An E.P.R. study of peptides after U.V. irradiation

Abstract— Various peptides of Gly, Ala, Phe, Tyr, and Trp have been irradiated with U.V. light in the solid state or in frozen aqueous solution. The radicals produced were studied by E.P.R. spectroscopy at low temperature and at room temperature. Radicals seem to occur preferentially on Gly or Ala when in the C-terminal position and there is evidence for a photosensitization of these amino acids by aromatic amino acids.     

Structural analyses of triglycerides containing isotopically-labelled fatty acids.

The stereospecific analysis of triglycerides is a complex, multistep procedure and some losses inevitably occur at every stage. Such losses are particularly important when the triglycerides contain isotopically-labelled fatty acids incorporated by incubation in vitro with the relevant enzyme systems, but they can be compensated for by adding, prior to the analysis, a triglyceride containing only the same labelled odd-chain fatty acid in each position.     

Regiospecific additions of hydrazoic acid and benzylamine to 1-(arylsulfonyl)bicyclo[1.1.0]Butanes. Application to the synthesis of cis and trans 2,7-methanoglutamic acids

Addition of hydrazoic acid or benzylamine to 1-(arylsulfonyl) bicyclobutanes introduces the nitrogen nucleophlle at position 3 of the derived cyclobutane, even when a carboxyl derivative is present at this position as a second activating group. Precursors of α-amino cyclobutane carboxylic acids may thus be obtained and these can be further transformed to the title diacids via carbonylation α to the sulfone and reduction.     

Tetrazoles. 13. Protonation of tetrazolylacetic acids

The protonation of isomeric 1H-, 2H-, and 5H-tetrazolylacetic acids, as well as a series of 5-aryl-1H- and 5-aryl-2H-tetrazolylacetic acids, in aqueous sulfuric acid solutions was studied by IR, UV, and PMR spectroscopy. It is shown that all of the investigated tetrazolylacetic acids are protonated in the tetrazole ring at sulfuric acid concentrations up to 96%; the proton adds to the nitrogen atom in the 4 position.See [1] for communication 12.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 10, pp. 1421–1425, October, 1982.     

Gas chromatography of fatty acids.

Lipids in foods contain a wide variety of fatty acids differing in chain length, degree of unsaturation, position and configuration of double bonds and the presence of special functional groups. Modern capillary gas chromatography offers excellent separation of fatty acids. Fused-silica capillary columns with stationary phases of medium polarity and non-polar methylsilicone stationary phases successfully separate most of the natural fatty acids. Special applications, such as the separation of complex cis-trans fatty acid mixtures and cyclic fatty acids, required particular chromatographic conditions, including the use of very long capillary columns or more polar stationary phases. The derivatization methods for the preparation of fatty acid esters also need to be optimized to obtain accurate quantitative results. This paper reviews the derivatization techniques, capillary columns and stationary phases commonly used in the gas chromatography of fatty acids in food.     

Oligomeric beta(beta)(alpha) miniprotein motifs: pivotal role of single hinge residue in determining the oligomeric state.

The role of a single glycine hinge residue in the structure of BBAT1, a beta(beta)(alpha) peptide that forms a discrete homotrimeric structure in solution, was evaluated with 11 new peptide sequences which differ only in the identity of the residue at the hinge position. The integrity of the structure and oligomeric state of the peptides was evaluated by using a combination of analytical ultracentrifugation and circular dichroism spectroscopy. Initially, it was discovered that the glycine hinge adopts backbone dihedral angles favored in D-amino acids and that incorporation of D-alanine at the hinge position stabilizes the trimer species. Subsequently, the effect of the side chains of different D-amino acids at the hinge position was evaluated. While incorporation of polar amino acids led to a destabilization of the oligomeric form of the peptide, only peptides including D-Ser or D-Asp at the hinge position were able to achieve a discrete trimer species. Incorporation of hydrophobic amino acids D-Leu and D-Phe led to oligomerization beyond a trimer to a tetrameric form. The dramatic differences among the thermodynamic stabilities and oligomeric states of these peptides illustrates the pivotal role of the hinge residue in the oligomerization of the beta(beta)(alpha) peptides.     

1-Aralkylated Tetrahydro-2-benzazepines. Part I: Synthesis from methoxylated phenylpropionamides

Phenylpropionamides acylated in the ortho position with aralkanecarboxylic acids were cyclised to give, after reduction, 1-aralkyl-tetrahydro-2-benzazepines.     

Directed ortho-metalation of unprotected benzoic acids. Methodology and regioselective synthesis of useful contiguously 3- and 6-substituted 2-methoxybenzoic acid building blocks

[reaction: see text] By treatment with s-BuLi/TMEDA at -78 degrees C, unprotected 2-methoxybenzoic acid is deprotonated exclusively in the position ortho to the carboxylate. A reversal of regioselectivity is observed when the acid is treated with n-BuLi/t-BuOK. These results are of general utility for the one-pot preparation of a variety of very simple 3- and 6-substituted 2-methoxybenzoic acids that are not easily accessible by conventional means. The potential usefulness of the method is demonstrated by the expedient synthesis of lunularic acid.     

Research on imidazo[1,2-a]benzimidazole derivatives. 25. Reaction of 2,9-disubstituted imidazo[1,2-a]benzimidazoles with acrylic acids and their derivatives

The substitutive addition of acrylic acids and their esters, amides, and nitriles to 2,9-disubstituted imidazo[1,2-a]benzimidazoles, which leads to 3-(imidazo[1,2-a]benzimidazol-3-yl)propionic acids and their derivatives, was studied. The rate of addition depends on the structure of the unsaturated compound, the nature of the substituent in the 2 position, the magnitude of the charge on the carbon atom in the 3 position of the heteroring, and the reaction conditions. The addition proceeds most smoothly in polyphosphoric acid (PPA). In the case of acrylonitrile imidazo[1,2-a]benzimidazol-3-ylpropionic acid amides were isolated in PPA. In the reaction of - or -substituted acrylic acids with 2-phenylimidazo[1,2-a]benzimidazoles in PPA, in addition to the corresponding imidazo[1,2-a]benzimidazol-3-ylpropionic acids, products of their intramolecular cyclodehydration at the ortho position of the phenyl substituent are formed.See [1] for Communication 24.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1496–1502, November, 1987.     

Synthetic studies on stevastelins. 2. Synthesis of lipidic- and peptidic-modified analogues

[Chemical reaction: See text] The synthesis of a series of stevastelin analogues with modification of the susbstituent at the C-2 position of the stearic acid chain (compounds 28 and 31), variation of the amino acids (compounds 41, 42, 73, and 78), or lacking the lipidic chain (compound 91) is described. The replacement of L-valine and L-threonine with other amino acids proceeded without difficulties for the synthesis of analogues 41 and 42; however, the substitution of L-serine with simple amino acids, such as glycine or L-alanine, proved to be elusive, which was adscribed to factors of conformational flexibility. Finally, the substitution with L-valine or L-threonine proceeded without difficulties to provide the analogues 73 and 78 respectively.     

Fluoro-containing Heterocycles: VI. New Derivatives of 1,3,4-Thiadiazino[6,5,4-i,j]quinoline

A series of new tricyclic fluoroquinolones was prepared by replacing fluorine atoms in derivatives of 2-R-8-Y-7-oxo-9,10-difluoro-7H-1,3,4-thiadiazino[6,5,4-i,j]quinoline-6-carboxylic acids. In acids and esters containing a hydrogen atom in position 8 occurred replacement of F¹⁰ by amine rests, and in compounds with a fluorine in position 8 was substituted either F⁸or F¹⁰ and F⁸depending on the amine character.     

Reactions of 2,3-Dioxopyrrolo[2,1-<Emphasis Type="Italic">a</Emphasis>]isoquinolines with Active N-Nucleophiles

It is shown that 2,3-dioxopyrrolo[2,1-a]isoquinolines react readily with aliphatic diamines and hydroxyamine with opening of the dioxopyrrole ring and formation of the corresponding bisenaminoketoamides and hydroxamic acids. Reaction with the thiosemicarbazide and hydrazides of aromatic acids proceeds without opening of the pyrrole ring at the ketone carbonyl. Derivatives of hexahydropyridazine are formed when compounds with carboxyethyl groups at position 1 react with hydrazine. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 9, 1383–1387, September, 2005.     

N-(间-取代苯基)氨基乙酸的离解常数

本文研究了N-苯基氨基乙酸中苯环间位不同取代基对氨基酸酸碱强度的影响。将按前文方法制得的N-(间-取代苯基)氨基乙酸乙酯用氢氧化钠水溶液皂化,然后用浓盐酸酸化即得N-间-取代苯基氨基乙酸。在0.1M NaClO_4存在下,于15±0.2,25±0.2,35±0.2℃,用配有231型玻璃电极和甘汞电极的PHS-2型酸度计测定了N-(间-取代苯基)氨基乙酸在30%(体积)乙醇中的离解常数。用氨基酸钠盐测定离解常数的方法业已报道。从所测得的氨基酸表观离解常数(表1)可以看出,如同N-(对-取代苯基)氨基乙酸一样,N-(间-硝基苯基)氨基乙酸(m-NO_2PhG)的pK_1值反而比N-(间-氯苯基)氨基乙酸(m-ClPhG)和N-(间-甲氧苯基)氨基乙酸(m-CH_3OPhG)的大。这是不能用诱导效应来解释的。一般说来,氨基酸具有两性离解的性质,存在下列平衡:     

Dicarba-closo-dodecaboranes as a pharmacophore. Novel potent retinoidal agonists.

The synthesis and biological evaluation of the dicarba-closo-dodecaborane (carborane) derivatives of retinoids are described. Retinoidal activity was examined in terms of the differentiation-inducing ability toward human promyelocytic leukemia HL-60 cells. High retinoidal activity (agonist or antagonist for the retinoid receptor RAR) requires a carboxylic acid moiety and an appropriate hydrophobic group located at a suitable position on the molecule. 4-[4-(1,2-Dicarba-closo-dodecaboran-1-yl)phenylamino]b enzoic acids and 4-[3-(1,2-dicarba-closo-dodecaboran-1-yl)phenylamino]b enzoic acids showed potent agonistic activity at concentrations of 10(-8)-10(-9) M. The results indicate that carboranes are applicable as the hydrophobic moiety of biologically active molecules.     

Benzazoles. 3*. Synthesis and arylsulfonylation of 2-substituted benzimidazoles

2-Alkylbenzimidazoles have been obtained from o-nitroaniline and aliphatic carboxylic acids by reductive cyclization. Interaction of the former with arenesulfonyl chlorides led to the synthesis of 2-alkyl-1-arylsulfonylbenzimidazoles, the yield of which depended on the structure of the substituent in position 2.     

Transformations of anthra[1,9-cd]isoxazol-6-ones in hydrohalic acids

4-Halo-1-aminoanthraquinones are formed when anthra [1,9-cd]isoxazol-6-ones are refluxed in hydrohalic acids. The 3 position undergoes halogenation when 5-substituted isoxazoles are used. The process takes place via a one-proton mechanism with the participation of halide ion in the rate-determining step, possibly with the intermediate formation of N-haloaminoanthraquinones.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 11, pp. 1471–1473, November, 1980.     

Reaction of esters of 2-arylcyclo-propanecarboxylic acids with nitrous acid. Synthesis of aryl-substituted 3-ethoxycarbonyl-4,5-dihydroisoxazoles and 3-ethoxycarbonylisoxazoles

Esters of 2-arylcyclopropanecarboxylic acids react with nitrous acid generated in situ with regioselective insertion of the nitrosyl cation into the cyclopropane ring. Depending on the substrate/nitrosylating agent ratio, the reaction proceeds with the formation of either aryl-substituted 3-ethoxycarbonyl-4,5-dihydroisoxazoles or the corresponding isoxazoles. The nature and position of the substituents in the aromatic ring of the starting 2-arylcyclopropanecarboxylic acid esters affect the reaction rate but have no effect on the regioselectivity of the attack by the nitrosyl cation on the three-membered ring. A dependence of the reactivity of isomeric substrates on their stereochemistry and position of the nitro group in the aromatic ring is noted for 2- and 4-nitrophenyl derivatives of esters of cis- and trans-2-arylcyclopropanecarboxylic acids.     

2-氨基-2-甲基丙醇化学修饰试剂用于气相色谱-质谱分析不饱和脂肪酸

以2-氨基-2-甲基丙醇为脂肪酸的化学修饰试剂,将不饱和脂肪酸羧基化学修饰成含氮杂环,从而避免了链烯基中碳碳双键在EI源中的移动,并使质谱呈现显示双键位置的规范信息。通过解析不饱和脂肪酸2-氨基-2-甲基丙醇化学修饰产物的EI质谱图,得到了不饱和脂肪酸中碳碳双键的定位规则,从而为分析不饱和脂肪酸精细结构提供了手段。用脂肪酸2-氨基-2-甲基丙醇化学修饰气相色谱-EI质谱法分析了螺旋藻脂肪酸,鉴定出9种不饱和脂肪酸,确定了螺旋藻脂肪酸中碳碳双键的位置,结果与文献一致。     

Modified apparatus for voltage gradient gel electrophoresis.

We built a modified version of voltage gradient gel electrophoresis system to correct distortions in nucleic acids electrophoretic migration patterns occurring at the edges of the gel when the original voltage gradient apparatus is used. The new device allows correct fractionation of nucleic acids also when electrophoresis is performed at high voltages.     

Phospholipid and fatty acid composition of Echinodermata. I. ClassOphiuroidea

The phospholipid compositions of five species of marine ophiuroids belonging to the classOphiuroidea have been investigated. It has been shown that the phosphatidylethanolamines contain almost solely ether bonds in the first position of the glycerophospholipids. The amount of the plasmalogen form in the phosphatidylethanolamines averages 89.8% (82.3–96.2%) and the amount of the alkyl form 9.8% (3.8–17.7%). The compositions of the fatty acids, fatty aldehydes, and alkyl ethers in the two main classes of phospholipids — phosphatidylethanolamine and phosphatidylcholine — have been studied. The main acids found were eicosatetraenoic and eicosapentaenoic, the total amount of which was 53%. It has been shown that the ophiuroids can be used as promising objects for the investigation of the metabolism of alkoxylipids and for their preparative isolation.