Photodimerizable ditopic ligand

[reaction: see text] The synthesis, photophysical properties, and structural characterization of a photodimerizable ditopic ligand are described. Upon irradiation at 366 nm, ligand 1 dimerizes to the head-to-tail tetra-bpy ligand 2. This thermally stable photodimer can be dissociated back to 1 using higher energy irradiation (254 nm).     

The application of (Z)-3-aryl-3-haloenoic acids to the synthesis of (Z)-5-benzylidene-4-arylpyrrol-2(5H)-ones

Studies directed at the synthesis of (Z)-5-benzylidene-4-arylpyrrol-2(5H)-ones from (Z)-3-aryl-3-haloenoic acids are described. The successful strategy relies on the preparation of (Z)-3-aryl-3-haloenoic acids from acetophenones through the corresponding (Z)-3-aryl-3-haloenals and the conversion of the (Z)-3-aryl-3-haloenoic acids to (Z)-5-benzylidene-4-aryl-5H-furan-2-ones. The furanones were subsequently treated with primary amines and dehydrated to the corresponding (Z)-5-benzylidene-4-arylpyrrol-2(5H)-ones.     

Epimerization of 2'-carbonylalkyl-C-glycosides via enolation, beta-elimination and intramolecular cycloaddition

Treatment of 2'-carbonyl-alpha-C-glycopyranosides of gluco, galacto, manno, 2-deoxy, and 2-azido sugars with 4% NaOMe resulted in anomeric epimerization to give their respective beta-anomers in good to excellent yields. The epimerization of the 2'-aldehyde of alpha-C-galactopyranoside (10) in deuterium methanol, which afforded the beta-anomer with exclusive deuterium replacements at the 1'-position, excluded the possibility of the exo-glycal as being involved as an intermediate. When 2'-aldehyde (36) and 2'-ketone (41) of 2,3-di-O-benzyl-alpha/beta-l-C-arabinofuranoside were used as substrates we were able to obtain the respective equatorial alpha-C-arabinopyranosides (37 and 42). These observations confirmed that the epimerization involves an acyclic alpha,beta-unsaturated aldehyde or ketone, which is formed by the enolation of 2'-carbonyl-alpha-C-glycoside with subsequent beta-elimination. Thereafter an intramolecular hetero-Michael cycloaddition occurs, leading to the formation of thermodynamically controlled stable products, which were exclusively the equatorial C-glycopyranosides, except in the case of 2'-carbonyl-C-furanosides, where a mixture of two anomers was obtained.     

Polyelectrolyte-induced peeling of charged multilamellar vesicles

We study mixtures of charged surfactants, which alone in solution form uni- and multilamellar vesicles, and oppositely charged polyelectrolytes (PEs). The phase behavior is investigated at fixed surfactant concentration as a function of the PE-to-surfactant charge ratio, x. We find that, for x > 0, aggregates form. Light microscopy and X-ray scattering experiments show that the isoelectric point plays a crucial role, since the morphology and the microscopic structure of the aggregates are different before (x < or = 1) and after the isoelectric point (x > 1). To better understand the dynamics for the formation of PE/surfactant complexes, we perform light microscopy experiments where we follow in real time the effect of a PE solution on one multilamellar vesicle (MLV). We find that the PE induces a peeling of the bilayers of the MLV one by one. The peeling is accompanied by strong shape fluctuations of the MLV and leads ultimately to a pile of small aggregates. This novel phenomenon is analyzed in detail and discussed in terms of PE-induced tension and pore formation and growth in a surfactant bilayer.     

Eine einfache und genaue Bestimmung des Vitamins B1

Zusammenfassung Die hier beschriebene Hefegärungsmethode nützt die Tatsache aus, daß Hefe aus einer aneurinhaltigen Lösung dieses quantitativ aufnimmt und in Carboxylase umwandelt, durch die in einem Gärsubstrat die CO₂-Bildung gefördert wird. Im Gegensatz zu den bisher bekannten Gärmethoden benutzt diese Methode praktisch vitamin-B₁-frei gezüchtete Hefereinkulturen, wodurch gleichmäßigere Versuchsergebnisse gewährleistet werden.Die auf Aneurin zu untersuchenden Substanzen werden in salzsaurer Lösung in der Hitze extrahiert, wodurch auch das carboxylasegebundene Aneurin, also somit das Gesamtaneurin, erfaßt wird. In einfachen Gärgefäßen wird je 1 ccm aneurinhaltige Lösung mit dem Gärsubstrat vermischt; die gebildeten CO₂-Mengen werden graphisch ausgewertet, auf Grund einer Proportionalität von CO₂-Entwicklungsgeschwindigkeit mit dem Logarithmus der Aneurinkonzentration. Es ist möglich, in 1 ccm Lösung Mengen zwischen 0,01 und 1,0 mit gleicher relativer Genauigkeit zu erfassen.Die hier beschriebene Methode erlaubt es, wenn nur die entsprechenden Mengen gleichartigen Gärsubstrates vorhanden sind (siehe S. 255/56) in einer 8-stündigen Versuchsperiode 64 und mehr Bestimmungen mit gleicher Genauigkeit durchzuführen.Die Fehlergrenze unserer Methode ist, peinlich sauberes Arbeiten und entsprechende Übung vorausgesetzt, äußerst niedrig und liegt bei ± 3%. Sie liegt daher unter dem mit ± 8% angegebenen Fehler des Phycomycestestes, obwohl dessen Erfassungsbreite geringer ist.Die Versuche wurden im Jahre 1944 in den Laboratorien des Anatomischen und des Medizinisch-chemischen Institutes der Universität Wien (Vorstände: Prof. Dr.E. Pernkopf bzw. Prof. Dr.H. K. Barrenscheen) und unter dankenswerter Unterstützung von Herrn Prof. Dr. Dr.Th. Leipert durchgeführt.K. Gratzl (dzt. I. Chem. Lab. der Univ. Wien).     

Synthesis of 24-Methylidene[24-14C]- and 24-Methylidene[7-3H]cholesterol

The syntheses of 24-methylidene[24-¹⁴C]cholesterol ( 7a ) and of 24-methylidene[7-³H]cholesterol ( 7b ) from commercially available (20S)-3-oxopregn-4-ene-20-carbaldehyde ( 1 ) are described. The method also provides simple preparations of 3β-acetoxy[24-¹⁴C]chol-5-en-24-oic acid ( 4 ) and 24-oxocholest-5-en-3β-yl acetate ( 6b ).     

High sensitivity determination of valproic acid in mouse plasma using semi-automated sample preparation and liquid chromatography with tandem mass spectrometric detection

A high-throughput liquid chromatography/electrospray ionization tandem mass spectrometry (LC/ESI-MS/MS) assay using automated sample preparation has been developed for the determination of valproic acid (VPA) in mouse plasma. A liquid-handling system was programmed to prepare calibration standard solutions in plasma, as well as quality controls and clinical samples. Plasma protein precipitation was performed on a 96-well plate, and the collected supernatant was directly injected into a reversed-phase LC/ESI-MS/MS system in the negative ionization mode. The calibration curve for VPA was linear over a dynamic range of 0.15-100 microg/mL. The limit of detection was 75 ng/mL and the lower limit of quantitation was 150 ng/mL. Intra- and inter-day validation assays of the semi-automated plasma analysis showed satisfactory accuracy and precision.