Peptide Coupling Agent Research Articles

Uronium peptide coupling agents: Another case of occupational airborne allergic sensitization induced by HBTU.

Uronium peptide coupling agents (HBTU, HATU, and HCTU) create a special hazard as they are immune sensitizers. Few reported cases are mentioned in the literature; despite that, it is important to raise the awareness on the subject and to highlight the risk and potential symptoms that could occur to those who directly work in contact with uronium peptide coupling agents, as well as to the safety deputies in the universities and industries. Based on a personal experience, the health impact of laboratory exposure to HBTU is described, and the insights gained from the experience are developed. A skin irritation reaction and allergy symptoms induced by HBTU exposure are shown here as well as the rate of worsening of symptoms since the first allergic reaction. Recommendations for handling coupling agents more safely in the research laboratory will also be given, and a casuistry of the matter to help other lab-users to recognize, assess, minimize, prepare for emergencies (RAMP) process.

Hyaluronic acid conjugates of glycine peptides and L-tryptophan

This work reports about the conjugation of glycine C-terminal ethyl and methyl ester peptides and L-tryptophan methyl ester with sodium hyaluronate in aqueous solutions using the peptide coupling agent DMTMM (or short DMT, 4-(4,6-dimethoxy-1,3,5-triazin-2-yl)-4-methyl-morpholinium chloride). Detailed infrared (IR) absorbance and 1H and 13C (2D) NMR studies (heteronuclear multi-bond correlation spectroscopy, HMBC) confirmed covalent and regioselective amide bonds with the D-glucuronate, but also proves the presence of DMT traces in all conjugates. The ethyl ester`s methyl protons on the peptides` C-terminal could be used to quantify the degree of substitution of the peptide on the hyaluronate scaffold by NMR. The ester group also proved stable during conjugation and work-up, and could in some cases be selectively cleaved in water whilst leaving the amide bond intact as shown by potentiometric charge titration, NMR and IR. The conjugates did not influence the capability of human umbilical vein endothelial cells (HUVECs) to reduce MTS (5-[3-(carboxymethoxy)phenyl]-3-(4,5-dimethyl-2-thiazolyl)-2-(4-sulfophenyl)-2H-tetrazolium inner salt) to a formazan dye, which points towards a low cytotoxicity for the obtained products. The conjugation method and products could be tested for tissue engineering gels or drug delivery purposes with alternative, biologically active peptides.

A Convenient Oligonucleotide Conjugation via Tandem Staudinger Reaction and Amide Bond Formation at the Internucleotidic Phosphate Position.

Staudinger reaction on the solid phase between an electronodeficit organic azide, such as sulfonyl azide, and the phosphite triester formed upon phosphoramidite coupling is a convenient method for the chemical modification of oligonucleotides at the internucleotidic phosphate position. In this work, 4-carboxybenzenesulfonyl azide, either with a free carboxy group or in the form of an activated ester such as pentafluorophenyl, 4-nitrophenyl, or pentafluorobenzyl, was used to introduce a carboxylic acid function to the terminal or internal internucleotidic phosphate of an oligonucleotide via the Staudinger reaction. A subsequent treatment with excess primary alkyl amine followed by the usual work-up, after prior activation with a suitable peptide coupling agent such as a uronium salt/1-hydroxybenzotriazole in the case of a free carboxyl, afforded amide-linked oligonucleotide conjugates in good yields including multiple conjugations of up to the exhaustive modification at each phosphate position for a weakly activated pentafluorobenzyl ester, whereas more strongly activated and, thus, more reactive aryl esters provided only single conjugations at the 5'-end. The conjugates synthesized include those with di- and polyamines that introduce a positively charged side chain to potentially assist the intracellular delivery of the oligonucleotide.

Two short approaches to the COVID-19 drug β-D-N4-hydroxycytidine and its prodrug molnupiravir.

Molnupiravir, the prodrug for β-D-N4-hydroxycytidine (NHC), is marketed by Merck as Lagevrio™ against mild-moderate COVID-19, under FDA emergency use authorization. It is the first oral drug against the disease. This work describes two synthetic approaches to NHC and molnupiravir by amide activation in uridine with a peptide-coupling agent and with a 4-chloropyrimidinone nucleoside intermediate.

Base Modifications of Nucleosides via the Use of Peptide-Coupling Agents, and Beyond.

Several naturally occurring purine and pyrimidine nucleosides contain an amide linkage as part of the heterocyclic aglycone. Enolization of the amide and conversion to leaving groups at the amide carbon atom permits base modification by addition-elimination types of processes. Although a number of methods have been developed over the years for accomplishing such conversions, the present Personal Account describes efforts from the Lakshman laboratories. Facile activation of the amido groups in nucleobases can be achieved with peptide-coupling agents. Subsequent reaction with nucleophiles then accomplishes the base modifications. In many cases, the activation and displacement steps can be done as two-step, one-pot processes, whereas in other cases, discrete storable activated nucleosides can be isolated for subsequent displacement reactions. Using such an approach a wide range of nucleoside base modifications is readily achievable. In many instances, mechanistic investigations have been conducted so as to understand the activation process.

Highlights: Safety Culture Conversations, Anaphylaxis Induced by Peptide Coupling Agents, Biological Safety Cabinet Explosion in a Biochemistry Laboratory, and More

Highlights: Safety Culture Conversations, Anaphylaxis Induced by Peptide Coupling Agents, Biological Safety Cabinet Explosion in a Biochemistry Laboratory, and More

Allergic to the lab

If you’re a chemist working with peptide coupling agents, you can literally become allergic to the lab, according to a new report. Over the course of 3 years, graduate student Kate McKnelly of the ...

Anaphylaxis Induced by Peptide Coupling Agents: Lessons Learned from Repeated Exposure to HATU, HBTU, and HCTU.

Peptide coupling agents pose a special hazard because they are immune sensitizers. Here, we present a case study of anaphylaxis induced by three uronium coupling agents, HATU, HBTU, and HCTU, as a cautionary note for researchers who handle peptide coupling agents frequently. We also include recommendations for handling coupling agents more safely in the research laboratory.

Synthesis and antiviral study of novel 4-(2-(6-amino-4-oxo-4,5-dihydro-1H-pyrrolo[2,3-d]pyrimidin-3-yl)ethyl)benzamide derivatives

A series of ten new compounds (7a–j) has been synthesized by absolutely replacing the glutamic acid part of Pemetrexed drug, chemically known as N-{4-[2-(2-amino-4-oxo-4,7-dihydro-3H-pyrrolo[2,3-d]pyrimidin-5-yl)ethyl]benzoyl}-l-glutamic acid, with primary, secondary, and aryl amines in high yields using diethylphosphorocyanidate (DEPC) as a peptide coupling agent. All the synthesized compounds are characterized by 1H and 13C NMR, LCMS, and FT-IR spectral techniques. All the synthesized novel non-glutamate 4-(2-(6-amino-4-oxo-4,5-dihydro-1H-pyrrolo[2,3-d]pyrimidin-3-yl)ethyl)benzamide derivatives showed 4- to 7-folds higher antiviral activity than its structurally similar commercial drug Pemetrexed against Newcastle disease virus, an avian paramyxovirus. Among the lot, compounds possessing carboxamide synthesized using five-membered heteroaryl amines (7i and 7j) exhibited the highest antiviral activity.

Dissipative Assembly of Aqueous Carboxylic Acid Anhydrides Fueled by Carbodiimides.

Biochemical systems make extensive use of chemically fueled processes (e.g., using ATP), but analogous abiotic systems remain rare. A key challenge is the identification of transformations that can be adapted to a range of applications and make use of readily available chemical fuels. In this context, the generation of transient covalent bonds is a fundamental tool for nonequilibrium systems chemistry. Here, we show that carbodiimides constitute a simple class of chemical fuels for dissipative assembly, taking advantage of their known reactivity to produce (hydrolytically unstable) anhydrides from carboxylic acids in water. Both aliphatic and aromatic anhydrides are formed on convenient time scales using the common, commercially available peptide coupling agent 1-ethyl-3-(3-(dimethylamino)propyl)carbodiimide (EDC). An important feature of this reaction is that no part of the carbodiimide is incorporated into the transient species; that is, the fuel is decoupled from the structure-and thus function-of the assembled state. We show that intramolecular anhydride formation of oligo(ethylene glycol) diacids gives macrocycles analogous to crown ethers, representing minimal examples of out-of-equilibrium supramolecular hosts. The kinetics and yields of macrocycle formation respond to cation guests, with the presence of matched cations decreasing their overall production.

Synthesis and Characterization of Betulinic Acid-Aminopropyltriethoxysilane Compounds and Their Assembly onto Nanoporous Alumina Surfaces as Potential Therapeutic Agents

The present study describes the synthesizing and attaching of betulinic acid-aminopropyl triethoxysilane (BA-APTES) on top of the nanoporous alumina (NA) surface. The NA was fabricated by using electrochemical anodization process under an applied voltage of 40 V for 20 hours resulting in average pore size of 45 nm characterized by Scanning Electron Microscope (SEM). The well-recognized therapeutic compound, betulinic acid (BA) was first extracted from the bark of Melaleuca cajuputi plant and further purified by column chromatography. The purified BA was incorporated with APTES using 1-hydroxybenzotriazole hydrate (HOBt) and O-(Benzotriazol-1-yl)-N,N,N’-tetramethyluronium hexafluorophosphate (HBTU) as a peptide coupling agent. The synthesized BA-APTES was silanized on top of the fabricated NA surface. The aromatic portion of 1H and 13C of the synthesized BA-APTES compound was validated by means of Nuclear Magnetic Resonance (NMR). The FTIR spectra show emerging peaks at 2900 cm-1 and 1250 cm-1 signifying the present of aldehyde and also aliphatic amine on NA, respectively. With the aid of XPS analysis, the chemical composition of BA-APTES has evidenced that the presence of the compounds on the surface of NA membrane. Hence, the authors suggest that the modified NA surface has a potential to be applied as a new material for therapeutic agent.

Comparative investigation of two methods for Acetylcholinesterase enzyme immobilization on modified porous silicon

In this work, Acetylcholinesterase enzyme (AChE) was immobilized on porous silicon (PSi) surface using two strategies. In the first method, acid chains were covalently grafted on the hydrogenated PSi by hydrosilylation reaction. The obtained acid-terminated surface was activated by a reaction with N-hydroxysuccinimide (NHS) in the presence of a peptide-coupling agent N-ethyl-N′-(3-dimethylaminopropyl)-carbodiimide (EDC), and then reacted with the amino linker of the lysine residues AChE to anchor the enzyme by a covalent amide bond. In the second procedure, the PSi surface was first hydroxylated in piranha solution, followed by a silanization reaction with 3-aminopropyltriethoxysilane (APTES) to form amine-terminated surface. Finally, AChE was attached to the terminal amine groups by an aminolysis reaction with carboxylic acid groups of AChE in the presence of NHS/EDC mixture. Fourier transform infrared spectroscopy (FTIR) confirmed the efficiency of the surface modifications. The enzymatic activity of immobilized AChE was determined by means of a colorimetric test and was discussed according to the enzyme orientation on the surface which was revealed by contact angle measurements.

Design, synthesis and docking studies of novel 1,2-dihydro-4-hydroxy-2-oxoquinoline-3-carboxamide derivatives as a potential anti-proliferative agents

A new series of 4-hydroxy-1-methyl-2-oxo-1,2-dihydroquinoline-3-carboxamide hybrids 8a-l have been designed and synthesized using peptide coupling agents with substituted N-phenyl piperazines and piperidines with good to excellent yields. The synthesized compounds were evaluated for their in vitro anti-proliferative activity against PANC 1, HeLa and MDA-MB-231. The compounds 8d, 8e, 8f, 8g, 8h and 8k exhibited considerable anti-proliferative activity with GI50 values ranging from 0.15 to 1.4 μM. The structure and anti-proliferative activity relationship was further supported by in silico molecular docking study of the active compounds against tubulin protein.

Luminescence Quenching and Enhancement by Adsorbed Metal Ions with Ruthenium Diimine Complexes Immobilized on Silica Polyamine Composites.

Luminescent ruthenium diimine complexes have been covalently bound to the surface of a silica polyamine composite (SPC) using peptide coupling agents. The loading of the complexes using this route is quite low (~0.01-0.04 mmol/g) leaving sufficient surface amines to coordinate added metal ions. When the composite particles containing the Ru complexes are exposed to solutions of Cu2+, Ni2+ or Zn2+, luminescence is quenched with efficiencies that follow concentration dependence and the relative binding affinities of the ions. When heavy metal ions such as mercury or lead are adsorbed onto the same surface, luminescence is enhanced by a factor of ~3.5. When the complexes are exposed to these metals in solution, no quenching or enhancement is observed. Both phenomena were shown to be the result of adsorption of the cations onto the polyamine surface by using the Stern-Volmer relationship. The mechanism of both quenching and enhancement is discussed and the options for further development of this novel metal sensing technique are presented.

Neuropeptide Substance-P-Conjugated Chitosan Nanofibers as an Active Modulator of Stem Cell Recruiting.

The goal to successful wound healing is essentially to immobilize and recruit appropriate numbers of host stem or progenitor cells to the wound area. In this study, we developed a chitosan nanofiber-immobilized neuropeptide substance-P (SP), which mediates stem cell mobilization and migration, onto the surfaces of nanofibers using a peptide-coupling agent, and evaluated its biological effects on stem cells. The amount of immobilized SP on chitosan nanofibers was modulated over the range of 5.89 ± 3.27 to 75.29 ± 24.31 ng when reacted with 10 to 500 ng SP. In vitro migration assays showed that SP-incorporated nanofibers induced more rapid migration of human mesenchymal stem cells on nanofibers compared to pristine samples. Finally, the conjugated SP evoked a minimal foreign body reaction and recruited a larger number of CD29- and CD44-positive stem cells into nanofibers in a mouse subcutaneous pocket model.

In vitro evaluation of substance-P conjugated nanofibers for potential wound dressing material

In vitro evaluation of substance-P conjugated nanofibers for potential wound dressing material

Total synthesis and anticancer activity of a cyclic heptapeptide from marine sponge using water soluble peptide coupling agent EDC

Present investigation comprises of synthesis of a novel proline containing cyclic heptapeptide – Euryjanicin A, which was previously isolated from the marine sponge – Prosuberites laughlini. Naturally isolated cyclic heptapeptide was synthesized using solution phase peptide technique. All the coupling reactions were performed at room temperature via 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide (EDC) – coupling reagent and triethylamine (Et3N) – base. The chemical structure of the finally synthesized cyclic heptapeptide was elucidated using FTIR, 1H &13C NMR and mass spectral data, as well as elemental analyses. The newly synthesized peptide was subjected to anticancer activity against HeLa (Human Colon) cancer cell line and showed potent anticancer activity.

Facile synthesis of 1-alkoxy-1H-benzo- and 7-azabenzotriazoles from peptide coupling agents, mechanistic studies, and synthetic applications

(1H-Benzo[d][1,2,3]triazol-1-yloxy)tris(dimethylamino)phosphonium hexafluorophosphate (BOP), 1H-benzo[d][1,2,3]triazol-1-yl 4-methylbenzenesulfonate (Bt-OTs), and 3H-[1,2,3]triazolo[4,5-b]pyridine-3-yl 4-methylbenzenesulfonate (At-OTs) are classically utilized in peptide synthesis for amide-bond formation. However, a previously undescribed reaction of these compounds with alcohols in the presence of a base, leads to 1-alkoxy-1H-benzo- (Bt-OR) and 7-azabenzotriazoles (At-OR). Although BOP undergoes reactions with alcohols to furnish 1-alkoxy-1H-benzotriazoles, Bt-OTs proved to be superior. Both, primary and secondary alcohols undergo reaction under generally mild reaction conditions. Correspondingly, 1-alkoxy-1H-7-azabenzotriazoles were synthesized from At-OTs. Mechanistically, there are three pathways by which these peptide-coupling agents can react with alcohols. From 31P{1H}, [18O]-labeling, and other chemical experiments, phosphonium and tosylate derivatives of alcohols seem to be intermediates. These then react with BtO− and AtO− produced in situ. In order to demonstrate broader utility, this novel reaction has been used to prepare a series of acyclic nucleoside-like compounds. Because BtO− is a nucleofuge, several Bt-OCH2Ar substrates have been evaluated in nucleophilic substitution reactions. Finally, the possible formation of Pd π–allyl complexes by departure of BtO− has been queried. Thus, alpha-allylation of three cyclic ketones was evaluated with 1-(cinnamyloxy)-1H-benzo[d][1,2,3]triazole, via in situ formation of pyrrolidine enamines and Pd catalysis.

Synthetic Utility of Propylphosphonic Anhydride–DMSO Media: An Efficient One-pot Three-component Synthesis of 2-Arylquinolines

Abstract Propylphosphonic anhydride (T3P®)–DMSO-mediated one-pot three-component synthesis which provides 2-arylquinolines in a single step from benzyl alcohols, anilines, and ethyl vinyl ether by the modified Povarov reaction has been demonstrated. T3P®–DMSO is a mild and low-toxic peptide coupling agent and an easy to handle reagent for bulk reactions at room temperature.

Propanephosphonic Acid Anhydride (T3P®) - A Benign Reagent for Diverse Applications Inclusive of Large-Scale Synthesis

Propanephosphonic acid anhydride (T3P®) is a prevailing coupling and dehydrating agent with many desirable properties which render it a reagent of choice for a plethora of reactions and, befittingly, its application in organic synthesis is rapidly increasing. Since its introduction as a peptide coupling agent in 1980, the realm of applications of T3P has expanded. Currently its use is found in a broad range of reactions, including condensation, functional group transformation, heterocycles preparation, rearrangements, and catalysis. It offers several advantages over traditional reagents, such as high yield, chemical and optical purity, broad functional group tolerance and easy work-up. The reagent is attractive for large-scale synthesis as well, and particularly so for multi-kilogram scale preparations of drug molecules. This article reviews the hitherto reported applications of T3P as a reagent in organic synthesis. Focus is also placed on the use of T3P for large-scale synthesis. 1 Introduction 2 Structure and Preparation 3 T3P in Peptide Chemistry 3.1 As a Coupling Agent 3.2 Synthesis of Amino Acid Derivatives and Peptidomimetics 4 General Applications 4.1 As a Carboxylic Acid Activator 4.2 As a Dehydrating Agent 4.3 Synthesis of Heterocycles 4.4 Oxidation Reactions 4.5 Carbon–Carbon Bond Formation 4.6 Rearrangement Reactions 4.7 Synthesis of Drugs on Laboratory and Large Scales 5 Recent Applications 6 Conclusion