Liquid-phase Peptide Synthesis Research Articles

Selenoglutathione Diselenide: Unique Redox Reactions in the GPx-Like Catalytic Cycle and Repairing of Disulfide Bonds in Scrambled Protein.

Selenoglutathione (GSeH) is a selenium analogue of naturally abundant glutathione (GSH). In this study, this water-soluble small tripeptide was synthesized in a high yield (up to 98%) as an oxidized diselenide form, i.e., GSeSeG (1), by liquid-phase peptide synthesis (LPPS). Obtained 1 was applied to the investigation of the glutathione peroxidase (GPx)-like catalytic cycle. The important intermediates, i.e., GSe- and GSeSG, besides GSeO2H were characterized by 77Se NMR spectroscopy. Thiol exchange of GSeSG with various thiols, such as cysteine and dithiothreitol, was found to promote the conversion to GSe- significantly. In addition, disproportionation of GSeSR to 1 and RSSR, which would be initiated by heterolytic cleavage of the Se-S bond and catalyzed by the generated selenolate, was observed. On the basis of these redox behaviors, it was proposed that the heterolytic cleavage of the Se-S bond can be facilitated by the interaction between the Se atom and an amino or aromatic group, which is present at the GPx active site. On the other hand, when a catalytic amount of 1 was reacted with scrambled 4S species of RNase A in the presence of NADPH and glutathione reductase, native protein was efficiently regenerated, suggesting a potential use of 1 to repair misfolded proteins through reduction of the non-native SS bonds.

Photo‐Triggered Fluorometric Hydrophobic Benzyl Alcohol for Soluble Tag‐Assisted Liquid‐Phase Peptide Synthesis

AbstractSolid phase methods have been central to the chemical synthesis of peptides, yet a liquid phase method would arguably be more appropriate with modern synthetic chemistry approaches to fine‐tune the molecular structures of peptides. Herein, we describe a simple and rational design for the synthesis of 2,5‐substituted hydrophobic benzyl alcohol (HBA) as a new soluble tag for liquid phase peptide synthesis. This tag allows the use of both 9‐fluorenylmethoxycarbonyl (Fmoc) and HF‐free tert‐butoxycarbonyl (Boc) methods. The HBA‐tagged peptides can be detected both colorimetrically and fluorometrically, enabling their quantitative assay. The Boc method is compatible with the HBA tag because it is mildly acid resistant, whereas commonly used acidic global deprotection conditions lead to the simultaneous cleavage of the side chain protecting groups and the HBA tag. The HBA tag was successfully applied to the synthesis of the angiotensin III selective antagonist peptide.

Novel Globular Polymeric Supports for Membrane-Enhanced Peptide Synthesis

Membrane-enhanced peptide synthesis (MEPS), a technique that combines liquid-phase peptide synthesis (LPPS) with organic solvent nanofiltration (OSN), has emerged as a new methodology to tackle current challenges in solid-phase peptide synthesis (SPPS), the current strategy of choice for the preparation of peptides. This new technology platform is scalable beyond kilogram scale, automatable, and compatible with established Fmoc chemistry, as it combines chemistry in solution with expedient membrane purification. Here we screened novel highly rejected soluble polymeric supports and studied their application for the preparation of a model peptide. Our findings make a significant contribution to the development of MEPS.

Acid-Triggered Colorimetric Hydrophobic Benzyl Alcohols for Soluble Tag-Assisted Liquid-Phase Synthesis.

Simple screening of acid-triggered reactions of methoxybenzyl alcohols led to the development of a novel colorimetric hydrophobic benzyl alcohol (HBA) tag. HBA tag-3 (14) retained high solubility in less polar solvents and excellent precipitation properties in polar solvents. Our routine procedure for tag-assisted liquid phase peptide synthesis was applied using HBA tag-3 (14), and an effective synthesis of β-sheet breaker peptide iAβ5 (4) was achieved. The tagged peptides showed a vivid blue color under acidic conditions both on TLC plates and in solution, enabling quantitative assay.

Hydrophobic benzyl amines as supports for liquid-phase C-terminal amidated peptide synthesis: application to the preparation of ABT-510.

C-terminal amidation is one of the most common modification of peptides and frequently found in bioactive peptides. However, the C-terminal modification must be creative, because current chemical synthetic techniques of peptides are dominated by the use of C-terminal protecting supports. Therefore, it must be carried out after the removal of such supports, complicating reaction work-up and product isolation. In this context, hydrophobic benzyl amines were successfully added to the growing toolbox of soluble tag-assisted liquid-phase peptide synthesis as supports, leading to the total synthesis of ABT-510 (2). Although an ethyl amide-forming type was used in the present work, different types of hydrophobic benzyl amines could also be simply designed and prepared through versatile reductive aminations in one step. The standard acidic treatment used in the final deprotection step for peptide synthesis gave the desired C-terminal secondary amidated peptide with no epimerization.

Synthesis of Leuprorelin Acetate

A method for preparing leuprorelin acetate – a synthetic agonist of natural gonadotropin-releasing hormone - was developed, using liquid-phase peptide synthesis. The new method yields target peptide with a main substance content of > 99% on a semi-industrial scale.

Fabrication of triblock ABA type peptide dendrimer based on glutamic acid dimethyl ester and PEG as a potential nano drug delivery agent.

Introduction: Peptide dendrimers build up from amino acids and they simulate to artificial proteins with globular architecture. These characteristics furnish peptide dendrimers with best biodegradability and biocompatibility in drug delivery systems. Methods: A barbell-like dendrimer from glutamic acid dimethyl ester-poly (ethylene glycol)-glutamic acid dimethyl ester as ABA-type triblock copolymer (PG-PEG-PG) was prepared with liquid-phase peptide synthesis via a divergent approach. PEG 600 diacid (PEG-A) and glutamic acid dimethyl ester were used as the core and the monomeric building blocks, respectively. Linear-dendritic copolymer was prepared in the presence of DCC in pyridine. Transmission electron microscope (TEM) was used for measuring the size of first generation (G1-COOH) and second generation (G2-COOH) of dendrimer compounds. Thermal behavior of the synthesized dendrimers was investigated using DSC. Results: The desired generations G1-COOH, G2-COOH and G3-COOH were prepared by divergent method using PEG diacid 600 as a core compound. The size range of the resulted particles was found to be 20-100 nm for various generations. The isolated dendrimer was examined as the drug-delivery agent and the controlled release was carried out for drug molecule in pH 7.4. Conclusion: Based on the obtained results, the synthesized biocompatible dendrimers could potentially be utilized as a drug carrier agent.

A New Liquid-Phase Method for the Synthesis of Octreotide

A method was developed for the production of octreotide – a synthetic analog of the natural hormone somatostatin - by liquid-phase peptide synthesis using the 4 + 2 + 2 strategy. The new method is easily scalable and produces the target peptide with a yield of 56.4%.

Synthesis and Characterization of Novel Peptido Calixarene Dimers

Aniliniumcalix[4]arene dimers with peptide bridges to increase hydrogen bonding between amino acids and nucleic acid bases have been synthesized. Three different kinds of peptide bridges containing L-Alanine, L-Phenylalanine, and L-Tyrosine were prepared by liquid phase peptide synthesis. The dimers were characterized by NMR, MS and ESIMS spectrometry. Keywords: Calix[4]arene, Dimer, Peptide bridges, Amino acid, Coupling reagent.

Synthesis and biological evaluation of potential threonine synthase inhibitors: Rhizocticin A and Plumbemycin A

Rhizocticins and Plumbemycins are natural phosphonate antibiotics produced by the bacterial strains Bacillus subtilis ATCC 6633 and Streptomyces plumbeus, respectively. Up to now, these potential threonine synthase inhibitors have only been synthesized under enzymatic catalysis. Here we report the chemical stereoselective synthesis of the non-proteinogenic (S,Z)-2-amino-5-phosphonopent-3-enoic acid [(S,Z)-APPA] and its use for the synthesis of Rhizocticin A and Plumbemycin A. In this work, (S,Z)-APPA was synthesized via the Still–Gennari olefination starting from Garner’s aldehyde. The Michaelis–Arbuzov reaction was used to form the phosphorus–carbon bond. Oligopeptides were prepared using liquid phase peptide synthesis (LPPS) and were tested against selected bacteria and fungi.

Silk-inspired polyurethane containing GlyAlaGlyAla tetrapeptide. II. physical properties and structure

Biomedical polyurethane (BPU) and silk fibroin have similarly molecular architecture in their primary and aggregate structure, both of which have amide bonds and microphase separation, and they have been employed as scaffold materials for biomedical applications. Based on this, as the featured peptide sequence of silkworm silk fibroin, GlycineAlanineGlycineAlanine (GlyAlaGlyAla) tetrapeptide was synthesized by using traditional liquid-phase peptide synthesis method with Boc-protected glycine and alanine as starting materials, and was transformed to its derivative with two amine-terminated functional groups. The derivative was introduced as a chain extender into the backbone to form the hard segment of a silk-inspired PU with urea-linkage. Related measurements show that molecular weight of the synthesized silk-inspired PU ranged from 13,000 to 15,000. Fourier transform infrared (FTIR) absorption bands of Amides I and II are at 1651 cm−1 and 1534 cm−1, and Raman absorption band of Amide III is at 1302 cm−1. UV-Vis absorption peak of the silk-inspired PU is at 266 nm. This new concept and strategy may allow the fabrication of a new class of thermoplastic polyurethane elastomers to mimic the structure and properties of silk fibroin of silkworms and spiders. Information provided by this study may be used to better understand the correlation between the natural and man-made materials. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Synthesis of the nonapeptide (B22−B30) of insulin B-chain using liquid and modified solid-phase methods

Background and objectiveThis work embraced a systematic search for potentiated methodologies for peptide synthesis through a di-dimensional approach for convenient synthesis of the nonapeptide (B 22 -B 30 ) of porcine insulin B-chain. Liquid-phase peptide synthesis (LPPS) and liquid-solid-phase peptide synthesis (modified SPPS) were used for the synthesis of this active part.Materials and methodsA nonapeptide Arg-Gly-Phe-Phe-Tyr-Thr-Pro-Lys-Ala-OH corresponding to B 22 -B 30 of porcine insulin B-chain was synthesized using different methods: LPPS and modified SPPS. Time consumption, yield and purity of all products using the different methods were compared with each other.Results and conclusionThe results indicated that modified SPPS is advantageous, as it consumes less solvent per coupling and deprotection reaction, thereby reducing operating costs and solvent waste. Reducing side reactions result in racemization, cyclization or premature peptide formation. Modified SPPS produces peptides with yields and purity better than LPPS. Also, it can reduce the time of coupling and deprotection reactions.

Tag-Assisted Liquid-Phase Peptide Synthesis Using Hydrophobic Benzyl Alcohols as Supports

A soluble tag-assisted liquid-phase peptide synthesis was successfully established based on simple hydrophobic benzyl alcohols, which can be easily prepared from naturally abundant materials. Excellent precipitation yields can be obtained at each step, combining the best properties of solid-phase and liquid-phase techniques. This approach can also be applied efficiently to fragment couplings, allowing chemical synthesis of several bioactive peptides.

Novel diphenylmethyl-Derived Amide Protecting Group for Efficient Liquid-Phase Peptide Synthesis: AJIPHASE

An efficient method for the synthesis of peptides bearing an amide at the C-terminal is described. This method involves the attachment of a C-terminal protecting group bearing long aliphatic chains, followed by the repetition of simple reaction and precipitation steps with the combined advantages of liquid-phase peptide synthesis (LPPS) and solid-phase peptide synthesis (SPPS). Using this method, a hydrophobic peptide was successfully synthesized in good yield and high purity, which cannot be obtained satisfactorily by SPPS.

Synthesis and application of a Sec2-containing oligopeptide for method evaluation purposes in selenium speciation

Sec2-containing oligopeptide was synthesized directly from Sec2 with the traditional liquid phase peptide synthesis without addressing the usually applied and complex solid phase (SPPS) protocol driving through a protected Sec residue and site-oriented oxidation into a diselenide bridge. Effective solubilization of Sec2 in dimethylformamide and its pH-controlled access to pentachlorophenol-activated peptides to couple with were of crucial importance to achieve good yield (>50%) of synthesis, monitored by HPLC-UV, SEC–ICP-MS and HPLC–ESI-MS techniques. To demonstrate the possible application of the new compound, (Boc-GGFG)–Sec2–(Boc-GGFG) (m/z 1173.3, [M+H]+), it was utilized to compare the effect of the two most addressed sample preparation techniques, i.e., methanesulphonic acid (MSA) based digestion and proteolytic digestion with protease XIV, on the Sec residue. The study revealed that the use of MSA resulted in the decomposition of Sec even after derivatization with iodoacetamide.

Development of an efficient liquid-phase peptide synthesis protocol using a novel fluorene-derived anchor support compound with Fmoc chemistry; AJIPHASE®

The development of a novel fluorene-type anchor support molecule and a liquid-phase peptide synthesis protocol (AJIPHASE®) is reported. With this support molecule, the synthesis of a protected peptide with a free carboxyl group could be carried out by repeated coupling/deprotection reactions and isolation by simple precipitation. Cleavage is performed under mild acidic conditions (2% TFA/CHCl3 or hexafluoroisopropanol) to release the products in good yield and purity. There were no signs of either diketopiperazine formation or the removal of protective groups in the side-chain.

Hydrophobic tag-assisted liquid-phase synthesis of a growth hormone-inhibiting peptide somatostatin

Hydrophobic tag-assisted liquid-phase peptide synthesis technique and disulfide bond formation have been well-combined, leading to the efficient and practical preparation of a growth hormone-inhibiting peptide somatostatin. Intramolecular disulfide bond formation has successfully been carried out even under relatively high concentrations, enabling the effective peptide modifications in preparative scale.

ChemInform Abstract: Development of Peptidic Endothelin Receptor Antagonists: Elucidating Physiological Roles of Endothelin and Medicinal Chemistry Efforts Toward Its Receptor Antagonists

Medicinal chemistry efforts on optimization of the endothelin receptor antagonistic natural products toward highly potent and selective ETA, ETB or ETA/B dual receptor antagonists are summarized. In order to get adequate biological tools for elucidating physiological and/or pathophysiological roles of endothelin as well as to identify highly potent antagonists possessing appropriate profiles, liquid phase and solid phase peptide synthesis, and their modification have been carried out. During these efforts, we have realized physiological roles of endothelin and its receptors, and have confirmed drug discovery values of its receptor antagonists as clinical drugs to modulate various kinds of disease.

NXO Building Blocks for Backbone Modification of Peptides and Preparation of Pseudopeptides

The design and synthesis of novel building blocks for peptide modification, termed "NXO", is reported. We describe the utility of these building blocks to prepare new pseudo- and oligopeptides and demonstrate the efficient assembly of modified tripeptides using both conventional liquid phase peptide synthesis and solid supported synthesis. Pertaining to the study of NXO in peptide mimicry, the structure of NXO-incorporating tripeptide beta-strand mimics was investigated in the N(L)AlaO incorporating beta-sheet model compound 13. Evidenced by spectroscopy and computation, 13 selectively adopts a beta-structure in chloroform and characteristically samples the NXO-modified backbone site in the core beta-sheet region. ROESY (HNMR) and molecular dynamics data suggest that when disrupting the cross-strand hydrogen-bonding pattern by switching the solvent from CDCl(3) to d(3)-MeOH, the main conformation with peptide and NXO-peptide backbones similar to that in root mean square deviation of corresponding backbone atoms (rmsd) is preserved.

Synthesis of Poly(ethylene glycol)-Polydiacetylene Conjugates and Their Micellar and Chromic Characteristics

In this report, novel polymer-lipid conjugates were synthesized and their unique micellar and chromic properties were studied. The conjugates were synthesized by the liquid-phase peptide synthesis method using methoxy(polyethylene glycol)-amine (mPEG-NH2, MW2000) as a supporting material. One and two 10,12-pentacosadiynoic acid (PCDA) groups were conjugated to mPEG-NH2 to prepare mPEG-PCDA and mPEG-PCDA2, respectively. The polymer conjugates could form nanometer-sized micelles in aqueous media and be further polymerized under the exposure of UV 254 nm due to the UV sensitive nature of PCDA. It was observed that mPEG-PCDA2 micelle showed very distinctive photochromism and thermochromism in response to UV or heat, whereas mPEG-PCDA did not display any chromic properties. Moreover, a distinctive chromic property change was observed by adding alpha-cyclodextrin as a model biological molecule to the micelle solution. Due to their unique properties such as high water-solubility, cross-linkable micelle formation with a nano-scaled size, and stimuli-responsive chromic nature, the polymer-lipid conjugates would be useful for various biomedical applications, in particular as a nano-carrier for drug delivery and biosensor.