Convenient method for preparation of esters of N-carbonyl-α-amino acids

Conclusions A convenient method was proposed for obtaining the esters of N-carbonyl--amino acids, which is based on the reaction of the esters of N-trimethylsilyl--amino acids with phosgene in the presence of a tertiary amine.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1682–1684, July, 1977.     

Molecular structure of ortho-nitrobenzyltriethylammonium bromide

It was established by x-ray crystallographic analysis that the molecular o-nitrobenzyltriethylammonium cation has an orthogonal orientation of the benzene ring and the vicinal C-N⁺ bond (=93.8°). The nitro group deviates from the plane of the aromatic ring by an angle of 26.9°. One of the ethyl groups at the quaternary nitrogen atom is in an ap-conformation (=176.2°); the other two are in sc-conformations, characterized by torsional angles 65.1 and 69.4°.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 8, pp. 1816–1818, August, 1991.     

Electrical conductivity of liquid and film polymer composites filled with anion-radical salts in the presence of crown ethers

In the example of alkali metal tetracyanoquinodimethanides (M⁺TCQDM), a study has been made of the influence of resonance charge exchange on the conductivity () of polymer composites filled with anion-radical salts. When neutral molecules TCQDM⁰ are introduced into such systems, this leads to an increase in as a result of the lower activation energy of jumps between states TCQDM and TCQDM⁰. The addition of molecules of crown ethers has an analogous effect: They favor the appearance in the polymer matrix (the same as in solution) of TCQDM molecules in different charge states (TCQDM⁰, TCQDM) with migration of the cation within the limits of ternary associates (CE...M⁺...A) that are formed in systems for which the ratio of the crown ether cavity diameter to the cation diameter 1.4. Symbaticity has been found in the dependences of the electrical conductivity of films and the limiting mobility of solutions with the same composition on the parameter .Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 25, No. 4, pp. 446–452, July–August, 1989.     

Atomic absorption inhibition titration of orthophosphate and polyphosphates

The atomic absorption inhibition titration of phosphates was studied for two types of burner. Dependence on gas Flow-rates was observed. The method with a pre-mix burner was employed to determine phosphate in surface and waste waters. The results are compared with those by the standard method. The proposed method was found to be rapid, simple and accurate.     

Structures of reagent residues resulting from reactions of divinyl sulfone with cotton cellulose

Cotton cellulose in fabric form was crosslinked with divinyl sulfone by catalysis with solutions of sodium hydroxide of normalities ranging from 0.1 to 4.0. The molecular chains of cellulose were hydrolyzed with sulfuric acid to yield hydrolyzates from which simple substituted glucoses (i.e., those bonded to a single unit of DVS), the simple crosslinked glucoses (i.e., those joined together by a single unit of DVS), and complex structures (i.e., those substituted or crosslinked with more than one unit of DVS in the chain) were isolated and measured. The fractions of the reagent residues in the forms of the structures noted above were found to change substantially with the concentration of base employed to catalyze the reaction. The constitution of the reagent residues resulting from reaction in 0.1N base was remarkably simple: 82% of the DVS residues in the form of simple crosslinks and 18% in the form of simple substituents. Complex structures accounted for as much as 70% of the DVS residues under other conditions of reaction.     

THE EFFECT OF NATIVE ISOLOGOUS DNA ON THE INCORPORATION OF THYMIDINE-H3INTO U.V. IRRADIATED L-STRAIN CELLS

Abstract— The effect of highlypolymerized deoxyribonucleic acid (DNA) upon the incorporation rate of thymidine-H³ into DNA of recipient L -strain cells has been studied. The rate of incorporation of thymidine-H³ is much faster in controls and irradiated cells than in irradiated treated with isologous DNA.     

Plant polysaccharides. IX. Isolation and anticoagulant activity of the polysaccharides ofLagochilus usunachmaticus

A polysaccharide possessing pronounced direct-action anticoagulant activity has been isolated from the epigeal part ofLagochilus usunachmaticus.Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 40 64 75. Translated from Khimiya Prirodnykh Soedinenii, No. 5, pp. 690–692, September–October, 1997.     

C(3)-azido cephem II

The major product from the thermolysis and photolysis of C(3)-azido cephem 2 is the ring expanded 1,4,6-thiadiazepine azetidinone.     

A spectrophotometric and polarographic investigation of three new cyclohexene-substituted benzodiazepines

Three recently introduced benzodiazepine derivatives, tetrazepam (I), nortetrazepam (II) and menitrazepam (III) have been subjected to spectral and polarographic investigation. From the ultraviolet spectral data their pK(a)-values have been determined: 4.28 (I), 4.3 (II) and 3.5 (III). From the polarographic measurements it can be concluded that in I and II the 4,5 CN double bond is reduced with 2 electrons. For the first time for the benzodiazepine series it has been observed that in slightly alkaline solutions this process takes place in two separate 1-electron steps. In III, first the aromatic nitro group is reduced to a hydroxylamine group, then at more negative potentials the CN double bond is also reduced; its reduction wave mostly coalesces with that for the 6-electron reduction of the nitro group to an amino group. A differential pulse polarographic method is presented, for the determination of I, II, III at concentrations as low as 10(-7)M.     

Complexation in Binary Pb(II)–Dithiooxamide System in Pb2[Fe(CN)6] Gelatin-Immobilized Matrices

Complexation processes that occur when hexacyanoferrate(II) immobilized in gelatin is brought into contact with aqueous solutions of dithiooxamide at pH 12 are studied. Unlike the binary metal ion–dithiooxamide systems studied so far, the final product in this case was Pb(II) sulfide, rather than the Pb(II) complex with the indicated ligand. Concentration of Pb(II) sulfide was shown to depend on dithiooxamide concentration in a solution in contact with the matrix. A scheme for the complexation process is proposed.