Solid-phase Synthesis Research Articles

Brønsted Acid-Lewis Acid (BA-LA) Induced Final Deprotection/Peptide Resin Cleavage in Fmoc/t-Bu Solid-Phase Peptide Synthesis: HCl/FeCl3 and AcOH/FeCl3 as Viable PFAS-Free Alternatives for TFA.

The widely used Fmoc/t-Bu solid-phase peptide synthesis (SPPS) is hampered by relying on corrosive, per/polyfluoroalkyl substance (PFAS) classified trifluoroacetic acid (TFA) as a universal protecting group (PG) removal/resin cleavage reagent. We report that suitable combinations of Brønsted acids (BAs) and Lewis acids (LAs) such as HCl/FeCl3 and AcOH/FeCl3 constitute viable alternatives for TFA as PFAS-free cleavage agents. Using water miscible dimethyl carbonate (DMC) and acetonitrile (MeCN) as solvents enabled diluting cleavage mixtures with suitable aqueous solutions, allowing for direct use in purification in which removal of >99.99% iron from an HCl/FeCl3 induced cleavage was demonstrated.

(Invited) Molecularly Imprinted Polymer “Antibodies” to Recognize Biological Species and Bioactive Molecules

Diagnostics, healthcare, and lifestyle are key drivers of sensors and assays that allow for measuring at home or at the point of care. Lateral-flow assays relying on antibodies are probably the most widely known examples for this. Despite their undisputed qualities, there is a strong drive to replace antibodies by artificial mimics that come at lower cost and are more stable. Molecularly imprinted polymers (MIPs) tick those boxes: they result from template-directed polymerization and, thus, from straightforward synthesis, and have appreciable binding properties [1]. Traditional imprinting approaches, however, suffer from limited reproducibility [2]. Solid-phase synthesis of MIP nanoparticles followed by enriching high-affinity fractions through sequential elution from the synthesis column can overcome such limitations [3].The approach has turned out very versatile for addressing analyte species almost any size. Originally, it has been focusing on proteins, probably because it follows the logic of interactions between antibodies and antigens. There are two different strategies for achieving that goal: using the entire protein molecule as the template for imprinting, or only a part of it. The former strategy, for instance, allows for establishing both direct and competitive sensing assays for human serum albumin (HSA) and insulin, respectively. Both aim at mass-sensitive sensing with quartz crystal microbalances (QCMs) as the transducers. Hence it is interesting to replace and/or complement the organic polymers with silica or titania particles to increase sensitivity: the number of available binding sites on MIP surface is limited by film and sensor dimensions. Using heavier particles hence increases the frequency shift per binding event. In the same manner, it turned out possible to access cardiac biomarkers, such as Gallectin3 (Gal3).Considering that protein molecules are large and structurally flexible makes it interesting to use only epitopes on their surfaces for imprinting. This leads to (surprisingly) high selectivity: In the case of a Dengue virus structural protein, imprinting with an epitope comprising 11 amino acids indeed leads to binding between the MIP nanoparticles and the respective protein. Changing only one amino acid reduces the sensor responses by a factor of more than two orders of magnitude thus revealing excellent selectivity bordering to specificity. Following that logic further, it is even possible to synthesize MIP nanobodies for small molecules, such as salbutamol. In such cases one usually applies a linker molecule to ensure synthesis. The resulting particles again highly selectively bind their target compound and are also useful for competitive assay formats.Going the other direction in terms of size, it is possible to use entire bacteria, such as S. epidermidis, as the template [4]. In contrast to the previous MIP nanobody approaches, this yields a variety of different nanoparticles that bind to different positions on the bacteria surface. The nanoparticle ensemble selectively interacts with its target species, even though the exact binding sites are unknown. Thus, when using them to incubate a different bacterium, such as E. coli, this reduces the fluorescence intensity by more than 80%. In other words: this means one can synthesize artificial antibodies for species without knowing the exact chemical details.[1] Bui BTS, Haupt K, Anal Bioanal Chem 398 (2010) 2481-92, doi: 10.1007/s00216-010-4158-x[2] Unger C, Lieberzeit PA, Reactive Funct Polym 161 (2021) 104855, doi: 10.1016/j.reactfunctpolym.2021.104855[3] a) Canfarotta F, Poma A, Guerreiro A, Piletsky S (2016) Solid-phase synthesis of molecularly imprinted nanoparticles. Nat Protoc 11:443–455. https://doi.org/10.1038/nprot.2016.030; b) Xu J, et al., Biomacromolecules 17 (2016) 345-353, doi: 1021/acs.biomac.5b01454 [4] Hlaoperm C et al. Sensors 23 (2023) 3526, doi: 10.3390/s23073526

Solid-phase synthesis of amphiphilic cyclic peptides as a surfactin mimetic

The cyclic lipopeptide surfactin, an anionic biosurfactant, has received increased interest owing to its unique characteristics and promising applications. Although surfactin is known to exhibit distinctive surface activities and self-assembly ability, the role of the cyclic peptide moiety in its physico-chemical properties requires further investigation. Here, we report the solid-phase peptide synthesis of surfactin mimics such as cyclic heptapeptides with the same amino acid sequence as surfactin (CSF) and cyclic octapeptides with dodecyl chains (CSF12). The structure–property relationships of the cyclic peptides were then examined. The acidic forms of CSF and CSF12 were poorly soluble in water, but the addition of 1.5 or 2.0 equiv. of NaOH increased their solubility in aqueous solutions. The disodium salt of CSF (CSF-2Na) reduced the surface tension of water to 39.0 mN/m despite its absence of a long alkyl chain, indicating that the cyclic peptide moiety plays a crucial role in the surface activity of the surfactin mimic. In the case of the disodium salt of CSF12 (CSF12–2Na), the introduction of a dodecyl chain to the cyclic peptide moiety led to an increase in molecular orientation such that saturation at the air–water interface was observed. Thus, a long alkyl chain enhances the molecular assembly of the cyclic peptide at the air–water interface. The introduction of a long alkyl chain also enhanced the solubilisation of phospholipids. For instance, CSF12–1.5Na induced the solubilisation of L-α-dimyristoylphosphatidylcholine (DMPC) multilamellar vesicles in phosphate-buffered saline (PBS). These findings greatly contribute to the fundamental understanding of the broad spectrum of physico-chemical properties and biological activities of bio-derived cyclic peptides. Furthermore, these insights can also be helping design libraries for developing cyclic peptides for challenging therapeutics in skin disease or as cosmeceuticals to enhance skin appearance.

Effective Immobilization of Novel Antimicrobial Peptides via Conjugation onto Activated Silicon Catheter Surfaces.

Antibiotic-resistant microorganisms have become a serious threat to public health, resulting in hospital infections, the majority of which are caused by commonly used urinary tract catheters. Strategies for preventing bacterial adhesion to the catheters' surfaces have been potentially shown as effective methods, such as coating thesurface with antimicrobial biomolecules. Here, novel antimicrobial peptides (AMPs) were designed as potential biomolecules to prevent antibiotic-resistant bacteria from binding to catheter surfaces. Thiolated AMPs were synthesized using solid-phase peptide synthesis (SPPS), and prep-HPLC was used to obtain AMPs with purity greater than 90%. On the other side, the silicone catheter surface was activated by UV/ozone treatment, followed by functionalization with allyl moieties for conjugation to the free thiol group of cystein in AMPs using thiol-ene click chemistry. Peptide-immobilized surfaces were found to become more resistant to bacterial adhesion while remaining biocompatible with mammalian cells. The presence and site of conjugation of peptide molecules were investigated by immobilizing them to catheter surfaces from both ends (C-Pep and Pep-C). It was clearly demonstrated that AMPs conjugated to the surface via theirN terminus have a higher antimicrobial activity. This strategy stands out for its effective conjugation of AMPs to silicone-based implant surfaces for the elimination of bacterial infections.

Access to Diverse Glutamic Acid Dendrons and a Janus Peptide Dendrimer Using an Atypical Solid Phase Synthesis.

The negligible cytotoxicity of anion surface-linked dendrons makes glutamic acid-based dendrons a potential candidate for materials and biological applications. Despite the inherent drawbacks of the conventional solution phase synthesis of glutamic acid-based dendrons, there have been no advancements in these protocols. Herein, we demonstrate the first-ever convergent solid phase synthesis of dendrons, up to fourth generation, having glutamic acid branching points produced by preactivation of dicarboxylic acid groups with N-hydroxysuccinimide and simultaneous coupling with amine groups of two growing peptide chains, with excellent yields (30-70%). In addition to the general advantages, such as the easy workup, a final single purification step, and an overall short synthesis duration, the convergent solid phase synthesis allowed us to chemically synthesize glutamic acid branching-based dendrons that cannot be accessed by standard divergent solid phase synthesis. This method has also been validated for its application in synthesizing hard-to-achieve Janus peptide dendrimers in a single stretch on a solid support. Our work corroborates the efficacy of controlled -COOH activation to accomplish an atypical solid phase synthesis of diverse glutamic acid dendrons in a convergent fashion. This is the first example of a Janus peptide dendrimer being synthesized on a solid support, utilizing both convergent and divergent approaches simultaneously.

The role of doping technology in the formation of nonlinear optical properties of LiNbO3:Mg:B crystals

Nonlinear optical coefficients dij were calculated quantitatively for two series of LiNbO3 crystals double-doped with Mg and nonmetallic B obtained by the methods of the solid-phase (SP) synthesis and homogeneous introduction (HG) of impurities. The addition of boron and the presence of MgLi extrinsic defects increased the efficiency of second-harmonic conversion. Homogeneously doped crystals have been found to be the most suitable medium for second-harmonic generation (SHG). The high value of the total nonlinear optical coefficient d33 (−70.742(5) × 10−9 cm/statV) and the extremely low photorefractive response make the LiNbO3:Mg:B crystal (4.2 mol%) obtained by the HG method promising for use in nonlinear optics.

Microwave Solid-Phase Synthesis of Ni-Co Ferrites and their Activities in Liquid-Phase Oxidation of m-Xylene

In this paper, the activity of mono- and di-substituted cobalt and nickel ferrites prepared by microwave solid-phase synthesis was studied in the reaction of liquid-phase oxidation of m-xylene to m-toluic acid. It was established that among the tested samples, the di-substituted ferrites of spinel structure with the composition of Ni0,6Co0,4Fe2O4 have the shortest induction period and the highest initial rate of oxygen absorption. In order to clarify the role of the active surface of the Ni0.6Co0.4Fe2O4 catalyst and the volumetric conversions of m‑xylene in the nucleation stage of primary xylyl radicals, the dependence of the induction period was studied. Furthermore the rate of oxygen absorption was investigated as a function of the time of introduction of the inhibitor into the oxidized m-xylene at different ratios of the total size of the heterogeneous surface to the volume of m‑xylene loaded into the reactor (S/V). The dependence of the selectivity of the process to the targeted product, m-toluic acid, on the specific surface area of the catalyst samples was established and it was shown that selectivity to the by-product, m-methylbenzyl alcohol, increased and selectivity to m-toluic acid decreased in the case of cobalt ferrite with a relatively low specific surface area.It was shown that at the first stage reaction (5–10 min.), ie., in conditions of an as yet undeveloped radical chain reaction, in the presence of disubstituted ferrites of the composition (Ni1–xCoxFe2O4), in comparison with monosubstituted ferrites, a higher initial rate of formation of the primary oxidation product of m-xylene — m-methylbenzylhydroperoxide (main intermediate product obtained during formation of m-toluic acid) is observed. The correlation of the activity of mono- and disubstituted Ni-Co ferrites, in the conditions of developed heterogeneous catalytic conversion of m‑xylene, disubstituted Ni-Co ferrites are also characterized by higher rate of heterogeneous nucleation of free radicals and heterogeneous catalytic conversion of the intermediate product — m-toluic aldehyde to m‑toluic acid. This, in turn, provides a high degree of selectivity for the targeted product with the yield of 79.8 %.

Multimaterial 3D Laser Printing of Cell-Adhesive and Cell-Repellent Hydrogels.

Here, a straightforward method is reported for manufacturing 3D microstructured cell-adhesive and cell-repellent multimaterials using two-photon laser printing. Compared to existing strategies, this approach offers bottom-up molecular control, high customizability, and rapid and precise 3D fabrication. The printable cell-adhesive polyethylene glycol (PEG) based material includes an Arg-Gly-Asp (RGD) containing peptide synthesized through solid-phase peptide synthesis, allowing for precise control of the peptide design. Remarkably, minimal amounts of RGD peptide (<0.1wt%) suffice for imparting cell-adhesiveness, while maintaining identical mechanical properties in the 3D printed microstructures to those of the cell-repellent, PEG-based material. Fluorescent labeling of the RGD peptide facilitates visualization of its presence in cell-adhesive areas. To demonstrate the broad applicability of the system, the fabrication of cell-adhesive 2.5D and 3D structures is shown, fostering the adhesion of fibroblast cells within these architectures. Thus, this approach allows for the printing of high-resolution, true 3D structures suitable for diverse applications, including cellular studies in complex environments.

Intense and sensitive green mechanoluminescence by Tb3+ doping in Y3GaO6

In this study, an efficient mechanoluminescent material, namely Y3GaO6:Tb3+, with green emission was prepared by high-temperature solid-phase synthesis. X-ray diffraction (XRD) shows that the samples belong to the orthorhombic crystal system with the space group Cmc21. The luminescence intensity of the materials is related to the content of the luminescent centers, and both photoluminescence (PL) and mechanoluminescence (ML) show that the optimum doping level of Tb3+ is 0.07. In both tensile and frictional applications, the ML intensity is linearly correlated with the magnitude of applied stress. Analysis of the thermoluminescence (TL) spectra indicates that the ML of the material arises from carriers released from the trap under stress stimulation, thus revealing its mechanism of ML property. Finally, the study demonstrates the mechanoluminescence pattern of Y3GaO6:Tb3+.

Solid-Phase Synthesis of Well-Defined Multiblock Copolymers by Atom Transfer Radical Polymerization.

Solid-phase polymer synthesis, historically rooted in peptide synthesis, has evolved into a powerful method for achieving sequence-controlled macromolecules. This study explores solid-phase polymer synthesis by covalently immobilizing growing polymer chains onto a poly(ethylene glycol) (PEG)-based resin, known as ChemMatrix (CM) resin. In contrast to traditional hydrophobic supports, CM resin's amphiphilic properties enable swelling in both polar and nonpolar solvents, simplifying filtration, washing, and drying processes. Combining atom transfer radical polymerization (ATRP) with solid-phase techniques allowed for the grafting of well-defined block copolymers in high yields. This approach is attractive for sequence-controlled polymer synthesis, successfully synthesizing di-, tri-, tetra-, and penta-block copolymers with excellent control over the molecular weight and dispersity. The study also delves into the limitations of achieving high molecular weights due to confinement within resin pores. Moreover, the versatility of the method is demonstrated through its applicability to various monomers in organic and aqueous media. This straightforward approach offers a rapid route to developing tailored block copolymers with unique structures and functionalities.

Condensation Domain Editing of the FR900359 Assembly Line Yields a Novel Analog Amenable to Late-Stage Functionalization.

The natural product FR900359 (FR) has generated significant attention lately, due to its characteristics as potent and selective inhibitor of Gq/11 mediated signal transduction of associated G protein-coupled receptors (GPCRs). This makes FR both a widely used pharmacological tool compound and a lead molecule for targeted cancer therapy. The exploration of structure-activity-relationship (SAR) of the scaffold by total synthesis has been complicated by its structural complexity and its incompatibility with standard approaches of solid-phase peptide synthesis. Options for late-stage functionalization of FR are limited due to a lack of tractable functional groups. Here we present a mixed approach combining (i) genetic engineering of the FR-assembly line in Chromobacterium vaccinii, to obtain a novel FR analog featuring a primary amine, with (ii) its subsequent synthetic modification and biological profiling for further SAR exploration of the FR scaffold.

Advanced Synthesis, Structural Characterization, and Functional Applications of Precision Polymers.

In the realm of biological macromolecules, entities such as nucleic acids and proteins are distinguished by their homochirality, consistently defined chain lengths, and integral sequence-dependent functionalities. Historically, these refined attributes have eluded traditional synthetic polymers, which often exhibit wide variabilities in chain lengths, limited batch-to-batch reproducibility, and stochastic monomer arrangements. Bridging this divide represents a pivotal challenge within the domain of polymer science - a challenge that the burgeoning discipline of precision polymer chemistry is poised to address. Recent advancements have yielded precision polymers that boast prescribed monomer sequences and narrow molecular weight distributions, heralding a new era for developing model systems to decipher structure-property correlations within functional polymers, analogous to those within biological matrices. This review discusses the innovative liquid-phase and solid-phase synthesis techniques for creating precision polymers and the advanced characterization tools essential for dissecting their structure and properties. We highlight potential applications in self-assembly, catalysis, data storage, imaging, and therapy, and provide insights into the future challenges and directions of precision polymers.

Dielectrophoretic bead-droplet reactor for solid-phase synthesis

Solid-phase synthesis underpins many advances in synthetic and combinatorial chemistry, biology, and material science. The immobilization of a reacting species on the solid support makes interfacing of reagents an important challenge in this approach. In traditional synthesis columns, this leads to reaction errors that limit the product yield and necessitates excess consumption of the mobile reagent phase. Although droplet microfluidics can mitigate these problems, its adoption is fundamentally limited by the inability to controllably interface microbeads and reagent droplets. Here, we introduce Dielectrophoretic Bead-Droplet Reactor as a physical method to implement solid-phase synthesis on individual functionalized microbeads by encapsulating and ejecting them from microdroplets by tuning the supply voltage. Proof-of-concept demonstration of the enzymatic coupling of fluorescently labeled nucleotides onto the bead using this reactor yielded a 3.2-fold higher fidelity over columns through precise interfacing of individual microreactors and beads. Our work combines microparticle manipulation and droplet microfluidics to address a long-standing problem in solid-phase synthesis with potentially wide-ranging implications.

Mixed Liquid and Solid Phase Synthesis of Isopeptidic Desferrioxamine Analogues for Complexation of Zirconium

Abstract89Zr has a number of advantageous properties for PET‐imaging, but optimal chelators for its widespread clinical application still need to be found. Tetrahydroxamates derived from the natural siderophore DFOB are promising candidates in this context. This study describes a solid‐phase approach to isopeptide analogs of DFOB (termed ipDFO*) with four hydroxamate groups for stable Zr(IV)‐chelation. The route uses either commercial or easily available Fmoc‐protected precursors and allows the synthesis of ipDFO* and clickable AZA−ipDFO* derivatives in only a few hours. The solid‐phase synthesis reduces the workload for the synthesis of ipDFO* and AZA−ipDFO* derivatives thus significantly compared to a previous multistep solution synthesis. The route is also modular and allows the synthesis of various ipDFO* derivatives with variation in the spacer length between the hydroxamate groups. This spacing is a critical parameter for finding the optimal chelator for hard metal cations like Zr(IV). It might thus help to speed up the search for an ideal Zr‐chelator for PET‐imaging and might also allow the extension to other metal cations of different size.

High-density perfusion cultures of the marine bacterium Rhodovulum sulfidophilum for the biomanufacturing of oligonucleotides

Therapeutic oligonucleotides (ONs) are typically manufactured via solid-phase synthesis, characterized by limited scalability and huge environmental footprint, limiting their availability. Biomanufactured ONs have the potential to reduce the immunogenic side-effects, and to improve the sustainability of their chemical counterparts. Rhodovulum sulfidophilum was demonstrated a valuable host for the extracellular production of recombinant ONs. However, low viable cell densities and product titer were reported so far. In this work, perfusion cell cultures were established for the intensification of ON biomanufacturing. First, the perfusion conditions were simulated in 50 mL spin tubes, selected as a scale-down model of the process, with the aim of optimizing the medium composition and process parameters. This optimization stage led to an increase in the cell density by 44 % compared to the reference medium formulation. In addition, tests at increasing perfusion rates were conducted until achieving the maximum viable cell density (VCDmax), allowing the determination of the minimum cell-specific perfusion rate (CSPRmin) required to sustain the cell culture. Intriguingly, we discovered in this system also a maximum CSPR, above which growth inhibition starts. By leveraging this process optimization, we show for the first time the conduction of perfusion cultures of R. sulfidophilum in bench-scale bioreactors. This process development pipeline allowed stable cultures for more than 20 days and the continuous biomanufacturing of ONs, testifying the great potential of perfusion processes.

Australian Marine and Terrestrial Streptomyces-Derived Surugamides, and Synthetic Analogs, and Their Ability to Inhibit Dirofilaria immitis (Heartworm) Motility.

A bioassay-guided chemical investigation of a bacterium, Streptomyces sp. CMB-MRB032, isolated from sheep feces collected near Bathurst, Victoria, Australia, yielded the known polyketide antimycins A4a (1) and A2a (2) as potent inhibitors of Dirofilaria immitis (heartworm) microfilaria (mf) motility (EC50 0.0013-0.0021 µg/mL), along with the octapeptide surugamide A (3) and the new N-methylated analog surugamide K (4). With biological data suggesting surugamides may also exhibit activity against D. immitis, a GNPS molecular network analysis of a library of microbes sourced from geographically diverse Australian ecosystems identified a further five taxonomically and chemically distinct surugamide producers. Scaled-up cultivation of one such producer, Streptomyces sp. CMB-M0112 isolated from a marine sediment collected at Shorncliff, Qld, Australia, yielded 3 along with the new acyl-surugamides A1-A4 (5-8). Solid-phase peptide synthesis provided additional synthetic analogs, surugamides S1-S3 (9-11), while derivatization of 3 returned the semi-synthetic surugamide S4 (12) and acyl-surugamides AS1-AS3 (13-15). The natural acyl-surugamide A3 (7) and semi-synthetic acyl-surugamide AS3 (15) were shown to selectively inhibit D. immitis mf motility (EC50 3.3-3.4 µg/mL), however, unlike antimycins 1 and 2, were inactive against the gastrointestinal nematode Haemonchus contortus L1-L3 larvae (EC50 > 25 µg/mL) and were not cytotoxic to mammalian cells (human colorectal carcinoma SW620, IC50 > 30 µg/mL). A structure-activity relationship (SAR) study on the surugamides 3-15 revealed that selective acylation of the Lys3-ε-NH2 correlates with anthelmintic activity.

Ternary cesium(rubidium) tungstates: production and impedance spectroscopy

The work is aimed at the directed synthesis of new phases of tungstates containing mono-, tri-, and tetravalent metals, as well as the determination of their crystallographic, thermal, and electrophysical properties. The study used the method of solid-phase synthesis to obtain tungstate phases with composition MRA0.5(WO4)3 (M – singly, R – triply-, and A – tetra-charged elements) within the temperature range of 400–750 °С. Their crystallographic and thermal characteristics were determined. The synthesized ternary tungstates crystallizing in a hexagonal system were studied using differential scanning calorimetry. The technique revealed an increase in the melting temperatures of compounds with increasing ionic radius of the trivalent cation in the series CsRTi0.5(WO4)3 (R = Al, Cr, Ga, Fe, In). The same correlation is observed when switching from rubidium to cesium derivatives. The thermal stability of ternary titanium and hafnium tungstates was compared. The melting temperatures of RbRTi0.5(WO4)3 are about 20 °С higher than those of their hafnium counterparts. The dielectric characteristics of CsRTi0.5(WO4)3 (R = Fe, Cr) belonging to the ternary tungstate family were analyzed via impedance spectroscopy. The temperature and frequency dependences of the conductivity of ternary tungstates at different frequencies (1 Hz – 1 mHz), measured in heating and cooling modes, are characterized by a slight temperature hysteresis, reaching 10-2–10-3 S/cm in the high-temperature region at activation energy values of 0.4–0.5 eV. The impedance frequency spectra measured within the range of 1 Hz – 1 mHz at different temperatures confirm the ion-conducting properties of the sample, which allows the obtained phases to be considered promising solid electrolytes.

Total Synthesis of a Peptide Diatom Sex Pheromone Bearing a Sulfated Aspartic Acid.

The peptide sex-inducing pheromone SIP+ (1) bearing an unusual sulfated aspartic acid residue induces sexual reproduction in diatom populations. Herein, we report the first total synthesis of SIP+ using both a sulfated building block approach and a solid-phase peptide synthesis (SPPS)-compatible late-stage sulfation strategy to assemble the natural product. The modular approaches provide concise routes to useful quantities of the natural product for future structure activity relationship studies examining the role of SIP+ in diatom biology.

Biocompatible Synthesis of Macrocyclic Thiazol(in)e Peptides.

Macrocyclic peptides containing a thiazole or thiazoline in the backbone are considered privileged structures in both natural compounds and drug discovery, owing to their enhanced bioactivity, stability, and permeability. Here, we present the biocompatible synthesis of macrocyclic peptides from N-terminal cysteine and C-terminal nitrile. While the N-terminal cysteine is incorporated during solid-phase peptide synthesis, the C-terminal nitrile is introduced during cleavage with aminoacetonitrile, utilizing a cleavable benzotriazole linker. This method directly yields the fully functionalized linear peptide precursor. The biocompatible cyclization reaction occurs in buffer at physiological pH and room temperature. The resulting thiazoline heterocycle remains stable in buffer but hydrolyzes under acidic conditions. While such hydrolysis enables access to macrocyclic peptides with a complete amide backbone, mild oxidation of the thiazoline leads to the stable thiazole macrocyclic peptide. While conventional oxidation strategies involve metals, we developed a protocol simply relying on alkaline salt and air. Therefore, we offer a rapid and metal-free pathway to macrocyclic thiazole peptides, featuring a biocompatible key cyclization step.

Novel Polypeptide Automated Synthesis Devices: A Review

Peptides are a unique class of proteins and one-dimensional biological nanomaterials that play an exceptionally important role in life science and industrial applications. At present, peptide synthesis equipment encounters issues like low synthetic efficiency, challenges in scaling up, and limited automation. This article provides an overview of the key technologies in peptide synthesis equipment, covering aspects such as peptide information screening, peptide synthesis, and detection. It analyzes and summarizes the principles, methods, and critical challenges of traditional solid-phase peptide synthesis technology, microwave-assisted solid-phase peptide synthesis technology, and continuous-flow solid-phase peptide synthesis technology. It also discusses microfluidic solid-phase peptide synthesis technology and future research trends, offering insights into the search for an efficient, high-yield, high-purity, scalable, and intelligent peptide synthesis method, which holds significant research significance.