Effect of the Composition of the Aqueous Organic Solvent on the Kinetics of N-Acylation of α-Amino Acids with 4-Nitrophenyl 4-Nitrobenzoate

Equations relating the N-acylation rate constants of glycine, L--alanine, DL-threonine, and L-proline with 4-nitrophenyl 4-nitrobenzoate in water-acetonitrile, water-2-propanol, and water-2-methyl-2-propanol solvents to the composition of the medium were obtained, and reaction rate constants in water were calculated.     

IR spectroscopic study of the conformational lability of 4′-ethyl-4-cyanobiphenyl

The conformational lability of 4-ethyl-4-cyanobiphenyl molecules in solid crystal (SC) and isotropic liquid (IL) states was investigated by IR spectroscopic techniques (experiment and theory). IR absorption spectra were measured at 28°C–95°C in the frequency range 400 cm^–1–4000 cm^–1. Spectrum simulation was performed using the fragment method with allowance for the conformational fluctuations of molecules. The experimental and calculated spectra were compared and analyzed, and it was shown that in the IL, the samples are mixtures of conformers. The temperature changes in the spectra in the stated range are caused by the conformational lability of molecules.Original Russian Text Copyright © 2004 by L. M. Babkov, I. I. Gnatyuk, G. A. Puchkovskaya, and S. V. TrukhachevTranslated from Zhurnal Strukturnoi Khimii, Vol. 45, No. 3, pp. 398–405, May–June, 2004.     

NaIO_4-Catalyzed Bromination of the Aromatic Ring of Lappaconitine

Lappaconitine 1, a bisnorditerpenoid alkaloid, was isolated from many plants of Aconitum species such as A. barbatum var. pulerulum and A. sinomontanum (Ranunculaceae)1-3, and used clinically for treatment of analgic disease as a nonaddicted drug in China4, and as an antiarrythmic in Uzbekistan5. In order to search for high activity, low toxicity compounds, we have carried out the structure modifications of lappaconitine. In this case, an attempt to induce the oxygenated group at C-10 in 1 b…     

Formation of organic peroxides in the photooxidation of CH_4

Ｏｒｇａｎｉｃｐｅｒｏｘｉｄｅｓａｒｅｔｈｅｉｎｔｅｒｍｅｄｉａｔｅｐｒｏｄｕｃｔｓｉｎｔｈｅｏｘｉｄａｔｉｏｎｏｆｈｙｄｒｏｃａｒｂｏｎｃｏｍｐｏｕｎｄｓ(ＨＣ).ＭｅｔｈａｎｅｉｓｔｈｅｍｏｓｔａｂｕｎｄａｎｔＨＣｉｎｔｈｅａｔｍｏｓｐｈｅｒｅ,ａｎｄｉｔｓｃｏｎｃｅｎｔｒａｔｉｏｎｉｓｓｔｉｌｌｉｎｃｒｅａｓｉｎｇａｔｔｈｅｒａｔｅｏｆ0.8%ａｎｎｕａｌｌｙ.Ｈｅｎｃｅ,ｔｈｅｏｘｉｄａｔｉｏｎｏｆＣＨ4ｍａｙｂｅａｎｉｍｐｏｒｔａｎｔｓｏｕｒｃｅｏｆｏｒｇａｎｉｃｐｅｒｏｘｉｄｅｓ.Ｈｏｗｅｖｅｒ…     

Structural variations of N-acetylneuraminic acid,part 19: Synthesis of both epimeric pairs of the 4-C-methyl- and 4-deoxy-4-C-methyl- as well as of the β-methylketoside of 4-deoxy-4-C-methylene-N-acetylneuraminic acid

Summary While the reaction of the 4-oxo-Neu 5 Ac derivative2 a with tributoxy methyl zirconate led exclusively to equatorial 4-C-methyl derivative3 a, the analogous reaction with tetramethyl zirconate yielded a 3:2 mixture of both diastereoisomeres3 a and4 a. After removal of protecting groups the 5-acetamido-3,4-dideoxy-4-C-methyl-D-glycero-D-galacto-2-nonulosonic acid5 a and 5-acetamido-3,4-dideoxy-4-C-methyl-D-glycero-D-talo-2-nonulosonic acid6 a were obtained. The 4-C-methylene derivative was prepared by treatment of the same 4-oxo-derivative with CH₂I₂/Zn/Cp ₂ZrCl₂. Subsequent hydrogenation led to both epimeric 4-deoxy-4-C-methyl derivatives8 a and9 a. Final removal of protecting groups gave the 5-acetamido-3,4,5-trideoxy-4-C-methyl-D-glycero-D-galacto-2-nonulosonic acid10 a respectively the 5-acetamido-2,7-anhydro-4-C-methyl-3,4,5-trideoxy-D-glycero-D-talo-2-nonulosonic acid11 a. The -methylketosides of the 4-deoxy-4-C-methyl- (16) and 4-C-methylene-Neu 5 Ac (15) were prepared via the peracetylated derivatives to obtain modell substrates for enzymatic studies. Thus all free acids were tested for inhibition of CMP-sialate synthease. Only the 4-C-methylene compound15 showed most unexpectedly a strong competitive inhibition of this enzyme.

---

Strukturelle Abwandlungen an N-Acetylneuraminsäure, 19. Mitt.: Synthese der beiden Epimerenpaare der 4-C-Methyl- und 4-Deoxy-4-C-methyl- sowie des -Methylketosids der 4-Deoxy-4-C-methylen-N-acetylneuraminsäure. Verhalten gegenüber CMP-Sialat-Synthase

Zusammenfassung Während die Umsetzung des 4-Oxoderivates2 a mit (BuO)₃ MeZr ausschließlich zur equatorialen 4-C-Methylverbindung3 a führt, wurde bei der Reaktion mitMe ₄Zr ein 3:2-Gemisch der beiden Diastereomeren3 a und4 a erhalten. Das 4-C-Methylenderivat7 a wurde durch Reaktion derselben 4-Oxoverbindung mit CH₂I₂/Zn/Cp ₂ZrCl₂ erhalten. Eine anschließende Hydrierung (H₂-Pd/C) führte zu einem trennbaren Germisch der beiden 4-Deoxy-4-C-methylderivative8 a und9 a. Diese Verbindungen konnten durch das Entfernen der Schutzgruppen einerseits in die 5-Acetamido-3,4,5-trideoxy-4-C-methyl-D-glycero-D-galacto-2-nonulosonsäure10 a und 5-Acetamido-2,7-anhydro-4-C-methyl-3,4,5-tridoxy-D-glycero-D-talo-2-nonulosonsäure11 a umgewandelt werden. Die Verbindungen Methyl-5-acetamido-4-C-methylen-3,4,5-trideoxy--D-manno-2-nonulopyranosidonat (15) und Methyl-5-acetemido-4-C-methyl-3,4,5-tridoxy--D-glycero-D-talo-2-nonulopyranosidonat (16) wurden als Modellverbindungen für enzymatische Untersuchungen über peracetylierte Zwischenstufen hergestellt. Überraschenderweise zeigte nur die 4-C-Methylenverbindung15 eine starke kompetitive Hemmung gegenüber CMP-Sialat-Synthase.

     

Synthesis of 4-vinyl substituted β-lactams of the oxamazin family

4-Vinyl-substituted oxamazins 15,16, and 3 have been prepared. Key steps of the synthesis are: the preparation of protected α-amino-β-hydroxyacid 6 through ester enolate condensation of ethyl glycinate STABASE adduct 8 with CH-protected propiolaldehyde 9, the coupling of this acid with an appropriate protected hydroxylamine, the cyclization of resulting hydroxamate, and finally the acylation of the amino-group in 3 with ATMO side chain.     

Stereochemistry of the asymmetric alkylation of Δ9,10-octahydroquinolin-4-ones

The asymmetric character of the alkylation of a series of metallated bicyclic enaminoketones has been established and its stereoselectivity has been investigated. The enantiomers of (3S*)-methyl- and (3S*)- and (3R*)-3-methyl-3-butyl-^9,10-octahydroquinolin-4-ones have been obtained. The possibility of inducing chirality at the 3 position of the enaminoketone molecule during methylation in the presence of chiral lithium amides has been established in principle.M. V. Lomonosov Moscow State University, Moscow 119899. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1531–1542, November, 1995. Original article submitted November 10, 1995     

Experimental investigation of the formation of double phosphates in the LaPO4–NaF system

In the course of segregation smelting of rare-earth and rare metal raw materials with a fluxing agent (NaF), two immiscible melts form, one of which is a silicate melt and the other is a phosphate–salt melt. The silicate melt is enriched with Fe₂O₃, Al₂O₃, SiO₂, and Nb₂O₅, and the phosphate–salt melt is dominated by P₂O₅, TR₂O₃, Sc₂O₃, and Y₂O₃, and also with Ca, Sr, and Ba oxides. Chemical reactions between lanthanum orthophosphate and sodium fluoride in the LaPO₄–NaF system were studied for developing a technology for processing the phosphate–salt (rare-earth metal) melt. It was found that a metathesis reaction gives double phosphate Na₃La[PO₄]₂ and binary fluoride NaLaF₄. The products of crystallization of melts in the LaPO₄–NaF system decompose in weak mineral acids unlike those in conventional technology for processing monazite raw material.     

Structure of Dimers and the Nature of Color in 4′-Nitro-4-dimethylaminoazobenzene Solutions

A mechanism is proposed for the formation of stable dimers of 4′-nitro-4-dimethylaminoazobenzene dye (4′-nitro-DAB)₂ in solution, the existence of which in a vapor phase was established in 1965. It is shown that (4′-nitro-DAB)₂ dimers are stable also in neutral and moderately acidic solutions. Their UV–Vis spectra are similar to the spectra of the same solutions of 4-dimethylaminoazobenzene (DAB) containing DAB₂ dimers as the ground state. Like DAB₂, (4′-nitro-DAB)₂ dimers are reversibly converted to di- and triprotonated dimers under conditions of low and moderate acidity. In the process, the yellow color of the initial solution changes to red. It is concluded that the great stability of the dimers in the liquid and vapor phases is due to their inter-monomer bonds being formed with the participation of electrons promoted from the sp²- orbitals of N-atoms in azo-groups N=N to the Rydberg 3s-orbitals of the N=N-group (Rydberg bonds). It is established that at high acidities, the triprotonated dimers (the red solution) decompose reversibly into diprotonated monomers (the yellow solution). Structural formulas are proposed for the protonated species.     

Use of HPLC in the Determination of the Molar Absorptivity of 4��-Geranyloxyferulic Acid and Boropinic Acid

Natural prenyloxycinnamic acids were shown to exert in vitro and in vivo remarkable and valuable anti-cancer and anti-inflammatory effects. Among these, 4??-geranyloxyferulic acid [3-(4??-geranyloxy-3??-methoxyphenyl)-2-trans-propenoic acid] was discovered as an efficient orally active chemopreventive agent of several types of cancer, and its structural analogue boropinic acid was shown to exert a valuable inhibitory effect both in vitro and in vivo against the growth of Helicobacter pylori. As a continuation of our chemical, chemico-physical, and pharmacological studies on these secondary metabolites, we report herein the comparison between traditional UV/Vis assays and HPLC?CDAD methods for the determination of the molar absorptivity coefficient of 4??-geranyloxyferulic acid (?? ₃₁₀ = 12,950 and ?? ₂₈₈ = 11,910 L mol^?1 cm^?1) and boropinic acid (?? ₃₁₀ = 13,510 and ?? ₂₈₈ = 12,350 L mol^?1 cm^?1). Ferulic acid was merely used as a reference standard to test the possibility of the application of these two assays to the oxyprenylated compounds. The data reported in the present study will represent an essential aid for future studies aimed to better define the pharmacological profile and the mechanism of action of these compounds and are an important starting point to evaluate other natural products where standard powders are not available.     

Investigations in the region of 2,3′-biquinolyl 4. Alkylation of the dianion of 2,3′-biquinolyl

With alkyl chlorides and alkyl phenyl ethers the dianion of 2,3-biquinolyl forms the products from alkylation at position 4. Their treatment with alkyl halides or water gives 1, 4-dialkyl-1, 4-dihydro-2,3-biquinolyls or 4-alkyl-1,4-dihydro-2,3-biquinolyls respectively.For communication 3, see [1].Stavropol State University, Stavropol, Russia 355009. Russian Chemical Technology University, Moscow 125190. Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, pp. 1214–1217, September, 1998.     

Spin-adduct of the P4 ·− radical anion during the electrochemical reduction of white phosphorus

The radical anion P₄·⁻ was detected and identified by the ESR method as a spin-adduct with nitrone during the electrochemical reduction of white phosphorus in the presence of a spin trap, viz., α-phenyl-N-tert-butylnitrone, in a special electrolysis cell with a helical platinum working electrode in the potentiostatic mode. The character of the behavior of P₄·⁻ and the spin trap during electrochemical reduction was monitored by cyclic voltammetry directly in the electrolysis cell, and the spin-adduct formed was detected by ESR.     

A Study on the Kinetics of the Catalytic Reforming Reaction of CH4 with CO2： Determination of the Reaction Order

The kinetics of the catalytic reforming reaction of methane with carbon dioxide to produce synthesis gas on a Ni/(α-A1203 and a HSD-2 type commercial catalyst has been studied. The results indicate that the reaction orders are one and zero for methane and carbon dioxide, respectively, when the carbon dioxide partial pressure was about 12.5-30.0 kPa and the temperature was at 1123-1173 K. However, when the carbon dioxide partial pressure was changed to 30.0-45.0 kPa under the same temperature range of 1123-1173 K, the reaction orders of methane and carbon dioxide are one. Furthermore, average rate constants at different temperatures were determined.     

A vibrational analysis of the MnO 4 − bands

Teltow'S [14,15] measurements of the permanganate bands are reanalyzed using the level scheme of Ballhausen and Liehr [2]. For KMnO ₄ dissolved in KClO ₄ the components of the first ¹ T ₂ state are found at 18050 cm^–1 18078 cm^–1 and 18043 cm^–1. The breathing frequency of the MnO _– ⁴ unit is in this state 768 ^–1. The electronic origin of the second ¹ T ₂ state is found at 30723 cm^–1 with a breathing frequency of 760 cm^–1.Evidence is further found for a ¹ T ₁ state with its split components located at 14446 cm^–1, 14526 cm^–1 and 14600 cm^–1. The breathing frequency is here found to be 800 cm^–1.Finally for KMnO ₄ dissolved in NaClO ₄ there are indications that one or two spin-triplets are located near 13200 cm^–1.

---

Zusammenfassung TeltowS Messungen des Permanganatspektrums [14, 15] werden mit Hilfe des Termschemas von Ballhausen und Liehr [2] von neuem analysiert. Für KMn ₄ in KClO ₄ findet man die zum ersten ¹ T ₂-Zustand gehörenden Komponenten bei 18050, 18078 und 18043 cm^–1. Die Valenzschwingung des MnO _– ⁴ liegt hier bei 768 cm^–1. Der Ursprung des zweiten ¹ T ₂-Systems wird bei 30723 cm^–1 gefunden, die dazugehörige Valenzfrequenz ist 760 cm^–1.Bei 14446, 14526 und 14600 cm^–1 liegen offenbar die Komponenten eines ¹ T ₁-Terms, wozu eine Valenzfrequenz von 800 cm^–1 gehört.Schließlich findet man für KMnO ₄ in NaClO ₄ Anzeichen für ein oder zwei Spin-Tripletts um 13200 cm^–1.

---

Résumé Les bandes d'absorption du permanganate, mesurées par Teltow [14,15], sont réanalysées à l'aide d'un système de termes proposé par Ballhausen et Liehr [2]. Pour KMnO ₄ dans KClO ₄, on trouve les composants du premier état ¹ T ₁ à 18050, 18078 et 18043 cm^–1. La vibration symétrique du MnO _– ⁴ dans cet état se situe à 768 cm^–1. L'origine électronique du second état ¹ T ₂ est trouvé à 30723 cm^–1, la fréquence oscillatrice correspondante est de 760 cm^–1.Un état ¹ T ₁ avec ses composants à 14446, 14526 et 14600 cm^–1 est mis en évidence, avec une vibration symétrique de 800 cm^–1.Finalement, au cas du KMnO ₄ dissous dans le NaClO ₄, il y a des indications pour un ou deux triplets de spin vers 13200 cm^–1.

     

The thermodynamic stability of the LaBr 4 − ion

The thermodynamic stability of the LaBr ₄ ^? anion was for the first time studied by high-temperature mass spectrometry and nonempirical quantum-chemical methods. The experimental and theoretical enthalpies of the reaction $ LaBr_4^ - = Br^ - + LaBr_3 The thermodynamic stability of the LaBr₄⁻ anion was for the first time studied by high-temperature mass spectrometry and nonempirical quantum-chemical methods. The experimental and theoretical enthalpies of the reaction were Δ_r H°(298.15 K) = 302 ± 14 and 303 kJ/mol, respectively. The value Δ_f H° (LaBr₄⁻, g, 298.15 K) = −1105 ± 14 kJ/mol was recommended as the enthalpy of formation of the LaBr₄⁻ anion. Original Russian Text ? M.F. Butman, L.S. Kudin, V.B. Motalov, D.A. Ivanov, V.V. Sliznev, K.W. Kr?mer, 2008, published in Zhurnal Fizicheskoi Khimii, 2008, Vol. 82, No. 5, pp. 885–890.     

Studies on Agarofurans VIII. Synthesis of the Metabolites of 4-Butyl-a-agarofuran

Agarofurans have been found to be active on the nervous system in our institute. 4-Butyl-a-agarofuran 1 is a promising drug candidate. In order to explore the pharmacokinetics of 1, the metabolism of 1 in vitro was studied with liver microsomes from rats. Five metabolites were isolated and structures were identified as compounds 2-6. But the absolute configuration of 2,4,5 and the position of carbonyl in 3 could not be unambiguously determined. Further determination was limited by the smal…     

Fitting of the voltage–Li+ insertion curve of LiFePO4

Fitting of the voltage vs. insertion curves of the LiFePO₄ electrode was based on theoretical expressions describing the Li⁺ diffusive process in a solid medium. The noninteracting gas model for the chemical potential of ions distributed in a solid matrix was taken into account, and the diffusion coefficient and the energy activation for the diffusion process were accordingly calculated. The polarization curves at various discharge stages were theoretically obtained, and a good agreement was found with the experimental data at all discharge rates. A mathematical relation describing the trend of the diffusion resistance vs. insertion degree was also developed.     

Effects of Bases on the Stabilities of Nucleoside C4'''' Radicals

C4'-H bond dissociation enthalpies of nucleosides were predicted using theoretical methods to a precision of 1-2 Kcal/mol. It was found that the stability of the C4' nucleoside radical is slightly dependent on the base. The orders of stability are dA < dG < dT < dC for deoxynucleosides and U < G < A = C for nucleosides.