Biomimetic approach to communesin B (a.k.a. nomofungin)

The development of an approach to the alkaloid communesin B (2) is presented. The approach is based on considerations of a possible biosynthetic sequence involving an oxidative coupling of tryptamine with a derivative of the ergot alkaloid aurantioclavine. Structure revision is also suggested for the recently isolated microfilament disrupting alkaloid nomofungin.     

(-)-Hydroxylindestrenolide, a new sesquiterpenoid from a gorgonian coral Menella sp. (Plexauridae)

(-)-Hydroxylindestrenolide (1), an enantiomer of the known sesquiterpenoid, (+)-hydroxylindestrenolide (2), was isolated from a gorgonian coral identified as Menella sp. The structure, including the relative stereochemistry of 1 was established by spectroscopic methods and by comparison the spectral and physical data with those of 2. Sesquiterpenoid 1 exhibited marginal cytotoxicity toward HL-60 and K562 leukemia tumor cells, and displayed a weak inhibitory effect on superoxide anion generation at a concentration of 10 μg/ml by human neutrophils.     

Squarato-metal(II) complexes. 2. unusual bonding mode for a squarato-bridged trinuclear copper(II) complex

Herein, we report the structural characterization and magnetic properties of the unique squarato-bridged-tricopper(II) complex, [Cu3(pmap)3(micro1,2,3-C4O4)](ClO4)(4).2H 2O (1), based on the tripod tripyridylamine ligand bis[2-(2-pyridyl)ethyl]-(2-pyridyl)methylamine (pmap). Each of the three copper centers is penta-coordinated by four N atoms of a pmap ligand and one bridging O atom of the central squarato dianion. This complex is the first example of a non-polymeric X-ray structurally characterized trimeric transition metal complex with the three metal cations being bridged by a single squarato ligand in a micro1,2,3 coordination mode. The magnetic properties of the complex were measured over the temperature range 2-300 K. The complex exhibits moderate bulk antiferromagnetic interaction. The three magnetic exchange pathways have J values of -27.8, -20.8, and -31.9 cm(-1). The DFT calculations corroborate the relatively strong antiferromagnetic couplings obtained from the fitting of the experimental magnetic susceptibility data and allow an assignment of the fitted J values. Several geometrical parameters have been analyzed using theoretical calculations to establish magnetostructural correlations for complex 1.     

Dalzin (diallyl-dithio-carbamido hydrazine) as a micro-reagent. I

Summary Methods for the gravimetric micro-determination of copper, zinc and nickel separately and separations of Cu-Zn and Cu-Ni, using diallyl dithiocarbamido-hydrazine as reagent, are described. Separation is achieved by pH-control.

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Zusammenfassung Verfahren zur getrennten, gravimetrischen Mikrobestimmung von Kupfer, Zink und Nickel sowie zur Trennung von Kupfer und Zink bzw. Kupfer und Nickel mit Hilfe von Diallyldithiocarbamidohydrazin als Fällungsreagens werden beschrieben. Die Trennungen lassen sich durch Einhaltung bestimmter PH-Werte erzielen.

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Résumé On décrit des méthodes de microdosage gravimétrique du cuivre, du zinc et du nickel séparément et des méthodes de séparation de Cu-Zn et de Cu-Ni, en utilisant comme réactif la diallyl dithiocarbamido hydrazine. La séparation s'effectue à PH donné.

     

Structure of 4-anilinopiperidine analgesics. II. The structure of 1(e)-(2-phenethyl)-2(e),5(a)-dimethyl-4(e)-(N-propyionyl-anilino)piperidine

Institute of Fine Organic Chemistry, Academy of Sciences of the Armenian SSR. Translated from Zhurnal Strukturnoi Khimii, Vol. 30, No. 5, pp. 185–189, September–October, 1989.     

Degradation of a poly(ester urethane) elastomer. II. Kinetic modeling of the hydrolysis of a poly(butylene adipate)

In preparation for studying the kinetics of the hydrolysis of Estane® 5703, published hydrolysis data for a similar poly(butylene adipate) (herein called 63 PBA) have been modeled. Poly(ester urethanes) are known to degrade by acid‐catalyzed hydrolysis of the ester links, and the data on 63 PBA show that this degradation is reversible at low relative humidities (RHs). Previous work with these data was unable to fit them with concentration‐independent rate coefficients. It is shown herein that, with the water‐concentration model of the preceding article and the A_AC2 mechanism of reversible hydrolysis/esterification, the experimental kinetic data that vary across temperature, RH, and starting molecular weight can be fit with a single set of concentration‐independent rate coefficients. © 2001 John Wiley & Sons, Inc. J Polym Sci Part B: Polym Phys 40: 192–200, 2002     

Ni(III) vs. Ni(II)-thiyl radical: charge-delocalisation in a binuclear Ni(III)Ni(II)-dithiolate complex

Multi-frequency EPR spectroscopy on 61Ni-labelled samples of [Ni2(L)]3+ confirms extensive charge-delocalisation between the Ni(III) centre and thiolate donors in the Ni(II)Ni(III) complex.     

Aurophilicity as a cofactor in crystal engineering. Dicyanoaurate(I) anion as a building block in a novel Co(II)-Au(I) bimetallic assembly

A 2D grid-shaped cyanide-bridged Co(II)-Au(I) bimetallic coordination polymer, [Co(DMF)2(Au(CN)2)2], has been prepared from the [Au(CN)2]- building block; sheets associate pair-wise by aurophilic interactions and the compound exhibits zeolite-like properties.     

A remarkable accidental degeneracy in the1H-n.m.r. Spectrum of a (cyanoethene)platinum (II) complex

Summary In the¹H-n.m.r. spectra of (acetylacetonato)chloro-(²-cyanoetheiie)platinum(II), the three protons of the ligand appear to be equivalent.¹³C-n.m.r., i.r. and further¹H-n.m.r. studies indicate that the metal-ligand bonding is of orthodox -olefin type (as formulated in the name of the compound above). The two 2-hydrogens are made equivalent by fluxion, but there is an accidental degeneracy with 1-hydrogen atom.     

Chemistry of Indolopyridines with a Bridgehead Heteroatom. (Review)

Published data on the synthesis and reactions of indolopyridines with one bridgehead heteroatom and their benzannelated derivatives are reviewed for the first time.     

Absorbance(a.Intensity(a.u.)

正the XAS is a bulk characterization rather than a sur‐face‐sensitive tool. The penetration depth is a function of X‐ray attenuation coefficient of the material at the relevant incident X‐ray energy, it is about 5–10 mm when measuring the LIII edge of Ce at around 6 keV [51,52]. Recently, Schmitt et al. [20] re‐viewed the XAS study on the defect structure and chemistry in ceria and its solution. Herein, we just survey this tool used for characterization of reduced ceria powder as a catalyst.In a partially reduced ceria, the XANES part of X‐ray absorp‐tion spectrum for the Ce LIII edge can be used to quantify Ce3+and Ce4+ valence states to study the effect of particle size, do‐