A new cine-substitution of alkenyl sulfones with aryltitanium reagents catalyzed by rhodium: mechanistic studies and catalytic asymmetric synthesis of allylarenes

The reaction of alkenyl sulfones with aryltitanium triisopropoxide (ArTi(OPr-i )3) in the presence of 3 mol % of [Rh(OH)((S)-binap)]2 in THF at 40 degrees C gave high yield of cine-substitution products. The catalytic cycle was established by deuterium-labeling studies, and it was applied to catalytic asymmetric synthesis of allylarenes which proceeds with over 99% enantioselectivity.     

Poisoning effect of carbon monoxide on the desorption process of hydrogen from palladium

The desorption of H₂ from clean and CO-poisoned Pd wires was studied by a temperature programmed desorption technique. Poisoning effect of CO on H₂ desorption process can be accounted for in terms of blockage of the surface sites for the recombination of H atoms.

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H₂ , CO, - . CO H₂ , , , .

     

Thermo-oxidative degradation of polyvinyl formal and measurement of thermally stimulated current

Changes in the chemical structure of polyvinyl formal with thermo-oxidation have been correlated with a thermally stimulated current in the material. Thermo-oxidation was initiated by cleavage of the formal ring and considerably accelerated by the formation of unsaturated bonds (> CO, CC). Two main peaks of thermally stimulated current were observed at 215 and 370 K in the oxidized polyvinyl formal. It became clear that the relaxation system, which corresponds to the peak at 370 K, was caused by cleavage of the formal ring. The peak at 215 K was attributed to carriers trapped by the unsaturated bonds.     

Determination of tryptophan and its metabolites in human plasma and serum by high-performance liquid chromatography with automated sample clean-up system

An automated high-performance liquid chromatographic method that incorporates direct injection of biological samples followed by chromatographic sample clean-up in a precolumn is described for the determination of tryptophan and its metabolites in human plasma and serum. The system gave reproducible data with a coefficient of variation of less than 3% with a sample size of 100 microliters of human plasma. The major tryptophan metabolites found in 100 microliters of human plasma were kynurenine, indolelactic acid, indoleacetic acid, indolepropionic acid, serotonin and 5-hydroxyindoleacetic acid. The level of tryptophan and kynurenine in individuals was constant in comparison with other metabolites. Analysis of samples from normal controls, diabetics, gravida and their foetuses showed a tendency for tryptophan metabolites to be low in maternal plasma.     

Binary and ternary complexes involving manganese(II), 2,2’-bipyridine and halide or thiocyanate ions inN,N-dimethylformamide

Ternary complexation involving the manganese(II) ion, 2,2’-bipyridine (bipy), and halide (chloride, bromide) or pseudohalide (thiocyanate) ions has been studied by precise titration calorimetry inN,N -dimethylformamide (DMF) at 298K. All the titration curves are explained well in terms of formation of mononuclear complexes of the type [MnX_m(bipy)_n](^2-m) + (X = CI, Br or SCN), and the formation of [MnCl(bipy)]⁺, [MnCl₂(bipy)], [MnCl(bipy)₂]⁺ and [MnCl₂(bipy)₂] has been established in the chloride system, [MnBr(bipy)]⁺, [MnBr₂(bipy)], [MnBr(bipy)₂]⁺ in the bromide system, and [Mn(NCS)(bipy)]⁺, [Mn(NCS)₂(bipy)], [Mn(NCS)₃(bipy)]^-, [Mn(NCS)(bipy)₂]⁺, and [Mn(NCS)₂(bipy)₂] in the thiocyanate system. The data were analyzed on the basis of the thermodynamic parameters for the binary Mn^lIbipy and Mn^II-X (X = Cl, Br and SCN) systems, the latter being determined in previous work. The formation constants, reaction enthalpies, and entropies of the ternary complexes were extracted. The thermodynamic parameters thus obtained are discussed in comparison with those of the corresponding systems of other transition metal(II) ions.     

Regulated interaction between polypeptide chain elongation factor-1 complex with the 26S proteasome during <Emphasis Type="Italic">Xenopus</Emphasis> oocyte maturation

Background  

During Xenopusoocyte maturation, the amount of a 48 kDa protein detected in the 26S proteasome fraction (p48) decreased markedly during oocyte maturation to the low levels seen in unfertilized eggs. The results indicate that the interaction of at least one protein with the 26S proteasome changes during oocyte maturation and early development. An alteration in proteasome function may be important for the regulation of developmental events, such as the rapid cell cycle, in the early embryo. In this study, we identified p48.     

5-Amino-4-sulfanylphthalhydrazide as a chemiluminescence derivatization reagent for aromatic aldehydes in liquid chromatography

5-Amino-4-sulfanylphthalhydrazide (ASPH) was synthesized as a chemiluminescence derivatization reagent for aromatic aldehydes in liquid chromatography (LC). Benzaldehyde, 4-tolualdehyde, 4-chlorobenzaldehyde, 4-formylbenzoic acid, 4-hydroxybenzaldehyde and vanillin were used as model compounds to optimize the derivatization conditions. This reagent, ASPH, reacts selectively with aromatic aldehydes in the presence of sodium sulfite and disodium hydrogenphoshite in acidic medium at 100 degrees C to give the corresponding highly chemiluminescent 2-arylbenzothiazole derivatives. The resulting derivatives generated intense chemiluminescence by reaction with hydrogen peroxide and potassium hexacyanoferrate(III) in alkaline solution. The ASPH derivatives of aromatic aldehydes were separated by reversed-phase liquid chromatography with isocratic elution, and detected chemiluminometrically after mixing with oxidizing agents. The detection limits (signal-to-noise ratio = 3) for aromatic aldehydes are in the range 0.2-4.0 fmol for a 20-microl injection volume. Currently, the method is not effective for aliphatic aldehydes because of interfering LC peaks.     

Biodegradation of Eu(III)-citrate complexes by Pseudomonas fluorescens

Summary We have investigated the structure of Eu(III)-citrate complexes in aqueous solution and their degradability by Pseudomonas fluorescens. Analysis of 1:1, 1:2, and 1:5 Eu(III):citrate solutions at pH 7 by electrospray ionization mass spectrometry (ESI-MS) showed that the 2:2 Eu(III)-citrate complex is the predominant complex species at a low citrate/Eu(III) ratio, while at a high ratio, a 1:2 Eu(III)-citrate complex is formed preferably. Studies on the biodegradation of Eu(III)-citrate complex by P. fluorescens have shown that a 2:2 Eu(III)-citrate complex is resistent to degradation while a 1:2 complex transforms to a 2:2 complex with the degradation of excess citric acid.     

Daphnicyclidins J and K, unique polycyclic alkaloids from Daphniphyllum humile

Two Daphniphyllum alkaloids with unprecedented polycyclic skeletons, daphnicyclidins J (1) and K (2), have been isolated from the stems of Daphniphyllum humile, and the structures and relative stereochemistry were elucidated on the basis of spectroscopic data. The absolute stereochemistry of 1 was established by chemical correlation with a known-related alkaloid, daphnicyclidin D (3), through a modified Polonovski reaction.