Über Reaktionen mit Betainen, 22. Mitt. Über S-Bétaine und ihre Beziehungen zu stabilen S-Yliden

A comparative study has been performed on ethyl-methyl- and diethyl-mercaptoacetic acid (1 and2), and thianeaceticacid betain (3) with respect to their reactivity towards haloacetic acid anhydrides and 4-nitrobenzene-diazonium tetrafluoroborate. The results show that in analogy to related N-betaines the alkyl substituents at the cationic reaction center display a strong influence on reactivity. The most stable S-ylides are obtained from the cyclic S-betain3 in high yield. The¹H-NMR spectra reveal that the protons of the methylene groups in compounds1–3 are fully exchanged for deuterium (in D₂O) in contrast to the behavior of the corresponding N-betaines.

Herrn Vizepräsident Dr. techn., Dr. rer. nat. h. c., Dr. phil. h. c.Willy G. Stoll, Bottmingen/Basel, zur Vollendung des 75. Lebensjahres in Freundschaft gewidmet.     

Untersuchungen zur Temperaturabhängigkeit charakteristischer IR-Absorptionen, 5. Mitt.: IR-spektroskopischer Nachweis von fixierten Molekülzuständen bei α-Diketonen

Zusammenfassung IR-spektroskopische Untersuchungen an -Diketonen bei erhöhter Temperatur zeigen, daß zwei räumlich unterschiedliche Anordnungen, denen auf Grund der C=O-Streckschwingungs-absorption quasi-cis-trans-Charakter zukommen muß, bei diesen Substanzen auftreten.

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An infrared spectroscopic study of the C=O stretching vibration with -diketones at elevated temperatures shows the existence of two different conformations with a quasi-cis-trans-character.

     

Über Reaktionen mit Betainen, 20. Mitt. Synthesen stabiler S-Ylide

Thetin (1) and the betain of-Thiolanyl-acetic acid,5 react with the anhydrides of trifluoroacetic acid (TFA) and trichloroacetic acid (TClA), respectively, to give stable diacyl-S-ylides2a,b and6a,b, respectively. In contrast to the corresponding N-betaines,1 and5 react with monochloroacetic anhydride (MClA) under formation of the diacyl-ylid2c from1, and the mixed anhydride of chloroacetic acid and chloroacetylthiolaniummethylid carboxylic acid9 from5. The formation of9 requires the establishment of an equilibrium between S-betain and S-ylid forms. An X-ray analysis has been performed on2a.

Herrn Dr. Dr. h.c.Herbert Hönel, Graz, mit besten Wünschen zur Vollendung des 95. Lebensjahres gewidmet.     

Production and stability testing of incurred reference materials for the anabolic steroid trenbolone in bovine urine.

The production of stable reference materials with incurred residues of veterinary drugs is necessary for the validation of methods of analysis, including the determination of critical performance characteristics. A reference material for trenbolone in bovine urine was produced and the long-term stability was tested. From a pilot 16 week stability study on seven batches containing different additives it was concluded that the use of preservatives does not improve the stability of the residue. A final batch of reference material of 800 vials each containing 5 ml of urine with a target concentration of 5 micrograms l-1 was prepared. The homogeneity and long-term stability of the material were tested. The material was found to be homogeneous. Based on the results of a 52 week stability study it was concluded that the material is stable, using the current analytical methodology. For the development of reference materials, highly accurate and precise analytical methods are necessary. However, the current analytical methodology is not suitable for full evaluation and certification. Currently, a new LC-MS method is being developed. After validation of this method, the stability and homogeneity study will be repeated.     

Infrarotspektroskopische Untersuchungen an Oximen aromatischer Chinone

Zusammenfassung Es wird der Versuch unternommen, die bei den Oximen aromatischer Chinone im Doppelschwingungsbereich auftretenden Banden zuzuordnen.

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The assignment of the infrared absorption bands in the 1700–1500 cm^–1 region has been tried for a number of oximes of aromatic ketones.

     

Synthesen von Heterocyclen, 141. Mitt.: Zur Chemie der 1,3-Oxazinone

Zusammenfassung N-substituierte Diphenylacetamide reagieren mit monosubstituierten Malonylchloriden zu Derivaten des 1,3-Oxazin-4,6-dions. Diese lassen sich thermisch zu den isomeren Tetrahydropyridin-2,6-dionen umlagern.

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Syntheses of heterocycles, CXLI: Chemistry of 1.3-oxazinones

N-substituted diphenylacetamides react with monosubstituted malonyl chlorides to give 1.3-oxazine-4.6-diones. These compounds are thermically rearranged to yield the isomeric tetrahydropyridine-2.6-diones.

     

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

4-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.

     

Biomedical simulation of heat transfer in a human heart

Theory and practical experiences from numerical simulations of heat transfer in the field of medicine are presented in this paper. The cooling of a human heart during surgery was taken as an illustrative example. All phases of the simulation process are described starting with the construction of an irregularly shaped 3-dimensional model. The mathematical model is based on diffusion and Navier-Stokes equations. The system of partial differential equations is solved by finite difference approximation using an explicit time-stepping scheme to obtain the time evolution of the solution for the complete simulated interval, which is typically 1 h. A typical domain is composed of several million voxels; therefore, the program was parallelized to speed up the simulation. A speed-up of 8.2 was obtained on 16 processors in a Linux cluster.     

X-filtering for a range of coupling constants: application to the detection of intermolecular NOEs

A new method for heteronuclear X-filtering is presented, which relies on repetitive applications of 90 degrees (1H)-tau(1/41J(HC))-180 degrees (1H,13C)-tau(1/41J(HC))-90 degrees (1H,13C)-PFG building blocks employing gradient-mediated suppression of magnetization built up for directly heteronuclear coupled protons. Thereby, a range of heteronuclear coupling constants can be suppressed by varying the delays of scalar coupling evolution both within and between individual transients. To achieve efficient destruction of 13C-coupled protons in macromolecular systems, the scalar coupling evolution delays were optimized using simulated annealing by including transverse relaxation effects. With a combination of regular hard pulses, delays and pulsed field gradients only, this method yields sufficient X-filtering to allow the observation of intermolecular nuclear overhauser effects in a molecular complex consisting of a 13C, 15N double-labeled, and an unlabeled protein. This is achieved by exciting magnetization of 12C- and 14N-bound protons and detecting 13C-bound 1H magnetization in a 3D 13C-filtered, 13C-edited NOESY-HSQC experiment. The method is tested on the 18 kDa homodimeric bacterial antidote ParD.