Biomimetic synthesis of α-amino acids from α-keto acids

Protonated α-imino acids, RC(=NH₂⁺)COOH, were easily reduced to α-amino acids by an acid-stable NADH analogue, 1-benzyl-3-carbamoyl-1,4-dihydroquinoline. This is the first model reaction of NADH-mediated α-amino acid synthesis from α-keto acids.     

Effect of acids and bases on the solubility of amino acids

The effect of acids and bases on the solubility of amino acids at 298.2 K, within the pH range, (pH from 2 to 10) and out of the pH range, was determined. The amino acids considered were glycine, dl-alanine, dl-valine and dl-serine. The acids used were HCl and HNO₃ and the bases NaOH and KOH. It was observed that in the pH range (pH from 2 to 10) there is no significant difference in the solubility of dl-alanine in the presence of different ions such as Na⁺ or K⁺ at high pH, and Cl⁻ or NO₃⁻ at low pH values. However, at higher concentrations of the acids or the bases, there is an effect of the counterions in solubilities. For all the amino acids considered here the solubility was higher in nitric acid, as compared to hydrochloric acid, and higher in potassium hydroxide than in sodium hydroxide.     

Liquid crystals comprising hydrogen-bonded organic acids II. Heterodimers in mixed mesogenic acids

Nematic mesophase stability, as determined by the excess mesophase range in mixtures of organic acids (supramesogen derived from par a-substituted phenyl, 4-substituted cyclohexane and bicyclo[2.2.2]octane carboxylic acids), is increased in mixtures of disparate species - mixed acids with differing substituent sizes (different supramesogen tail lengths) and different acid types (aliphatic and aromatic supramesogen cores). These trends enable one to estimate contributions to mesophase stability stemming from tail disparity and core differences, contributions that appear to carry over into analogous covalent mesogens. IR measurements of solid mixtures of acids suggest that the heterodimer acids population dominates, and deuterium NMR studies of labelled acids in the nematic phase emphasize the dynamic character of this class of supramesogens: dimer lifetimes are shorter than microseconds.     

Determination of polyfluoroalkyl phosphoric acid diesters, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, perfluoroalkyl carboxylic acids, and perfluoroalkane sulfonic acids in lake trout from the Great Lakes region

A comprehensive method to extract perfluoroalkyl carboxylic acids, perfluoroalkane sulfonic acids, perfluoroalkyl phosphonic acids, perfluoroalkyl phosphinic acids, and polyfluoroalkyl phosphoric acid diesters simultaneously from fish samples has been developed. The recoveries of target compounds ranged from 78?% to 121?%. The new method was used to analyze lake trout (Salvelinus namaycush) from the Great Lakes region. The results showed that the total perfluoroalkane sulfonate concentrations ranged from 0.1 to 145?ng/g (wet weight) with perfluorooctane sulfonate (PFOS) as the dominant contaminant. Concentrations in fish between lakes were in the order of Lakes Ontario ≈ Erie > Huron > Superior ≈ Nipigon. The total perfluoroalkyl carboxylic acid concentrations ranged from 0.2 to 18.2?ng/g wet weight. The aggregate mean perfluorooctanoic acid (PFOA) concentration in fish across all lakes was 0.045?±?0.023?ng/g. Mean concentrations of PFOA were not significantly different (p?>?0.1) among the five lakes. Perfluoroalkyl phosphinic acids were detected in lake trout from Lake Ontario, Lake Erie, and Lake Huron with concentration ranging from non-detect (ND) to 0.032?ng/g. Polyfluoroalkyl phosphoric acid diesters were detected only in lake trout from Lake Huron, at levels similar to perfluorooctanoic acid.     

Novel selenium-containing non-natural diamino acids

The general synthesis of a new class of non-natural diamino acids, 2-amino-3-[(2′-aminoalkyl)seleno]propanoic acids, or Se-(aminoalkyl)selenocysteines, is reported. Under the conditions devised, enantiopure N-Boc-protected β-l-iodoamines, which are readily generated from proteinogenic α-amino acids, were treated with the selenolate anion obtained from NaBH₄ splitting of the Se-Se bond in commercial l-selenocystine. The Se-alkylation products were enantiomerically pure and the reaction is high yielding (92-98%), without any detectable traces of accompanying by-products.     

Determination of slight contamination by D-amino acids in natural amino acids

Conclusions The problem of using gas chromatography for the estimation of slight contamination by D-amino acids in natural L-amino acids has been examined. The threshold amount of D-isomer detectable by the gas chromatographic method, using a drift conpensating integrator, amounts to 0.5%.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 12, pp. 2771–2772, December, 1967.     

Prevalent intrinsic emission from nonaromatic amino acids and poly(amino acids)

Nonaromatic amino acids are generally believed to be nonemissive, owing to their lack of apparently remarkable conjugation within individual molecules. Here we report the intrinsic visible emission of nonaromatic amino acids and poly(amino acids) in concentrated solutions and solid powders. This unique and widespread luminescent characteristic can be well rationalized by the clustering-triggered emission(CTE) mechanism, namely the clustering of nonconventional chromophores(i.e. amino, carbonyl,and hydroxyl) and subsequent electron cloud overlap with simultaneous conformation rigidification. Such CTE mechanism is further supported by the single crystal structure analysis, from which 3 D through space electronic communications are uncovered.Besides prompt fluorescence, room temperature phosphorescence(RTP) is also detected from the solids. Moreover, persistent RTP is observed in the powders of exampled poly(amino acids) of ε-poly-L-lysine(.-PLL) after ceasing UV irradiation. These results not only illustrate the feasibility of employing the building blocks of nonaromatic amino acids in the exploration of new luminescent biomolecules, but also provide significant implications for the emissions of peptides and proteins at aggregated or crystalline states. Meanwhile, they may also shed lights on further understanding of autofluorescence from biological systems.     

Phenothiazinylaminoalkylphosphinous acids

Conclusions Some previously unknown phenothiazinylaminoalkylphosphinous acids were synthesized.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1571–1573, July, 1971.     

The thermodynamics of ionization of polycarboxylic acids

Thermodynamic parameters for the successive ionizations of a number of monomeric polycarboxylic acids have been determined from a temperature-dependence study of the ionization constants calculated from potentiometric data obtained using cells without liquid junction. Specifically the acids are: 1,2,3-propanetri-; 1,2,3,4-butanetetra-; 1,3-benzenedi-; 1,2,3-, 1,2,4-, and 1,3,5-benzenetri-; 1,2,4,5-benzenetetra-; and 1,2,3,4,5,6-benzenehexacarboxylic acids. The data are critically discussed in terms of the common models of ionization and of reactivity effects of substituents on ionization for monomeric and polymeric polybasic acids.Abstracted from M.B.T.'s doctoral disseration, Oklahoma State University, May 1972. Copies of the computer programs and directions for their use will be available from University microfilms.     

Synthesis of different deuterated carboxylic acids from unsaturated acids promoted by samarium diiodide and D2O

An easy, and rapid reduction of the Cdbond;C bond of alpha,beta-unsaturated acids by means of samarium diiodide in the presence of D(2)O provides an efficient method for synthesizing 2,3-dideuterio acids. Starting from alka-2,4-dienoic acids, (E)-alpha,delta-dideuterio-betagamma-unsaturated acids are obtained, the new Cdbond;C bond being generated with complete diastereoselectivity. When H(2)O is used instead of D(2)O, saturated carboxylic acids and (E)-beta,gamma-unsaturated acids are isolated. A mechanism to explain each synthesis has been proposed.     

Polyurethanes made from bile acids

New polyurethanes based on bile acids were synthesized from alcohol derivatives of cholic and lithocholic acids and hexamethylene diisocyanate, in an effort to improve the biocompatibility and biodegradability of polyurethanes through the use of natural compounds. The hydrogen bonding in the polymers is confirmed by IR spectral analysis. The glass transition temperatures of the polymers are in the range of 82-138 ℃ and degradation temperatures in the range of 267-298 ℃ as studied by thermal analyses. Thermogravimetric studies indicate that the comonomers are of equimolar amounts in the polyurethanes derived from both bile acids.     

Cyclization of acetylenylpyrazolecarboxylic acids

Conclusions Acetylenyl-N-methylpyrazolecarboxylic acids containing an acetylenic substituent and a carboxyl group on adjacent carbon atoms cyclize in pyridine in the presence of copper phenylacetylenide to pyranopyrazoles. The same compounds are obtained by the acetylenide cyclocondensation of the appropriate iodopyrazolecarboxylic acids, but at a much lower rate.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 6, pp. 1342–1348, June, 1981.     

Desulfolanylation of N-sulfolanyl amino acids

N-Sulfolanyl amino acids are cleaved at the C-N bond in ammonium hydroxide and aqueous solutions of amines to give the corresponding aminosulfolanes and amino acids.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1340–1341, October, 1973.     

Liquid crystals comprising hydrogen-bonded organic acids I. Mixtures of non-mesogenic acids

Stable nematic phases are reported for binary mixtures of p-alkylbenzoic acids (nBA; where n = 1,2,3 denotes methyl, ethyl and propyl), p-alkoxybenzoic acids (nOBA, n = 1,2), and p-fluorobenzoic acid, which separately do not exhibit liquid crystalline phases. The mesophase stability increases in equimolar mixtures of acids having incomensurate lengths; the larger the difference in the tail substituents in the mixed organic acids, the broader the nematic phase. The trends in excess nematic range exhibited by the H-bonded supramesogens in binary mixtures parallels the behaviour of covalent mesogens. This is indicative of an influence of heterodimers comprising H-bonded pairs of the two different acids in equimolar mixtures of the non-mesogenic acids. It would appear that dimerized organic acids constitute a viable molecular-structural 'bread-board' for rapid screening for potential mesogen constituents.     

Dicarboxylic acids and hydroxy fatty acids in different species of fungi

Secondary metabolites of fungi can be responsible for allergies; therefore, the identification of compounds produced by these organisms is very important. Fungi produce large amounts of secondary metabolites, which belong to groups of chemicals such as: dicarboxylic acids, hydroxy acids, alcohols, hydrocarbons, esters, fatty acids, sterols, amino acids and mycotoxins. The presence of all these compounds in human proximity contributes to many diseases. Therefore, the aim of the study was a qualitative and quantitative analysis of hydroxy and dicarboxylic acids produced by fungi occurring in student hostel in Poland, in the province of Pomerania. The following species of fungi were subjected to extraction: Aspergillus niger, Aspergillus fumigatus, Aspergillus candidus, Rhizopus sp., Geotrichum candidum, and Penicillium chrysogenum. A mixture of ethyl acetate and methanol was used for the extraction. The obtained extracts were further analyzed by gas chromatography mass spectrometry (GC–MS). In all samples of fungi, the presence of a total of 22 acids, including 13 dicarboxylic and 9 hydroxy acids, was confirmed. Most acids (17 different acids) were identified in A. fumigatus. Only 10 acids were identified in the mycelium of G. candidum and A. niger. Acids which were identified in all samples of the mycelium were 22-hydroxydocosanoic acid, 24-hydroxytetracosanoic acid and adipic acid. The most abundant compounds were 22-hydroxydocosanoic acid in A. fumigatus, A. candidus, Rhizopus sp., G. candidum and P. chrysogenum, and succinic acid in A. niger. More experiments are needed to understand the physiological role of hydroxy and dicarboxylic acids. We hope that our results are an important contribution to further studies on the human health.     

Tetrazoles. 11. Acidities of tetrazolylacetic acids

The acidities of two series of substituted 1- and 2-tetrazolylacetic acids, as well as some 1- and 2-substituted 5-tetrazolylacetic acids, in water and 50% ethanol were investigated. All of the investigated compounds are stronger acids than acetic acid and are comparable to haloacetic acids. The induction constants (_I) of the 1-, 2-, and 5-tetrazolyl groups (0.65, 0.62, and 0.41, respectively) were calculated from data on the acidities of tetrazolylacetic acids.See [1] for communication 10.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 2, pp. 264–266, February, 1982.     

Synthesis of furaxanenitrolic acids

Previously unreported furoxanenitrolic acids have been synthesized.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1117–1119, August, 1993.     

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.     

Acid chlorides of O-alkylchloroformimino-O-alkylphosphoric acids

Reaction of 1,1-dichloro-1-nitrosoalkanes with dialkyl chlorophosphites yields acid chlorides of O-alkylchloroformimino-O-alkylphosphoric acids. Hydrolysis of these compounds leads to nucleophilic substitution of the Cl atom at the phosphorus atom and not that in the alkylchloroformimino part of the molecule. The O-alkylchloroformimino-O-alkylphosphoric acids were isolated and characterized in the form of the corresponding ammonium salts.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 5, pp. 1122–1125, May, 1990.     

Synthesis of nucleoside aminooxy acids

First nucleoside aminooxy acids were synthesized from furanoid sugar phthalimidooxy acids by N-glycosylation with uracil, thymine, N-benzoylcytosine, 6-N-benzoyladenine and 2-N-acetyl-6-O-diphenylcarbamoylguanine. Boc or Fmoc protected uridine aminooxy acid derivatives have also been prepared. As oxyamine protecting group, the phthalimido group was shown to be instable in MeOH, leading to the imide ring-opening product in a reversible way. This reaction was accelerated under acid or basic conditions. A uridine dimer linked by N-oxy amide has also been prepared by coupling of uridine aminooxy ester with uridine phthalimidooxy acid. These nucleoside aminooxy acids might constitute useful building blocks for the development of novel RNA mimics and conjugates with other biomolecules or reporter compounds.