Synthese von (R)-β, β-Carotin-2-ol und (2R, 2′R)-β, β-Carotin-2,2′-diol

Synthesis of (R)-β, β-Caroten-2-ol and (2R, 2′R)-β, β-Carotene-2,2′-diol Starting from geraniol, the two carotenoids (R)-β, β-caroten-2-ol ( 1 ) and (2R, 2′R)-β, β-carotene-2,2′-diol ( 3 ) were synthesized. The optically active cyclic building block was obtained by an acid-catalysed cyclisation of the epoxide (R)- 4 . The enantiomeric excess of the product was > 95 %.     

Organocatalytic synthesis of carbohydrates

The key role of carbohydrates in biological processes and their visible existence in our everyday life have stimulated the interest of leading research groups on the smart and simple synthesis of common and rare sugar molecules. Now, more than 120 years after Fischer's first synthesis of (D)-glucose (1890), we are witnessing important development in this field of total synthesis. Using modern methods of direct activation of carbonyl compounds chemists can prepare sugars in an elegant and efficient way similar to that of Nature. This tutorial review presents recent impressive progress in the area of de novo synthesis of carbohydrates by using organocatalytic direct aldol reaction as a key step.     

Influence of Pt and Pd on the catalytic activity of tungsten and molybdenum oxides in the deep oxidation of methane

It has been shown that the phases H_xMO₃ and MO_3−x (M = Mo, W), obtained by reduction of the oxides WO₃ and MoO₃ with hydrogen with supported Pt(Pd) (0.5 mass %), have higher catalytic activity in the deep oxidation of methane than the catalysts Pt/Al₂O₃ and Pd/Al₂O₃ with the same amount of supported metal. At temperatures above 700 K the activity of these catalysts decreases in consequence of the thermal decomposition of the phases H_xMO₃ and MO_3−x and they become similar in activity with Pt(Pd)/Al₂O₃. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 44, No. 2, pp. 126–129, March–April, 2008.     

Effect of Pt,Pd, and Cs<Superscript>+</Superscript> Additives on the Surface State and Catalytic Activity of WO<Subscript>3</Subscript> in Oxidation of Hydrogen

We have shown that additions of Pt(Pd) and Cs⁺ to WO₃ significantly increase its specific surface area and catalytic activity in H₂ oxidation. After reduction, the promoted specimens contain the phases WO₃, WO_2.9, H_xWO₃; and in the case of Cs⁺ additions, Cs_xWO₃. According to X-ray photoelectron spectroscopy (XPS), the Pt and Pd have an oxidation state close to 0, while tungsten has a +5 oxidation state. The W:O ratio indicates the content of oxygen vacancies in the surface layer. The data are explained taking into account hydrogen spillover from Pt(Pd) to the support.__________Translated from Teoreticheskaya i Eksperimental’naya Khimiya, Vol. 41, No. 2, pp. 126–129, March– April, 2005.     

Photochromism in CaS:Sm

CaSfREhasbeenknownforalongtimeasanexcellentphosphor'.ThephotochronismofSinScrystal'hasbeenfound.Yasuski'repoFtedthatSin' ionstrapedelectronsandchangedintoSin' intheinfraredstimulablephosphorCaScontainingEuandSinions,butphotochromismhasnotbeenobserved.Inthepresentletter,thephotochromismwasobservedinCaS:Sm.Activatedcarbon,calciumsulfate,sodiumsulfateandSin(NO,),weremixedandground,andthen,themixturewasputintoanalumiacrucibleandheatedat950"Cfor3--4hours.Thesampleswereanalyzedbyx-raydiffrac…     

Die Zetafunktion,die Klassenzahl und die Kronecker'sche Grenzformel eines beliebigen Kreiskörpers

Ohne Zusammenfassung     

Die Aufstellung der Klassen- und Ringklassen-Gleichungen der absolut invarianten Modulfunktion

Ohne Zusammenfassung     

Über die Gradteilerzerlegung in gewissen relativ-ikosaedrischen Zahlkörpern

Ohne Zusammenfassung     

多中心牛顿定理及其应用

本文将论文［１］推广到离散型的多中心泰勒定理。即多中心牛顿定理．从而得到相应的论文［２］．即高阶差分的插值公式，并给出其应用。     

Eilatin as a bridging ligand in ruthenium(II) complexes: synthesis,crystal structures,absorption spectra,and electrochemical properties

The potential of the heptacyclic aromatic alkaloid eilatin (1), that features two nonequivalent binding sites, to serve as a bridging ligand is reported. The nonequivalency of the binding sites allowed the selective synthesis of both mono- and dinuclear complexes. The mononuclear Ru(II) complexes [Ru(dmbpy)(2)(eilatin)](2+) (2) and [Ru(tmbpy)(2)(eilatin)](2+) (3) in which eilatin selectively binds "head-on" were synthesized and employed as building blocks in the synthesis of the dinuclear complexes [[Ru(dmbpy)(2)](2)(mu-eilatin)](4+) (4) and [[Ru(tmbpy)(2)](2)(mu-eilatin)](4+) (5). Complete structure elucidation of the complexes in solution was accomplished by 1D and 2D NMR techniques. The X-ray structures of the mononuclear complex 3 and of the two dinuclear complexes 4 and 5 were solved, and absorption spectra and electrochemical properties of the complexes were explored. Both dinuclear complexes formed as racemic mixtures in a 3:1 diastereoisomeric ratio, the major isomer being the heterochiral one (Delta Lambda/Lambda Delta) as revealed by crystallography. The mononuclear complexes feature an exceptionally low energy MLCT band around 600 nm that shifted to over 700 nm upon the binding of the second Ru(II) center. The mononuclear complexes show one reversible oxidation and several reversible reduction waves, the first two reductions being substantially anodically shifted in comparison with [Ru(bpy)(3)](2+), attributed to the reduction of eilatin, and consistent with its low lying pi* orbital. The dinuclear complexes follow the same reduction trend, exhibiting several reversible reduction waves, and two reversible well-resolved metal centered oxidations due to the nonequivalent binding sites and to a significant metal-metal interaction mediated by the bridging eilatin.