- Novel chiral stationary phases based on 3,5-dimethyl phenylcarbamoylated β-cyclodextrin combining cinchona alkaloid moiety
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Novel chiral selectors based on 3,5-dimethyl phenylcarbamoylated β-cyclodextrin connecting quinine (QN) or quinidine (QD) moiety were synthesized and immobilized on silica gel. Their chromatographic performances were investigated by comparing to the 3,5-dimethyl phenylcarbamoylated β-cyclodextrin (β-CD) chiral stationary phase (CSP) and 9-O-(tert-butylcarbamoyl)-QN-based CSP (QN-AX). Fmoc-protected amino acids, chiral drug cloprostenol (which has been successfully employed in veterinary medicine), and neutral chiral analytes were evaluated on CSPs, and the results showed that the novel CSPs characterized as both enantioseparation capabilities of CD-based CSP and QN/QD-based CSPs have broader application range than β-CD-based CSP or QN/QD-based CSPs. It was found that QN/QD moieties play a dominant role in the overall enantioseparation process of Fmoc-amino acids accompanied by the synergistic effect of β-CD moiety, which lead to the different enantioseparation of β-CD-QN-based CSP and β-CD-QD-based CSP. Furthermore, new CSPs retain extraordinary enantioseparation of cyclodextrin-based CSP for some neutral analytes on normal phase and even exhibit better enantioseparation than the corresponding β-CD-based CSP for certain samples.
- Zhu, Lunan,Zhu, Junchen,Sun, Xiaotong,Wu, Yaling,Wang, Huiying,Cheng, Lingping,Shen, Jiawei,Ke, Yanxiong
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p. 1080 - 1090
(2020/05/25)
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- Unwanted hydrolysis or α/β-peptide bond formation: How long should the rate-limiting coupling step take?
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Nowadays, in Solid Phase Peptide Synthesis (SPPS), being either manual, automated, continuous flow or microwave-assisted, the reaction with various coupling reagents takes place via in situ active ester formation. In this study, the formation and stability of these key active esters were investigated with time-resolved 1H NMR by using the common PyBOP/DIEA and HOBt/DIC coupling reagents for both α- and β-amino acids. Parallel to the amide bond formation, the hydrolysis of the α/β-active esters, a side reaction that is a considerable efficacy limiting factor, was studied. Based on the chemical nature/constitution of the active esters, three amino acid categories were determined: (i) the rapidly hydrolyzing ones (t 24 h) in solution. The current insight into the kinetics of this key hydrolysis side reaction serves as a guide to optimize the coupling conditions of α- and β-amino acids, thereby saving time and minimizing the amounts of reagents and amino acids to be used-all key factors of more environmentally friendly chemistry.
- Goldschmidt G?z, Viktória,Nagy, Adrienn,Farkas, Viktor,Keszei, Ern?,Perczel, András
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p. 30720 - 30728
(2019/10/28)
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- Fmoc-OPhth, the reagent of Fmoc protection
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Fmoc-OSu has been widely used for Fmoc protection of amino groups, especially amino acids, in solid phase peptide synthesis. However, it has been recognized that Fmoc-βAla-OH is formed as a by-product via the Lossen rearrangement during the reaction. Since we reconfirmed the formation of Fmoc-βAla-OH during the preparation of Fmoc-AA-OH by Fmoc-OSu, Fmoc-OPhth was designed and synthesized as a new Fmoc reagent to avoid the formation of Fmoc-βAla-OH. Furthermore, Fmoc protection by Fmoc-OPhth and Fmoc-SPPS were evaluated. The various Fmoc-amino acids prepared by Fmoc-OPhth were carried out in good yields and these are applicable in Fmoc-SPPS.
- Yoshino, Ryo,Tokairin, Yoshinori,Kikuchi, Mari,Konno, Hiroyuki
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supporting information
p. 1600 - 1603
(2017/04/03)
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- Caged xanthones: Potent inhibitors of global predominant MRSA USA300
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Total of 22 caged xanthones were subjected to susceptibility testing of global epidemic MRSA USA300. Natural morellic acid showed the strongest potency (MIC of 12.5 μM). However, its potent toxicity diminishes MRSA therapeutic potential. We synthetically modified natural morellic acid to yield 13 derivatives (3a-3m). Synthetically modified 3b retained strong potency in MRSA growth inhibition, yet the toxicity was 20-fold less than natural morellic acid, permitting the possibility of using caged xanthones for MRSA therapeutic.
- Chaiyakunvat, Pongkorn,Anantachoke, Natthinee,Reutrakul, Vichai,Jiarpinitnun, Chutima
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supporting information
p. 2980 - 2983
(2016/06/13)
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- Aqueous MW eco-friendly protocol for amino group protection
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In this paper a new catalyst-free and on-water method for protection of amines and amino acids with di-tert-butyl dicarbonate, 9-fluorenylmethoxycarbonyl chloride, acetyl chloride and tosyl chloride is presented. The protection can be realized in a few minutes under microwave-assistance. The reaction proved to be chemoselective in presence of ambident nucleophiles and water solution of di-tert-butyl carboxylic acid or chloride acid are the only wastes produced.
- Nardi,Cano, N. Herrera,Costanzo,Oliverio,Sindona,Procopio
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p. 18751 - 18760
(2015/06/15)
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- A one-pot procedure for the preparation of N-9-fluorenylmethyloxycarbonyl- α-amino diazoketones from α-amino acids
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The study describes a new "one-pot" route to the synthesis of N-9-fluorenylmethyloxycarbonyl (Fmoc) α-amino diazoketones. The procedure was tested on a series of commercially available free or side-chain protected α-amino acids employed as precursors. The conversion into the title compounds was achieved by masking and activating the α-amino acids with a single reagent, namely, 9-fluorenylmethyl chloroformate (Fmoc-Cl). The resulting N-protected mixed anhydrides were reacted with diazomethane to lead to the α-amino diazoketones, which were isolated by flash column chromatography in very good to excellent overall yields. The versatility of the procedure was verified on lipophilic α-amino acids and further demonstrated by the preparation of N-Fmoc-α-amino diazoketones also from α-amino acids containing side-chain masking groups, which are orthogonal to the Fmoc one. The results confirmed that tert-butyloxycarbonyl (Boc), tert-butyl (tBu), and 2,2,4,6,7-pentamethyldihydrobenzofuran-5-sulfonyl (Pbf), three acid-labile protecting groups mostly adopted in the solution and solid-phase peptide synthesis, are compatible to the adopted reaction conditions. In all cases, the formation of the corresponding C-methyl ester of the starting amino acid was not observed. Moreover, the proposed method respects the chirality of the starting α-amino acids. No racemization occurred when the procedure was applied to the synthesis of the respective N-Fmoc-protected α-amino diazoketones from l-isoleucine and l-threonine and to the preparation of a diastereomeric pair of N-Fmoc-protected dipeptidyl diazoketones.
- Siciliano, Carlo,De Marco, Rosaria,Guidi, Ludovica Evelin,Spinella, Mariagiovanna,Liguori, Angelo
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p. 10575 - 10582
(2013/02/22)
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- Liquid-chromatography quantitative analysis of 20 amino acids after derivatization with FMOC-CI and its application to different origin Radix isatidis
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We developed a simple, rapid and reliable method for determination of 20 common amino acids based on derivatization with 9-fluorenylmethyl chloroformate (FMOC-CI) and RP-LC/UV, this method was first introduced into quantitative analysis of amino acids. The amino groups of amino acids were trapped with FMOC-CI to form amino acid-FMOC-Cl adducts which can be suitable for LC-UV. Chromatographic separation was performed on a C18 column with a mobile phase gradient consisting of acetonitrile and sodium acetate solution. This method was shown to be sensitive for 20 common amino acids. In the intra-day precisions assay, the range of RSDs was 3.21-7.67% with accuracies of 92.34-102.51%; for the inter-day precisions assay, the range of RSDs was 5.82-9.19% with accuracies of 90.25-100.63%. The results also indicated that solutions of amino acids-FMOC-Cl can be kept at room temperature for at least 24 h without showing significant losses in the quantified values. The validated method was successfully applied to the determination of major four kinds of amino acids in R. isatidis samples (Arg, Pro, Met and Val). The total content of amino acids in different origin R. isatidis was 13.32-19.16 mg/g. The differences between R. isatidis samples were large using HCA.
- Zhou, Wei,Zhang, Xiao-Yan,Duan, Geng-Li
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experimental part
p. 509 - 515
(2012/01/04)
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- Derivates of Polyethylene Glycol Modified Thymosin Alpha 1
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Pharmaceutical compositions that include thymosin alpha 1 peptide derivatives modified at the C-terminal of the peptide chain with polyethylene glycol, and their pharmaceutical acceptable salts, are generally disclosed. Also, new methods used to prepare these thymosin alpha 1 peptide derivatives modified at the C-terminal of the peptide chain with polyethylene glycol are generally provided. The presently disclosed compounds and their salts can be prepared administered to humans to treat immune disease and can also be used in adjuvant treatment.
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- Efficient procedure for the preparation of oligomer-free N-fmoc amino acids
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A two-step method is presented for the peptide-free, high-purity, and high-yield synthesis of N-Fmoc amino acids. The first step involves the preparation of stable dicyclohexylammonium-amino acid ionic adduct in acetone. Subsequently, the ionic adducts, on reaction with Fmoc-Nosu under mild alkaline conditions, give dipeptide-free N-Fmoc amino acids. The positive charge of the dicyclohexylammonium counterion in the ionic salt has a longer radius, moderating the nucleophilicity of the carboxylate ion of the amino acid and preventing by-products by arresting the formation of mixed anhydrides, the precursors of oligopeptide impurities.
- Nowshuddin, Shaik,Rao,Reddy, A. Ram
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experimental part
p. 2022 - 2031
(2009/11/30)
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- Alternative and chemoselective deprotection of the α-amino and carboxy functions of N-Fmoc-amino acid and N-Fmoc-dipeptide methyl esters by modulation of the molar ratio in the AlCl3/N,N-dimethylaniline reagent system
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The amino and carboxy functions in N-Fmoc-α-amino acid and N-Fmoc-peptide methyl esters can be alternatively and chemoselectively deprotected by treatment with the reagent system AlCl3/N,N- dimethylaniline (DMA). The chemoselectivity of the process is controlled by modulating the relative molar ratio of the Lewis acid and DMA. Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004.
- Di Gioia, Maria Luisa,Leggio, Antonella,Le Pera, Adolfo,Liguori, Angelo,Perri, Francesca,Siciliano, Carlo
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p. 4437 - 4441
(2007/10/03)
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- Treatment of obesity
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A method for the treatment of obesity in an animal such as a human, comprises administering to the animal an effective amount of a peptide which comprises an analogue of the carboxyl-terminal sequence of a growth hormone, particularly an analogue of the carboxyl-terminal sequence of human growth hormone containing amino acid residues 177-191. A pharmaceutical composition for use in the treatment of obesity is also disclosed.
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- GLP-2 compounds, formulations, and uses thereof
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The present invention relates to novel human glucagon-like peptide-2 (GLP-2) peptides and human glucagon-like peptide-2 derivatives which have a protracted profile of action as well as polynucleotide constructs encoding such peptides, vectors and host cells comprising and expressing the polynucleotide, pharmaceutical compositions, uses and methods of treatment.
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- A new polymer-supported reagent for the Fmoc-protection of amino acids
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A new polymer-supported Fmoc-OSu (Fmoc-P-OSu) has been prepared from polymer-bound N-hydroxysuccinimide (P-HOSu), and used as a solid-supported reagent for the Fmoc-protection of amino groups. The residual P-HOSu generated after the protection reaction can be separated by simple filtration and reused.
- Chinchilla, Rafael,Dodsworth, David,Nájera, Carmen,Soriano, José
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p. 7579 - 7581
(2007/10/03)
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- An Effective Water-Free Aprotic System for Dissolving Free Amino Acids
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An effective water-free system was proposed for dissolution and subsequent use in peptide synthesis of free amino acids and their derivatives. It consists of dimethylformamide, a tertiary base, and inorganic additives. Neutral salts (CF3COONa, Ba(ClO4)2, Ca(ClO4)2, NaClO4, BaI2, or Ca(NO3)2) serve as the inorganic additives that increase the solubility of free amino acids in dimethylformamide and provide true 0.2-3 M amino acid solutions. Triethylamine and N-methylmorpholine are most suitable as the tertiary bases. This system was used in reactions with acylating agents: Boc2O, ZOSu, FmocOSu, and activated derivatives of Nα-protected amino acids or peptides. The corresponding amino acid derivatives or Nα-protected di-, tri-, and tetrapeptides were obtained in yields of 80-99 percent at the reaction times of 30-240 min.
- Raydnov, M. G.,Klimenko, L. V.,Mitin, Yu. V.
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p. 283 - 287
(2007/10/03)
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- Apparatus and methods for detecting antibodies
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A single, unitary, solid phase support apparatus having a planar surface divided into a plurality of separate zone functions to detect antibodies. Each zone has bonded to it, a different peptide through its C-terminal end. The zones are incubated with the analyte sample and observed for reaction, indicating the virus-specific or bacteria specific presence or absence.
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- Mild, selective cleavage of amino acid and peptide β-(trimethylsilyl)ethoxymethyl (SEM) esters by magnesium bromide
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Magnesium bromide etherate has been previously shown to cleave β-(trimethylsilyl)ethoxymethyl (SEM) esters of aliphatic acids. This methodology has now been extended to amino acid and peptide derivatives in the presence of protecting groups typically encountered in peptide chemistry, including the Boc, Cbz, Fmoc and Troc carbamates as well as benzyl-, tert-butyl- and tert-butyldimethylsilyl ethers. The stability of fluoride sensitive protecting groups to magnesium bromide allows for added selectivity in the removal of SEM esters in organic synthesis.
- Chen, Wei-Chuan,Vera, Matthew D.,Joullie, Madeleine M.
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p. 4025 - 4028
(2007/10/03)
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- A New Synthesis of Thymosin α1
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Thymosin α1, an N-acetylated octacosa thymus peptide, isolated first from thymosin fraction 5, is synthesized by the solid phase method using the p-benzyloxybenzyl alcohol/polystyrene/divinylbenzene resin, Nα-Fmoc-amino acids and those with tert-butyl or Boc side chain protection.All couplings are performed with the Bop reagent.The peptide is purified by a combination of gel chromatography and preparative HPLC, its purity checked by amino acid analysis and analytical HPLC, and the biological activity tested by the E-rosette assay.
- Echner, Hartmut,Voelter, Wolfgang
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p. 1095 - 1098
(2007/10/02)
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- 9-Fluorenylmethyl Pentafluorophenyl Carbonate as a Useful Reagent for the Preparation of N-9-Fluorenylmethyloxycarbonylamino Acids and their Pentafluorophenyl Esters
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9-Fluorenylmethyl pentafluorophenyl carbonate is a useful reagent for the efficient, side reaction-free introduction of N-9-fluorenylmethyloxycarbonyl protecting group into amino acids and for the subsequent preparation of their pentafluorophenyl esters.Some new compounds of both types are described.
- Schoen, Istvan,Kisfaludy, Lajos
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p. 303 - 305
(2007/10/02)
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