Use of α-2-cyanoethyl tert-butoxycarbonylaspartate as an intermediate for synthesis of β-esters

The use of -2-cyanoethyl Boc-aspartate is proposed for the first time for the synthesis of -esters of Boc-aspartic acid. The -2-cyanoethyl protective group is selectively split out by strong organic bases under hydrolytic conditions without the -ester bond being affected. Using the -2-cyanoethyl derivative, -cyclohexyl, -benzyl, and -tert-butyl Boc-aspartates have been synthesized in good yields.All-Union Scientific-Research Institute of Molecular Biology. Vektor Scientific-Industrial Association. Ministry of the Medical and Biochemical Industries, Koltsovo, Novosibirsk Province. Translated from Khimiya Prirodnykh Soedinenii, No. 2, pp. 241–245, March–April, 1990.     

Metal complexes of phytohormones. Part IV. Interactions of tetrakis-μ-acetato dirhodium(II) with 6-furfurilaminopurine, 6-benzylaminopurine, 6-furfurilaminopurine riboside and 6-benzylaminopurine riboside

Summary Interactions of tetrakis--acetato-dirhodium(II) with purine-derived ligands of biological interest such as the cytokinins 6-furfurilaminopurine (K), 6-benzylaminopurine (BAP), 6-furfurilaminopurine riboside (KR) and 6-benzylaminopurine riboside (BAPR) have been studied by means of magnetic susceptibility measurements at room temperature, i.r. and electronic spectroscopy and thermogravimetric analysis 11 metal:ligand adducts were obtained with all ligands; in addition 12 adducts were obtained with KR and BAPR. The most plausible structure for the 11 adducts is a polymeric bridging one, involving both axial positions of the Rh^II dimer and two N-sites of the purine moiety; for the 12 adducts only one N-site is involved.     

New Synthesis of β-Iodostyrenes

A general procedure for the synthesis of -iodostyrenes is proposed. Aromatic aldehyde and ketone hydrazones are converted into the corresponding -iodostyrenes by treatment with CHI₃ in the presence of a catalytic amount of CuCl.     

Structural Transformations in Polydisperse Ferrofluids

Real polydisperse ferrofluid is modeled by a bidispersed magnetic colloid composed of large and small particles. It is assumed that the energy of magnetodipole interaction for small particles is much lower and that of large particles is substantially higher than their thermal energy. Therefore, large particles can combine into the chain and droplet aggregates that are present in a sea of small particles. The influence of small particles on the structurization in the ensemble of large particles is studied. It is shown that small particles can either prevent or stimulate these structural transformations depending on the parameters of a medium.     

Pheromones of coleoptera Communication 4. Synthesis of multistriatin with the application of the thermal hydroxy-cope rearrangement under high pressure

Conclusion The synthesis of multistriatin (in the form of the , , and isomers) was accomplished in three stages from 2-methyl-1-penten-3-one (IV) with the total yield of 13%. The thermal hydroxy-Cope rearrangement of 3-ethyl-2-methyl-1,5-heptadien-3-ol (II) at the pressure of 10 kbar was utilized at the key stage of the synthesis.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2776–2780, December, 1986.     

Synthesis of 1-O-acyl derivatives of carbohydrates through tert-butyl esters

Conclusions The synthesis of-D-glucopyranose pentaacetate,-maltose octaacetate, 1-O-benzoyl-2,3,4,6-tetra-O-acetyl--D-glucopyranose, and 1-O--(N-carbobenzoxy-L-alanyl)-2,3,4,6-tetra-O-acetyl-D-glucopyranose was accomplished by the reaction of acylhaloses with the tert-butyl esters of the corresponding acids.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1657–1658, July, 1972.     

Reduction of some D-homosteroids with an aromatic a ring with alkali metals under the conditions of Birch's reaction. II.

Summary 1. The reduction of 3-methoxy-D-homoestra-1, 3, 5(10), 8-tetraen-17a-ol (IV) with alkali metals in the presence of ammonium chloride or alcohol gives, in addition to 8, 9-dihydro derivatives, the 8, 9 and 8, 9-epimers, the structure of which has been shown partly by independent synthesis and partly on the basis of chemical reactions and NMR spectra.2. Hydrolysis of the reduction products has given 19-nor-D-homotestosterone (III) and its 8- and 9, 10-epimers (V) and (VI). The ketols (III) and (V) readily form hydroperoxides in air.3. The reduction of the ethylene ketal of 3-methoxy-D-homoestra-1, 3, 5(10), 8-tetraen-17a-one (XIX) takes place stereodirectively and gives only 8, 9-dihydro derivatives.Khimiya Prirodnykh Soedinenii, Vol. 1, No. 2, pp. 90–100, 1965     

Isoxazole derivatives in the synthesis of bifunctional compounds by cleavage of the heteroring (review)

The pathways and methods of transformation of isoxazoles to give various acyclic difunctional derivatives (-cyano ketones, -diketones, imino and amino ketones, -amino alcohols, ,-unsaturated ketones, etc.) by opening of the heteroring are examined in the review from the point of view of latent functionality. The prospects for the application of acyclic functional derivatives of isoxazoles and 2-isoxazolines — adducts of 1,3-dipolar cycloaddition of nitrile oxides to olefins and acetylenes — for regio- and stereospecific synthesis are discussed.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1155–1173, September, 1981.     

Metallurgical factors determining the coercivity of ND-FE-B magnets

In Nd-Fe-B based permanent magnets a high magnetocrystalline anisotropy of the hardmagnetic phase is necessary for a high intrinsic coercivity. In fact, metallurgical parameters (distribution of phases, chemical composition and crystal structures of phases) and processing parameters (alloy preparation, size and shape of particles, sintering and annealing treatments) determine the value of the coercive force of each sintered Nd-Fe-B magnet. Our analytical electron microscope study shows that melt-spun and sintered Nd-Fe-B based magnets contain more or less a distribution of nucleation centres for reversed domains, such as iron-rich phases and-iron precipitates within the hardrnagnetic 2141-grains. A continuous non-magnetic layer phase between the hardrnagnetic 2141-grains increases the expansion field of reversed domains and increase the coercivity. In melt-spun magnets the contribution of the pinning of magnetic domain walls becomes effective during the magnetization reversal process.     

Does the p-Ps lifetime agree with expectations from magnetic quenching?

Magnetic quenching experiments with naphthalene give small value of density parameter . Corresponding lifetime of p-Ps should be equal or close to that of free annihilation. Contrary to expectations, we obtained the lifetime of short-lived component ₁=180ps (its intensity is larger than predicted by statistical weight rule). Generally, the experiments with the use of magnetic field give smaller value than these using zero-field methods.     

Homogeneous kinetics with programmed temperature variations,I

A new method is proposed for the derivation of kinetic parameters of reactions in homogeneous systems, by carrying out kinetic measurements under conditions of programmed temperature variations, instead of performing them under isothermal conditions at different temperatures. The basic relations are given for simple, paralle and complex reactions, without specifying the analytical shape of the temperature programme function.

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Zusammenfassung Es wurde eine neue Methode zur Ableitung kinetischer Parameter von in homogenen Systemen verlaufenden Reaktionen vorgeschlagen. Die kinetische Messung wurde unter programmierten Temperaturänderungen ausgeführt, anstatt unter isothermischen Bedingungen bei verschiedenen Temperaturen. Die grundlegenden Beziehungen wurden für einfache, parallele oder komplexerweise verlaufende Reaktionen beschrieben, ohne auf die Form der Funktion des Temperaturprogrammes Rücksicht zu nehmen.

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Résumé On propose une nouvelle méthode de calcul des paramètres cinétiques des réactions en milieu homogène. Les mesures cinétiques sont effectuées en programmant les variations de température au lieu d'opérer en thermostat à différentes températures. On donne les relations fondamentales pour les réactions simples, parallèles et complexes, sans prendre en considération la forme analytique de la fonction du programme de la température.

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, , , . , .

     

peri-Naphthylenediamines. 38. Naphthalene and acenaphthene “proton sponges” with +M substituents in ortho positions with respect to peri-dimethylamino groups

Previously unknown 4,5,6,7-tetrakis(dimethylamino)acenaphthene, which is the first acenaphthene derivative containing four vicinal dialkylamino groups, was synthesized based on 5,6-bis(dimethylamino)-4,7-dinitroacenaphthene. The total synthesis of 1,2,7,8-tetrakis(dimethylamino)naphthalene was carried out starting from 3,6-dinitronaphthalic anhydride. Other proton sponges of this type, viz., 1,7,8-tris(dimethylamino)-2-methoxy- and 1,8-bis(dimethylamino)-2,7-dipiperidinonaphthalenes, were prepared by the nucleophilic substitution in 2,7-dimethoxy-1,8-dinitronaphthalene. In solutions, 1,2,7,8-tetrakis(dimethylamino)naphthalene and its analogs can form di- and trications in the presence of acids. The basicity constants pK _a ¹ of the compounds measured in DMSO depend in a complex way on their structures but correlate with the basicity index B, which is determined by changes in the chemical shifts _H after the addition of the first proton. Due to low C-nucleophilicity of ortho-disubstituted proton sponges in combination with high basicity, these compounds hold considerable promise as reagents in organic synthesis.     

Solid-state decomposition studies on fluoroperoxo species of transition metals part II

The kinetics of isothermal decomposition of solid K₂Zr₂(O₂)₂F₆·2H₂O have been studied in the temperature range 100–226° under vacuum. The fractional decomposition has been determined by measuring the pressure of evolved oxygen during pyrolysis with the help of a McLeod gauge. The values ranged from 0.05 to 0.62. The vs. t data showed that the kinetics are deceleratory throughout the course of the reaction. The initial part of the decomposition reaction could be best described by a unimolecular decay law, while the later stages obey contracting volume kinetics. The activation energies have been determined and the respective values for the above stages are 13.6 and 6.9 kcal·mole^–1.

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Zusammenfassung Die Kinetik der isothermen Zersetzung von festen K₂Zr₂(O₂)₂F₆·2H₂O wurde im Temperaturbereich von 100–226° im Vakuum untersucht. Die fraktionierte Zersetzung wurde durch Messung des Druckes des während der Pyrolyse entwickelten Sauerstoffs mit einem McLeod-Manometer bestimmt. Die -Werte variierten von 0.05 bis 0.62. Die -t Daten zeigen, daß die Kinetik im Verlauf der Reaktion herabgesetzt wird. Der erste Teil der Zersetzungsreaktion konnte am besten durch ein unimolekulares Zerfallgesetzt beschrieben werden, während die späteren Phasen der Kinetik der Volumenkontraktion gehorchten. Die Aktivierungsenergien wurden berechnet und die entsprechenden Werte für obige Reaktionen ergaben sich 13.6 bzw. 6.9 Kcal mol^–1.

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K₂Zr₂(O₂)₂F₆·2₂ 100–226°. «» , , . «» 0.05 0.62. –t , . , — . , , , 13.6 6.9 .^–1.

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One of the authors (SMK) is grateful to I.I.T. Delhi for a research scholarship.     

In situ laser thermal analysis of bulk materials

The application of thermal analysis techniques directly to the materials being processed could open up new opportunities in the fields of non-destructive testing and process monitoring on the industrial floor. In this paper, a convergent-thermal-wave technique is proposed for the measurement of thermal diffusivity when access to the material is restricted to one side only. Such a technique permits measurement of the thermal properties of samples of large or unknown thickness, as well as coated or stratified materials. A finite-difference numerical model is used to evaluate the possibilities and the accuracy offered by such a technique, and a laser-based experimental apparatus for the non-contact generation and monitoring of annular thermal waves is described.

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Zusammenfassung Die direkte Anwendung thermischer Analysenverfahren auf darzustellende Materialien könnte neue Möglichkeiten auf dem Gebiet der nichtzerstörenden Materialprüfung und der industriellen Prozeßüberwachung bieten. In diesem Artikel wird eine Konvergenzthermowellen-Technik zur Messung des thermischen Diffusionsvermögens vorgeschlagen, die auch dann anwendbar ist, wenn das Material nur von einer Seite her zugänglich ist. Diese Technik ermöglicht die Messung thermischer Eigenschaften von Porben unbekannter Größe oder Dicke sowie die von belegten oder beschichteten Materialien. Ein numerisches endliches Differenz-Modell wird zur Bewertung der durch solch eine Technik gebotenen Möglichkeiten und deren Genauigkeit herangezogen. Eine auf Laser basierende Versuchsapparatur zur Nicht-Kontakt-Erzeugung und Aufzeichnung von ringförmigen thermischen Wellen wird beschrieben.

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. , . , . . .

     

Synthesis of new arylidene derivatives of 3-aminorhodanine

The synthesis of new arylidene derivatives of 3 -aminorhodanine has been effected. It has been established that the condensation of 3-aminorhodanine with aldehydes in an alcoholic medium gives 3-arylidene derivatives. Similar reactions in an ammoniacal medium lead to 5-derivatives of 3-aminorhodanine. 3, 5-Diarylidene derivatives can be obtained by condensing 3-aminorhodanine with an excess of an aldehyde in glacial acetic acid, except for the salicylidene and 9-anthrylidene derivatives, the synthesis of which can be carried out only in two stages.     

Crystallization of iron phosphate glasses

Differential thermal analysis (DTA), thermogravimetric analysis (TG), X-ray diffraction and Mössbauer spectroscopy were employed in the investigation of crystalline products of FeO_x-P₂O₅ glasses generated by various heat treatments. In glasses with a high value of =Fe²⁺/(Fe²⁺ + Fe³⁺), absorption of oxygen occurs in a broad temperature range identified by TG. Depending on the value of , two exotherms appear in the DTA curves, the low-temperature one corresponding to crystallization of the Fe₃(PO₄)₂ type regions, and the high-temperature one being related to various phases with dominating FePO₄. Each exotherm has its own transformation region, identical in absolute value. The Mössbauer spectra of glasses which underwent thermal treatment at higher temperatures exhibit some indication of phases of the types Fe₃(PO₄)₂ · xH₂O and FePO₄ · xH₂O.

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Zusammenfassung Differentialthermoanalyse (DTA), thermogravimetrische Analyse (TG), Röntgendiffraktion und Mössbauerspektroskopie wurden bei der Untersuchung (von kristalliner Produkte) durch verschiedene thermische Behandlungen hergestellten FeO_x-P₂O₅ Gläsern eingesetzt. In den Glasarten mit einem hohen Wert von =Fe²⁺/(Fe²⁺ + Fe³⁺) erfolgt die Sauerstoffabsorption in einem durch TG [nachgewiesenen breiten Temperaturbereich. In Abhängigkeit von dem -Wert erscheinen zwei Exothermen in den DTA-Kurven, von denen der bei niedriger Temperatur die Kristallisation des Fe₃(PO₄)₂ entspricht, und jener bei höheren Temperaturen in verschiedenen Phasen dem FePO₄. Jede Exotherme hat ihr eigenes Umwandlungsgebiet, das in absolutem Wert identisch ist. Die Mössbauer-Spektren der Gläser welche einer Wärmebehandlung bei höheren Temperaturen unterzogen worden sind, weisen einige Indikationsphasen der Typen Fe₃(PO₄)₂ · xH₂O und FePO₄ · xH₂O auf.

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, , FeO_x-P₂O₅, . , =Fe²⁺/(Fe²⁺+Fe³⁺) . , - : Fe₃(PO₄)₂, – FePO₄. , . , , Fe₃(PO₄)₂ · ₂ FePO₄ · ₂.

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The authors thank Mrs. Simonyiová for assistance in the experimental part of these investigations, and Dr. Horváth and Dr. Vondrovic for performing the X-ray and TG analyses.     

Electrostatic interactions in phospholipid membranes I: Influence of monovalent ions

Electrostatic interactions in monolayers and vesicles of acidic phospholipids are studied by thermodynamical and optical techniques in conjunction with numerical calculations. A nonmonotonic ionic strength dependence with an extremum at 0.1 M (NaCl) is observed for the phase transition temperature of vesicles as well as for the surface pressure of monolayers at low molecular density. This finding is in accordance with the calculations predicting the dominance of charge screening by monovalent counterions only for concentrations above 0.1 M. For lower salt content, however, its increase causes an elevation of the degree of dissociation and thus also electrostatic repulsion. This leads to a higher surface pressure, a lower transition temperature and a smaller size of solid domains observed in the liquid/solid coexistence range of monolayers. This supports the previously published idea, that finite size and repulsion of the domains arise from a different surface charge density in fluid and solid lipid phases.Abbreviations DLPA L--dilauryl-phosphatidic-acid - DMPA L--dimyristoyl-phosphatidic-acid - EDTA Ethylenediamine-tetraacetic acid (sodium salt) - DP-NBD-PE L--dipalmitoyl-nitrobenzoxadizol-phosphatidylethanolamine     

Aspects and prospects of the chemistry of organic heterocycles (review). Part I

The systematics of heterocycles, their place in organic chemistry, and their significance for theory and practice are discussed. Problems of the chemistry of heterocycles are discussed on the examples of systems with various types of conjugation and ring sizes. The focus is on the principles of synthesis of heterocycles, in particular, those based on acetylene, various C₃ fragments, carbon disulfide, and maleic anhydride. Individual sections of the survey are devoted to the role of heterocycles in biosynthesis, as well as certain problems common to the chemistry of heterocycles, biochemistry, and macromolecular chemistry.The present survey represents a reworking of material on the major pressing problems of the chemistry of heterocyclic compounds, previously published by the author [1, 2]. It should be mentioned that in this case a whole series of synthetic methods that are still important were used (chlorolysis, pyrolysis, photolysis, electrolysis, relay synthesis of intermediate products, and an auxiliary synthetic role of heteroatoms). Only here was the independence of the chemistry of carbon compounds from vis vitalis substantiated and accorded universal recognition (see the notes in [6, p. 199; 7, p. 156; 8, p. 7]). F. Wohler's student, H. Kolbe, also emphasized that it is impossible to construct a boundary between organic and inorganic. Each approach associated with the chemistry of the organism should have received its logical development in the biochemistry and molecular biology of our time: Sciences as a whole, in the course of their development, have moved away from light and are being rejoined only by roundabout routes (I, W. Goethe, in: Maximen und Reflexionen. Freiburg/Br. (1950), p. 115: originally quoted in the book Wilhelm Meisters Wanderjahre (1829) i.e., only a year after Wohler's discovery — a curious coincidence). The use of the term synthesis instead of the term artificial formation, a unique sort of metamorphosis, was long overdue; this concept was already coined in 1845 by H. Kolbe [4] and A. Hofmann [9]; however, in the modern sense this term was introduced and first comprehensively defined in 1860 by M. Berthelot [10] (see also [8, p. 8]).Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1443–1470, November, 1985.     

Synthesis and electrochemical studies of a new series of pendantarmed hexaazamacrocyclic transition metal complexes

Summary The synthesis of a new series of 14- and 16-membered hexaazamacrocyclic complexes has been achieved by the template condensation of ethylenediamine or 1,3-propylenediamine with formaldehyde and acetamide in a 121 molar ratio in the presence of metal chlorides. Octahedral structural formulae for selective metal complexes are proposed on the basis of physico-chemical and spectroscopic data. The redox behaviour in DMSO solution of the Cu^II complexes has been studied by cyclic voltammetry.     

Kinetics and mechanism of isothermal dehydration of LiKC4H4O6 · H2O single-crystals

The kinetics of isothermal dehydration of LiKC₄H₄O₆.H₂O single-crystals was investigated in the [001] crystallographic direction under a dynamic vacuum of 6.7×10^–5 Pa with a quartz crystal microbalance. The removal of H₂O molecules may be described by a diffusion equation for a semi-infinite medium. The diffusion coefficients vary from 2.13×10^–11 cm² s^–1 at 391.7 K to 9.9×10^–9 cm² s^–1 at 453.2 K. The scanning electron microscope data provide some evidence that the dehydration is not a topochemical reaction. From the experimental data it is concluded that the anhydrous product is in the state of premelting. This explains the anomalous diffusion energyE _D=37±1 kcal mol^–1 and preexponential factorD ₀=5×10⁹ cm² s^–1.

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Zusammenfassung Die Kinetik der Entwässerung von LiKC₄H₄O₆.H₂O in [001] — Richtung unter dynamischem Vakuum wurde mit einer Quarzkristall-Mikrowaage verfolgt. Die Abgabe von Wasser kann mit einer Diffusionsgleichung für ein halb-unendliches Medium beschrieben werden, die Diffusionskoeffizienten variieren von 2, 13 · 10^–11 cm²s^–1 bei 391,7 K bis 9,9 · 10^–9 cm² s^–1 bei 453,2 K. Rasterelektronenmikroskopische Aufnahmen zeigen, daß die Entwässerung nicht topochemisch abläuft. Nach dem experimentellen Ergebnis befindet sich das entwässerte Produkt in einem Vorschmelz-Stadium. Daraus erklären sich die anomalen Werte für die DiffusionsenergieE _D=(37±1) kcal mol–1 und den präexponentiellen FaktorD ₀=5 · 10⁹ cm² s^–1.

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6,7 · 10. LiKC₄H₄O₆.H₂O [001]. . 2,13·10^{–11 2 –1} 391,7 9,9·10^{–9 2 –1} 453,2 . , . , «», E =37±1 ·^{– 1} ₀=5·10⁹²·^–1.