Efficient preparation of carbohydrate- and related polyol-amphiphiles by hydrazone ligation

The hydrazone ligation can be used to couple clustered-glycosides or glycomimetics functionalized with a hydrazino group with lipophilic glyoxylyl acid derivatives to give the corresponding amphiphiles in high yield and purity.     

Efficient preparation of (Z)-alkenyl derivatives from (Z)-vinyl (N,N-diisopropyl)carbamate via Ni-catalysed coupling reactions

A (Z)-vinyl (N,N-diisopropyl)carbamate treated with Grignard reagents, under Wenkert Nickel-catalysed conditions, gave access to several substituted (Z)-alkenyl derivatives. These Nickel-catalysed reactions, carried out with vinyl-, phenyl-, p-methoxyphenyl-, trimethylsilylmethylmagnesium bromide and benzylmagnesium chloride, led to the corresponding (Z)-alkenyl derivatives in good yields and high stereoselectivities.     

Participation d'un groupe amide a la formation de sels de dioxolanne-1,3 ylium-2; Modele biomimetique de reaction de peptidation

An amide group is shown to be capable of intramolecular participation in the formation of an 1,3-dioxolan 2-ylium cation giving a tricyclic organic cation of a new type $\text{5a}$,$\text{b}$. This cation may be considered as a model of an electrophilic intermediate which might be formed from a peptidyl t-RNA during protein biosynthesis.The tricyclic salt $\text{5a}$,$\text{b}$ reacts with water and methanol like a classical dioxolenium salt. An amide acetal $\text{18}$ can be obtained from dimethylamine and 5a; hydrolysis of $\text{18}$ does not lead to the corresponding amide $\text{20}$ but to the cleavage of the CN. bond.     

Deposition of long-lived radionuclides after the chernobyl accident in the forestal massif of boreon

After the reactor accident at Chernobyl, samples of soil, moss, lichen and fern were collected in the forest around the Vesubie valley in the South East of France and analyzed by low energy photon and gamma spectrometry. Activity concentrations as high as 42.8, 9.4 and 3.8 kBq.m^–2 were measured for¹³⁷Cs,¹³⁴Cs and¹⁰⁶Ru, respectively, in soil, in October 1988.¹²⁵Sb and^110mAg were also detected. The contamination was found to be the most important between 1400 and 1700 m altitude.     

Simultaneous non-destructive determination of long-lived radionuclides in contaminated seaweed by X-ray spectrometry

Summary Planar high purity germanium detectors have been used for activity determination of fission nuclides, as well as transuranic elements, in a contaminated seaweed. The activity of a given isotope was deduced from the absolute detection efficiency of the detector and from the branching ratioR=N _k /N of the K-X photons emitted by desintegration; in case of monoenergeticy emitters, these branching ratios have been calculated from nuclear data decay. These low-energy measurements require one standard sample only for simultaneous determination of several isotopes. The data obtained in this work for the¹³⁷Cs specific activity by non-destructive analysis are in good agreement with the results of an intercomparison exercise performed by the IAEA. Moreover, this method allows us to measure in this seaweed the specific activity of the previously not detected¹²⁹I nuclide, both by destructive and nondestructive analysis, and that of²⁴¹Pu which generally needs complicated radiochemical separations.

---

Gleichzeitige nicht-destruktive Bestimmung langlebiger Radionuklide in verunreinigtem Seetang durch Röntgenspektrometrie

Zusammenfassung Planäre hochreine Germanium-Detektoren wurden zur Aktivitätsbestimmung von Spaltnukliden und von Transuranen in Seetang verwendet. Die Aktivität eines bestimmten Isotops wurde abgeleitet aus der absoluten Nachweisanzeige des Detektors und aus dem VerhältnisR=N _k /N der durch Desintegration freigesetzten K-X-Photonen; bei monoenergetischen Gammastrahlen wurde dieses Verhältnis aus der Abnahme der nuklearen Daten berechnet. Diese Messungen geringer Energien erfordern nur eine Standardprobe für die gleichzeitige Bestimmung verschiedener Isotoper. Die von uns durch nichtdestruktive Analyse ermittelten Werte für die spezifische Aktivität von¹³⁷Cs stimmen mit den Ergebnissen einer vergleichenden Untersuchung der IAEA gut überein. Außerdem konnten wir mit diesem Verfahren in diesem Seetang die spezifische Aktivität des bisher nicht festgestellten Nuklids¹²⁹J sowohl durch destruktive wie durch nicht-destruktive Analyse messen und ebenso die von²⁴¹Pu, wozu im allgemeinen komplizierte radiochemische Trennverfahren nötig sind.

---

---

Presented in part at the 9th International Microchemical Symposium, Amsterdam, August 28–September 2, 1983.     

Use of uranium isotopes for the determination of river tributary flow rates: Case of the Var and the Vésubie

When a river flow rate is known on one point, it is possible to determine the one of upstream tributaries. This can be done by measuring the concentrations of a dissolved element (for example Ca²⁺), provided that no chemical precipitations have occurred in mixture waters. In this later case, the determination of flow rate is however possible by isotopic geochemistry, by knowing isotopic ratios of an element, for ex. ²³⁴U/²³⁸U, in each river considered and the ratio of the concentrations in dissolved ²³⁸U in two of them. A study of the Var and its tributary the Vésubie is performed: in January 31st, 2001, the flow rate D₃, downstream the confluence was 35 m³/s. The ratio of the ²³⁸U concentrations in the Vésubie river and in the Var upstream (²³⁸U₁/²³⁸U₂) was 5.5. The isotopic ratios ²³⁴U/²³⁸U measured in the Var, downstream the confluence were R₃ = 1.51, upstream R₂ = 1.75, and in the Vésubie R₁ = 1.08. We have calculated the Vésubie flow rate as D₁ = 3.2 m³/s.     

Alkoxyallene‐ynes: Selective Preparation of Bicyclo[5.3.0] Ring Systems Including a δ‐Alkoxy Cyclopentadienone

The development of an intramolecular rhodium(I)‐catalyzed Pauson–Khand reaction of alkoxyallene‐ynes with a proximal alkoxy group is reported. This reaction, in the presence of a [Rh(cycloocta‐1,5‐diene)Cl]₂/propane‐1,3‐diylbis(diphenylphosphane) system under a CO atmosphere, constitutes a powerful tool for selectively accessing carbo‐ and heterobicyclo[5.3.0] frameworks featuring an enol ether moiety. Through this procedure, a straightforward access to guaiane skeletons with a tertiary hydroxy group at the C10 position was achieved.     

Effect of polymerization of synthetic glycolipids on their supramolecular assemblies

Sugar-derived surfactants bearing a polymerizable acryloyl moiety on one of the branches of the double-chain hydrophobic tail were prepared. The non–ionic hydrophilic head and the biantennary hydrophobic tail were built on, respectively, an aspartic acid and a tris(hydroxymethyl)aminomethane core. Ultraviolet irradiation of aqueous dispersions of these surfactants above their transition phase temperature (T_c) was achieved. The morphology of self-assemblies produced in such a way were investigated by transmission electron microscopy. TEM photographs revealed that irradiation leads to the formation of unilamellar vesicles. Neither fibers nor tubules were detected in contrast to what was observed before polymerization.