An enantioselective synthesis of the C1C9 segment of antitumor macrolide peloruside A

A stereocontrolled synthesis of the C₁C₉ segment of the marine natural product peloruside A is described. The key steps involve Sharpless's catalytic asymmetric dihydroxylation reaction, a chelation-controlled reduction of chiral β-alkoxy ketones to elaborate the syn-1,3-diol functionality and a ring-closing olefin metathesis of a homoallylic alcohol-derived acrylate ester to form an α,β-unsaturated δ-lactone.     

Complex citrates of metals in inorganic analysis

Summary A new method has been described for the quantitative separation of silver and lead in a solution. The method consists of adding an excess of sodium citrate solution to the solution of the mixture, when the insoluble citrates of silver and lead which at first precipitate out, redis-solve due to the formation of complex citrates. By the addition of hydro-chlorid acid to the solution, only silver chloride precipitates out and may be estimated gravimetrically. In the filtrate lead may be estimated gravimetrically as lead chromate. The method described here is quite reliable, as the results obtained by the analysis of a number of mixtures of different compositions have been found to be very satisfactory, the errors lying within permissible limits.     

Chemistry of the phenylglyoxal-p-diethylaminoanil and/or thiourea substituted ammine complexes

Summary Mixed ligand complexes of chromium(III), cobalt(II), cobalt(III), copper(II) and zinc(II) involving either the phenylglyoxal-p-diethylaminoanil and/or thiourea, and ammonia have been obtained by the partial or complete replacement of the strongly coordinated ammonia of ammine complexes. All the products were characterized by elemental analysis, molar conductance, magnetic susceptibility and i.r. and electronic spectral measurements for their bonding and structures.     

Conformations of laulimalide in DMSO-d6

Laulimalide is one of the newest naturally occurring macrolides known to act as a microtubule stabilizing agent with properties similar to Taxol. It also stands as being one of the most flexible with 18 rotatable bonds. This large number of rotatable bonds allows for approximately 3(18) potential conformers. To examine the conformational energy surface of laulimalide, we have performed an NAMFIS deconvolution analysis for laulimalide in DMSO-d6. The latter has been supplemented with a post-NAMFIS energy analysis at the Becke3LYP/6-31G level that examines the opposing effects of internal hydrogen bonding and syn-pentane interactions. In this way, we have identified 15 laulimalide conformations that can be classified into 5 different families: Supine, Convex, Cobra, Stretch, and Concave motifs.     

Fabrication of submicron scale patterned plastic thin film fluidic devices with controllable thickness

We present a soft-lithography based method to fabricate plastic thin film fluidic devices on glass and plastic substrates. Principles of soft-lithography and spin casting were used to generate the films. The thickness of these films is controllable and the patterns we have generated have submicron scale dimensions. By using commercially available compact disc (CD) components as molds, we have been able to generate parallel line and cross patterns on these thin films. These patterned films could be lifted from the substrates and further folded into rolls.     

Distinction between stepwise and concerted mechanisms in reductive cleavage reactions—use of voltammetric current function in the analysis of non-linear kinetic laws

A systematic way of distinguishing stepwise and concerted mechanisms in reductive cleavage reactions has been formulated involving current function analysis of the voltammetric data. The electrochemical reductive cleavage of the carbon-iodine bond in 1,3-dichloro-2-iodobenzene has been analyzed from a mechanistic point of view to illustrate the methodology. 1,3-Dichloro-2-iodobenzene undergoes an initial stepwise electron transfer obeying quadratic activation-driving force relationship. The current function analysis yields the reorganization energy for the reduction of 1,3-dichloro-2-iodobenzene and the results have been verified independently using convolution potential sweep voltammetry.     

A systematic scheme for the analysis of common anions using the Weisz ring oven technique

Summary A systematic scheme for the identification of the common anions: sulphate, sulphite, nitrate, nitrite, fluoride, chloride, bromide, iodide, ferricyanide, ferrocyanide, thiocyanate, phosphate, sulphide, thiosulphate and borate in a mixture by the ring oven technique has been described.

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Zusammenfassung Ein systematischer Analysengang zum Nachweis folgender Anionen mit Hilfe des Ringofens wurde beschrieben: Sulfat, Sulfit, Nitrat, Nitrit, Fluorid, Chlorid, Bromid, Jodid, Cyanoferrat(III), Cyanoferrat (II), Rhodanid, Phosphat, Sulfid, Thiosulfat und Borat.

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Résumé On a décrit un plan d'identification systématique des anions usuels dans leurs mélanges: sulfate, sulfite, nitrate, nitrite, fluorure, chlorure, bromure, iodure, ferricyanure, ferrocyanure, thiocyanate, phosphate, sulfure, thiosulfate et borate, au moyen de la technique du four annulaire.

     

Separation,detection and determination of uranium,thorium, bismuth,and lead in a drop of solution by the ring oven technique

Summary The separation of uranium, lead, bismuth and thorium from a drop of solution containing uranyl acetate, lead nitrate, bismuth nitrate and thorium nitrate has been achieved, using the ring oven technique. The drop was taken on a circular filter paper, treated with1 N HNO₃ and uranium was washed to the ring zone with n-butanol. Lead was next washed to the ring zone on another filter paper using 20% aqueous ethylenediamine hydrate. The spot was then treated with 1% aqueous sodium diethyldithioearbamate and bismuth was transported to the ring zone on a third paper with ethyl acetate. Finally 0.5N HNO₃ was employed to transfer thorium to the ring zone. The separated rings were then compared with standard rings prepared similarly to compute the amounts of the ions present.

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Zusammenfassung Die Trennung von U, Pb, Bi und Th wurde mit dem Ringofen durchgeführt. Ein Tropfen der Lösung wird auf ein Rundfilter gebracht, mit n-HNO₃ behandelt und das U mit n-Betanol in den Ring gewaschen. Blei wird auf einem anderen Filterpapier mit 20%iger wäßriger Äthylendiaminlösung in den Ring gewaschen, dann wird der Tüpfel mit 1%iger, wäßriger Lösung von Na-Diäthyldithiocarbamat behandelt und Wismuth auf einem 3-Filter mit Äthylacetat in den Ring gewaschen. Schließlich wäscht man Thorium mit 0,5-n Salpetersäure in den Ring. Die einzelnen Ringe werden mit Standardproben verglichen, um die Mengen abzuschätzen.

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Résumé On a réussi à séparer par la technique du four annulaire l'uranium, le plomb, le bismuth et le thorium dans une goutte de solution contenant de l'acétate d'uranyle, du nitrate de plomb, du nitrate de bismuth et du nitrate de thorium. La goutte est déposée sur un papier-filtre circulaire, traitée par HNO₃ N et l'uranium est entraîné vers la zone annulaire par lavage avec du butanolN. Le plomb est ensuite entraîné vers la zone annulaire sur un autre papier filtre à l'aide d'éthylènediamine en solution aqueuse à 20%. La tache est alors traitée avec le diéthyldithiocarbamate de sodium en solution aqueuse à 1% et le bismuth transporté sur la zone annulaire sur un troisième papier par l'acétate d'éthyle. Finalement, on utilise HNO₃ 0,5N pour le transport comparé avec des anneaux types préparés de la même manière pour estimer les quantités d'ions présents.

     

Chelate formation of ammonium aurintricarboxylate with bivalent copper : Micro-determination of copper by the colorimetric method

The formation of a coloured copper II chelate by ammonium aurintricarboxylate with λmax at 540 mμ may be utilised in the colorimetric determination of cupric ions on a micro-scale. It has been found that, for satisfactory results, at least a twentyfold molar excess of the reagent should be added. The colour intensity can be measured by using a spectrophotometer or a photoelectric colorimeter with a suitable filter.The colour is stable at room temperature for sufficiently long periods, but the intensity decreases above 30°C. For the formation of a colour suitable for measurement, the pH should be within 5.3–6.7. The smallest amount of copper that can be detected by the reagent is 1.7 p.p m. Details have been worked out for the use of this reagent, and the interference by various foreign ions has been noted and tolerance limits determined spectrophotometrically.     

Sodium alizarin-3-sulphonate as a chromophoric reagent

Summary A method has been recommended for the determination of thorium and molybdenum when present in micro-quantities, based on the formation of a red coloured water soluble chelate ( _max=520 nm for thorium and _max=470 nm for molybdenum) of the composition MRe=12, with sodium-alizarin-3-sulphonate. A large number of ions, however, interfere and should be removed before measurements are made. The solution of thorium chloride or ammonium molybdate may then be treated with a freshly prepared solution of Alizarin Red S. The p_H should be kept within the range 3.2 to 8.0 for thorium, 3.5 to 5.6 (preferably at 5.0) for molybdenum and the colour intensity may be measured with a photoelectric colorimeter or with a spectrophotometer. Temperature has no influence on the colour intensity. Determinations are possible between 0.23 and 16.70 ppm of thorium and 0.19 to 6.9 ppm of molybdenum.

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Zusammenfassung Zur Bestimmung von Mikromengen Thorium und Molybdän wird ein Verfahren vorgeschlagen, das auf der Bildung einer rotgefärbten, wasserlöslichen Komplexverbindung mit Natriumalizarin-3-sulfonat beruht. Die Zusammensetzung des Komplexes beträgt in beiden Fällen MeReagens=12. Die Absorptionsmaxima liegen bei 520 nm (Th) bzw. bei 470 nm (Mo). Viele Fremdionen verursachen Störungen und müssen vor der Messung entfernt werden. Die Lösung von Thoriumchlorid bzw. Ammoniummolybdat werden mit frisch bereiteter Alizarinrot S-Lösung behandelt; der p_H-Wert soll im Bereich 3,2–8,0 für Thorium bzw. 3,5–5,6 (am besten 5,0) für Molybdän liegen. Die Farbintensität wird mit einem photoelektrischen Colorimeter oder einem Spektrophotometer gemessen; sie wird von der Temperatur nicht beeinflußt. Die Bestimmung läßt sich im Bereich 0,23–16,70 ppm Thorium bzw. 0,19–6,9 ppm Molybdän durchführen.

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Part. II: Sinha, S. N., and A. K. Dey: Z. analyt. Chem. 183, 182 (1963).