Reagents for (ir)reversible enzymatic acylations

Commonly, hydrolase-catalysed reactions are used for kinetic resolutions of alcohols, amines and acids. Only a few applications in total syntheses have been described. Most of these examples are for the synthesis of amides and peptides. Here, the synthesis of all the different types of activated acids that can be applied in hydrolase-catalysed acylations is described. The application of these activated acids for both the formation of esters and amides is discussed and the different reactions are compared with the equivalent chemical reactions.     

Zur Ermittlung und rechnerischen Überprüfung thermodynamischer Daten aus experimentell gefundenen Werten, 7. Mitt.: Dampfdruckmessungen an binären,azeotropen Systemen und ihre Auswertung mit Hilfe des Matrizenkalküls

Zusammenfassung An Hand zweier binärer Systeme (Äthylamin/n-Butan und Benzol/Äthanol) wird die Anwendbarkeit verschiedener Ansätze zur Berechnung der Aktivitätskoeffizienten und zur Zerlegung der Totaldrucke in die Partialdrucke diskutiert. Die Koeffizienten desMargules-Ansatzes werden mit Hilfe des Matrizenkalküls hergeleitet. Für stark assoziierende Systeme wird die parktische Anwendbarkeit von Ansätzen mit logarithmischen Zusatzgliedern und ihre Auswertbarkeit nach der Methode der kleinsten Quadrate besprochen. DerMargules-Ansatz mit wenigstens vier Parametern vermag die Verhältnisse im stark verdünnten Bereich richtig wiederzugeben und ist zufolge seiner thermodynamischen Konsistenz jedem Ansatz mit logarithmischen Gliedern vorzuziehen. Voraussetzung für seine uneingeschränkte Anwendbarkeit ist allerdings die Benützung einer modernen elektronischen Rechenanlage.

---

Various statements for the calculation of activity coefficients are discussed for the two binary systems ethylamin/n-butane and benzene/ethanol. The statement ofMargules is deduced under application of the matrix calculation. Statements with logarithmic terms are used for systems with considerable association. The methode ofGauss of the smallest squares is shown to be applied in first and second approximation. The statement ofMargules with at least four parameters is able to describe correctly the thermodynamic conditions in very diluted concentrations. This statement must therefore be preferred to all these ones with logarithmic terms. In making use of the statement ofMargules a modern electronic computer has to be employed, if the number of the parameters increases.

---

---

Mit 4 Abbildungen     

Ein Dreikomponenten-Zweiphasensystem für die schnelle Flüssigkeits-Chromatographie

Zusammenfassung Für die Hochdruck-Flüssigkeits-Chromatographie wird ein Dreikomponenten-Zweiphasensystem beschrieben. Die Mischungslücke besteht zwischen dem wenig polaren Methylenchlorid und dem stark polaren Wasser und kann durch Zugabe von Äthanol als Lösungsvermittler geschlossen werden. Durch den Anteil der stark polaren Komponente in den jeweils koexistenten Phasen ist die Polarität von stationärer und mobiler Phase als stationäre gebunden und aus der mobilen immer wieder regeneriert. Durch Verteilungs-Chromatographie in der Mischungslücke ist eine Vielzahl von Stoffklassen der Trennung zugänglich, so z.B. Corticosteroide, Östrogene, Phenole, Phenolcarbonsäuren usw.

---

A three-component two-phase system for high speed liquid chromatography

Summary High pressure liquid chromatography with a three-component two-phase system is described. For the less polar methylenechloride and the highly polar water a wide range of incomplete miscibility exists which can be decreased with ethanol. The water content of the coexistent phases determines the polarity of the stationary and the mobile phases. The more polar phase is adsorbed on silicagel as the column support material and serves as the stationary phase. Numerous compounds can be separated by partition chromatography between the coexistent phases, for instance; corticosteroids, estrogens, phenols, phenol-carboxylic acids and so on

     

Chemische Vitamin D<Subscript>3</Subscript>-Bestimmung in Lebertran

The different aspects of Vitamin D₃ determination and the data reported in the literature are discussed. The spectrophotometric determination of Vitamin D₃ in cod-liver oil is carried out after the alkaline saponification, extraction of unsaponified parts, precipitation of accompanying sterols and the column- and thin-layer chromatographic purification and separation of vitamin D₃ on 40 cm plates from other vitamins. The dyestuff α-naphtholbenzein is suited well as standard substance for the better location and identification of vitamin D₃ zone on the thin-layer plate. The results obtained from the chemical method were checked through the simultaneous biological determination.     

(6-4)-photolyase activity requires a charge shift reaction

A model compound containing a thymine oxetane moiety linked to a flavin chromophore was investigated regarding (6-4)-photolyase activity. The need for a charge shift reaction was demonstrated by a detailed pH-dependent kinetic analysis.     

Strukturaufklärung gemischter Komplexe von Eisen(II), Kobalt(II) und Nickel

Iron(II), cobalt(II) and nickel form complexes of the formula [Me(TTA)₂B¹] with 1-(2′-thenoyl)-3,3,3-trifluoroacetone (HTTA) and 2-pyridinalphenylimines (B¹) or bis-(2-pyridinal-R-diimines) (B²) and — in dependence of the -R group in the B² compounds — complexes of the formula [Me₂(TTA)₄B₂] and [Me₂(TTA)₂B²]. The octahedral geometry of the complexes can be unequivocally proven by means of electron spectra, IR spectra and from magnetic measurements. The labelling of solid [Ni(TTA)₂B¹] complexes with the nickel isotopes⁵⁸Ni or⁶²Ni permits an allocation of the Me-O- and Me-N-valency oscillations in the FIR.     

Theory of chirality functions,generalized for molecules with chiral ligands

The theory of chirality functions described in a previous publication is generalized to allow for chiral ligands. In the earlier theory, all symmetry operations of the molecular frame could be thought of as permutations of the ligands among the sites; in the present work, improper rotations not only permute the ligands, but convert them into mirror images. The group that generates all isomers from a given ordered molecule belonging to a frame with n sites is now the hyperoctahedral group of order 2ⁿ n! consisting of all possible combinations of permutations and site reflections. The representation theory of these groups is described, and applied to the problem of constructing qualitatively complete chirality functions, and of deciding which ligand partitions, and which isomer mixtures, are chiral. It is found useful to classify chiral representations of the covering group as ligand specific and class specific. The ligand specific representations describe chiral properties which are common to all frames and arise purely from the chirality of the ligands, while the class specific representations describe the chiral properties of the frame. A number of examples are explicitly worked out.     

Über die Cyclisierung von Histidinderivaten

Cyclisierung vonl-Histidin-methylester und Histamin über die (nicht isolierten) N-Phenylthiocarbonyl-derivate (Ia) führt durch intramolekulare Harnstoffbildung zu Derivaten des neuartigen bicyclischen Ringsystems Imidazo(1,5-c)tetrahydrooxopyrimidin (II, III).Dieses ist relativ beständig gegen saure Hydrolyse; Einwirkung von basischen Reagenzien (Alkali und Amine) und von Lithiumaluminiumhydrid führt unter Öffnung des Pyrimidinringes (zwischen 4 und 5) zur Bildung von 4(5)-substituierten Imidazolderivaten, wobei mit Aminen N-Carbonsäure-amide (V bis IX) und mit LAH in der Seitenkette N-methylierte Produkte (X, XI) entstehen.Untersuchungen an offenkettigen Modellsubstanzen mit ähnlicher Struktur (XVI, XVII) führten zu ähnlichen Ergebnissen — Abspaltung von Imidazol und entsprechender Substitution der zweiten Komponente, die in manchen Fällen primär als Isocyanat abgespalten wird. Für diese Reaktionen wird ein möglicher Mechanismus diskutiert.DieR _F-Werte einiger Imidazolderivate wurden bestimmt.     

Determination of isotopic composition of lithium by neutron activation analysis; comparison with mass spectrometry

An activation analysis method is described for routine determination of⁶Li-abundances in various lithium compounds on the basis of the reaction sequence⁶Li(n,α)T and¹⁶O(t, n)¹⁸F and the measurement of¹⁸F. Irradiations of diluted equeous solutions of samples containing CrO₃ as internal flux monitor were carried out at a thermal neutron flux density of ϕ≤10¹¹ n·cm⁻²·sec⁻¹. Interferences from variations in neutron self-shielding oxygen concentration and triton range do not exceed 0.5% when using the dilution technique. The results for⁶Li abundances from 3.52 to 7.60% with standard deviations of 1 to 2.5% were confirmed by mass spectrometric measurements.     

Schnelle Trennung von Rückstoßprodukten in der Gasphase

Experiments are described in which recoil products are separated fast and selectively. The aim of these investigations is an identification of short-lived nuclides, either for the study of nuclear reactions or for the study of decay properties of new products. The recoil products were provided by a Cf-252 source. The transportation zone and the identification zone could be heated to different temperatures. Using N₂ as carrier gas it was possible to separate Te selectively under certain experimental conditions. When Cl₂ was added, Sb, Tc, Nb, Mo, Zr, Ru and Sn were transported. Transport output was determined in dependence of temperature and composition of the gas.