Solution-phase Peptide Synthesis Research Articles

Hypervalent Iodine Amino Acid Building Blocks for Bioorthogonal Peptide Macrocyclization

Ethynylbenziodoxol(on)es (EB(X)xs) reagents have emerged as useful reagents for peptide/protein modification due to their versatile reactivity and high selectivity. Herein, we report the successful introduction of ethynylbenziodoxoles (EBxs) on different amino acid building blocks (Lys/Orn/Dap), and show their compatibility with both solid phase peptide synthesis (SPPS) and solution phase peptide synthesis (SPS). The selective incorporation of the EBx core into peptide sequences enable efficient macrocyclizations under mild conditions for the synthesis of topologically unique cyclic and bicyclic peptides.

Hypervalent Iodine Amino Acid Building Blocks for Bioorthogonal Peptide Macrocyclization.

Ethynylbenziodoxol(on)es (EB(X)xs) reagents have emerged as useful reagents for peptide/protein modification due to their versatile reactivity and high selectivity. Herein, we report the successful introduction of ethynylbenziodoxoles (EBxs) on different amino acid building blocks (Lys/Orn/Dap), and show their compatibility with both solid phase peptide synthesis (SPPS) and solution phase peptide synthesis (SPS). The selective incorporation of the EBx core into peptide sequences enable efficient macrocyclizations under mild conditions for the synthesis of topologically unique cyclic and bicyclic peptides.

Foldamers controlled by functional triamino acids: structural investigation of α/γ-hybrid oligopeptides

Peptide-like foldamers controlled by normal amide backbone hydrogen bonding have been extensively studied, and their folding patterns largely rely on configurational and conformational constraints induced by the steric properties of backbone substituents at appropriate positions. In contrast, opportunities to influence peptide secondary structure by functional groups forming individual hydrogen bond networks have not received much attention. Here, peptide-like foldamers consisting of alternating α,β,γ-triamino acids 3-amino-4-(aminomethyl)-2-methylpyrrolidine-3-carboxylate (AAMP) and natural amino acids glycine and alanine are reported, which were obtained by solution phase peptide synthesis. They form ordered secondary structures, which are dominated by a three-dimensional bridged triazaspiranoid-like hydrogen bond network involving the non-backbone amino groups, the backbone amide hydrogen bonds, and the relative configuration of the α,β,γ-triamino and α-amino acid building blocks. This additional stabilization leads to folding in both nonpolar organic as well as in aqueous environments. The three-dimensional arrangement of the individual foldamers is supported by X-ray crystallography, NMR spectroscopy, chiroptical methods, and molecular dynamics simulations.

A Facile Solution Phase Synthesis of Peptide Assemblies as Functional Moiety for Antimicrobial and Anticancer Peptides

In recent years, human being are affected by various types of cancer and are highly microbial infected due to changes in environmental conditions and hence, the recovery from this cause of disease using peptide-based drugs as a function of both activities like antimicrobial peptides (AMPs) and anticancer peptides (ACPs). Herein, we report the solution phase peptide synthesis using α-amino acids such as alanine, phenylalanine and lysine. The structural parameters of the polypeptides were investigated by circular dichroism, FT-IR, MALDI-TOF ESI-mass, NMR, etc. Water-soluble hydrophilic-based synthesized polypeptides possess various biological applications throughout, especially antibacterial and anticancer activities–short reaction process, less cost of chemicals, minimum glassware and no hazardous chemicals involved. Multiple species have innate immune systems that contain antimicrobial peptides (AMPs). Most of them have been proved to possess dual action, both as antibacterial and anticancer peptides, making them most promising alternative to conventional compounds used today to treat these infections. Present approach offers unique opportunities for developing highly potent and focused antibacterial and anticancer peptide-based drugs.

Fast Solution-Phase and Liquid-Phase Peptide Syntheses (SolPSS and LPPS) Mediated by Biomimetic Cyclic Propylphosphonic Anhydride (T3P®).

The growing applications of peptide-based therapeutics require the development of efficient protocols from the perspective of an industrial scale-up. T3P® (cyclic propylphosphonic anhydride) promotes amidation in the solution-phase through a biomimetic approach, similar to the activation of carboxylic moiety catalyzed by ATP-grasp enzymes in metabolic pathways. The T3P® induced coupling reaction was applied in this study to the solution-phase peptide synthesis (SolPPS). Peptide bond formation occurred in a few minutes with high efficiency and no epimerization, generating water-soluble by-products, both using N-Boc or N-Fmoc amino acids. The optimized protocol, which was successfully applied to the iterative synthesis of a pentapeptide, also allowed for a decrease in the solvent volume, thus improving process sustainability. The protocol was finally extended to the liquid-phase peptide synthesis (LPPS), where the isolation of the peptide was performed using precipitation, thus also showing the suitability of this coupling reagent to this emerging technique.

Sintesis Senyawa Heksapeptida Siklik Analog Pipecolisporin (Pro-Lys-Pip-Trp-

Pipecolisporin compounds isolated from the fungus Nigrospora oryzae from theroots of Triticum sp. is one of the compounds that has potential as an antimalarial with its activity against Plasmodium falciparum of 3.21 μM. The modification of the amino acid sequence to Pro-Lys-Pip-Trp-β-Ala-Phe aims to determine the best arrangement of pipecolisporin analogues as antimalarials. Analogues of pipecolisporin linear hexapeptide compounds were synthesized using the solid phase peptide synthesis (SPPS) method with the use of buffers in the form of 2-chlorotrityl chloride resins, Fmoc and Boc protective groups, and DIC, Oxyma, Dipea coupling reagent solutions. The synthesis results were obtained as much as 9 mg and then characterized using mass spectroscopy with a peak m/z of 959.5246 [M]. Analogues of linear pipecolisporin hexapetide compounds were successfully cyclized using the solution phase peptide synthesis (LPPS) method with the use of DIPEA, HATU, DCM reagent solutions. The synthesis results were characterized using mass spectroscopy with an m/z peak of 743.78 [M+H]+.
 Senyawa pipecolisporin hasil isolasi jamur Nigrospora oryzae dari akar Triticum sp. merupakan salah satu senyawa yang berpotensi sebagai antimalaria dengan aktivitasnya terhadap Plasmodium falciparum sebesar 3,21 μM. Modifikasi urutan asam amino menjadi Pro-Lys-Pip-Trp-

Late-Stage, Stereoretentive, and Site-Selective Modification of Synthetic Peptides by Using Photoredox Catalysis.

Late-stage functionalisation is an attractive method to generate peptide analogues containing non-natural residues. It is shown that cysteine residues can be activated as Crich-type thioethers, either by alkylation of a synthetic cysteine-continuing peptide or by incorporation of a modified cysteine unit into solid phase or solution phase peptide synthesis. Photoredox catalysed reaction of the thioether generates an alanyl radical intermediate in a stereoretentive and site-selective manner, even in the presence of free cysteine residues. The radical can react with non-activated alkenes to form non-natural residues bearing aliphatic, hydrophobic units. A method to avoid unwanted alkylation of amine residues was identified and the process was applied to the functionalization of both linear and cyclic synthetic peptides.

Computer vision as a new paradigm for monitoring of solution and solid phase peptide synthesis.

We report a strategy for the camera-enabled non-contact colourimetric reaction monitoring and optimisation of amide bond formation, mediated by coupling reagents. For amide bond formation in solution phase, investigation of reactions mediated by HATU, PyAOP, and DIC/Oxyma evidenced correlations between colour parameters extracted from video data and conversion to amide product measured by off-line HPLC analysis of concentration. These correlations, supported by mutual information analysis, were further investigated using video recordings of solid phase peptide synthesis (SPPS), co-analysed by off-line HPLC to track remaining unreacted substrate in solution. An optimisation method of coupling time in SPPS was derived from ΔE (a measurement of colour contrast), giving comparable isolated peptide yield and purity at 65-95% reduced overall reaction time. The same colour data enabled data-rich monitoring of reaction rate attenuation, consisted with computationally-derived measures of amino acid steric bulk. These findings provide a foundation for exploring the use of camera technology and computer vision towards automated and online mechanistic profiling of SPPS.

Speeding up sustainable solution-phase peptide synthesis using T3P® as a green coupling reagent: methods and challenges

A fast and greensolution-phase peptide synthesis (GSolPPS) via continuous protocol, addressed with propylphosphonic anhydride T3P® as coupling reagent and N-benzyloxycarbonyl-protecting group easily removed by hydrogenation is herein reported.

Synthesis of malformin‐A1, C, a glycan, and an aglycon analog: Potential scaffolds for targeted cancer therapy

AbstractImprovement in therapeutic efficacy while reducing chemotherapeutic side effects remains a vital objective in synthetic design for cancer treatment. In keeping with the ethos of therapeutic development and inspired by the Warburg effect for augmenting biological activities of the malformin family of cyclic‐peptide natural products, specifically anti‐tumor activity, a β‐glucoside of malformin C has been designed and synthesized utilizing precise glycosylation and solution phase peptide synthesis. We optimized several glycosylation procedures utilizing different donors and acceptors. The overarching goal of this study was to ensure a targeted delivery of a glyco‐malformin C analog through the coupling of D‐glucose moiety; selective transport via glucose transporters (GLUTs) into tumor cells, followed by hydrolysis in the tumor microenvironment releasing the active malformin C a glycon analog. Furthermore, total synthesis of malformin C was carried out with overall improved strategies avoiding unwanted side reactions thus increasing easier purification. We also report on an improved solid phase peptide synthesis protocol for malformin A1.

Extended Solution-phase Peptide Synthesis Strategy Using Isostearyl-Mixed Anhydride Coupling and a New C-Terminal Silyl Ester-Protecting Group for N-Methylated Cyclic Peptide Production

Extended Solution-phase Peptide Synthesis Strategy Using Isostearyl-Mixed Anhydride Coupling and a New C-Terminal Silyl Ester-Protecting Group for <i>N</i>-Methylated Cyclic Peptide Production

In Silico Identification of Tripeptides as Lead Compounds for the Design of KOR Ligands.

The kappa opioid receptor (KOR) represents an attractive target for the development of drugs as potential antidepressants, anxiolytics and analgesics. A robust computational approach may guarantee a reduction in costs in the initial stages of drug discovery, novelty and accurate results. In this work, a virtual screening workflow of a library consisting of ~6 million molecules was set up, with the aim to find potential lead compounds that could manifest activity on the KOR. This in silico study provides a significant contribution in the identification of compounds capable of interacting with a specific molecular target. The main computational techniques adopted in this experimental work include: (i) virtual screening; (ii) drug design and leads optimization; (iii) molecular dynamics. The best hits are tripeptides prepared via solution phase peptide synthesis. These were tested in vivo, revealing a good antinociceptive effect after subcutaneous administration. However, further work is due to delineate their full pharmacological profile, in order to verify the features predicted by the in silico outcomes.

Synthesis of Pentapeptide FWKVV (Phe-Trp-Lys-Val-Val) and Its Activity as Antioxidants

Antioxidant pentapeptides are pentapeptide compounds that have antioxidant activity. One of the pentapeptide compounds that have antioxidant activity is FWKVV. FWKVV is a linear pentapeptide with the amino acid sequence phenylalanine-tryptophan-lysine-valine-valine, which was first isolated to hydrolyzate the muscle protein of Miiuy croaker (Miichthysmiiuy). In addition to isolation, FWKVV compounds can be produced by the peptide synthesis method because this method requires a shorter time than the isolation method from natural materials. Synthesis methods commonly used are solution-phase peptide synthesis and solid-phase peptide synthesis (SPPS). However, the SPSS method is more efficient because it does not require purification in every process. The purpose of this study was to synthesize FWKVV compounds using the SPPS method and test their antioxidant activity. FWKVV has been synthesized using the SPPS method with HBTU/HOBt coupling reagent and Fmoc protective group. The FWKVV crud produced was 148.8 mg and had antioxidant activity against DPPH radicals with an IC50 value of 4.2 mg/mL.

A platinum nanoparticle doped self-assembled peptide bolaamphiphile hydrogel as an efficient electrocatalyst for the hydrogen evolution reaction.

Noble metal-based nanomaterials have shown great potential for catalytic application with higher selectivity and activity. Owing to their self-assembly properties with various molecular interactions, peptides play an essential role in the controlled synthesis of noble metal-based catalysts with high surface area. In this work, a phenylalanine (F) and tyrosine (Y) based peptide bolaamphiphile is prepared by solution-phase peptide synthesis. The peptide bolaamphiphile readily self-assembles into a hydrogel with a cross-linked nanofibrillar network. The platinum nanoparticles (Pt NPs) are in situ generated within the cross-linked nanofibrillar network of the hydrogel matrix of the peptide bolaamphiphile. Benefiting from the synergistic properties of the Pt nanoparticles doped on three-dimensional fibrous networks, Pt6@hydrogel shows efficient catalytic activity for the electrochemical hydrogen evolution reaction (HER) in 0.5 M H2SO4 solution. The Pt6@hydrogel requires an overpotential of 45 mV at −10 mA cm−2 with a Tafel slope of 52 mV dec−1. The Pt6@hydrogel also shows electrocatalytic activity in basic and neutral pH solutions. The excellent activity and stability of Pt6@hydrogel for the HER shows great potential for energy conversion applications.

Dedicated to a peptide chemist of few words and immense impact: Louis A. Carpino

Dedicated to a peptide chemist of few words and immense impact: Louis A. Carpino

Synthesis and Evaluation of Antimycobacterial and Antiplasmodial Activities of Hirsutellide A and Its Analogues.

Hirsutellide A is nature-derived cyclic hexadepsipeptide with reported antimycobacterial and antiplasmodial activities. To verify its structure, hirsutellide A was synthesized following a solution-phase peptide synthesis approach. A detailed analysis of the 1H and 13C NMR spectra of the synthesized compound revealed structural variation from what had been originally assigned for hirsutellide A, despite the use of identical building blocks. This variation occurred at the two allo-Ile moieties. To investigate the structure–activity relationship, the depsipeptide and peptide analogues of hirsutellide A were prepared and tested for antimycobacterial and antiplasmodial activities. The compounds displayed antiplasmodial potency against Plasmodium falciparum 3D7 while showing weak or no activity against Mycobacterium tuberculosis H37Rv. The drug-likeness of the series was assessed through in vitro absorption, distribution, metabolism, and excretion (ADME) profiling, revealing systematic differences between the pharmacokinetic properties of cyclic hexapeptides and hexadepsipeptides.

Synthesis of Novel Peptides Using Unusual Amino Acids.

Small peptides are valuable peptides due to their extended biological activities. Their activities could be categorized according to their low antigenicity, osmotic pressure, and also because of their astonishing bioactivities. For example, the aggression of Phe-Phe fibers via self-assembly and intermolecular hydrogen bonding is the main reason for the formation of Alzheimer’s β-amyloid fibrils. Hydrogen bonding is the main intramolecular interaction in peptides, while the presence of aromatic ring leads to the π-π stacking and affects the self-assembly and aggression. Thus, insertion of an unusual amino acid into peptide sequence facilitates the formation of intramolecular bonds, lipophilicity and its conformation. To design new small peptides with remarkable lipophilicity, it is an idea to employ γ-amino acid, such as gabapentin (H2N-Gpn-OMe) and baclofen (H2N-Baclofen-OMe), in the structure of small peptides to increase cell-penetrating properties and to prevent aggression of Phe-Phe fibrils in β-amyloids of Alzheimer’s disease. Some new tri- and tetrapeptides were synthesized through introducing biologically active gabapentin and baclofen to dipeptide of phenylalanine (Phe-Phe) through solution phase peptide synthesis strategy.

Synthesis and anticancer activity of conformationally constrained Smac mimetics containing pseudo β turns

Herein, we report synthesis and in vitro anticancer activity of conformationally constrained Smac mimetics containing reverse turn inducing motifs “Ant-Pro” and “sAnt-Pro”. The synthesis of Smac analogs with diverse hydrophobic groups at the C-terminus was carried out using solution phase peptide synthesis. The synthesis of Ant-Pro containing analogs 3a–j was carried out by ring opening of benzoxazinones 7a–c, whereas, their sulfonamide counterparts 4a–h were synthesized by using routine acid-amine coupling reaction. In vitro anticancer studies against breast cancer cell line MDA-MB-231 revealed that some of the new analogs had better anticancer activity than the standard AVPI Smac tetrapeptide.

Recyclable hypervalent-iodine-mediated solid-phase peptide synthesis and cyclic peptide synthesis.

The system of the hypervalent iodine(III) reagent FPID and (4-MeOC6H4)3P was successfully applied to solid-phase peptide synthesis and cyclic peptide synthesis. Four peptides with biological activities were synthesized through SPPS and the bioactive cyclic heptapeptide pseudostellarin D was obtained via solution-phase peptide synthesis. It is worth noting that FPID can be readily regenerated after the peptide coupling reaction.

Total synthesis of teixobactin and its stereoisomers

The total syntheses of teixobactin and a series of its stereoisomers at positions 2, 5, 6, 10 and 11 were achieved via a combined strategy of solution and solid phase peptide synthesis.