Formation of Isoindole Derivatives of Sulfidopeptide Leukotrienes by Reaction with O-Phthalaldehyde and Separation by Reverse Phase High Performance Liquid Chromatography

Abstract

A method is described for the formation of fluorescent conjugates of the sulfidopeptide leukotrienes (LTC₄, LTD⁴, and LTE⁴) by reaction of the primary amine moiety of these metabolites with o-phthalaldehyde. Separation of the fluorescent derivatives was achieved by reverse-phase high performance liquid chromatography in less than 30 minutes using a convex gradient of methanol-50 mM Na Acetate-5% Tetrahydrofuran pH 5.5. Detection limits realized under the conditions described were 0.35 ng, 3.8 ng and 3.7 ng for LTC₄, LTD₄, and LTE₄, respectively. This represents an Increased sensitivity over detection of these metabolites by ultra-violet spectroscopy. The leukotriene-OPA derivatives are fully stable for 50 minutes at 23°C and for at least 4 hours at 0°C. The method is applied to the detection of LTC₄ generated by zymosan stimulated murine peritoneal macrophages.     

Negative ion tandem mass spectrometry of leukotriene E4, and LTE4, metabolites: Identification of LTE4, in human urine

The sulfidopeptide leukotrienes, leukotriene E₄, (LTE₄,) and its N-acetyl derivative and several ω? and β-oxidized metabolites of LTE₄, have been analyzed by tandem mass spectrometry. [M?H]^? ions were produced by continuous flow fast atom bombardment, and collision-induced dissociation of these ions was studied by using a triple quadrupole instrument. The product ion spectra obtained were characteristic of the structure of LTE₄, and mechanisms of ion formation were investigated by using deuterated compounds. β-Elimination of the peptide portion of LTE₄, by loss of CO₂, and ethylene amine leaves the C-l carboxyl group ionized in the most abundant fragment ion for LTE₄, and all metabolites. Tandem mass spectrometry of fast atom bombardment-generated anions from ω? and β-oxidized metabolites of LTE₄, produced similar ions with only a minor influence of the third carboxyl group at the omega terminus evident. Tandem mass spectrometry was used to identify unequivocally the presence of unmodified LTE₄, in a high performance liquid chromatography-purified fraction of urine from a normal healthy volunteer after infusion with LTE₄.     

The preparation of octahydro leukotrienes C,D, and E via a stereoselective sulfenyllactonization reaction

Sulfenyl halides derived from the N-trifluoroacetamido methyl ester derivatives of cysteine, cysteinyiglycine and glutathione react stereoselectively with (5E)- and (5Z)-eicosenoic acids to provide, after separation of diastereomers and hydrolysis of the protecting groups, the fully saturated analogues of leukotrienes LTC₄, LTD₄, and LTE₄.     

Preparation of a diketopiperazine analog of leukotriene D4 (LTD4)

A LTD₄ analog has been synthesized in which the peptidyl fragment has been replaced by a nonionic diketopiperazine. Biological evaluation showed agonist activity, giving key information on LTD₄ geometry to the receptor.     

Simultaneous quantification of leukotrienes and hydroxyeicosatetraenoic acids in cell culture medium using liquid chromatography/tandem mass spectrometry

Leukotrienes (LTs) and hydroxyeicosatetraenoic acids (HETEs) are important bioactive lipid mediators that participate in various pathophysiological processes. To advance understanding of the mechanisms that regulate these mediators in physiological and pathological processes, an analytical method using liquid chromatography/tandem mass spectrometry for the simultaneous quantification of LTB₄, LTC₄, LTD₄, LTE₄, 5‐HETE_, 8‐HETE, 12‐HETE and 15‐HETE in cell culture media was developed. A Supel?‐Select HLB solid‐phase extraction cartridge was used for sample preparation. The compounds were separated on a C₁₈ column using gradient elution with acetonitrile–water–formic acid (20:80:0.1, v/v/v) and acetonitrile–formic acid (100:0.1, v/v). The calibration curves of LTB₄, LTD₄, LTE₄ and HETEs were linear in the range of 0.025–10 ng/mL, and the calibration curve of LTC₄ was linear in the range of 0.25–10 ng/mL. Validation assessment showed that the method was highly reliable with good accuracy and precision. The stability of LTs and HETEs was also investigated. Using the developed method, we measured LTs and HETEs in the culture supernatant of the human mast cell line HMC‐1. The present method could facilitate investigations of the mechanisms that regulate the production, release and signaling of LTs and HETEs. Copyright © 2014 John Wiley & Sons, Ltd.     

Tetrahedral [Tt4]4– Zintl Anions Through Solution Chemistry: Syntheses and Crystal Structures of the Ammoniates Rb4Sn4·2NH3, Cs4Sn4·2NH3, and Rb4Pb4·2NH3

The crystalline isotypic solvates Rb₄Sn₄·2NH₃, Cs₄Sn₄·2NH₃, and Rb₄Pb₄·2NH₃ have been synthesized using the direct reduction of elemental tin or tetraphenyltin, respectively, with heavier alkali metals or the dissolution of the binary phase RbPb in liquid ammonia. These compounds contain the cluster ions [Sn₄]^4– or [Pb₄]^4– respectively. This is the first time that[Tt₄]^4– ions (Tt = tetrels) are detected as result of a solution reaction. The accommodation of the ammonia molecules, which build up ion‐dipole interactions to alkali metal cations, requires some modifications of the crystal structures compared to the binary phases RbSn, CsSn, and RbPb. The tetrahedral [Tt₄]^4– anions have a slightly lower coordination by Rb⁺ or Cs⁺ cations and, furthermore, the intercluster distances show a remarkable increase.     

HPLC Analysis of [3H]-Arachidonic Acid Metabolites Produced by Smooth Muscle and Endothelial Cells in Response to Leukotriene D4

Abstract

Clonally derived murine and rat smooth muscle cells and bovine endothelial cells were incubated with [³H]-arachidonic acid for 16 hours (10 μCi/ml). The cells were then rinsed twice with saline and then treated with leukotriene D₄ (LTD₄) (1 μM) for 10 min. The supernatants from these cells were acidified with phosphoric acid (0.1% vol:vol), and then extracted with two volumes of ethylacetate. The radioactivity in the organic phase was analyzed by HPLC using an on-line radioactivity detector equipped with a solid scintillating flow cell. This procedure allowed us to monitor the arachidonic acid metabolites produced in response to LTD₄. From data obtained by this method we conclude that LTD₄ increases both lipoxygenase and cyclooxygenase product formation in these cells and that this method may be useful in obtaining qualitative information concerning eicosanoid metabolism in other biological systems.     

Oxidized leukotrienes: Synthesis of 20-OH and 20-COOH LTD4. Possible metabolites in the lipoxygenase pathway

Leukotriene LTD₄ analogs 20-OH LTDA₄ 16 and 20-COOH LTD₄ 17 were synthesized. These ω-oxidative derivatives are possible metabolites of the natural product.     

A VERSATILE AND REGIOSELECTIVE SYNTHESIS OF VICINAL AZIDOALCOHOLS USING CROSS-LINKED POLY（4-VINYLPYRIDINE） SUPPORTED AZIDE ION UNDER SOLVENT-FREE CONDITIONS

A new polymeric reagent, cross-linked poly（4-vinylpyridine） supported azide ion, [P4-VP]N3, was introduced as polymeric reagents for efficient and regioselective conversion of epoxides to azidohydrins in the presence of cross-linked poly（4-vinylpyridine） supported sulfuric acid, [P4-VP]H2SO4, as a solid proton source and as catalyst under solvent-free conditions. The advantages of this polymeric reagent over some of those reported in the literature are easy work-up procedure and regeneration of the reagent.     

Comparative study of pertechnetate reduction by thiourea using spectrophotometric,solvent extraction and ion-exchange methods

The results of a comparative study of pertechnetate reduction by thiourea in mineral acid (HCl, HNO₃, HClO₄, H₂SO₄) media using spectrophotometric, solvent extraction and ion-exchange chromatographic methods are presented. Changes of spectral characteristics of redox systems and distribution characteristics of reduced technetium (cationic) forms on extraction with bis(1,2-dicarbollide)cobaltic acid and on ion exchange on Dowex 50WX8 were established as a function of time and either aqueous or organic phase composition. Thiourea was tested as a reagent for reduction back-extraction of technetium from organic phases containing the amines Aliquat 336 and trilaurylmethylammonium as convenient extraction reagents for pertechnetate.     

Fluorodiazadiphosphetidine, 12. Mitt.: Reaktionen von Oktafluoro-1,3,2λ6,4λ6-diazoniadiphosphatetidinen

Reaction of (CH₃NHPF₄)₂ with selected organometallic reagents yields (CH₃NPF₃)₂, while reaction with non-nucleophilic bases such as 1,4-diazabicyclo[2.2.2]octane (DABCO) or 1,8-Bis(dimethylamino)naphthalin and with alkali fluorides yields ionic compounds with the diazoniadiphosphatetidine ring as a dianion.     

Determination of thyroxine enantiomers in pharmaceutical formulation by high-performance liquid chromatography-mass spectrometry with precolumn derivatization

A sensitive and specific liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method for the separation and analysis of d- and l-thyroxine was developed using R(−)/S(+)-4-(3-isothiocyanatopyrrolidin-1-yl)-7-(N,N-dimethylaminosulfonyl-2,1,3-benzoxadiazole, [R(−)/S(+)-DBD-PyNCS] as a chiral derivatization reagents. The T₄ derivatives with R(−)-DBD-PyNCS were efficiently separated on a reversed-phase column with water-acetonitrile containing 0.1% formic acid (41:59, v/v) as the eluent and analyzed using ESI-MS with negative selected ion monitoring (SIM) mode. The calibration curves of both the d-T₄ and l-T₄ were linear over the concentration range of 0.13-13 μg/ml. The detection limits (S/N = 3) were 28 ng/ml for d-T₄ and 40 ng/ml for l-T₄, respectively. The relative standard deviations (RSD, n = 5) were less than 3.6% at 1.3 μg/ml for both T₄ enantiomers. The proposed method was applied to the determination of l-T₄ enantiomer in a pharmaceutical formulation.     

Origin of spurious bands in the infrared spectrum of Ba2TiO4

The IR spectrum of Ba₂TiO₄ synthesized from “pure” commercial samples of TiO₂ and BaCO₃ exhibits between 1200 and 950 cm⁻¹ a more-or-less complex pattern of sharp, very weak bands whose intensity depends on the origin of the reagents, and which disappear completely if very pure reagents are used for the synthesis. It is shown that most of these bands are due to a small quantity (e.g. 0.5 mole % or less) of phosphate and/or sulfate ions (brought by the reagents) replacing the TiO₄ tetrahedra in the Ba₂TiO₄ structure and thus forming a “dilute” solid solution. This is responsible for the sharpness of the IR bands and for their easy observation, even at fairly low concentrations [e.g. 0.1 mole % for the (PO₄)³⁻ ion]. The four investigated TiO₂ samples are free from sulfate, but all of them (including pro analysi samples) contain a small amount (0.5-0.1%) of phosphate, not disclosed in TiO₂ itself, but easily evidenced after transformation into Ba₂TiO₄.     

Synthesis,Structure, and Stability of Cs4ZrO4

The colorless Cs₄ZrO₄ is obtained from the reaction of stoichiometric proportions of Cs, CsO₂, and finely divided ZrO₂ in a sealed Ag container at 400–650°C for several days. Regrinding and re-reaction provide a single phase sample. The compound is monoclinic (P2₁/c, Z = 4, a = 7.172 (1) Å, b = 19.907 (1) Å, c = 7.157 (1) Å, β = 113.1 (1)Å, R = 0.032) and isostructural with Cs₄PbO₄, with isolated ZrO₄^4? tetrahedra (d(Zr–O) = 1.97 Å). The compound decomposes to Cs₂ZrO₃ (a) in the presence of excess oxygen or CsO₂, (b) in high vacuum near 275°C, or (c) in a sealed container at about 730 ± 10°C.     

Structure-dependent transformations of the tetrachlorocyclopentadienone dimer and the product of its substitutive rearrangement in reactions with NaBH4, CrCl2, LiAlH4, and Zn

Dechlorination of the tetrachlorocyclopentadienone dimer and perchloro-7-oxotricyclo[6.1.0.0^4,8]nona-2,5-diene-9-carboxylic acid N,N-diethylamide with hydride ion donors (NaBH₄, LiAlH₄, etc.) and electron donors (CrCl₂ or Zn) were studied. The possible pathways of unusual transformations of both sterically hindered molecules are considered. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1001–1007, June, 2006.     

OXIDATIVE ADDITION OF SOME HALOGENS,INTERHALOGENS AND PSEUDOHALOGENS TO [(n-C4H9)4N]2[Pt(CN)4]

Abstract

The results of the treatment of [(n–C₄H₉)₄N]₂ [Pt(CN)₄] with seventeen oxidizing agents, including halogens, inter halogens, and molecules such as N₂O₄, ICN, (SCN)₂, S(CN)₂ and C₆ H₅SCl, are reported. In cases where the reagents were not symmetrical molecules, two different ligands were added to platinum. The competition between parts of the oxidizing agent and other potential ligands in solution is also examined.     

On [Na(POCl3)4]+ Complex Ion Formation: Conductivity,Raman, and NMR studies in the system phosphoryl chloride–sodium tetrachloro aluminate and related compounds

The system POCl₃–NaAlCl₄ was investigated by measuring the conductivity and the Raman and NMR spectra (²⁷Al, ²³Na and ³¹P) as a function of the mol fraction x of NaAlCl₄ in POCl₃. Additionally, Raman spectra of POCl₃ solutions of NaFeCl₄, LiAlCl₄, LiFeCl₄, and KAlCl₄ were recorded. In solutions containing Li⁺ or Na⁺ ions a liquid to solid (or jelly) phase transition was observed under certain conditions, dependent on salt concentration and temperature. Observed changes in the Raman spectra of the electrolyte solutions in comparison to the pure solvent POCl₃ demonstrate the existence of interactions. Clearly, the POCl₃ eigenfrequencies and hence the molecules are pertubed. The formation of [M(POCl₃)₄]⁺ complexes (M = Li, Na) can be deduced from the Raman measurements. NMR investigations support this conclusion. For assigning of Raman spectra, (Li⁺, K⁺) cation and ([FeCl₄]^?, [SbCl₆]^?) anion substitutions were employed.     

Pt2(HSO4)2(SO4)2, the First Binary Sulfate of Platinum

Red single crystals of Pt₂(HSO₄)₂(SO₄)₂ were obtained by the reaction of elemental platinum with conc. sulfuric acid at 350 °C in sealed glass ampoules. The crystal structure (monoclinic, P2₁/c, Z = 2, a = 868.6(2), b = 826.2(1), c = 921.8(2) pm, β=116.32(1)°, R_all = 0.0348) shows dumbbell shaped Pt₂⁶⁺ cations which are coordinated by four SO₄^2— and two HSO₄^— ions. Each of the sulfate ions is attached to another Pt₂⁶⁺ ion yielding layers according to equation/tex2gif-stack-1.gif[Pt₂(SO₄)_4/2(HSO₄)_2/1]. The layers are connected by hydrogen bonds with the OH group of the hydrogensulfate ion as donor and the non‐bonding oxygen atom of the sulfate ion as acceptor.     

Synthesis,characterization, and antitumor evaluation of 4-aminoximidofurazan derivatives

Reactions of 3-amino-4-aminoximidofurazan (AAOF) with Wittig–Horner reagents, trialkylphosphites, trisdialkylaminophosphines as well as the thiating Lawesson and Japanese reagents were studied. Elemental analysis and spectroscopic measurements were in good accord with the structures postulated for the new products. The antitumor activities of certain selected new compounds were screened, in vitro, against a panel of five (liver; HepG2; breast; MCF-7; lung; A549; colon; HCT116; and prostate PC3) human solid tumor cell lines.     

Solubility Behaviour of TiCl4, ZrCl4, and HfCl4 in Chloroaluminate Ionic Liquids

The solubility of NbCl₅, TaCl₅, TiCl₄, ZrCl₄, and HfCl₄ in neutral [BMIM][AlCl₄] (BMIM = 1‐butyl‐3‐methylimidazolium) was determined. While TiCl₄ was immiscible with the neutral ionic liquid, 0.80 molar equivalents of ZrCl₄ and stoichiometric amounts of HfCl₄ dissolved in the melt at ambient temperature. The crystal structures and the unit cell parameters of [BMIM]₂[Ti₂Cl₁₀], [BMIM]₂[Zr₂Cl₁₀], and [PhNMe₃][Hf₂Cl₉] were determined. [BMIM]₂[Ti₂Cl₁₀], and [BMIM]₂[Zr₂Cl₁₀] were crystallised from basic chloroaluminate melts. With a trimethylanilinium cation, [PhNMe₃][Hf₂Cl₉] crystallised from an equimolar composition of PhNMe₃Cl, AlCl₃, and HfCl₄. Obviously, HfCl₄ abstracted a chloride ligand from [AlCl₄]^– to give highly Lewis acidic [Al₂Cl₇]^– anions.