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Auteur : Grafiati
Publié le 10 mars 2023

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1

Adamczyk, Maciej, et Rajarathnam E. Reddy. « A stereoselective synthesis of bis-β-amino acids ». Tetrahedron : Asymmetry 9, no 22 (novembre 1998) : 3919–21. http://dx.doi.org/10.1016/s0957-4166(98)00429-7.

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2

Adamczyk, Maciej, et Rajarathnam E. Reddy. « ChemInform Abstract : A Stereoselective Synthesis of Bis-β-amino Acids. » ChemInform 30, no 17 (16 juin 2010) : no. http://dx.doi.org/10.1002/chin.199917208.

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3

Villemin, Didier, Bernard Moreau et Nathalie Bar. « MCR under Microwave Irradiation : Synthesis in Water of New 2-Amino-bis(2-phosphonoacetic) Acids ». Organics 2, no 2 (11 mai 2021) : 98–106. http://dx.doi.org/10.3390/org2020009.

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Novel 2-amino bis(2-phosphonoacetic) acids were prepared by microwave irradiation of a mixture of amine, glyoxylic acid and phosphorous acid. The reaction takes place with various amines including primary and secondary amines and polyamines, but this reaction is more sensitive to steric hindrance of amine than the similar Kabachnik–Fields reaction. Amino acids can be also transformed into the expected bis(2-phosphonoacetic) acids, with the exception of tryptophan, which gives a β-carboline product.
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4

Kulsi, Goutam, Abhijit Ghorai, Basudeb Achari et Partha Chattopadhyay. « Design and synthesis of conformationally homogeneous pseudo cyclic peptides through amino acid insertion : investigations on their self assembly ». RSC Advances 5, no 79 (2015) : 64675–81. http://dx.doi.org/10.1039/c5ra11850f.

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Macrocyclic C2 symmetric peptides have been synthesized that contain bis furanoid triazole amino acids linked to a d-α-amino acid or a β-amino acid in each half. Only the former undergoes parallel homo-stacking in solution.
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5

Tagle, Luis H., Claudio A. Terraza, Alain Tundidor-Camba et Pablo A. Ortiz. « Silicon-containing oligomeric poly(imido-amides) with amino moieties. Synthesis, characterization and thermal studies ». RSC Adv. 4, no 57 (2014) : 30197–210. http://dx.doi.org/10.1039/c4ra04291c.

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Silicon-containing oligomeric poly(imido-amides) (PIAs) were synthesized from dicarboxylic imido-acids containing a Si atom, which were obtained from dianhydrides, amino acids and p-aminobenzoic acid, were polymerized with the diamine bis(4-aminophenyl)diphenylsilane.
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6

Lindahl, Fredrik, Huy N. Hoang, David P. Fairlie et Matthew A. Cooper. « Facile synthesis of mono- and bis-methylated Fmoc-Dap, -Dab and -Orn amino acids ». Chemical Communications 51, no 21 (2015) : 4496–98. http://dx.doi.org/10.1039/c4cc09780g.

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7

Kuprat, Marcus, Axel Schulz, Max Thomas et Alexander Villinger. « Synthesis and characterization of a stable non-cyclic bis(amino)arsenium cation ». Canadian Journal of Chemistry 96, no 6 (juin 2018) : 502–12. http://dx.doi.org/10.1139/cjc-2017-0420.

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The reaction of Li[Mes*NH] (1, Mes* = 2,4,6-tri-tert-butylphenyl) with aminoarsane Mes*N(H)AsCl2 (2, Mes* = 2,4,6-t-Bu3C6H2) at −80 °C resulted in the formation of bisamino(chloro)arsane (Mes*NH)2AsCl (3Cl) by elimination of LiCl. 3Cl reacted with the Lewis acids such as AlCl3, GaCl3, and Ag[X] (X = AsF6−, OTf−, BF4−; OTf = trifluoromethanesulfonate = OSO2CF3−) upon chloride ion abstraction to give salts bearing the cation [(Mes*NH)2As]+ (3[X]; X = AsF6−, OTf−, BF4−, ECl4; E = Al, Ga). 3+ represents the first NH-functionalized acyclic bis(amino)arsenium cation. The formation of the salts bearing 3+ could also be observed in the reaction of cyclo-1,3-diarsa-2,4-diazane [ClAs(μ-NMes*)]2 (4) with Lewis acids (AlCl3, GaCl3) in the presence of proton sources in solution. All presented salts 3[X] were stable at room temperature and fully characterized.
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8

Sarmiento-Sánchez, Juan I., Adrián Ochoa-Terán et Ignacio A. Rivero. « Synthesis and Antioxidant Evaluation of Enantiomerically Pure Bis-(1,2,3-triazolylmethyl)amino Esters from Modifiedα-Amino Acids ». Scientific World Journal 2014 (2014) : 1–7. http://dx.doi.org/10.1155/2014/264762.

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The efforts for synthesis of enantiomerically pure bis-(1,2,3-triazolylmethyl)amino esters6are reported in good yields from anin situgeneratedα-azidomethyl ketone. Optimum experimental conditions were established for preparation ofα-halomethyl ketones10andα-N,N-dipropargylamino esters11, all derived fromα-amino acids. The starting materials reacted under conventional click chemistry conditions, revealing a specific reactivity of bromomethyl ketones over chloromethyl ketones. The antioxidant activity of compounds6was assayed by DPPH method. The compound6cwith an IC50of 75.57 ± 1.74 μg mL−1was the most active. Technically, this methodology allows the preparation of a combinatorial library of analogues with different structural characteristics depending on the nature of the modifiedα-amino acids employed in the synthesis.
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9

Miličević, Ante, et Nenad Raos. « Theoretical analysis of apical bonding in copper(II) chelates withN-substituted amino acids ». Journal of Applied Crystallography 43, no 1 (9 décembre 2009) : 42–47. http://dx.doi.org/10.1107/s0021889809047748.

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The interdependence between the side of apical coordination of H2O and steric crowding at the apical positions was investigated on a set of 34 copper(II) bis-complexes withN- andN,N-substituted amino acids. As a measure of steric crowding, overlapping volumesV* were used, calculated using a modified overlapping spheres method. Steric crowding around the apically bonded ligand was the same for this set of complexes as for the copper(II) bis-complexes with naturally occurring amino acids, with the optimal occupied volume values between 1 and 1.5 Å3. The interdependence between the length of the apical bond and distortion of the coordination polyhedron was also studied. The apical bond length showed sigmoidal dependence on the magnitude of distortion.
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10

Chen, Jingtang, Thomas Pili et Wolfgang Beck. « Metallkomplexe mit biologisch wichtigen Liganden, L [1] Palladium(II)-, Platin(II)- und Kupfer(II)-Komplexe von α-Aminosäure-N-Glykosiden und von Fructose-Aminosäuren (Amadori-Verbindungen) / Metal Complexes of Biologically Important Ligands, L [1] Palladium(II), Platinum(II) and Copper(II) Complexes of α-Amino Acid-N-Glycosides and of Fructose-Amino Acids (Amadori-Compounds) ». Zeitschrift für Naturforschung B 44, no 4 (1 avril 1989) : 459–64. http://dx.doi.org/10.1515/znb-1989-0414.

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Various N-glycosides derived from glucose and α-amino acids and the isomeric Amadori compounds form bis(chelate) complexes of copper(II), palladium (II) and platinum (II). The IR spectra indicate that the ligands are coordinated through the amino group and a carboxylate oxygen atom.
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11

Ang, SG, et SH Low. « Studies on the Stereochemical Characterization of N-Methylated Amino Acids ». Australian Journal of Chemistry 44, no 11 (1991) : 1591. http://dx.doi.org/10.1071/ch9911591.

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Various methods that could be used to determine the absolute configuration of N,N- dimethylated amino acids were investigated. Two methods utilizing 1H nuclear magnetic resonance (N.M.R.) spectroscopy were successful. The first involved the conversion of the N,N- dimethylated amino acids into diastereoisomers by reaction with methyl (S)-(+)- mandelate . In the second method, the N,N- dimethylated amino acids were amidated with 3,5-dinitroaniline, and 1H n.m.r. analysis was carried out with the addition of a chiral solvating agent, (R)-(-)-1-(9-anthryl)-2,2,2-trifluoroethanol [(R)-(-)-atfe ]. Another method involving the use of high-performance liquid chromatography ( h.p.l.c .), with bis (L-aspartic cyclohexylamide )copper(II) complex CuII (L- Aspchex )2, as the chiral mobile phase was also examined but was found to be unsuccessful in resolving the D- and L-isomers of N,N- dimethylated amino acids.
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12

Livoreil, A., T. Hayashi, J. P. Sauvage et H. Ogoshi. « Study of recognition of amino-acids by a bis-porphyrinic transition metal complex ». Journal of Inorganic Biochemistry 67, no 1-4 (juillet 1997) : 117. http://dx.doi.org/10.1016/s0162-0134(97)89997-7.

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13

Hartshorn, RM, et AM Sargeson. « Reactions of Chelated β-Functionalized Amino Acids With Thionyl Chloride ». Australian Journal of Chemistry 45, no 1 (1992) : 5. http://dx.doi.org/10.1071/ch9920005.

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A variety of bis (ethane-1,2-diamine)cobalt(III) complexes containing chelated β-functionalized amino acids have been treated with SOCl2 in dimethylformamide. These compounds undergo β-elimination reactions to give chelated enamines followed by either rearrangement to the related imine complexes or further reactions with SOCl2 to give chelated isothiazole-3-carboxylato complexes. Mechanisms are proposed for the reactions.
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14

Rueda, Ángela Alcazar, José Marcos Jurado, Fernando de Pablos et Manuel León-Camacho. « Differentiation between Ripening Stages of Iberian Dry-Cured Ham According to the Free Amino Acids Content ». Foods 9, no 1 (12 janvier 2020) : 82. http://dx.doi.org/10.3390/foods9010082.

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In this paper, the differentiation of three ripening stages, postsalting, drying, and cellar, of Iberian dry-cured ham has been carried out according to their free amino acids contents. Eighteen L-amino acids, alanine, 2-aminobutanoic acid, aspartic acid, cysteine, glutamine, glycine, histidine, hydroxyproline, isoleucine, leucine, lysine, methionine, phenylalanine, proline, serine, threonine, tyrosine, and valine have been determined by gas chromatography with derivatization with N,O-bis(trimethylsilyl)-trifluoroacetamide. Gas chromatography–mass spectrometry was used to confirm the presence of the eighteen amino acids in the ham samples, and gas chromatography using a DB-17HT column and flame ionization detector was used for quantitative determination. Extraction with a mixture methanol-acetonitrile has been carried out, achieving recoveries in the range 52–164%. Methimazole was used as internal standard. Limits of detection ranged between 7.0 and 611.7 mg·kg−1. Free amino acids have been used as chemical descriptors to differentiate between the ripening stages. Principal component analysis and linear discriminant analysis have been used as chemometric techniques, achieving complete differentiation between the ripening stages. Alanine, tyrosine, glutamine, proline, 2-aminobutanoic acid, cysteine, and valine were the most differentiating amino acids.
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15

Mahammed, Atif, et Zeev Gross. « Chlorosulfonated corrole : a versatile synthon for advanced materials ». Journal of Porphyrins and Phthalocyanines 14, no 10 (octobre 2010) : 911–23. http://dx.doi.org/10.1142/s1088424610002768.

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The easily accessible 2,17-bis-chlorosulfonated 5,10,15-trispentafluorophenylcorrole is demonstrated as a highly versatile synthon for the preparation of corroles with functional groups that may be used for advanced applications and materials. Examples presented here are useful for donor-acceptor dyads, water-solubility inducing carbohydrates, chirality-inducing sugars and amino acids, and biotin-avidin technology.
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16

Lobanova, I. A., M. Ya Berzina, I. B. Sivaev, P. V. Petrovskii et V. I. Bregadze. « A novel approach to the synthesis of amino acids based on cobalt bis(dicarbollide) ». Russian Chemical Bulletin 59, no 12 (décembre 2010) : 2302–8. http://dx.doi.org/10.1007/s11172-010-0392-9.

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17

Undheim, K., Jon Efskind et G. B. Hoven. « Stereocontrolled construction of conformationally constrained and rigid bis(a-amino acid) derivatives ». Pure and Applied Chemistry 75, no 2-3 (1 janvier 2003) : 279–92. http://dx.doi.org/10.1351/pac200375020279.

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Cystine is regarded as a four-atom bridged bis(α-amino acid). The bridge between the two glycine moieties in cystine has been replaced with all-carbon C4-bridges between the α-carbon of the glycines. The products are dicarba analogs of cystine. Conformational constraints have been conferred on these molecules by insertion of cis- and trans- double bonds in the bridge, by alkylidene substituents, by insertion of a triple bond, by insertion of aromatic or heteroaromatic rings, or otherwise by ring formation. Particularly rigidified dicarba analogs of cystine have been prepared where the α-amino acid carbon is quaternary and part of tricyclic ring structures. Ru(II)-catalyzed ring-closing metathesis (RCM) reactions have been widely used in the preparation of cyclic amino acids. Conformational constraints in acyclic structures result from substitution by simple alkyl, alkenyl, or alkynyl groups at the α-amino acid carbon in the formation of α-quaternary amino acid derivatives.
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18

Ramesh, Remya, et D. Srinivasa Reddy. « Zinc mediated allylations of chlorosilanes promoted by ultrasound : Synthesis of novel constrained sila amino acids ». Org. Biomol. Chem. 12, no 24 (2014) : 4093–97. http://dx.doi.org/10.1039/c4ob00294f.

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A simple, fast and efficient method for allylation and propargylation of chlorosilanes through zinc mediation and ultrasound promotion is reported. As a direct application of the resulting bis-allylsilanes, three novel, constrained sila amino acids are prepared for the first time.
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19

Larkina, M. S., E. V. Podrezova, O. D. Bragina, E. A. Tagirova, V. I. Chernov, M. S. Yusubov, E. A. Nesterov et al. « Development of a method for preparing octreotide derivative for diagnosis of neuroendocrine tumors ». Bulletin of Siberian Medicine 18, no 3 (27 octobre 2019) : 72–80. http://dx.doi.org/10.20538/1682-0363-2019-3-72-80.

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Currently the development of technologies for labeling somatostatin with technetium-99m for diagnosing radionuclide neuroendocrine tumors is under way. Somatostatin analogues are binded with technetium99m only by the preliminary addition of a chelating agent. Therefore, it is important to develop a method for preparation of an octreotide derivative by modifying octreotide with precursors: ligands with high chelating ability for its tight binding with technetium-99m. ω-Bis(pyridin-2-ylmethyl)amino)aliphatic acids can be used successfully as such precursors.The purpose of the study was to develop a method for obtaining a new octreotide derivative for diagnosing neuroendocrine tumors.Materials and methods. The somatostatin octreotide analogue was used as the object of the study; succinimid-1-yl 6-(bis(pyridin-2-ylmethyl)amino)hexanoate was used as a chelating agent. Methods of high performance liquid chromatography and mass spectrometry were used to separate and analyze the synthesized compounds.Results. A method to produce an original octreotide derivative using a succinimid-1-yl 6-(bis(pyridin2-ylmethyl)amino)hexanoate as a chelating agent was proposed. The conditions of analytical and semipreparative HPLC for the analysis and purification of the active octreotide derivative (a monosubstituted derivative of the amino acid residue of D-phenylalanine) were suggested.Conclusion. The synthesized derivative of octreotide has a chelating center for strong binding to technetium-99m in its structure, which can be useful for diagnosing neuroendocrine tumors.
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20

Bernier, Chad M., et Joseph S. Merola. « Design of Iridium N-Heterocyclic Carbene Amino Acid Catalysts for Asymmetric Transfer Hydrogenation of Aryl Ketones ». Catalysts 11, no 6 (24 mai 2021) : 671. http://dx.doi.org/10.3390/catal11060671.

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A series of chiral complexes of the form Ir(NHC)2(aa)(H)(X) (NHC = N-heterocyclic carbene, aa = chelated amino acid, X = halide) was synthesized by oxidative addition of α-amino acids to iridium(I) bis-NHC compounds and screened for asymmetric transfer hydrogenation of ketones. Following optimization of the reaction conditions, NHC, and amino acid ligands, high enantioselectivity was achieved when employing the Ir(IMe)2(l-Pro)(H)(I) catalyst (IMe = 1,3-dimethylimidazol-2-ylidene), which asymmetrically reduces a range of acetophenone derivatives in up to 95% enantiomeric excess.
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21

Yoshimura, Kazuhisa, Ryohei Kato, Mark F. Kavlick, Aline Nguyen, Victor Maroun, Kenji Maeda, Khaja A. Hussain et al. « A Potent Human Immunodeficiency Virus Type 1 Protease Inhibitor, UIC-94003 (TMC-126), and Selection of a Novel (A28S) Mutation in the Protease Active Site ». Journal of Virology 76, no 3 (1 février 2002) : 1349–58. http://dx.doi.org/10.1128/jvi.76.3.1349-1358.2002.

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ABSTRACT We identified UIC-94003, a nonpeptidic human immunodeficiency virus (HIV) protease inhibitor (PI), containing 3(R),3a(S),6a(R)-bis-tetrahydrofuranyl urethane (bis-THF) and a sulfonamide isostere, which is extremely potent against a wide spectrum of HIV (50% inhibitory concentration, 0.0003 to 0.0005 μM). UIC-94003 was also potent against multi-PI-resistant HIV-1 strains isolated from patients who had no response to any existing antiviral regimens after having received a variety of antiviral agents (50% inhibitory concentration, 0.0005 to 0.0055 μM). Upon selection of HIV-1 in the presence of UIC-94003, mutants carrying a novel active-site mutation, A28S, in the presence of L10F, M46I, I50V, A71V, and N88D appeared. Modeling analysis revealed that the close contact of UIC-94003 with the main chains of the protease active-site amino acids (Asp29 and Asp30) differed from that of other PIs and may be important for its potency and wide-spectrum activity against a variety of drug-resistant HIV-1 variants. Thus, introduction of inhibitor interactions with the main chains of key amino acids and seeking a unique inhibitor-enzyme contact profile should provide a framework for developing novel PIs for treating patients harboring multi-PI-resistant HIV-1.
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22

Ziyaei Halimehjani, Azim, Petr Beier, Maryam Khalili Foumeshi, Ali Alaei et Blanka Klepetářová. « Tandem Alkylation/Michael Addition Reaction of Dithiocarbamic Acids with Alkyl γ-Bromocrotonates : Access to Functionalized 1,3-Thiazolidine-2-thiones ». Synthesis 53, no 13 (25 janvier 2021) : 2219–28. http://dx.doi.org/10.1055/a-1372-1619.

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AbstractThiazolidine-2-thiones were prepared via a novel multicomponent reaction of primary amines (amino acids), carbon disulfide, and γ-bromocrotonates. The reaction proceeds via a domino alkylation/intramolecular Michael addition to provide the corresponding thiazolidine-2-thiones in high to excellent yields. By using diamines in this protocol, bis(thiazolidine-2-thiones) derivatives were synthesized. The synthetic utility of the adducts was demonstrated by hydrolysis, amidation, and oxidation reactions.
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23

Chan, Chung Ying, et Peter J. Barnard. « Rhenium complexes of bidentate, bis-bidentate and tridentate N-heterocyclic carbene ligands ». Dalton Transactions 44, no 44 (2015) : 19126–40. http://dx.doi.org/10.1039/c5dt03295d.

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Rhenium(i) tricarbonyl complexes of a range of bidentate, bis-bidentate and tridentate NHC ligands have been prepared. These NHC ligands are of interest for possible applications in the development of Tc-99m or Re-186/188 radiopharmaceuticals and the stability of two complexes were evaluated in ligand challenge experiments using the metal binding amino acids l-histidine or l-cysteine.
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24

Chamorro, C., E. De Clercq, J. Balzarini, M.-J. Camarasa et A. San-Félix. « TSAO-T Analogues Bearing Amino Acids at Position N-3 of Thymine : Synthesis and Anti-Human Immunodeficiency Virus Activity ». Antiviral Chemistry and Chemotherapy 11, no 1 (février 2000) : 61–69. http://dx.doi.org/10.1177/095632020001100106.

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Novel analogues of the anti-HIV-1 lead compound [1-[2‘,5’-bis- O-( tert-butyldimethylsilyl)-β-D-ribofuranosyl]thymine]-3‘-spiro-5’-(4“-amino-1”,2“-oxathiole-2‘,2’-dioxide) (TSAO-T) bearing different amino acids at position N-3 of thymine were prepared and evaluated as inhibitors of HIV replication. The synthesis of the target compounds was accomplished by coupling of the appropriate TSAO intermediate with a conveniently protected (L) amino acid in the presence of BOP and triethylamine, followed by depro-tection of the amino acid moiety. Several TSAO derivatives, bearing at N-3 position of the thymine base an L-amino acid retaining the free carboxylic acid, acquired activity against HIV-2, in addition to their inhibitory effect on HIV-1.
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25

Vrbovská, Silvie, Antonín Holý, Radek Pohl et Milena Masojídková. « Bifunctional Acyclic Nucleoside Phosphonates. 1. Symmetrical 1,3-Bis[(phosphonomethoxy)propan-2-yl] Derivatives of Purines and Pyrimidines ». Collection of Czechoslovak Chemical Communications 71, no 4 (2006) : 543–66. http://dx.doi.org/10.1135/cccc20060543.

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We report here a general method for the synthesis of new symmetrical bis-phosphonates of acyclic nucleosides. 1,3-Bis[(diisopropoxyphosphoryl)methoxy] derivatives of purine and pyrimidine bases were prepared by their reaction with 1,3-bis[(diisopropoxyphosphoryl)-methoxy]propan-2-yl tosylate. Cytosine, uracil and thymine provided regiospecificallyN1-isomers. This alkylation regiospecificity applies to several other tosylates of primary and secondary alcohols as well. 6-Chloropurine and 2-amino-6-chloropurine were alkylated in N9position. Resulting bis-phosphonates were converted to the respective free phosphonic acids and tested for antiviral and cytostatic activity. Despite the fact that no biological activity was found so far, the outcome of this work can serve as a useful tool in synthesis of novel groups of acyclic nucleoside phosphonates (ANPs).
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26

Gennari, Cesare, Chiara Monti et Umberto Piarulli. « Rhodium-catalyzed asymmetric reactions with a dynamic library of chiral tropos phosphorus ligands ». Pure and Applied Chemistry 78, no 2 (1 janvier 2006) : 303–10. http://dx.doi.org/10.1351/pac200678020303.

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Nineteen chiral tropos phosphorus ligands, based on a flexible (tropos) biphenol unit and a chiral P-bound alcohol (11 phosphites) or secondary amine (8 phosphoramidites), were screened, individually and as a combination of two, in various Rh-catalyzed asymmetric reactions. In the Rh-catalyzed asymmetric conjugate addition of phenylboronic acid to cyclic enones, enantiomeric excesses (ee's) up to 95 % were obtained with a 1:1 mixture of a phosphite [derived from (1R,2S)-2-(1-methyl-1-phenylethyl)cyclohexanol] and a phosphoramidite [derived from (S,S)-2,5-diphenylpyrrolidine]. In the mixed Rh precatalyst, which was characterized via 31P-NMR, the biphenol-derived phosphite is free to rotate (tropos) while the biphenol-derived phosphoramidite shows a temperature-dependent tropos/atropos behavior (coalescence temperature = 310 K). The ligands were also screened in the hydrogenation of dehydro-α-amino acids and dehydro-β-amino acids. Ee's up to 98% were obtained for the dehydro-α-amino acids, using the combination of a phosphite [derived from (1R,2S)-2-phenyl-1-cyclohexanol] and a phosphoramidite [derived from (S,S)-bis(α-methylbenzyl)amine]. The reaction was optimized by lowering the phosphite/phosphoramidite ratio to 0.25:1.75 with a resulting improvement of the product ee.
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27

Nsofor, Winifred Njideka, Reginald Nwazue Nwaoguikpe, Favour Ntite Ujowundu, Collins Obinna Keke, Muhammad Tasi’u Uba et Chibuike Valentine Edom. « Phytochemical, GC-MS, FTIR and Amino acid profile of methanol extract of Tetrapleura tetraptera fruit ». Journal of Drug Delivery and Therapeutics 13, no 2 (15 février 2023) : 61–69. http://dx.doi.org/10.22270/jddt.v13i2.5739.

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The methanolic fruit extract of Tetrapleura tetraptera was analyzed for the presence of phytocompounds, their bioactivity, the functional groups involved in this activity, and its amino acid profile using standard procedures. Phytochemicals such as tannins, phenols, flavonoids, and alkaloids were identified as being highly present. Gas chromatographic-mass spectrometric (GC-MS) analysis identified 16 bioactive compounds, with 2-thiopheneethanol (58.77%) being the most abundant. Curcumin, with the most diverse pharmacological role, and other bioactive compounds such as cedren-13-ol, 8 (1.56%), N-benzyl stearamide (4.46%), a prominent fatty acid amide hydrolase (FAAH) inhibitor; pthalic acid, butyl undecyl ester (1.49%); and phenol, 2, 6-bis (1,1 dimethyl ethyl) (1.46%), were also present. Fourier transform infrared (FTIR) analysis confirmed the presence of alkanes, esters, benzene rings, aliphatic, sulfonic acid, and methylene chains. Also, the amino acid analysis of the T. tetraptera revealed that the fruit contains 18 amino acids. Leucine (4.20%), phenylalanine (3.37%), and valine (3.25%) were the most abundant essential amino acids identified, with glutamic (7.20%) and aspartic acid (5.61%) having the highest concentrations as non-essential amino acids. This therefore indicates that T. tetraptera fruit could be used as a pharmacological or therapeutic agent as well as a dietary condiment, particularly at this time when there is a demand for novel protein sources. Keywords: Tetrapleura tetraptera, phytochemicals, GC-MS, FTIR, amino acid, curcumin
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28

Travagliante, Gabriele, Massimiliano Gaeta, Roberto Purrello et Alessandro D’Urso. « Recognition and Sensing of Chiral Organic Molecules by Chiral Porphyrinoids : A Review ». Chemosensors 9, no 8 (3 août 2021) : 204. http://dx.doi.org/10.3390/chemosensors9080204.

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Porphyrinoids are extremely attractive for their electronic, optical, and coordination properties as well as for their versatile substitution at meso/β-positions. All these features allow porphyrinoids to behave as chiroptical hosts for chiral recognition by means of non-covalent interactions towards chiral guests. Over the years, chiral discrimination of chiral molecules such as amino acids, alcohols, amines, hydroxy-carboxylic acids, etc. has aroused the interest of the scientific community. Hence, this review aims to report on the progress to date by illustrating some relevant research regarding the chiral recognition of a multitude of chiral organic guests through several chiral mono- and bis-porphyrins via different spectroscopic techniques.
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29

Liu, Chang, Zhi-Li Wei, Hao-Ran Mu, Wen-Kui Dong et Yu-Jie Ding. « A novel unsymmetric bis(salamo)-based chemosensor for detecting Cu2+ and continuous recognition of amino acids ». Journal of Photochemistry and Photobiology A : Chemistry 397 (juin 2020) : 112569. http://dx.doi.org/10.1016/j.jphotochem.2020.112569.

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30

Baba, M., D. Schols, P. Mohan, E. De Clercq et S. Shigeta. « Inhibition of HIV-1-Induced Cytopathogenicity, Syncytium Formation, and Virus-Cell Binding by Naphthalenedisulphonic Acids through Interaction with the Viral Envelope gp120 Glycoprotein ». Antiviral Chemistry and Chemotherapy 4, no 4 (août 1993) : 229–34. http://dx.doi.org/10.1177/095632029300400405.

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Bis-naphthalenedisulphonic acid derivatives with a biphenyl spacer, 4,4′-[4,4′-biphenyldiylbis(sulphonyl-amino)]bis(5-hydroxy-2,7-naphthalenedisulphonic acid) and 3,3′-[4,4′-biphenyldiylbis(sulphonyl-amino)]bis(1,5-naphthalenedisulphonic acid), have previously been reported as potent and selective inhibitors of human immunodeficiency virus type 1 (HIV-1) replication in cell culture. These compounds have also proved inhibitory to syncytium formation in cocultures of MOLT-4 cells with HIV-1-infected HUT-78 cells. They also inhibit the binding of HIV-1 virions to MT-4 cells as determined by a flow cytometric (FACS) method. Further studies on their mechanism of action by the FACS have revealed that the compounds inhibit the binding of anti-gp120 monoclonal antibody to the viral envelope glycoprotein gp120. Binding of OKT4A/Leu3a monoclonal antibody to the cellular CD4 receptor is not affected by the compounds. These results suggest that the anti-HIV-1 activity of the naphthalenedisulphonic acid derivatives can be attributed to inhibition of the gp120-CD4 interaction through binding of the compounds to the viral gp120 antigen.
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31

Mayr, Florian, Lisa-Marie Mohr, Elsa Rodriguez et Thorsten Bach. « Synthesis of Chiral Thiourea-Thioxanthone Hybrids ». Synthesis 49, no 23 (19 octobre 2017) : 5238–50. http://dx.doi.org/10.1055/s-0036-1590931.

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Four different 1-aminocyclohexanes bearing a tethered thioxanthone group in the 2-position were prepared. The synthesis commenced with the respective N-protected β-amino acids, the carboxyl group of which was employed for the introduction of the thioxanthone moiety. After construction of the thioxanthone and protecting group removal, the conversion of the amino group into the respective thiourea was accomplished by treatment with N-3,5-bis(trifluoromethyl)phenyl isothiocyanate and yielded the title compounds in which the thioxanthone resides in different spatial positions relative to the thiourea motif. Overall yields varied between 20–35%.
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32

Urriolabeitia, Esteban P., Pablo Sánchez, Alexandra Pop, Cristian Silvestru, Eduardo Laga, Ana I. Jiménez et Carlos Cativiela. « Synthesis of esters of diaminotruxillic bis-amino acids by Pd-mediated photocycloaddition of analogs of the Kaede protein chromophore ». Beilstein Journal of Organic Chemistry 16 (25 mai 2020) : 1111–23. http://dx.doi.org/10.3762/bjoc.16.98.

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The stereoselective synthesis of truxillic bis-amino esters from polyfunctional oxazolones is reported. The reaction of 4-((Z)-arylidene)-2-(E)-styryl-5(4H)-oxazolones 2 with Pd(OAc)2 resulted in ortho-palladation and the formation of a dinuclear open-book complexes 3 with carboxylate bridges, where the Pd atom is C^N bonded to the oxazolone. In 3 the two exocyclic C=C bonds of the oxazolone are in a face-to-face arrangement, which is optimal for their [2 + 2] photocycloaddition. Irradiation of dimers 3 in CH2Cl2 solution with blue light (465 nm) promoted the chemo- and stereoselective [2 + 2] photocycloaddition of the exocyclic C=C bonds and the formation of cyclobutane-containing ortho-palladated complexes 4. Treatment of 4 with CO in a MeOH/NCMe mixture promoted the methoxycarbonylation of the palladated carbon and the release of the corresponding ortho-functionalized 1,3-diaminotruxillic bis-amino esters 5 as single isomers.
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33

Jeon, Hara, Lee Ku Kwac, Hong Gun Kim et Jin-Hae Chang. « Comparison of properties of colorless and transparent polyimide films using various diamine monomers ». REVIEWS ON ADVANCED MATERIALS SCIENCE 61, no 1 (1 janvier 2022) : 394–404. http://dx.doi.org/10.1515/rams-2022-0044.

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Abstract Six different types of polyamic acids were synthesized by reacting 1,2,4,5-cyclohexanetetracarboxylic dianhydride with the diamine monomers 3,4-oxydianiline, 1,3-bis(3-aminopheno-xy)benzene, 1,4-bis(4-amino-phenoxy)benzene, m-bis[4-(3-aminophenoxy)phenyl]sulfone, p-bis[4-(4-aminophenoxy)-phenyl]sulfone, and 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane. Thereafter, polyimide (PI) films were prepared via various heat treatment processes. The diamine monomers used in this study for the synthesis of colorless and transparent PI (CPI) were characterized by a bent meta-structure or a para-linear chain containing ether (–O–) bonds. In addition, some monomers included fluorine (–CF3) substituents and sulfone (–SO2–) groups. Furthermore, the thermal and mechanical properties, optical transparency, and solubility of the CPI films with six different diamine monomer structures were investigated. The correlation between CPI film properties and related monomer structures was specifically emphasized.
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34

Vetrichelvan, Muthalagu, Vijayabhaskar Bokkala, Surendran Renganathan, Arvind Mathur, Richard Rampulla et Anuradha Gupta. « A Short and Scalable Synthesis of Orthogonally Protected Bis(aminomethyl)malonic Acid : Access to Bioactive Macrocyclic Peptides ». Synthesis 49, no 22 (1 août 2017) : 5039–44. http://dx.doi.org/10.1055/s-0036-1588505.

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A short and scalable process for the preparation of multi-gram quantities of orthogonally protected bis(aminomethyl)malonic acid in good yield from readily available starting material is described. These orthogonally protected amino acids are important building blocks to make peptides based drugs, glycoconjugates, and in the total synthesis of peptide natural products. The newly developed route has only six steps with an overall yield of 27%, which involves nucleophilic attack of a malonate on an imide as one of the key steps.
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35

Tanase, Tomoaki, Tomoko Inagaki, Yasuko Yamada, Masako Kato, Emi Ota, Mikio Yamazaki, Mitsunobu Sato et al. « Tetranuclear iron(III) complexes with amino acids involving a planar (μ-oxo)(μ-hydroxo)bis(μ-alkoxo)bis(μ-carboxylato)tetrairon core † ». Journal of the Chemical Society, Dalton Transactions, no 4 (1998) : 713–18. http://dx.doi.org/10.1039/a707008j.

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36

Pouzar, Vladimír, et Ivan Černý. « Coupling of Steroid O-(Carboxymethyl)oxime Derivatives with Amino Alcohols ». Collection of Czechoslovak Chemical Communications 61, no 2 (1996) : 288–97. http://dx.doi.org/10.1135/cccc19960288.

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New approach to the preparation of steroids with connecting bridge, based on an O-carboxymethyloxime (CMO) structure, and with terminal hydroxy group, is presented. 17-CMO derivatives of 3β-acetoxy- and 3β-methoxymethoxyandrost-5-en-17-one were condensed with α,ω-amino alcohols to give derivatives with a chain of seven to nine atoms. After THP-protection, these compounds were converted to 3-keto-4-ene derivatives. An alternative synthesis consisted in transformation of 17-CMO derivatives with bonded amino acids by reduction of the terminal carboxyl. The resulting compounds were designed as building blocks for the preparation of bis-haptens for sandwich immunoassays.
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37

Baxter, Ryan, Akil Hamsath et Jordan Galloway. « Quinone C–H Alkylations via Oxidative Radical Processes ». Synthesis 50, no 15 (6 juin 2018) : 2915–23. http://dx.doi.org/10.1055/s-0037-1610005.

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A brief survey of radical additions to quinones is reported. Carboxylic acids, aldehydes, and unprotected amino acids are compared as alkyl radical precursors for the mono- or bis- C–H alkylation of several quinones. Two methods for radical initiation are discussed comparing inorganic persulfates and Selectfluor as stoichiometric oxidants. Kinetic analysis reveals dramatic differences in the rate of radical initiation depending on the identity of the radical precursor and oxidant. Synthetic strategies for efficiently producing alkyl-quinones are discussed in the context of selecting optimum radical precursors and initiators depending on quinone identity and functional groups present.
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38

Doi, Ryohei, Taichi Okano, Iman Abdullah et Yoshihiro Sato. « Nickel-Catalyzed β-Carboxylation of Ynamides with Carbon Dioxide ». Synlett 30, no 09 (8 mai 2019) : 1048–52. http://dx.doi.org/10.1055/s-0037-1611529.

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A nickel-catalyzed β-selective hydrocarboxylation of ynamides to give protected dehydro-β-amino acids was developed. The key to exclusive β-selectivity was the use of diethylzinc as a reductant in the presence of a magnesium salt. The reaction was conducted with bis(acetylacetonato)nickel(II) instead of costly and sensitive bis(1,5-cyclooctadiene)nickel(0). In addition, the optimized ligand was inexpensive 1,5-cyclooctadiene. Investigation of the substrate scope revealed that both nitrogen and alkyne substituents have marked effects on the reaction efficiency. We obtained experimental clues that indicated the formation of a vinylzinc intermediate that forms a C–C bond with CO2.
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39

Tung, Roger D., et Daniel H. Rich. « Bis(2-oxo-3-oxazolidinyl)phosphinic chloride (1) as a coupling reagent for N-alkyl amino acids ». Journal of the American Chemical Society 107, no 14 (juillet 1985) : 4342–43. http://dx.doi.org/10.1021/ja00300a051.

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40

Duréault, A., I. Tranchepain, C. Greck et J.-C. Depezay. « Nucleophilic opening of chiral bis-aziridines : A route to enantiomerically pure α-amino acids and polysubstituted piperidines ». Tetrahedron Letters 28, no 29 (janvier 1987) : 3341–44. http://dx.doi.org/10.1016/s0040-4039(00)95507-2.

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41

Schulte, Michael L., Alexandra B. Khodadadi, Madison L. Cuthbertson, Jarrod A. Smith et H. Charles Manning. « 2-Amino-4-bis(aryloxybenzyl)aminobutanoic acids : A novel scaffold for inhibition of ASCT2-mediated glutamine transport ». Bioorganic & ; Medicinal Chemistry Letters 26, no 3 (février 2016) : 1044–47. http://dx.doi.org/10.1016/j.bmcl.2015.12.031.

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42

Grigorjeva, Liene, et Aigars Jirgensons. « Lewis Acid Catalyzed Intramolecular Allylic Substitution of Bis(trichloroacetimidates) : A Versatile Approach to Racemic Unsaturated Amino Acids ». European Journal of Organic Chemistry 2011, no 13 (8 mars 2011) : 2421–25. http://dx.doi.org/10.1002/ejoc.201100060.

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43

Roche, Stéphane P. « In the Pursuit of (Ald)Imine Surrogates for the Direct Asymmetric Synthesis of Non-Proteinogenic α-Amino Acids ». Synthesis 53, no 16 (24 mars 2021) : 2767–76. http://dx.doi.org/10.1055/a-1463-4266.

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AbstractNature remarkably employs posttranslational modifications of the 20 canonical α-amino acids to devise a far larger structural, conformational, and functional diversity found in non-proteinogenic amino acids (NPAAs), which ultimately translates into a plethora of complex biological functions. Synthetic chemists are continuously trying to reproduce and even extrapolate the repertoire of NPAA building blocks to build structural diversity into bioactive molecules and materials. The direct asymmetric functionalization of α-imino esters represents one of the most robust and attractive routes to NPAAs. This review summarizes the most prominent examples of bench-stable (ald)imine surrogates exploited for the synthesis of NPAAs, including our most recent results in the nucleophilic substitution of α-haloglycines and other α-halo­aminals. A synopsis of kinetic studies, reaction optimizations, and enantio­selective catalytic methods is also presented.1 Introduction2 Asymmetric Synthesis of Tertiary α-Substituted NPAAs2.1 From N,O-Acetals (α-Hydroxy/Alkyloxy/Acetoxyglycines)2.2 From α-Amido Sulfones2.3 From α-Haloglycine Esters2.4 From N,O-Bis(Boc) Hydroxyglycine3 Asymmetric Synthesis of Acyclic Quaternary α,α-Disubstituted NPAAs4 Concluding Remarks
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44

Vašš, František, et Jozef Lustoň. « Functional Derivatives of Sterically Hindered Amines. Polyalkylpiperidine Diesters ». Collection of Czechoslovak Chemical Communications 60, no 9 (1995) : 1529–35. http://dx.doi.org/10.1135/cccc19951529.

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Several diesters of dicarboxylic acids with pendant polyalkylpiperidine structural units were prepared from α-bromo and α,α'-dibromo substituted aliphatic dicarboxylic acid diesters by a nucleophilic replacement reaction with 2,2,6,6-tetramethyl-4-hydroxypiperidine, 1,2,2,6,6-pentamethyl-4-hydroxypiperidine, and 2,2,6,6-tetramethyl-4-aminopiperidine, by a nucleophilic addition of amino derivative to the α,β-unsaturated dicarboxylic acid diester and by an acid catalyzed condensation of 2,2,6,6-tetramethyl-4-oxopiperidine with diethyl bis(hydroxymethyl)malonate.
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45

Okorochenkov, Sergei A., Galina A. Zheltukhina, Vitaly A. Roginsky, Nikolai N. Nossik, Sergei L. Zheltukhin et Vladimir E. Nebolsin. « Amino acid and peptide hemin derivatives as new promising virucidal agents ». Journal of Porphyrins and Phthalocyanines 16, no 03 (mars 2012) : 297–309. http://dx.doi.org/10.1142/s1088424612500344.

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We synthesized a series of hemin derivatives (HDs) substituted by residues of amino acids and peptides at either one or two propionic-acid residues, and studied the virucidal activity of the compounds obtained against herpes simplex virus. Compounds 6,7-bis-(methyl ester N0 L-seryl)-protohemin (IX) (2) and 6,7-bis-[methyl ester N0-L-arginyl)-protohemin (IX) (6) shown the highest virucidal activity. We also investigated the interaction between HDs and lipid-membrane components as a possible mechanism of virucidal action. A model system including Clark's electrode and a micellar solution of methyl linoleate was used to quantitatively assess the capability of HDs to catalyze the oxidation of polyunsaturated fatty acids as components of lipid membranes. Another model system including liposomes that consisted of dioleoylphosphatydylcholine and was loaded with the fluorescent dye carboxyfluorescein was employed to examine the effect of HDs on lipid-membrane permeability. The kinetics and efficacy of increasing liposome-membrane permeability on exposure to HDs appeared to depend on the nature of the substituents in the HDs. The findings are strongly suggestive of the presence of two different modes of interaction between an HD and the lipid membrane, i.e. oxidative and non-oxidative mechanisms possibly underlie the virucidal action of HDs.
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46

Mulamreddy, Ramakotaiah, et William D. Lubell. « Constrained Dipeptide Surrogates : 5- and 7-Hydroxy Indolizidin-2-one Amino Acid Synthesis from Iodolactonization of Dehydro-2,8-diamino Azelates ». Molecules 27, no 1 (23 décembre 2021) : 67. http://dx.doi.org/10.3390/molecules27010067.

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The constrained dipeptide surrogates 5- and 7-hydroxy indolizidin-2-one N-(Boc)amino acids have been synthesized from L-serine as a chiral educt. A linear precursor ∆4-unsaturated (2S,8S)-2,8-bis[N-(Boc)amino]azelic acid was prepared in five steps from L-serine. Although epoxidation and dihydroxylation pathways gave mixtures of hydroxy indolizidin-2-one diastereomers, iodolactonization of the ∆4-azelate stereoselectively delivered a lactone iodide from which separable (5S)- and (7S)-hydroxy indolizidin-2-one N-(Boc)amino esters were synthesized by sequences featuring intramolecular iodide displacement and lactam formation. X-ray analysis of the (7S)-hydroxy indolizidin-2-one N-(Boc)amino ester indicated that the backbone dihedral angles embedded in the bicyclic ring system resembled those of the central residues of an ideal type II’ β-turn indicating the potential for peptide mimicry.
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47

Adaeze, Bob-Chile A., et Peter U. Amadi. « Evaluation of Bioactive Component, Free Radical Scavenging Potentials and Protein Qualities of Gomphrena celosoides and Zea mays Leaves ». Current Bioactive Compounds 16, no 7 (28 octobre 2020) : 1108–15. http://dx.doi.org/10.2174/1573407215666191125105900.

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Background: The assessment of underexploited leaves has become crucial to supplement the rapidly depleting sources of bioactive components as well as provide available nutrient sources for local inhabitants. Methods: This study thus investigated the bioactive components of the oil, and fatty acid composition, free radical scavenging potentials, and protein qualities of leaves of Z. mays and G. celosioides using standard methods. The bioactive components of the oils and fatty acids were determined by Gas Chromatograpy, while the amino acid and in-vitro antioxidant potentials were determined using a Technicon Sequential Multi-Sample (TSM) Amino Acid Analyzer, and spectrophotometer, respectively. Results: The Z. Mays leaves showed the abundance of farnesene, hexadecanoic acids, and caryophellene while G. celosioides produced high level of octadecadienoic acid, hexadecanoic acid, and phytol. Z. mays and G. celosioides contained 72.48% and 60.55% unsaturated fatty acids respectively, with the abundance of linolenic acid for Z. mays and oleic acid for G. celosioides. The result for the in vitro antioxidant % inhibition showed a concentration dependent free radical scavenging potentials of the leaves. Both G. celosioides and Z. mays produced greater 1,1-diphenyl-2- picrylhydrazyl (DPPH), and hydrogen peroxide radical scavenging potentials than ascorbic acid, while at 40ppm the nitric oxide and 2,2- azino-bis(3-ethylbenzthiazoline-6-sulphonic acid) (ABTS) radical % inhibition of Z. mays leaves were lower than those for ascorbic acid. Discussion: The number of essential amino acids in both plants were 48.20 and 39.25 g/100g, total branched chain amino acids (TBCAA) were 21.15 and 16.92 g/100g, predicted protein efficiency ratios (P-PERs) were in the range of 3.02-3.23 and 2.68-2.77, and the essential amino acid index (EAAI) were 1.52 and 1.48, for Z. mays and G. celosioides leaves respectively. Conclusion: From these results, the utilization of Z. mays and G. celosioides for high quality protein, unsaturated fatty acids and potent antioxidant sources, should be massively encouraged.
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48

Abo-Ghalia, Mohamed H., Abd El-Galil E. Amr et Mohamed M. Abdalah. « Synthesis of Some New (Nα-Dipicolinoyl)-bis-L-leucyl-DL-norvalyl Linear tetra and Cyclic octa Bridged Peptides as New Antiinflammatory Agents ». Zeitschrift für Naturforschung B 58, no 9 (1 septembre 2003) : 903–10. http://dx.doi.org/10.1515/znb-2003-0912.

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In continuation to our search for new amino acid and peptide based anti-inflammatory agents, the suggestion, synthesis, structure elucidation of some Nα -bis-dipicolinoyl amino acids, linear tetra and cyclic octa bridged peptides 1-9, of which four are new compounds 6-9, were herein realized. Accordingly, Nα -bis-dipicolinoyl-L-leucine methyl ester 1, the corresponding acid 2, its bis-DL-norvalyl methyl ester homologue 3, the acid 4 and hydrazide 5 analogues were conventionally prepared.The tetrachlorophthalic acid hydrazine conjugate 6, anisaldehyde hydrazone 7, the benzenetetracarboxylic acid and naphthalenetetracarboxylic acid bis-L-leucyl-DL-norvalyl cyclic octa bridged peptides 8 and 9 respectively, were newly synthesized via condensation of the hydrazide 5 with the corresponding aldehyde or anhydride.The chromatographic, IR, NMR and mass spectral analysis confirmed the identities of the synthesized compounds.Comparable to the two reference antiinflammatory drugs indomethacin® and voltaren® (100%), the determined antiinflammatory potency of the candidates (carrageenan® induced paw edema in rats) revealed a general significant activity (66 - 94%), except for the practically inactive 6 (∼1.5 % activity).In particular, the potency of the (Nα -dipicolinoyl)-bis-L-leucyl-DL-norvalyl anisaldehyde hydrazone 7 was of 94 and 87%, comparable to the reference drugs. However, 7 also showed 58% protection against ulcer formation, comparable to null for indomethacin®. Additionally, an acceptable acute toxicity was observed (LD50: 2833 mg/kg, comparable to 2700 and 2850 for indomethacin® and voltaren® respectively).
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49

Weni, Mustika, Mega Safithri et Djarot Sasongko Hami Seno. « Molecular Docking of Active Compounds Piper crocatum on the A-Glucosidase Enzyme as Antidiabetic ». Indonesian Journal of Pharmaceutical Science and Technology 7, no 2 (11 juillet 2020) : 64. http://dx.doi.org/10.24198/ijpst.v7i2.21120.

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Ethanol extract of Piper crocatum leaves has inhibitory activity of α-glucosidase enzyme. Ethyl acetate fraction from Piper crocatum leaves has the highest antioxidant activity. Previous research has provided information that the ethyl acetate fraction of Piper crocatum leaves has an inhibition of α-glucosidase containing 6XO32ZSP1D, Ethyl L-serinate hydrochloride compound, Schisandrin B compound, Columbin compound, 4- (4-methoxy-phenylamino) -2 compound, 3-dihydro-1H-4a, 9-diazacyclopenta (b) fluorine-10-carbonitrile, compound 6-Amino-4- [3- (benzyloxy) phenyl] -3-tert-butyl-2,4-dihydropyrano [2, 3-c] pyrazole-5-carbonitrile, compound 4 - {{4.6-Bis [(3R, 5S) -3,5-diamino-1-piperydinyl] -1,3,5-triazine-2-yl} amino) benzenesulfonamide and compound 1.1 '- (1,4-butanediyl) bis {2,6-dimethyl-4 - [(3-methyl-1,3-benzothiazol-2 (3H) ylidene) methyl] pyridinium. This study aims to study the interaction between bioactive compounds contained in ethyl acetate fraction of Piper crocatum leaves with α-glucosidase enzyme in In Silico using AutoDock Vina, Columbin shows the lowest binding energy with binding sites with amino acids Ser240, Asp242, His280, Arg315, Glu411, Phe159, Arg442, Tyr158 and Phe303. Columbin has the stability and inhibits the α-glucosidase enzyme from S. cerevisiae better than the seven other compounds, because it has OH and CH3 groups which play a role in the interaction with around the active side of the α-glucosidase enzyme.Keywords: Columbin, In Silico, α-Glucosidase
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50

Miličević, Ante, et Nenad Raos. « Theoretical analysis of apical bonding in copper(II) chelates with amino acids ». Journal of Applied Crystallography 42, no 5 (1 août 2009) : 793–97. http://dx.doi.org/10.1107/s0021889809023589.

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The interdependence between the side of apical coordination (H2O, >C=O, dimethyl sulfoxide and Cl−) and steric crowding at the apical positions was investigated for a set of 20 copper(II) bis complexes with naturally occurring amino acids. As a measure of steric crowding the overlapping volumes,V*, were used, calculated by the modified overlapping spheres method. It was found that the apically coordinated side of a complex is more hindered by the side-chain atoms. In addition, if both sides are apically coordinated, the apical bond is shorter at the more crowded side. The interdependence between the length of the apical bond and distortion of the coordination polyhedron was also studied. The apical bond length shows sigmoidal dependence on the magnitude of distortion, and is also dependent on the kind of distortion (square-pyramidal or tetrahedral).
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