Eine quantitative Bestimmung des Cumarins und der Melilots?ure im Melilotus officinalis

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Interaction of triols with formaldehyde and acetone: Experimental and theoretical study

Experimental and theoretical aspects of the condensation of glycerol and its homologs (1,2,3- and 1,2,4-butanetriols) with formaldehyde and acetone are studied under conditions of acid catalysis. Calculation of the thermodynamic parameters of the resulting products by the composite method CBS-QB3 shows that the six-membered heterocycles, the products of the interaction of triols with formaldehyde, are thermodynamically more stable than the five-membered acetals, while the reaction of the same triols with acetone is preferable for the formation of the five-membered acetals. This is due to the fact that the regioselectivity of the studied reactions is determined by the structural features and reactivity of the carbocations formed in a condensed medium during the course of the reaction. According to the theoretical data obtained experimentally, during the condensation of glycerol and 1,2,4-butanetriol with formaldehyde in the most stable form of the six-membered cyclic carbocation, intramolecular hydrogen bonding and anomeric stabilization due to the axially oriented hydroxyl group take place. As a result, cation 1b–1 is 1.2–1.6 kJ/mol more stable than its five-membered isomers ( 1a–1 and 1b–2 ). It leads to the predominant formation of 1,3-dioxane ( 3b ). However, upon condensation of butanetriol-1,2,3 with formaldehyde, the intermediate cation 4a–1 turns out to be significantly more stable than the other isomers due to the strong intramolecular hydrogen bond in the six-membered ring with the participation of the hydroxyl group of the substituent and the hydroxyl group of the cationic center, leading to the predominant formation of the dioxolane 6a .     

Diimidazo[4,5-b:4′,5′-e]pyridine: synthesis and nucleophilic aromatic substitution reaction

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Interwoven hydrogen‐bonded network assembly and supramolecular isomerism of meso‐5,10,15,20‐tetrakis(4‐carboxyphenyl)porphyrin as its dimethylformamide solvate

Molecules of the title compound, porphyrin‐5⁴,10⁴,15⁴,20⁴‐tetrabenzoic acid, C₄₈H₃₀N₄O₈, lie on sites of 2/m symmetry in the space group Cmca. The crystals consist of doubly interwoven two‐dimensional supramolecular arrays sustained by multiple (COOH)₂ cyclic dimeric hydrogen bonds, each molecule of the porphyrintetrabenzoic acid coordinating to four neighbouring species. This structure, which encloses substantial spaces occupied by disordered dimethylformamide solvent molecules, represents yet another supramolecular isomer of this porphyrin.     

Solvability of Semilinear Hemivariational Inequalities at Resonance Using Generalized Landesman–Lazer Conditions

In this paper we examine semilinear hemivariational inequalities at resonance at any eigenvalue of the negative Laplacian with Dirichlet boundary condition. Our approach is variational based on the Nonsmooth Critical Point Theory and it uses a generalized Landesman–Lazer condition. We prove two existence theorems using two different forms of the generalized Landesman–Lazer condition. In the last section we show that our Landesman-Lazer condition is more general than the ones existing in the literature.     

Chemo-Enzymatic Epoxidation of <Emphasis Type="Italic">Lallemantia Iberica</Emphasis>Seed Oil: Process Development and Economic-Ecological Evaluation

The chemo-enzymatic epoxidation of Lallemantia iberica seed oil (LISO), a novel plant oil characterized by its exceptional high content of alpha-linolenic acid (>?60%), was developed using an immobilized lipase from Pseudozyma antarctica and hydrogen peroxide as oxidant. A statistical approach was used to study the effect of enzyme amount, temperature, time, and solvent amount on the oxirane oxygen content obtained during epoxidation. An oxirane oxygen content of 8.6 ± 0.2% corresponding to a yield of 82% was obtained under optimized conditions that were identified to be at an enzyme load of 8.2 g/mol of double bonds, a solvent amount of 56.4 wt.%, a temperature of 33 °C, and an incubation time of 17 h. In addition, the experimental investigation was combined with a techno-economic and ecological assessment gaining detailed information regarding cost structure and environmental impact for the chemo-enzymatic epoxidation of the novel plant oil.     

Highly anisotropic orbitally dependent superexchange in cyano-bridged clusters containing Mn(III) and Mn(II) ions.

We study the orbitally dependent magnetic exchange in cyanide-based clusters as a source of the barrier for reversal magnetization. We consider the Mn(III)-CN-Mn(II) dimer and linear Mn(II)-NC-Mn(III)-CN-Mn(II) trimer containing octahedrally coordinated Mn(III) and Mn(II) ions with special emphasis on the magnetic manifestations of the orbital degeneracy of the Mn(III) ion. The kinetic exchange mechanism involves the electron transfer from the single occupied t(2) orbitals of the Mn(II) ion [6A1(t2(3)e2) ground state] to the singly occupied t(2) orbitals of the Mn(III) ion [3T1(t2(4)) ground state] resulting in the charge-transfer 5T2(t2(2)e2)Mn(III) - 2T2(t2(5))Mn(II) state of the pair. The deduced effective exchange Hamiltonian that takes into account orbital degeneracy leads to an essentially non-Heisenberg energy pattern. The energy levels are shown to be dependent on both spin and orbital quantum numbers, thus providing direct information about the magnetic anisotropy of the system. Along with the magnetic exchange, the model includes an axial component of the crystal field and spin-orbit coupling operating within the ground 3T1(t2(4)) cubic term of the Mn(III) ion. We have shown that under certain conditions both named interactions lead to the occurrence of the barrier for the reversal of magnetization, which significantly increases when passing from the dimer to the trimer. This provides a possible way for raising the magnetic barrier in the family of cyano-bridged manganese clusters.     

Study of alkaloids of the Siberian and Altai flora. 10. Synthesis of N(20)-deethyllappaconitine derivatives

Efficient procedures were developed for N-deethylation of lappaconitine to give N(20)-deethyllappaconitine. Alkyl derivatives of N(20)-deethyllappaconitine, including labeled lappaconitine, and N(20)-acetoxy-N(20)-deethyllappaconitine were prepared for the first time. The assignments of the signals for the carbon atoms in the ¹³C NMR spectra of lappaconitine and related lappaconine were refined using ¹³C—¹³C 2D INADEQUATE and 2D ¹³C—¹H correlation experiments.     

Hydrogen‐bonded supra­molecular arrays of aqua­[20‐(4‐carboxy­phen­yl)‐5,10,15‐triphenyl­porphyrinato]zinc(II) in crystals of its nitro­benzene disolvate

Crystals of the title compound, [Zn(C₄₅H₂₈N₄O₂)(H₂O)]·2C₆H₅NO₂, consist of multiporphyrin supra­molecular assemblies sustained by inter­molecular COOH⋯COOH and Zn(H₂O)⋯COOH hydrogen bonds. One of the two nitro­benzene solvent mol­ecules hydrogen bonds peripherally to these arrays.     

KINETICS OF SIMIAN VIRUS 40 AND LAMBDA INACTIVATION BY PHOTOADDITION OF PSORALEN DERIVATIVES

Abstract The kinetics of psora/en photoinactivation of two distinct DNA viruses, bacteriophage λ and the papovavirus SV40 were investigated. When λ is treated with near ultraviolet light (UVA, 320-400 nm) and 4,5',8-trimethylpsoralen (TMP) at 1 μg/m/, the phage is rapidly inactivated. The survival curve exhibits a distinct shoulder indicating second or higher-order kinetics. SV40, on the other hand, is much more resistant to psoralen photoinactivation and the survival curve is linear, reflecting first order or'pseudo-first order'kinetics. Two TMP derivatives with increased solubility in aqueous solutions, 4'-aminomethyl-TMP and 4'-hydroxymethyl-TMP, were similarly tested. In both virus systems, TMP was much more effective. In experiments designed to examine the role of psoralen cross-link formation in virus inactivation, treated samples were irradiated a second time in the absence of drug. Since reirradiation causes a decline in λ infectivity as great as that observed in continuously irradiated samples, cross-links are implicated as the primary lethal event. In the case of SV40, the results of such a protocol suggest that both monoadducts and cross-links may be lethal or that monoadduct formation may be rate-limiting.