noise in nanocrystal field-effect transistors.

We report the evolution of electrical transport and grain size during the sintering of thin films spin-cast from soluble phosphine and amine-bound, chloride-terminated cadmium selenide nanocrystals. Sintering of the nanocrystals occurs in three distinct stages as the annealing temperature is increased: (1) reversible desorption of the organic ligands (≤150 °C), (2) irreversible particle fusion (200-300 °C), and (3) ripening of the grains to >5 nm domains (>200 °C). Grain growth occurs at 200 °C in films with 8 atom % Cl(-), while films with 3 atom % Cl(-) resist growth until 300 °C. Fused nanocrystalline thin films (grain size = 4.5-5.5 nm) on thermally grown silicon dioxide gate dielectrics produce field-effect transistors with electron mobilities as high as 25 cm(2)/(Vs) and on/off ratios of 10(5) with less than 0.5 V hysteresis in threshold voltage without the addition of indium.

Electrical transport and grain growth in solution-cast, chloride-terminated cadmium selenide nanocrystal thin films.

Ambient ionization is achieved by spraying from a carbon nanotube (CNT)-impregnated paper surface under the influence of small voltages (≥3 V). Organic molecules give simple high-quality mass spectra without fragmentation in the positive or negative ion modes. Conventional field ionization is ruled out, and it appears that field emission of microdroplets occurs. Microscopic examination of the CNT paper confirms that the nanoscale features at the paper surface are responsible for the high electric fields. Raman spectra imply substantial current flows in the nanotubes. The performance of this analytical method was demonstrated for a range of volatile and nonvolatile compounds and a variety of matrices.

Molecular ionization from carbon nanotube paper.

Proteome studies on hematological malignancies contribute to the understanding of the disease mechanism and to the identification of new biomarker candidates. With the isobaric tag for relative and absolute quantitation (iTRAQ) method we analyzed the protein expression between B-cells of healthy people and chronic lymphocytic leukemia (CLL) B-cells. CLL is the most common lymphoid cancer of the blood and is characterized by a variable clinical course. By comparing samples of patients with an aggressive vs. indolent disease, we identified a limited list of differentially regulated proteins. The enhanced sensitivity attributed to the iTRAQ labels led to the discovery of a previously reported but still not clarified proteolytic product of histone H2A (cH2A) which we further investigated in light of the suggested functional properties of this modification. In the exploratory proteome study the Histone H2A peptide was up-regulated in CLL samples but a more specific and sensitive screening of a larger patient cohort indicated that cH2A is of myeloid origin. Our subsequent quantitative analysis led to a more profound characterization of the clipping in acute monocytic leukemia THP-1 cells subjected to induced differentiation.

Quantitative proteomics to characterize specific histone H2A proteolysis in chronic lymphocytic leukemia and the myeloid THP-1 cell line.

We show here that oxidative stress is involved in both sclerotial differentiation (SD) and aflatoxin B1 biosynthesis in Aspergillus flavus. Specifically, we observed that (i) oxidative stress regulates SD, as implied by its inhibition by antioxidant modulators of reactive oxygen species and thiol redox state, and that (ii) aflatoxin B1 biosynthesis and SD are comodulated by oxidative stress. However, aflatoxin B1 biosynthesis is inhibited by lower stress levels compared to SD, as shown by comparison to undifferentiated A. flavus. These same oxidative stress levels also characterize a mutant A. flavus strain, lacking the global regulatory gene veA. This mutant is unable to produce sclerotia and aflatoxin B1. (iii) Further, we show that hydrogen peroxide is the main modulator of A. flavus SD, as shown by its inhibition by both an irreversible inhibitor of catalase activity and a mimetic of superoxide dismutase activity. On the other hand, aflatoxin B1 biosynthesis is controlled by a wider array of oxidative stress factors, such as lipid hydroperoxide, superoxide, and hydroxyl and thiyl radicals.

Tri-n-butylphosphine

99%

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