Pyrrolothiénopyrazines: Etude chimique de la pyrrolo[1,2-a]thiéno[2,3-e]pyrazine

The reactivity of pyrrolo[1,2-a]thieno[2,3-e]pyrazine towards quaternisation, bromination, nitration, Friedel-Crafts, Vilsmeier-Haack and Reissert reactions was studied. Assignment of structures to the product is based upon ir, nmr and mass spectral studies.     

Synthesis of new thienocyclopenta[3,2-d]-oxazole and thiazole derivatives

Synthesis of thieno[2′,3′:5,4]cyclopenta[3,2-d]oxazole and thiazole derivatives are achieved by insertion of carbon dioxide and disulfide into 4-amino-5-chloro-5,6-dihydro-4H-cyclopenta[b]thiophen-6-one.     

Natural Occurrence of Enantiomeric and meso-Astaxanthin. 5. Ex wild salmon (Salmo salar and Oncorhynchus)

The configurational isomers of astaxanthin (3,3′-dihydroxy-β,β-carotene-4,4′-dione) from the flesh of salmon (Salmo salar and Oncorhynchus) caught at different places in Europe and Canada were isolated and analyzed as (?)-camphanic acid diesters by means of HPLC. The biological variation in the composition of the configurational isomers in seven fish was surprisingly similar: 78 to 85% of (3S, 3′S)-astaxanthin, 12 to 17% (3R, 3′R)-astaxanthin and 2 to 6% meso-astaxanthin.     

Metabolism of Carotenoids in Salmonids. Part 3. Metabolites of astaxanthin and canthaxanthin in the skin of atlantic salmon (salmo salar,L.)

Diets supplemented with astaxanthin and canthaxanthin, respectively, and a control diet without carotenoid additions, were fed to 1½-year-old Atlantic salmon (Salmo salar, L.) for one year. The integuments were investigated as to their quantitative and qualitative carotenoid composition. Astaxanthin and canthaxanthin deposited in the skin amounted to 20 and 14% of the total carotenoids only. Seventy % must be considered as metabolites of astaxanthin and canthaxanthin and 10% as basic xanthophylls also present in the control groups. Astaxanthin apparently underwent the following metabolic pathway: astaxanthin→idoxanthin→adonixanthin→zeaxanthin→zeaxanthin 5,6-epoxides. Reduction of the 4′-carbonyl group was stereospecific leading to the (4′R)-idoxanthin. Canthaxanthin was obviously converted to β,β-carotene via 4′-hydroxyechinenone, echinenone, and 4-hydroxy-β,β-carotene.     

Techniques in chemometrical modeling for micro-pollutants assessment

Summary Chemometrics have been described as effective tools for exploring chemical data, and many software packages are now available on micro-computers. This work evaluate their suitability for environmental analytical chemistry. Guidelines for multivariate method selection are proposed. They are based on the type of variables and the goal of the study. Two examples are proposed to illustrate these methods and their efficiency. Firstly it is shown that a global assessment of Rhine basin mercuric pollution in the Alsace region is possible with Multiple Correspondence Factor Analysis. Several goals are simultaneously reached: a mapping of pollution, a detection of pollution changes during the study period and an evaluation of bio-accumulation as a function of fish species. Secondly the modeling of industrial soil pollution by heavy metals is studied by Multiple Linear Regression. It demonstrates that chemometrics provide us with necessary tools for environmental analytical chemistry but also for toxicological studies or ecosystem modeling.     

The determination of chlorinated biphenyls,chlorinated dibenzodioxins,and chlorinated dibenzofurans by GC-MS

High resolution gas chromatography, with mass selective detection, has been used for the analysis of PCB on methyl 50 % octyl polysiloxane (SB 50 Octyl), methyl octadecyl polysiloxane, and a smectic polysiloxane (SB Smectic); and for the analysis of polychlorodibenzodioxins and polychlorodibenzofurans with 1 to 8 chlorine substituents on 100 % cyanopropyl siloxane (SP 2331), smectic polysiloxane (SB Smectic), a new polar stationary phase (DB-Dioxin). The analysis has also been performed by column coupling.     

A new route to vinyltributyltin compounds by flash pyrolysis of alkyltributyltin acetates

Flash pyrolysis of alkyltributyltin acetates, at high temperatures (600–850° C) under a moderate vacuum provides a convenient route to vinyltin derivatives.     

Ion solvation in water clusters

We describe here molecular dynamics computer simulations performed to study the solvation of ions (Cl^? and Na⁺) in water clusters. Our simulations show that the calculated structure and dynamics of the clusters is very sensitive to the potential model which is used to describe the interactions. From the comparison with thermodynamic data and data from the photoelectron spectra we conclude that in Cl^?(H₂O)_n (n≤20) clusters the ion is located on the surface of the cluster.     

Quantities of adult, fetal and embryonic globin chains in the blood of eighteen- to twenty-week-old human fetuses

The prenatal diagnostic program, established at Hacettepe University in Ankara for the purpose of detecting beta-thalassemia (beta-thal), sickle cell anemia (SS), and Hb S-beta-thal, offered the opportunity of evaluating the relative quantities of adult (beta A, beta S), fetal (G gamma, A gamma, A gamma T), and embryonic (epsilon, zeta) chains in 26 fetuses, aged 18-20 weeks. Methodology involved micro high-performance liquid chromatographic (HPLC) procedures and immunology using an mAb, specific for the embryonic epsilon chain. A good correlation was observed between the beta/gamma in vitro chain synthesis ratio and the level of beta A and/or beta S chains determined by reversed-phase HPLC; the combination of these two sets of data strengthens the prenatal diagnostic approach of detecting beta-thal major but not beta-thal trait. The levels of the different gamma chains were about as observed in newborn babies; the frequency of the A gamma T variant in the 26 fetuses was the same as observed for a larger group of Turkish newborn babies. The level of the embryonic zeta chain was higher than seen in full-term babies and varied between 0 and 1.3%; 5 of the 26 fetuses showed the complete absence of zeta. The embryonic epsilon chain was not detectable, not even in babies with beta-thal major. These data indicate that the synthesis of epsilon is completely turned off in fetuses at the age of 18-20 weeks, while that of zeta continues, albeit at a low level.     

Identifizierung von sechs Komponenten des Spurpheromons der Ameisenart Lasius fuliginosus. Vorläufige Mitteilung

Hexanoic acid, heptanoic acid, octanoic acid, nonanoic acid, decanoic acid, and dodecanoic acid are components of the trail pheromone of the ant species Lasius fuliginosus. The acids were extracted from the contents of the rectal ampullae and identified by the mass spectra and gas chromatographic retention times of the corresponding methyl esters.