Alkene and alkyne insertion into the Ir-H bond: Synthesis of new mono- and dinuclear alkyl and alkenyl iridium-pybox complexes

The treatment of the complex [Ir(η²-C₂H₄)₂(L)][PF₆] (L = κ³-N,N,N-(S,S)-ⁱPr-pybox) with acetic acid (1:1 molar ratio) at −10 °C affords the complex [Ir(C₂H₅)(κ²-O,O-O₂CCH₃)(L)][PF₆] (1). The dinuclear iridium(III) complex [Ir₂(μ-Cl)₂(C₂H₅)₂(L)₂][PF₆]₂ (2) is stereoselectively obtained by spontaneous intramolecular insertion of ethylene into the iridium-hydride bond of the mononuclear complex [IrClH(η²-C₂H₄)(L)][PF₆]. The single bridging chloride dinuclear derivative [Ir₂(μ-Cl)(C₂H₅)₂Cl₂(L)₂][PF₆] (3) is prepared by reaction of 2 with one equivalent of NaCl. The intramolecular insertion reaction of methyl and ethyl propiolate into the Ir-H bond of the complex [IrClH(MeCN)(L)][PF₆] gives stereoselectively the dinuclear complexes [Ir₂(μ-Cl)₂(HCCHCO₂R)₂(L)₂][PF₆]₂ (R = Me (4), Et (5)). The reaction of the complexes 4, 5 with one equivalent of NaCl or with an excess of sodium acetate yields the dinuclear [Ir₂(μ-Cl)(HCCHCO₂R)₂Cl₂(L)₂][PF₆] (R = Me (6), Et (7)) or the mononuclear [IrCl(HCCHCO₂Et)(κ¹-O-O₂CMe)(L)] (8) complexes, respectively. The structure of the dinuclear complex 3 · CH₂Cl₂ has been determined by an X-ray monocrystal study.     

Analysis of ochratoxin A in milk after direct immunoaffinity column clean-up by high-performance liquid chromatography with fluorescence detection

The present work describes a new analytical method for direct immunoaffinity column clean-up of ochratoxin A (OTA) in milk samples followed by determination of the toxin using high-performance liquid chromatography with fluorescence detection (HPLC-FD). Two different immunoaffinity cartridges (IAC) were investigated, and Ochraprep columns were chosen because they showed the best results. An average recovery of 89.8% and a mean RSD of 5.8% for artificially contaminated cow's milk in the range of 5-100 ng/L were attained. The calculated limit of detection (LOD) and limit of quantitation (LOQ) were as low as 0.5 and 5 ng/L, respectively. This new easy and fast method avoids a previous liquid-liquid extraction step and therefore the use of toxic chlorinated solvents. Chromatograms of the final extracts were clean and OTA could be easily detected at a retention time of 8.4 min without interferences. To assess the presence of the toxin in cow's milk eight samples of skimmed and four samples of whole milk were analysed and OTA was not detected over the established detection limit.     

A simple method for measuring long-range 1H-13C coupling constants in organic molecules

This study presents a simple method for measuring long-range heteronuclear coupling constants between protons and proton-bearing carbons. The approach involves recording two conventional 1D-TOCSY experiments in which the offset of the selective proton pulse is set on the low- and high-frequency 13C satellites of an isolated proton signal, Hi. Long-range heteronuclear coupling values between the 13Ci bonded to Hi and the protons Hj,k...n that belong to the same spin system were easily determined from the relative displacement of the relayed Hj,k...n signals in the satellite-selective TOCSY spectra. The sense of the displacement indicated the sign of the coupling constants.     

IPy2BF4/HF-pyridine: a new combination of reagents for the transformation of partially unprotected thioglycosides and n-pentenyl glycosides to glycosyl fluorides

The combination of bis(pyridinium)iodonium (I) tetrafluoroborate (IPy2BF4), and hydrogen fluoride pyridine (HF-py) forms an iodine monofluoride (IF) synthetic equivalent that can be used in the preparation of partially unprotected glycosyl fluorides from partially unprotected n-pentenyl glycosides and thioglycosides, thus avoiding the need for the protection/deprotection steps normally required in that transformation.     

Solid-phase synthesis of novel trimers containing a phenylstatine core and analysis by high-resolution magic angle spinning

Here we describe a multistep solid-phase synthetic approach for the addition of amino acid residues to both the C- and N-termini of a phenylstatine core, yielding a library aimed at the development of structure-activity relationships in the S2 and S2' regions of the aspartyl proteases. Optimization of the synthetic strategy was performed on the basis of the in situ analysis of the compounds bound to the solid support through high-resolution magic angle spinning NMR Spectroscopy (HR-MAS NMR).     

Medium dependence of multiplicity distributions in MLLA

We study the modification of the multiplicity distributions in MLLA due to the presence of a QCD medium. The medium is introduced through a multiplicative constant (f _med) in the soft infrared parts of the kernels of the QCD evolution equations. Using the asymptotic ansatz for mean multiplicities of the quark and gluons, 〈n _G〉=e ^{γ y} and 〈n _Q〉=r ⁻¹e ^{γ y} , respectively, we study two cases: fixed γ as previously considered in the literature, and fixed α _s . We find opposite behaviors of the dispersion of the multiplicity distributions with increasing f _med in both cases. For fixed γ the dispersion decreases, while for fixed α _s it increases.     

Design, synthesis, evaluation, and structure of vitamin D analogues with furan side chains

Based on the crystal structures of human vitamin D receptor (hVDR) bound to 1α,25-dihydroxy-vitamin D(3) (1,25 D) and superagonist ligands, we previously designed new superagonist ligands with a tetrahydrofuran ring at the side chain that optimize the aliphatic side-chain conformation through an entropy benefit. Following a similar strategy, four novel vitamin D analogues with aromatic furan side chains (3a, 3b, 4a, 4b) have now been developed. The triene system has been constructed by an efficient stereoselective intramolecular cyclization of an enol triflate (A-ring precursor) followed by a Suzuki-Miyaura coupling of the resulting intermediate with an alkenyl boronic ester (CD-side chain, upper fragment). The furan side chains have been constructed by gold chemistry. These analogues exhibit significant pro-differentiation effects and transactivation potency. The crystal structure of 3a in a complex with the ligand-binding domain of hVDR revealed that the side-chain furanic ring adopts two conformations.     

[6‐Amino‐3‐methyl‐5‐nitro­so­pyrimidine‐2,4(1H,3H)‐dionato]­sodium dihydrate at 150 K: coordination‐polymer ladders linked by hydrogen bonds

In the title compound, [Na(C₅H₅N₄O₃)]·2H₂O, each Na cation is linked to three C₅H₄N₄O₃^? anions and two water mol­ecules, forming approximately octahedral NaNO₅ units; the cations and the anions form molecular ladders, and each ladder is linked to four neighbouring ladders by O—H?O and O—H?N hydrogen bonds.     

Effect of Ylang-Ylang (Cananga odorata Hook. F. & Thomson) Essential Oil on Acute Inflammatory Response In Vitro and In Vivo

The aim of this study is to evaluate the phytochemical profile, oral acute toxicity, and the effect of ylang-ylang (Cananga odorata Hook. F. & Thomson) essential oil (YEO) on acute inflammation. YEO was analyzed by gas chromatography/mass spectrometry. For in vitro tests, YEO was assessed using cytotoxicity, neutrophil chemotaxis induced by N-formyl methionyl leucyl phenylalanine (fMLP), and phagocytic activity tests. YEO was orally administered in zymosan-induced peritonitis, carrageenan-induced leukocyte rolling, and adhesion events in the in situ microcirculation model and in carrageenan-induced paw edema models. YEO (2000 mg/kg) was also tested using an acute toxicity test in Swiss mice. YEO showed a predominance of benzyl acetate, linalool, benzyl benzoate, and methyl benzoate. YEO did not present in vitro cytotoxicity. YEO reduced the in vitro neutrophil chemotaxis induced by fMLP and reduced the phagocytic activity. The oral treatment with YEO reduced the leukocyte recruitment and nitric oxide production in the zymosan-induced peritonitis model, reduced rolling and adherent leukocyte number induced by carrageenan in the in situ microcirculation model, and reduced carrageenan-induced edema and mechanical hyperalgesia. YEO did not present signs of toxicity in the acute toxicity test. In conclusion, YEO affected the leukocyte activation, and presented antiedematogenic, anti-hyperalgesic, and anti-inflammatory properties.