N,N-bis[2-oxo-3-oxazolidinyl]phosphorodiamidic chloride: a novel coupling reagent in the synthesis of oligodeoxyribonucleotides

Use of a novel coupling reagent, N,N-bis[2-oxo-3-oxazolidinyl]phosphorodiamidic chloride (BOPDC) in the synthesis of oligodeoxyribonucleotides is described. This reagent allows the synthesis of phosphotriesters in high yields (70–80%) without detectable side reactions. Synthesis of a hexanucleotide, d(A-A-C-C-C-G) is presented as an example.     

Isolation and identification of the sex pheromone of females of Heliothis maritima (Lepidoptera,Noctuidae)

Four components have been isolated from an extract of the sex pheromone of the mothHeliothis maritima and have been identified: hexadecanal, hexadec-cis-11-enal, hexadec-cis-9-enal, and hexadec-cis-11-en-1-ol. All-Union Scientific-Research Institute for Biological Methods of Plant Protection, Kishinev. Don Zonal Scientific-Research Institute of Agriculture. Don Scientific-Production Combine. Ecology Division of Lund University, Lund, Sweden. Translated from Khimiya Priorodnykh Soedinenii, No. 4, pp. 574–577, July–August, 1991.     

Structure of isoregelinone

From a fraction of the bases ofColchicium kesselringii Rgl., growing in the Tashkent Province, a new compound which has been called isoregelinone has been isolated. On the basis of spectral characteristics, especially the INDOR spectrum, and chemical transformations, a structure epimeric with that of regelinone has been proposed for it.V. I. Lenin Tashkent State University. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 195–199, March–April, 1981.     

Effect of additives on the amination of 2-oxoglutaric acid by gamma-radiation

The effect of added substances was studied on the yield of glutamic acid produced by gamma-ray irradiation of 2-oxoglutaric acid and ammonia in aqueous solution. The contents of amino acids in the irradiated solutions were determined with amino acids analyzer. Sodium nitrate, allyl alcohol or sodium formate was used as an added substance. The yield of glutamic acid significantly decreased by the addition of nitrate, and it was little affected by the addition of allyl alcohol. In the presence of formate the yield increased from G = 0.4 (2-oxoglutaric acid 0.05M and ammonium hydroxide 2M) to G = 1.1. As a result, it was found that hydrated electron contributes on the formation of glutamic acid, but hydroxyl radical does not. The yield showed a maximum at ca. 0.1 M ammonium hydroxide concentration. These facts indicate that NH2 radical does not contribute to the formation of glutamic acid. As a reaction mechanism, it can be explained that 2-oxoglutaric acid which had been reduced by hydrated electron reacts with ammonia.     

The ellipsoid algorithm as a method for the determination of polypeptide conformations from experimental distance constraints and energy minimization

A new method for constrained nonlinear optimization known as the ellipsoid algorithm is evaluated as a means of determining and refining the conformations of peptides. Advantages of the ellipsoid algorithm over conventional optimization methods include that it avoids many local minima that other methods would be trapped by, and that it is sometimes able to find optimum solutions in which the constraints are satisfied exactly. The dihedral angles about single bonds were used as variables to keep the dimensionality low (the rate of convergence decreases rapidly with increasing dimensionality of the problem). The method is evaluated on problems involving distance constraints, and for minimization of conformational energy functions. In an initial application, conformations consistent with an experimental set of NMR distance constraints were obtained in a problem involving 48 variable dihedral angles.     

Direkte photometrische Bestimmung von Kobalt in Eisen, St?hlen, Erzen und Schlacken mit Nitroso-R-Salz

Zusammenfassung Die direkte Bestimmung von Kobalt in unterschiedlichen Substanzen im Gehaltsbereich von 0,001 bis 5% ist nach einem einfachen Verfahren möglich, wenn die Komplexbildungsreaktion und der tatsächliche Störeffekt durch andere Elemente bekannt sind. Die für eine Bestimmung benötigte Zeit beträgt 25 min. Die relative Standardabweichung liegt zwischen 0,02–20%.

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Direct photometric determination of cobalt in iron, steels, ores and slags using nitroso-R-salt

A simple procedure without any separation is described; the complex formation and the interfering effects of other elements are studied. This method is suitable for the accurate determination of 0.001 to 5% of cobalt in several materials. The time required for one determination is 25 min only. The coefficients of variation are within 0.02–20%.

     

Paper chromatography in the separation of ions

Summary A study has been made of the separation of alkali and alkaline earth metals. With mixtures of solvents, such as ethyl cellosolve, water and hydrochloric acid and acetone, water and hydrochloric acid in the ratio of 702010 and at different temperatures, a complete separation of alkaline earth metals was effected. Of the alkali metals only lithium, sodium and potassium could be separated from each other but rubidium and caesium always accompanied potassium.     

Palladium-catalyzed electrophilic substitution of allyl chlorides and acetates via bis-allylpalladium intermediates

Palladium-catalyzed electrophilic allylic substitution of functionalized allyl chlorides and allyl acetates can be achieved in the presence of hexamethylditin under mild and neutral reaction conditions. This efficient one-pot procedure involves palladium-catalyzed formation of transient allylstannanes followed by generation of a bis-allylpalladium intermediate, which subsequently reacts with electrophiles. Using this catalytic transformation, various aldehydes and imines can be allylated providing highly functionalized homoallyl alcohols and amines. Furthermore, tandem bis-allylation reactions could be performed by employing tosyl isocyanate and benzylidenemalonitrile as substrates. A particularly interesting mechanistic feature of this reaction is that palladium catalyzes up to three different transformations in each catalytic cycle. Various allylic functionalities, including COOEt, CONH(2), COCH(3), CN, Ph, and CH(3), are tolerated in the catalytic reactions due to the application of neutral and mild reaction conditions. The substitution reaction occurs with very high regioselectivity at the branched allylic terminus. Moreover, in several reactions, a high stereoselectivity was observed indicating that this new catalytic process has a high potential for stereoselective synthesis. The regioselectivity of the reaction can be explained on the basis of DFT calculations. These studies indicate that the allylic substituent prefers the gamma-position of the eta(1)-allyl moiety of the reaction intermediate.     

A chemoenzymatic total synthesis of ent-bengamide E

The cis-1,2-dihydrocatechol 3, which can be obtained in enantiomerically pure form by microbial dihydroxylation of bromobenzene, has been converted into the enantiomer, ent-1, of the cyclolysine-based marine natural product bengamide E (1).     

Can the highest occupied molecular orbital of the uranyl ion be essentially 5f?

Recent relativistic calculations on the uranyl ion suggest that the low wave numbers of the first electron transfer bands are due to a bonding 5f-like orbital containing the two loosest bound electrons. Comparison with UF₆ makes it more likely that if indeed σ_u (and not π_u) is the highest occupied MO, it is rather due to “pushing from below” by U 6p (like N 2s in N₂).