H. Sterk

Reaktionen mit cyclischen Oxalylverbindungen, XXIV. Zur Reaktion von 4-Benzoyl-5-phenyl-furan-2,3-dion mit Phenylhydrazonen bzw. Phenylhydrazin

Abstract4-Benzoyl-5-phenyl-furan-2,3-dione (1) reacts with various phenylhydrazones2 at 60–80°C to the pyrazole carboxylic acid3 a, which then can be decarboxylated to 4-benzoyl-1,5-diphenyl-pyrazole (5).1 and phenylhydrazine combine again yielding3 a as the main product and the isomeric pyridazinone6 as by-product. At higher temperatures (120–140°C) the reaction of1 with2 a leads to the formation of dibenzoyl acetic acid hydrazide derivatives8.The structures of all products were confirmed by IR, MS,15N- and13C-NMR spectroscopic measurements, in the case of the pyridazinone6 also by an X-ray study.6 crystallizes with one moleDMSO monoclinically in space group P 21/n (Nr. 14) with 4 molecules6 andDMSO per cell.The reaction pathways leading to the compounds3, 6 and8 are discussed.

Investigation of the hyaluronic acid-copper complex by N.M.R. spectroscopy

Analysis of the 13C and 1H relaxation data of the hyaluronic acid-copper complex indicates a binding site involving the carboxyl group and O-1 of the D-glucuronic acid moiety. The paramagnetic relaxation of Cu2+ is discussed within the framework of the Solomon-Bloembergen formalism and it is shown that various atoms experience, in addition to the dipolar paramagnetic relaxation, a strong scalar relaxation contribution. E.s.r. spectra have also been obtained in order to determine the binding constants, and measurements at 69 K gave the g-values of the complex.

Investigations of lignocellulosic materials by the carbon-13 N.M.R. C.P.-M.A.S. method

Abstract High resolution solid state 13 C-n.m.r. spectra have been taken on several celluloses as well as on untreated and pretreated lignocellulosic materials (poplar, birch, beech, pine, spruce, wheat straw). The results indicate that milling and streaming have dramatic effects on the cellulose structure. Moreover it was found that sample preparation, particularly moisture content, markedly affects the features of the 13 C spectra.

Molecular dynamics studies of a molecular switch in the glucocorticoid receptor

The glucocorticoid receptor (GR) is a hormone dependent nuclear receptor that regulates gene transcription when bound to the glucocorticoid response element (GRE). The GRE acts as an allosteric effector, inducing a structural change in the GR DNA-binding domain (GR DBD) upon binding, thereby switching the GR to an active conformation. A similar conformational change can be induced by two single point mutations: Ser459Ala and Pro493Arg. Structural and dynamical aspects of the conformational switch have been investigated by molecular dynamics simulations. Our results indicate that these two mutants, which share a similar phenotype, exert their action at a structural level through different mechanisms. In the Arg(493) mutant, the D-loop and the second helix are stabilized in a conformation that preforms the protein-protein dimer interface. In the Ala(459) mutant, the structurally important hydrogen bond between Arg(496) and Ser(459) is missing, which leads to a core reorganization and a reorientation of the second helical region. Although remote, both in sequence and three dimensional structure, these two mutations induce structural changes that are ultimately reflected in similar regions of the GR DBD structure, namely the D-loop and the short second helical region. These correspond to hot area of the GR DBD that are important both for DNA-binding and for the proper formation of the protein-protein interface. The conformational rearrangements in these area are proposed to decrease unfavorable protein-DNA and protein-protein contacts and allow unspecific DNA-binding leading to the squelching phenotype of the mutants. The GR DBD can thus exist in two states, a transcriptionally active and an inactive state. Switching between these states can be accomplished either by GRE binding or by the described mutations.

Über Heterocyclen, 12. Mitt.: Zur Bromierung der 2-Oxo-6-methyltetrahydropynimidine

Die Bromierung von 2-Oxo-6-methyl- bzw. 2-Oxo-5-carbathoxy-6-methyltetrahydropyrimidinen verlauft unter Substitution an der CH3-Gruppe am C-6. 2-Oxo-5-carbathoxy-6-brommethyl-bzw.-dibrommethyltetrahydropyrimidine konnen in 2-Oxo-6-hydroxymethyl-tetrahydropyrimidin-5-carbonsaurelactone umgewandelt werden. Im Gegensatz zu Brom reagiert Chlor mit 2-Oxo-5-carbathoxy-6-methyltetrahydropyrimidinen unter Addition.

Cross-correlation effects in the transverse relaxation of multiple-quantum transitions of heteronuclear spin systems

Abstract The relaxation of multiple quantum transitions in a heteronuclear three-spin system is described in terms of Redfield theory including intramolecular dipolar and chemical shift anisotropy (CSA) mechanisms. CSA-dipolar cross-correlations, interference terms between CSA terms at different nuclear sites and cross-correlations between different dipolar interactions are illustrated and discussed. It is shown that cross-correlations between various relaxation mechanisms lead to non-exponential relaxation behaviour of multiple-quantum transitions, thus causing differential line broadening.

SYNTHESIS OF CARBOHYDRATE DERIVED α-METHYLENE-γ-LACTONES BY DIASTEREOSELECTIVE, LOW TEMPERATURE REFORMATSKY-TYPE REACTIONS

Abstract Hexopyranoside- and hexofuranose uloses with either ethyl 2-(branamethyl)acrylate in the presence of laminar Zn/Ag-graphite or ethyl 2-(trimethylsilylinethyl)acrylate/tetra-n-butylanrnonium fluoride undergo stereoselective branching, mainly with formation of spiro α-methylene-γ-lactones.

Preparation and Chemistry of an Unexpectedly Stable α‐Oxoketene−Pyridine Zwitterion, 2,2‐Bis(tert‐butylcarbonyl)‐1‐[4‐(dimethylamino)pyridinio]ethen‐1‐olate

Treatment of dipivaloylketene 1 and its dimers 2 and 3 with 4-(dimethylamino)pyridine (DMAP) in acetonitrile affords the alpha -oxoketene-pyridine zwitterion 4 as a pale yellow solid. This is the first example of a stable zwitterion obtained from a true alpha -oxoketene. In anhydrous solution at room temp., compound 4 largely cleaves into the reactants 1 and DMAP. At -60 degreesC the equilibrium is shifted entirely towards the zwitterion 4, as shown by C-13 NMR measurements. Calculations using density functional theory (B3LYP/6-311+G**) are in excellent agreement with the formation and relative stability of 4. N-15 labelling experiments demonstrate that the ring nitrogen atom of DMAP is involved in generating the new zwitterionic C-N bond. Reactions of 4 with NH and OH nucleophiles in solution afforded the corresponding dipivaloyl acetic acid derivatives 6 and 7, whereas acetone or benzylidene aniline undergo cycloaddition reactions of the hetero-Diels-Alder type.

5-Deoxy-5-Fluoro-D-Glucofuranose and -L-Idofuranose Synthesis and NMR Studies

Abstract Starting from 1,2-O-isopropylidene-α-D-gluco- and -β-L-ido-furanurono-6,3-lactone, 5-deoxy-5-fluoro-α/β-D-gluco- and -L-idofuranose, respectively, were prepared by the following sequence of reactions: trifluoromethanesulfonylation, nucleophilic substitution with inversion of configuration, lactone reduction and deprotection. On the basis of H-H-, H-C-, H-F-, and C-F-couplings, the stereochemistry of the products is discussed.

Zur thermischen Bildung von Ketenen

ZusammenfassungDas beim Erhitzen von Salicylsäurechlorid (1), Isatosäureanhydrid (2), 2,4-Dioxo-1,3-benzodioxan (4) und ähnlichen Verbindungen auftretende Keten wird über seine Folgeprodukte IR-spektroskopisch nachgewiesen.AbstractThe thermal decomposition of salicyloylchloride (1), isatoic anhydride (2), 2.4-dioxo-1.3-benzodioxane (4) and similar compounds leads to ketenes identified by IR spectroscopic methods. *** DIRECT SUPPORT *** A3615129 00014