Selective phosphitylation of the primary hydroxyl group in unprotected carbohydrates and nucleosides

[reaction: see text] Carbohydrates and nucleosides containing a phosphate at the less-hindered primary hydroxyl group are often prepared using a protection/deprotection strategy. Herein we report that the phosphoramidite method can be used to selectively incorporate phosphorus at the primary hydroxyl group of O-unprotected carbohydrates and nucleosides; in situ oxidation of the resulting phosphite triester yields the phosphate triester.     

The effect of the ionic environment during precipitation on the structure of hydrous titanium dioxide

Summary Samples of titanium dioxide have been prepared by hydrolysis of alkyl titanates in sulphuric acid solution of differing concentrations. The sulphate content of the resulting precipitate has been determined, and the specific surface and pore volume investigated by sorption methods. The results show that the surface properties of the oxide are determined by the conditions of hydrolysis and subsequent precipitation. It has been found possible to reproduce within a few per cents the surface area and the pore volume of the samples. A model has been put forward to account for the observed phenomena, and an equation relating the specific surfaceS of the precipitate with the activityn of sulphate ions in the hydrolysing medium has been deduced:S=S ₀−k√n whereS ₀ andk are constants.

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Zusammenfassung Proben von Titandioxyd wurden durch Hydrolyse von Alkylanaten in Schwefels?urel?sung verschiedener Konzentration pr?pariert. Die Sulfatgehalte des resultierenden Niederschlags wurden bestimmt und die spezifische Oberfl?che und das Porenvolumen durch Sorptionsmethoden untersucht. Die Ergebnisse zeigen, da\ die Oberfl?cheneigenschaften des Oxydes durch die Bedingungen der Hydrolyse und die anschlie\ende F?llung bestimmt werden. Es war m?glich, die Oberfl?che und das Porenvolumen der Proben innerhalb weniger Prozente zu reproduzieren. Es wurde ein Modell entworfen, die beobachteten Ph?nomene zu erkl?ren, und eine Gleichung abgeleitet, die die spezifische Oberfl?cheS des Pr?zipitates mit der Aktivit?tn der Sulfationen im hydrolysierenden Medium in Beziehung setzt:S=S ₀−k√n;S ₀ undk=const.

     

Multiple Diastereomers of [M n+(α m -P2W17O61)2](20−n)− (M=UIV, ThIV, CeIII; m=1, 2). Syn- and Anti-Conformations of the Polytungstate Ligands in α1α1, α1α2, and α2α2 Complexes

Several examples of the complexes, [M(P₂W₁₇O₆₁)₂] ^n? (M=U^IV, Th^IV, Ce^III), containing both α ₁ (C ₁) and α ₂ (C _s ) isomers of the tungstophosphate ligands, have been synthesized and characterized by X-ray crystallography and ³¹P NMR spectroscopy. In every case the heteroatom M has the anticipated square antiprism coordination. When both ligands are α ₂ (the U^IV and Ce^III complexes) the solid state structure adopts a syn-conformation of the ligands, as had been previously demonstrated for M=Ce^IV and Lu^III; in solution a single set of P-NMR lines is observed, consistent with a single unique structure or rapid interconversion of syn- and anti-forms. When one or both ligands are α ₁ (Uα ₁ α ₁, Uα ₁ α ₂, Thα ₁ α ₁, Ceα ₁ α ₂) multiline P-NMR spectra reveal the presence of two major diastereomers in solution, presumably the syn- and anti-forms. In the solid state, crystals of ammonium or potassium salts of the U and Ce complexes contain anti-conformers, while the Th complex proves to be syn. Variable temperature (～25–～60°C) P-NMR spectroscopy of solutions of the Uα ₁ α ₁ complex reveals the onset of syn-anti interconversion together with the irreversible formation of minor amounts of other diastereomers generated by dissociation and scrambling of the enantiomers of the polytungstate ligands.     

Gel encapsulated microorganisms: Saccharomyces cerevisiae—Silica gel biocomposites

“Is it possible to incorporate a living microorganism as a second phase in a man-made, engineered material?” In this preliminary study, Saccharomyces cerevisiae has been encapsulated in a transparent matrix of porous, gel-derived silica. After gelation, aging, and prolonged storage at 5°C, S. cerevisiae bioactivity could be triggered. Bioactivity was followed by evolution of alcohol within the S. cerevisiae as a function of time during incubation by the molecular probe molecule pyranine using fluoresence spectrophotometry. Described also are some of the potential applications of this new class of biocomposite material incorporating a “living” second phase.     

Rhenium fac tricarbonyl bisimine complexes: biologically useful fluorochromes for cell imaging applications

A series of lipophilic and hydrophilic fac tricarbonyl rhenium bisimine complexes have been prepared, their membrane-permeabilities explored in liposomes and their potential for application in fluorescence microscopy cell imaging demonstrated in the first application of MLCT-fluorescent rhenium complexes in cell imaging.     

Removal of sodium and potassium adducts using a matrix additive during matrix-associated laser desorption/ionization time-of-flight mass spectrometric analysis of peptides

Monovalent cations often associate with peptides and proteins under mass spectrometry (MS) conditions, resulting in a discernable, but often misleading, adduct cluster pattern. These adduct cluster peaks reduce the signal intensity of specific peptide species by splitting the ion population into multiple mass peaks, suppressing the ionization of neighboring low-abundance peaks, and interfering with identification of post-translational modifications. Further, monovalent contaminants tend to form a distribution of matrix cluster peaks in matrix-associated laser desorption/ionization time-of-flight (MALDI-TOF) spectra causing interference and suppression in the mass range below 1400 Da. The most common method for reduction or elimination of adduct clusters is solid-phase extraction via a pipette tip or spin column, which often leads to loss of low-abundance peptide components. In this study we describe the use of a commercially available surfactant blend that markedly reduces the adduction of monovalent cations during peptide analysis by MALDI-TOFMS.     

Bis(dimethyl sulfoxide‐S)tetrakis(μ‐p‐hydroxybenzoato‐O:O′)dirhodium(II)–tetrakis(μ‐butyrato‐O:O′)bis(dimethyl sulfoxide‐S)dirhodium(II) cocrystal ethanol disolvate

The title structure, [Rh₂(C₇H₅O₃)₄(C₂H₆OS)₂]·[Rh₂(C₄H₇­O₂)₄(C₂H₆OS)₂]·2C₂H₆O, contains two discrete neutral Rh–Rh dimers cocrystallized as the ethanol disolvate. Each dimer is situated on an inversion center. The butyrate chain displays disorder in one C‐atom position. In each dimer, the di­methyl sulfoxide ligand (dmso) is bound via S, as expected. The ethanol is a hydrogen‐bond acceptor for one p‐hydroxy­benzoate hydroxyl group and acts as a hydrogen‐bond donor to the dmso O atom of a neighboring p‐hydroxy­benzoate dirhodium complex. A third hydrogen bond is formed from the other p‐hydroxy­benzoate hydroxyl group to the dmso O atom of a butyrate–dirhodium complex.     

Ion Dynamics in a Mixed‐Cation Alkoxy‐Ammonium Ionic Liquid Electrolyte for Sodium Device Applications

The ion dynamics in a novel sodium‐containing room‐temperature ionic liquid (IL) consisting of an ether‐functionalised quaternary ammonium cation and bis(trifluoromethylsulfonyl)amide [NTf₂] anion with various concentrations of Na[NTf₂] have been characterised using differential scanning calorimetry, impedance spectroscopy, diffusometry and NMR relaxation measurements. The IL studied has been specifically designed to dissolve a relatively large concentration of Na[NTf₂] salt (over 2 mol kg^?1) as this has been shown to improve ion transport and conductivity. Consistent with other studies, the measured ionic conductivity and diffusion coefficients show that the overall ionic mobility decreases with decreasing temperature and increasing salt content. NMR relaxation measurements provide evidence for correlated dynamics between the ether‐functionalised ammonium and Na cations, possibly with the latter species acting as cross‐links between multiple ammonium cations. Finally, preliminary cyclic voltammetry experiments show that this IL can undergo stable electrochemical cycling and could therefore be potentially useful as an electrolyte in a Na‐based device.