Complete separation of ephedrines by graphite-layer open-tubular (GLOT) column

Summary A reversed phase high performance liquid chromatographic (RP-HPLC) method for the analysis of amino acids in kelp, using precolumn derivatization, is described. Phenylisothiocyanate (PITC) was used as the reagent for derivatization. The kelp samples were prepared by microwave hydrolysis in only 5 min; seventeen PTC amino acids were separated after hydrolysis and derivatization within 12 min. The coefficients of variation were >1.94 and the correlation coefficients for concentration versus response were >0.999 for all derivatives. The ratio of branched amino acid (BAA) to aromatic amino acid (AAA) was also studied. The method has the advantage of shorter hydrolysis and analysis times with optimum separation. In addition, it gives high repeatability of retention times and peak areas for all the amino acids present.     

Reaction of Azalactone with Hydroxylamine Synthesis of β -Aminophenylalanine

Treatment of azlactones^1–5 with hydroxylamine under different experimental conditions yields hydroxamic acids (2), disubstituted hydroxamic acids (3), β -hydroxylamino-hydroxamic acids (10) and several other compounds. The acid (10a) upon Catalytic hydrogenation gives M-benzoylamino-β aminophenylalanine amide (15) which gave β -aminophenylalanine (16) on hydrolysis.     

o-Nitrobenzoyl group as a new amino protecting group for peptide synthesis and the synthesis of some anthranilyl peptides

N (o-nitrobenzoyl)amino acids can be coupled with other amino acids using DCC and the resulting product on hydrogenation gives peptides, containing the anthranilyl group as —NH₂ end group. N (anthranilyl)amino acids or peptides can also be obtained by reaction of isatoic anhydride on amino acids or peptides. The anthranilyl end group is easily cleaved by metal (Cu⁺²) catalysed hydrolysis to give α-amino acid peptides and the insoluble copper(II) anthranilate.     

Phosphorus-containing Aminocarboxylic Acids: XIV. Synthesis of Analogs of α-Substituted Glutamic Acid

Addition of Schiff bases derived from amino acid esters to appropriate vinylphosphoryl compounds, followed by hydrolysis of the adducts formed gives a series of new α-alkylated phosphorus-containing α-aminocarboxylic acids, viz. phosphonic and phosphinic analogs of glutamic acid.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 7, 2005, pp. 1140–1147.Original Russian Text Copyright © 2005 by Saratovskikh, Ragulin.     

Research in the imidazole series

The hydrolysis of 7-cyano derivatives of pyrrolo[1,2-a]imidazole in 85–90% sulfuric acid at 100°C gives amides of pyrroloimidazole-7-carboxylic acids. Under more severe conditions, the resulting carboxylic acids are decarboxylated to the corresponding pyrroloimidazole derivatives with a free 7 position.See [1] for communication XC.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 12, pp. 1658–1659, December, 1976.     

Über einen neuartigen synthetischen Zugang zu β,γ-ungesättigten α-Aminocarbonsäuren

A New Synthetic Route to β,α-Unsaturated α-Amino Acids A versatile new synthetic pathway for the preparation of βγ-unsaturated α-amino acids ( 1 ) is presented. Cu(I)-catalyzed addition of ethyl isocyanoacetate ( 2 ) to α-chloro carbonyl compounds ( 3 ) gives 5-chloroalkyl-2-oxazolin-4-carboxylates ( 4 ) in high yields. A reductive elimination on 4 by means of zinc yields the N-formyl derivatives of βγ-unsaturated α-amino carboxylates ( 5 ), which on acid hydrolysis lead to the free amino acids 1 . The five different βγ-dehydro-α-amono acids 1b-1f have been prepared by this method.     

Chemistry of 4-fluoroglutamic acid. Part 2. Separation of the diastereomers on a large scale. Preparation of cis- and trans-4-fluoro-5-pyrrolidone-2-carboxylic acids (4-fluoropyroglutamic acids)

Separation of the 4-fluoroglutamic acid diastereomers has been achieved by crystallizationof the hydrochlorides of their dialkyl esters 1b and 2d. Subsequent hydrolysis affordedthe diastereomers 1a and 2a in 100% steric purity. Conversion of the acids into the 5-methyl esters followed by treatment with ammonia gives rise to the trans and cis isomersof 4-fluoro-5-pyrrolidone-2-carboxylic acid, 3 and 4. NMR data are given.     

A method of synthesis of phosphinic acids on the basis of hypophosphites: VII. Synthesis of pseudo-γ-aminobutanoyl peptides and other phosphinic analogs of γ-aminobutyric acid

A method of synthesis of pseudo-γ-aminobutanoyl peptides and other phosphinic analogs of γ-aminobutyric acid from hypophosphites is suggested. Silyl phosphonites formed by in situ addition of bis-(trimethylsilyl) hypophosphite to the corresponding α-substituted acrylates, styrene, or vinyl phosphonate used as unsaturated components in the synthesis react in situ with N-(ω-bromoalkyl)phthalimides by an Arbuzov reaction scheme, affording ω-(phthalimido)alkylphosphinic acids possessing β-substituted β-(alkoxycarbonyl)ethyl, β-phenylethyl, or β-(diethoxyphosphinoyl)ethyl substituents. Acid hydrolysis of these reaction products gives the target aminophosphinic acids: phosphinic analogs of γ-aminobutyric acid.     

Heteroatomic derivatives of aziridine. 12. Reaction of 1-(carbomethoxyalkyl)aziridines with thiols and mercapto acids

The reaction of 1-(carbomethoxyalkyl)aziridines with thiols and mercapto acids, which leads to the formation of the corresponding sulfides and esters of S-substituted N-(2-mercaptoethyl)amino acids, was studied. The acid hydrolysis of o-[(N-carbomethoxyethyl)-2-aminoethylthio]benzoic acid and o-[(N-cyanoethyl)-2-aminoethylthio]benzoic acid leads to o-[N-(carboxyethyl)-2-aminoethylthio]benzoic acid hydrochloride. The cyclization of 1-[(N-carbomethoxyethyl)-2-aminoethylthio]benzoic acid in the presence of PCl₃ gives 5-oxo-4-(carbomethoxyethyl)-6,7-benzoperhydro-1,4-thiazepine.See [1] for communication 11.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 921–923, July, 1981.     

Ketoreductases in the synthesis of valuable chiral intermediates: application in the synthesis of α-hydroxy β-amino and β-hydroxy γ-amino acids

A general method for the synthesis of β-alkyl α-hydroxy β-amino and α- and γ-alkyl substituted β-hydroxy-γ-amino acids is described. The synthesis of all three classes of amino acids proceeds through a common chiral alcohol intermediate that is generated from a pro-chiral ketone diester via the action of a nicotinamide-dependent ketoreductase. Regioselective chemical or enzymatic hydrolysis followed by rearrangement under Hofmann or Curtius conditions gives the final amino acid products. High yields of single diastereomers of the final amino acids are obtained. Amino acids with both natural and unnatural alkyl substituents can be accessed using this methodology.     

Kinetic and mechanism of reactions of L-α-Glutamic acid and L-Glutamine with pyridoxal

The kinetics and mechanisms of condensation of pyridoxal with L-α-glutamic acid and L-glutamine were studied by UV spectroscopy and polarimetry. L-α-Glutamic acid reacts with pyridoxal to form a Schiff base whose subsequent hydrolysis gives rise to pyridoxamine and α-ketoglutaric acid. The reaction of Lglutamine with pyridoxal involves the Γ-NH₂ group and affords a Schiff base whose subsequent hydrolysis gives rise to pyridoxamine and L-α-glutamic acid.     

Synthesis of vitamin b6 derivatives. II. 3-Hydroxy-4-hydroxymethyl-2-methyl-5-pyridine acetic acid and related substances

The syntheses of 3-hydroxy-4-hydroxymethyl-2-methyl-5-pyridineacetic and -5-pyridine-propionic acids and several related compounds are described. Although acid hydrolysis of α⁴,3-O-isopropylidene-5-pyridoxic acid gives 5-pyridoxic acid lactone (α-pyracin), its higher homolog α⁴,3-O-isopropylidene-pyridoxylformic acid gave a corresponding free alcohol whose carboxylic acid proton was shown to be exchanged rapidly with the 3-phenolic and -4-alcoholic - protons in nuclear magnetic resonance studies. Inter-molecular hydrogen bonding between the side chain carboxylic acid and pyridine nitrogen atoms is suggested in the solid state.     

An efficient and general enantioselective synthesis of some isoxazole-containing analogues of the neuroexcitant glutamic acid

Isoxazole amino acids are an important class of neuroexcitant which are difficult to prepare in enantiopure form. Diastereoselective alkylation of the enantiomerically pure glycine derivative, tert-butoxycarbonyl-2-(tert-butyl)-3-methyl-4-oxo-1-imidazolidinecarboxylate (Boc-BMI) with 4-bromomethyl-2-methoxymethyl-5-methylisoxazolin-5-one 5 or 5-bromomethyl-4-bromo-3-methoxyisoxazole, gives intermediates which under mild hydrolysis conditions produce the amino acids (S)- and (R)-bromohomoibotenic acid and (S)- and (R)-2-amino-3-(3-hydroxy-5-methylisoxazol-4-yl) propionic acid with e.e. >99%.     

High-performance CE: an effective method to study lactonization of alpha2,8-linked oligosialic acid

A sensitive and efficient method using high-performance CE (HPCE) and neuraminidase hydrolysis was developed to study the lactonization and hydrolysis of alpha2,8-pentasialic acid. Eleven lactone species of pentasialic acid formed in glacial acetic acid were detected and classified into three groups based on the number of carboxylic acids: monolactones with four carboxylic acids, dilactones with three carboxylic acids, and trilactones with two carboxylic acids. These lactones eluted between the original pentamer (with five carboxylic acids) and the fully lactonized species (with one carboxylic acid) in HPCE. Eight of the isomers were identified by hydrolysis with neuraminodase. Results obtained from previous reports and from this study together reveal a general rule for predicting the subtle difference in the acidity of each carboxylic acid in oligosialic acids: the closer the carboxylic acid is to the nonreducing end, the more acidic it is. Therefore, the elution order of lactone isomers having the same number of carboxylic groups can be predicted from the position of the free carboxylic groups in pentasialic acid. We used this principle and the results of hydrolysis with neuraminidase to identify hexamer lactone isomers separated by HPCE.     

The synthesis of diastereo- and enantiomerically pure beta-aminocyclopropanecarboxylic acids

The synthesis of diastereo- and enantiomerically pure beta-aminocyclopropanecarboxylic acids (beta-ACCs) is described. Starting from pyrrole, (rac)-4 is readily obtained, which was kinetically resolved by enzymatic hydrolysis. Subsequent oxidation of (-)-4 and deformylation gives rise to the cis-beta-ACC derivative (ent)-9, while (+)-10 was converted to the trans-beta-ACC derivative 8. Both 8 and (ent)-9 and their benzyl esters 13 and 16, being conformationally restricted beta-alanine or gamma-aminobutyric acid (GABA) derivatives, represent useful building blocks for peptides containing unnatural amino acids.     

Assignment of the configurations of the amino acids in peptidic siderophores

Pyoverdins and azotobactins contain beta-hydroxyaspartic acid, N delta-hydroxyornithine, citrulline and homoserine, in addition to the common protein amino acids. Configuration assignment of all of these was achieved by acid hydrolysis of the peptide, derivatization of the constituent amino acids to the N-pentafluoropropionyl amino acid esters and gas chromatographic separation of the stereoisomers on capillaries coated with Chirasil-Val. This approach is straightforward for the protein amino acids, but the less common amino acids are either partially degraded during acid hydrolysis or their derivatives exhibit unfavourable gas chromatographic properties. By judicious combination of partial and total hydrolysis and dual derivatization, these problems may be overcome.     

Micellar catalysis by perfluorooctanoic acid

Rates of acidic hydrolysis of hexano-, octano-, and decanohydroxamic acids and of 4-bromophenylaceto- and phenylacetohydroxamic acids have been determined in aqueous perfluorooctanoic acid—a reactive counterion surfactant system. Typical micellar catalysis was observed for the hydrolyses of the n-alkyl hydroxamic acids but not for the arylacetohydroxamic acids. The Arrhenius activation energy for hydrolysis of octano-hydroxamic acid is smaller above the cmc of the surfactant than it is below the cmc.     

Acylation of Amino Acids with Furancarboxylic Acid Chlorides

Acylation of aromatic amino acids with furancarboxylic acid chlorides effectively proceeds in water-acetone medium at pH 8-9. Aliphatic amino acids are acylated at higher pH values, but under these conditions hydrolysis of acid chlorides becomes the main process. Acylation of chlorohydrates of methyl esters of aliphatic amino acids proceeds smoothly in chloroform in the presence of triethylamine. Alkaline hydrolysis of obtained products leads to N-acylated amino acids containing furan heteroring in the acyl radical.     

The effect of hydrolysis time on amino acid analysis

Determining the amino acid content of a protein involves the hydrolysis of that protein, usually in acid, until the protein-bound amino acids are released and made available for detection. Both the variability in the ease of peptide bond cleavage and differences in the acid stability of certain amino acids can significantly affect determination of a protein's amino acid content. By using multiple hydrolysis intervals, a greater degree of accuracy can be obtained in amino acid analysis. Correction factors derived by linear extrapolation of serial hydrolysis data are currently used. Compartmental modeling of the simultaneous hydrolysis (yield) and degradation (decay) of amino acids by nonlinear multiple regression of serial hydrolysis data has also been validated and applied to determine the amino acid composition of various biological samples, including egg-white lysozyme, human milk protein, and hair. Implicit in the routine application of serial hydrolysis in amino acid analysis, however, is an understanding that correction factors, derived either linearly or through the more accurate nonlinear multiple regression approach, need to be determined for individual proteins rather than be applied uniformly across all protein types.     

Die 1,3-dipolare Cycloaddition von Acetylendicarbonsäure-estern an 2-Methyl-4-phenyl-chinazolin-3-oxid

The 1,3-dipolar addition of acetylenedicarboxylic esters (IX and X) to 2-methyl-4-phenyl-quinazoline 3-oxide (VIII) in benzene/methanol and benzene/ethanol, respectively, gives the esters XI and XII of 3-amino-3-phenyl-2-(2-acetamidophenyl)-acrylic acid as main products and the esters XIII and XIV of 2-methyl-4-phenyl-5H-benzo[d][1,3]diazepin-5-carboxylic acid as by-products. The constitutions of XI and XII are elucidated by acid hydrolysis to the 2-phenylindole-3-carboxylic esters VI and VII, respectively, and by ozonolysis of XII to give benzamide and ethyl o-acetamido-mandelate (IV). The alkaline hydrolysis of XI or XII gives the enamine derivative XVIII, which is hydrolysed by acid to oxindole and benzoic acid. The structure elucidation of XIII and XIV is based on spectroscopic data together with thc formation of XV by alkaline hydrolysis. Mechanisms arc proposed for the reaction paths.