Synthesen von Carotinen mit ψ-Endgruppen und (Z)-Konfiguration an terminalen konjugierten Doppelbindungen

Syntheses of Carotenes with ψ-End Groups and (Z)-Configuration at Terminal Conjugated Double Bonds Five carotenes bearing (5Z)-ψ-end groups were synthesized and carefully characterized: (5Z)-lycopene ( 6 ), (5Z5′Z)-lycopene ( 7 ), (5′Z)-neurosporene ( 8 ), (5′Z)-β,ψ-carotene ( 12 ), and (5′Z)-ε,ψ-carotene ( 14 ).     

NaGaS2: An Elusive Layered Compound with Dynamic Water Absorption and Wide‐Ranging Ion‐Exchange Properties

Most ternary sulfides belonging to the MGaS₂ structure‐type have been known for many years and are well‐characterized. Surprisingly, there have been no reports of the NaGaS₂ composition, which contains Na, a monovalent cation slightly larger in size than Li, found in LiGaS₂, a compound known for its non‐linear optical properties. Now it is demonstrated for the first time that the unique reversible water absorption in NaGaS₂ has resulted in its absence from previous reports owing to difficulties encountered when characterizing this compound by SC XRD. The layered structure of this compound coupled with uniquely easy migration of water molecules between the layers allows for ion exchange with 3d and 5f metal cations. Some cations, for example, Ni²⁺, facilitate exfoliation of the layers, providing a facile synthetic route to a new class of 2D chalcogenide materials and furthermore demonstrating that NaGaS₂ can readily uptake uranyl species from aqueous solutions.     

Light Lanthanide Metallocenium Cations Exhibiting Weak Equatorial Anion Interactions

As the dysprosocenium complex [Dy(Cp^ttt)₂][B(C₆F₅)₄] (Cp^ttt=C₅H₂tBu₃-1,2,4, 1-Dy ) exhibits magnetic hysteresis at 60 K, similar lanthanide (Ln) complexes have been targeted to provide insights into this remarkable property. We recently reported homologous [Ln(Cp^ttt)₂][B(C₆F₅)₄] ( 1-Ln ) for all the heavier Ln from Gd–Lu; herein, we extend this motif to the early Ln. We find, for the largest Ln^III cations, that contact ion pairs [Ln(Cp^ttt)₂{(C₆F₅-κ¹-F)B(C₆F₅)₃}] ( 1-Ln ; La–Nd) are isolated from reactions of parent [Ln(Cp^ttt)₂(Cl)] ( 2-Ln ) with [H(SiEt₃)₂][B(C₆F₅)₄], where the anion binds weakly to the equatorial sites of [Ln(Cp^ttt)₂]⁺ through a single fluorine atom in the solid state. For smaller Sm^III, [Sm(Cp^ttt)₂][B(C₆F₅)₄] ( 1-Sm ) is isolated, which like heavier 1-Ln does not exhibit equatorial anion interactions, but the Eu^III analogue 1-Eu could not be synthesised due to the facile reduction of Eu^III precursors to Eu^II products. Thus with the exception of Eu and radioactive Pm this work constitutes a structurally similar family of Ln metallocenium complexes, over 50 years after the [M(Cp)₂]⁺ series was isolated for the 3d metals.     

Synthesis of a Ferrolite: A Zeolitic All‐Iron Framework

Crystals of the first sodalite‐type zeolite containing an all‐iron framework, a ferrolite, Ba₈(Fe₁₂O₂₄)Na_y(OH)₆?x H₂O, were synthesized using the hydroflux method in nearly quantitative yield. Ba₈(Fe₁₂O₂₄)Na_y(OH)₆?x H₂O crystallizes in the cubic space group with a=10.0476(1) Å. Slightly distorted FeO₄ tetrahedra are linked to form Fe₄O₄ and Fe₆O₆ rings, which in turn yield channels and internal cavities that are characteristic of the sodalite structure. Barium, sodium, and hydroxide ions and water molecules are found in the channels and provide charge balance. Magnetic measurements indicate that the ferrolite exhibits magnetic order up to at least 700 K, with the field‐cooled and zero‐field‐cooled curves diverging. Analysis of the ⁵⁷Fe Mössbauer spectra revealed two spectral components that have equal spectral areas, indicating the presence of two subsets of iron centers in the structure. Dehydrated versions of the ferrolite were also prepared by heating the sample.     

Detection of vanadium by means of spot tests

Zusammenfassung Zwei neue Tüpfelreaktionen für Vanadinum werden beschrieben.-Benzoinoxim gibt einen gelben Niederschlag in schwefelsauren Vanadatlösungen, der auf der Tüpfelplatte den Nachweis von 1 Vanadinum ermöglicht. Der Nachweis der durch Zusatz von Vanadylsalz zu Ferrichlorid gebildeten Ferroionen kann auf der Tüpfelplatte mit,-Dipyridyl oder mit o-Phenanthrolin durchgeführt werden. In beiden Fällen wird eine Erfassungsgrenze von 0,1 Vanadinum erreicht und nur wenige Ionen stören den Nachweis.Der Nachweis der Ferroionen mit Hilfe von Dimethylglyoxim (1 V) und auch der Vanadatnachweis durch die durch Wolframat erzeugte Gelbfärbung (0,3 V) wurden in bezug auf Störungen durch gleichzeitig anwesende Stoffe gründlich untersucht. Die Dimethylglyoximprobe wird durch Zusatz von Phosphat wesentlich verbessert.

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Résumé Deux nouvelles réactions à la touche sont décrites pour le vanadium. L'-benzoinoxime donne un précipité jaune en solution sulfurique de vanadate qui, sur la plaquette à touche, rend possible la recherche de 1 vanadium. La recherche des ions ferreux formés par addition d'un sel de vanadyle au chlorure ferrique peut être conduite sur plaquette avec l', -dipyridyle ou l'o-phénanthroline. Dans les deux cas, on atteint une limite de sensibilité de 0,1 de vanadium et quelques ions seulement gênent la recherche.Celle des ions ferreux au moyen de la diméthylglyoxime (1 de vanadium) et aussi la recherche des vanadates par la coloration jaune donnée avec un tungstate (0,3 de vanadium) furent expérimentées d'une manière approfondie en fonction des interférences par les substances simultanément présentes. L'essai à la diméthylglyoxime est essentiellement amélioré par addition de phosphate.

     

A photoactivated diazopyruvoyl cross-linking agent for bonding tissue containing type-I collagen

On the basis of the earlier examples of diazopyruvoyl (DAP) groups reported by Lawton for covalent binding and cross-linking of proteins and oligopeptides and our recent demonstration that a coumaryl diazopyruvamide was used to label Type-I collagen, we have extended our investigations to the synthesis and cross-linking capabilities of a bis-DAP polyethylene glycol to cross-link Type-I collagen. The new photoactivated cross-linking agent, N,N'-bis(3-diazopyruvoyl)-2,2'-(ethylenedioxy)bis(ethylamine) (DPD, 2), has been designed and synthesized specifically to "weld" collagenous tissues by cross-linking Type-I collagen. A working model for the photochemical welding studies of collagenous tissues was developed using gelatin strips (gel strips) composed of denatured Type-I collagen. Gel strips are transparent to near-UV and visible light, uniform in thickness, and have reproducible composition. Furthermore, the availability of nucleophilic amine sites in gel strips was demonstrated by reaction with o-phthalaldehyde, producing a fluorescent derivative of the protein. Gel strips were coated with a solution of DPD in chloroform 7 irradiated at 320-390 nm, and the resulting bonded gel strips were tested for the strength of the weld. The welds were generally brittle and had average tensile strengths that exceeded 100 N/cm2. Welds were not formed in the absence of light or DPD. Scanning electron microscopy studies revealed a pockmarked surface from severed welds. Welds of rabbit Achilles tendon were also obtained using the tethered diazopyruvamide. These welds were much weaker, having an average tensile strength of 11.95 N/cm2 for DPD-2,2'-ethylenedioxy(bis)ethylamine comonomers in the cross-linking reaction. In both studies the welds obtained by this method were significantly stronger than the controls.     

Horminon,Taxochinon und weitere Royleanone aus 2 abessinischen Plectranthus-Spezies (Labiatae)

Horminone, taxoquinone and other royleanones, obtained from two Abyssinian Plectranthus species (Labiatae). From the coloured glands on the leaves of two botanically unclassified Plectranthus sp. from Abyssinia, a series of royleanones has been isolated, namely royleanone ( 1 ) and 6,7-dehydroroyleanone ( 2 ) from one species, and 6,7-dehydroroyleanone, horminone ( 3 ), taxoquinone ( 4 ), 6β, 7α-dihydroxyroyleanone ( 5 ), 7α-acetoxy-6β-hydroxyroyleanone ( 6 ) and 7-oxoroyleanone ( 7 ) respectively, from the other.     

The Crystal and Molecular Structures of Two Acid-Catalysed Rearrangement Products of Taxochinon

The structures of two acid catalysed rearrangement products of taxochinone ( 1 ) have been determined by X-ray analysis. One of the products turned out to be a 20 (10→9) abeo-abietane ( 2 ), the other an optically inactive phenalenone ( 3 ). Crystals of the former compound, C₂₀H₂₆O₃, belong to space group P2₁2₁2₁ with four molecules per cell and the structure was refined with 879 significant reflexions to R = 0.032. Crystals of the latter compound, C₂₀H₂₂O₂, belong to space group P2₁/c with 12 molecules per cell and the structure was refined with 1823 significant reflexions to R = 0.058.     

Utilization of the p-nitrobenzyloxycarbonyl (pNZ) amine protecting group and pentafluorophenyl (Pfp) esters for the solid phase synthesis of spiroligomers

Spiroligomers are a class of peptidomimetics that connect interchangeable, stereochemically pure, cyclic monomers through pairs of amide bonds to form diketopiperazines between the monomers. This enables them to adopt predictable and programmable structure due to the rigidity of the final molecule. We present a new method for the solid phase synthesis of highly functionalized spiroligomers that incorporates the use of the p-nitrobenzyloxycarbonyl (pNZ) as a temporary amine protecting group and the pentafluorophenyl ester for monomer activation. This new method allows for the synthesis of spiroligomers with higher purity and increased yields when compared to previous methods. This improved method of synthesis of functionalized spiroligomers will facilitate the development of applications as catalysts, therapeutics and membrane channels.     

[UIII{N(SiMe2tBu)2}3]: A Structurally Authenticated Trigonal Planar Actinide Complex

We report the synthesis and characterization of the uranium(III) triamide complex [U^III(N**)₃] [ 1 , N**=N(SiMe₂tBu)₂^?]. Surprisingly, complex 1 exhibits a trigonal planar geometry in the solid state, which is unprecedented for three‐coordinate actinide complexes that have exclusively adopted trigonal pyramidal geometries to date. The characterization data for [U^III(N**)₃] were compared with the prototypical trigonal pyramidal uranium(III) triamide complex [U^III(N“)₃] (N”=N(SiMe₃)₂^?), and taken together with theoretical calculations it was concluded that pyramidalization results in net stabilization for [U^III(N“)₃], but this can be overcome with very sterically demanding ligands, such as N**. The planarity of 1 leads to favorable magnetic dynamics, which may be considered in the future design of U^III single‐molecule magnets.