Asymmetric synthesis of (4S,5S)-2-oxo-4-phenyloxazolidine-5-carboxylic acid using a 1,2-addition of PhMgBr to an N-sulfinimine derived from (R)-glyceraldehyde acetonide and (S)-t-BSA

We report an asymmetric synthesis of (4S,5S)-2-oxo-4-phenyloxazolidine-5-carboxylic acid via stereoselective addition of phenylmagnesium bromide (PhMgBr) to an N-sulfinimine derived from (R)-glyceraldehyde acetonide. (S)- and (R)-Glyceraldehyde acetonides, important chiral synthons in synthetic organic chemistry, are prepared from the corresponding epichlorohydrin using an identical synthetic methodology.     

Einstein<Emphasis Type="Italic">A</Emphasis>-coefficients for rotational transitions in the ring-chain isomer of C<Subscript>5</Subscript>H<Subscript>2</Subscript>

Laboratory formation of four isomers of C⁵H² molecule is reported and detection of the ring-chain isomer (isomer 1) of C₅H₂ in cosmic objects has been suggested. For identification of a molecule in cosmic objects, one of the required input data is EinsteinA-coefficients (radiative transition probabilities) for the molecule. Here, we report EinsteinA-coefficients for electric dipole transitions in the ring-chain isomer of C₅H₂ among the rotational levels of the ground electronic and ground vibrational states up to 21 cm⁻¹.     

A modified volumetric method for the estimation of streptomycin sulphate in pharmaceuticals

Summary A volumetric method for the estimation of streptomycin sulphate in pharmaceuticals is based on the quantitative discharge of the violet colour of the maltol-iron complex, produced when streptomycin is hydrolysed in alkaline medium and treated with ferric chloride, by potassium permanganate. It is simple, accurate and other antibiotics such as dihydrostreptomycin, sodium salt of benzyl penicillin, chloramphenicol do not interfere. Procain penicillin has to be separated by extractio with chloroform.

---

Zusammenfassung Die beschriebene volumetrische Streptomycinbestimmung in Arzneimitteln beruht auf dem Abbau des Streptomycins in alkalischer Lösung zu Maltol, Bildung des Maltol-Eisen(III)-Komplexes und Titration mit Permanganat bis zur Entfärbung. Das Verfahren ist einfach auszuführen und gibt Werte von befriedigender Genauigkeit. Dihydrostreptomycin, Chloramphenicol sowie das Natriumsalz des Benzylpenicillins stören nicht. Procain-Penicillin muß vorher durch Extraktion mit Chloroform abgetrennt werden.

     

Molecular configurations in heavy-ion collisions

High spin properties of ²⁴Mg, ³²S and ³⁶S have been studied by means of the Strutinsky method. A separation degree of freedom is explicitly included by using a two-center model for the shellmodel part of the calculations. It is found that for the first two systems special configurations exist that are in their structure directly related to molecular ¹²C + ¹²C and ¹⁶O + ¹⁶O configurations and merge continuously into these with increasing separation. On the basis of these results the general problem of molecular states is discussed.     

Pseudohalide derivatives of (η -cyclopentadienyl-η-methylcyclopentadienyl) titanium (IV)

Summary Pseudohalide complexes of the (-cpL)TiXZ type (where cp = cyclopentadienyl, L = -McCs₅-H₄ and X = N3, NCS, NCO or NCSe) have been prepared in aqueous and nonaqueous media and characterized by elemental analyses, i.r. and n.m.r. spectroscopy. I.r. spectroscopy shows that NCS, NCO and NCSe are bonded to the titanium atom through nitrogen in these complexes which are thus true isothiocyanato, isocyanato and isoselenocyanato derivatives respectively.     

Secular-free solution up to third order of a model nonlinear equation for dispersive waves

The perturbation method of Lindstedt is applied to study the non linear effect of a nonlinear equation $$\nabla ^2 {\rm E} - \frac{1}{{c^2 }}\frac{{\partial ^2 {\rm E}}}{{\partial t^2 }} - \frac{{\omega _0^2 }}{{c^2 }}{\rm E} + \frac{{2v}}{{c^2 }}\frac{{\partial {\rm E}}}{{\partial t}} + E^2 \left[ {\frac{{\partial {\rm E}}}{{\partial t}} \times A} \right] = 0,$$ where (A. E)=0 andA,c, ω ₀ andν are constants in space and time. Amplitude dependent frequency shifts and the solution up to third order are derived.     

Mössbauer studies in disordered (NiFe)1−xCrx alloys

The variation of hyperfine field, isomer shift and Curie temperature with chromium concentration has been studied for the alloys (NiFe)_1?xCr_x for x = 0, 5, 10 and 15 at .%. The decrease in hyperfine field and isomer shift suggests an emptying of the majority spin d-band with increasing Cr concentration (reducing number of average 3d + 4s electrons per atom). The Curie temperature is also found to reduce rapidly with Cr concentration in agreement with magnetisation data. But the Curie temperatures as determined from Mössbauer spectra are considerably lower than those given by magnetisation studies and for the 10 and 15 at .% Cr concentrations the magnetic transition is spread out over a range of temperatures suggesting a mictomagnetic behaviour.     

Positron annihilation in annealed and quenched teflon and in sulphur

The value (τ₂) and the intensity (I₂) of the delayed component in the lifetime spectra of positrons annihilating in annealed and quenched teflon and in sulphur and crystex (polymer sulphur), at room temperature and at 77° K are reported. These data and the X-ray diffraction patterns for these materials are discussed in terms of the free volume model for the formation and quenching of positronium atoms in molecular materials.