Azides of N-substituted aziridine-2-carboxylic acids. Reaction with methyl esters of amino acids

The corresponding azide was obtained by nitrosation of 1-benzylaziridine-2-carboxylic acid hydrazide. Reaction of the azide with methyl esters of amino acids gave N-(1-benzyl-2-aziridinylcarbonyl)-substituted methyl esters of amino acids.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1350–1352, October, 1980.     

Empirical and ab initio calculations of thermochemical parameters of amino acids: IV. Non-Typical amino acids: Hydroxyamino acids, thioamino acids, and heterocyclic amino(imino) acids

Using a set of computational methods we calculated the basic thermochemical characteristics of the fifteen non-typical L-??-amino acids of hydroxyaminocarboxylic and thioaminomonocarboxylic series, and of some heterocyclic amino(imino)carboxylic acids.     

Tautomerism in barbituric and thiobarbituric acids

The molecular geometry of barbituric and thiobarbituric acid tautomers have been fully optimized using the AMI method in order to estimate the relative energies of the tautomers. The results are in agreement with available experimental data and indicate that in the vapour the barbiturate ring is essentially planar. In both unsubstituted compounds the trioxo structure is found to be the most stable one, in agreement with experimental findings in the solid. Tautomeric equilibria are sensitive to phase change and to substitution at the C₅ position. On passing from the vapour to the water the population of the most polar structure increases, although the order of stability remains unchanged and only for the Br and I derivatives it can be suggested the coexistence of two forms in solution. The substitution at C₅ does not alter the order of stability except for the 5-nitro derivatives where the dioxo form predominates, in agreement with experimental results in the solid. Electron affinities and ionization potentials of the tautomers have been evaluated and briefly discussed. It is suggested that gas-phase uv photoelectron spectroscopy should be able in analysing the tautomeric equilibria of barbituric and thiobarbituric acids in the vapour.     

Interaction between N-phosphoryl-α, β- and γ-amino acids and nucleosides

The reactions of four different N-(O,O′-diisopropyl) phosphoamino acids (DIPP-aa),such as N-phosphoryl-L-α-alanine (DIPP- L-α-Ala),N-phosphoryl-D-α-alanine (DIPP-D-α-Ala),N-phosphoryl-β-alanine (DIPP-β-Ala) and N-phosphoryl-γ-amino butyric acid (DIPP-γ-Aba),and four nucleosides,adenosine (A),guanosine (G),cytidinc (C) and uridine (U),were studied by electrospray ionization tandem mass spectrometry (ESI-MS/MS) and HPLC/ESI-MS.DIPP-L-α-Ala and DIPP-D-α-Ala produced the same phosphorylated nucleosidcs,dinucleotidcs and phosphoroligopeptide.However,DIPP-β-Ala and DIPP-γ-Aba gave no relevant products.     

Synthesis of pyrimidyl-N1-α-amino acids

-(5-Fluoro-N₁-uracilyl)--alanine, -(5-bromo-N₁-uracilyl)--alanine, -(5-chloro-N₁-uracilyl)--alanine, -(N₁-thyminyl)--alanine, -(N₁-cytosinyl)--alanine, -(2-oxo-4-carboxymethylamino-1, 2-dihydro-N₁-pyrimidyl)--alanine, -(N₁-uracilyl)--aminobutyric acid, -(N₁-thyminyl)--aminobutyric acid, and -(N₁-cytosinyl)--aminobutyric acid were synthesized by the reactions involving the cyanohydrin synthesis and other transformations. In addition, a number of substituted N₁-pyrimidylacetaldehydes and N₁pyrimidylpropionaldehydes and their diethylacetals were synthesized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 4, pp. 530–534, April, 1971.     

4-Thiazoline-2-thiones. IV. Preparation from amino acids

4-Thiazoline-2-thiones derived from amino acids have been obtained by an improved procedure. Depending on substitution, the type of intermediate product isolated may be a 4-hydroxythiazolidine-2-thione or a dithiocarbamate.     

Interaction of dipropyltin(IV) with amino acids,peptides, dicarboxylic acids and DNA constituents

Interaction of dipropyltin(IV) with selected amino acids, peptides, dicarboxylic acids or DNA constituents was investigated using potentiometric techniques. Amino acids form 1?:?1 and 1?:?2 complexes and, in some cases, protonated complexes. The amino acid is bound to dipropyltin(IV) by the amino and carboxylate groups. Serine is complexed to dipropyltin(IV) with ionization of the alcoholic group. A relationship exists between the acid dissociation constant of the amino acids and the formation constants of the corresponding complexes. Dicarboxylic acids form both 1?:?1 and 1?:?2 complexes. Diacids forming five- and six-membered chelate rings are the most stable. Peptides form complexes with stoichiometric coefficients 111(MLH), 110(ML) and 11-1(MLH_?1)(tin: peptide: H⁺). The mode of coordination is discussed based on existing data and previous investigations. DNA constituents inosine, adenosine, uracil, uridine, and thymine form 1?:?1 and 1?:?2 complexes and the binding sites are assigned. Inosine 5′-monophosphate, guanosine 5′-monophosphate, adenosine 5′-monophosphate and adenine form protonated species in addition to 1?:?1 and 1?:?2 complexes. The protonation sites and tin-binding sites were elucidated. Cytosine and cytidine do not form complexes with dipropyltin(IV) due to low basicity of the donor sites. The stepwise formation constants of the complexes formed in solution were calculated using the non-linear least-square program MINIQUAD-75. The concentration distribution of the various complex species was evaluated as a function of pH.     

Electrochemical behavior of the N-nosyl-protected amino acids in N,N-dimethylformamide

The electrochemical reduction of serine, glycine, and leucine protected by the 4-nitrobenzenesulfonyl group in N,N-dimethylformamide at mercury cathode occurs at two steps. The first one at −0.8 V vs. SCE, after a one-electron transfer, leads the anion radical formation that dimerizes and adsorbs at electrode. In the second step at −1.4 V, an instable dianion forms which then cleaves. The mechanism is discussed. Published in Russian in Elektrokhimiya, 2006, Vol. 42, No. 4, pp. 377–381. The text was submitted by the authors in English.     

Study of the temperature effect on IR spectra of crystalline amino acids,dipeptides, and polyamino acids. IV. L-cysteine and DL-cysteine

A study of the IR spectra of L- and DL-cysteine is carried out in a range of frequencies from 4000 cm^?1 to 600 cm^?1 and temperatures from 333 K to 83 K. Changes in the spectra of L- and DL-cysteine (NH ₃ ⁺ CH(CH₂SH)-COO^?) on cooling are analyzed in comparison with the spectra of L- and DL-serine (NH ₃ ⁺ CH(CH₂OH)-COO^?) and three polymorphs of glycine (NH ₃ ⁺ CH₂-COO^?) previously studied under temperature variation. Changes in the IR spectra at variable temperatures are correlated with previously obtained diffraction data on anisotropic compression of the structure and changes in the geometric parameters of hydrogen bonds. Special attention is paid to temperature regions in which anomalies were detected by vibrational spectroscopy, X-ray diffraction, and calorimetry.