Sequence-Defined Oligomers from Hydroxyproline Building Blocks for Parallel Synthesis Applications

Bactericidal Biodegradable Linear Polyamidoamines Obtained with the Use of Endogenous Polyamines

The work presents the synthesis of a series of linear polyamidoamines by polycondensation of sebacoyl dichloride with endogenous polyamines: putrescine, spermidine, spermine, and norspermidine-a biogenic polyamine not found in the human body. During the synthesis carried out via interfacial reaction, hydrophilic, semi-crystalline polymers with an average viscosity molecular weight of approximately 20,000 g/mol and a melting point of approx. 130 °C were obtained. The structure and composition of the synthesized polymers were confirmed based on NMR and FTIR studies. The cytotoxicity tests performed on human fibroblasts and keratinocytes showed that the polymers obtained with spermine and norspermidine were strongly cytotoxic, but only in high concentrations. All the other examined polymers did not show cytotoxicity even at concentrations of 2000 µg/mL. Simultaneously, the antibacterial activity of the obtained polyamides was confirmed. These polymers are particularly active against E. Coli, and virtually all the polymers obtained demonstrated a strong inhibitory effect on the growth of cells of this strain. Antimicrobial activity of the tested polymer was found against strains like Staphylococcus aureus, Staphylococcus epidermidis, and Pseudomonas aeruginosa. The broadest spectrum of bactericidal action was demonstrated by polyamidoamines obtained from spermine, which contains two amino groups in the repeating unit of the chain. The obtained polymers can be used as a material for forming drug carriers and other biologically active compounds in the form of micro- and nanoparticles, especially as a component of bactericidal creams and ointments used in dermatology or cosmetology.

Iridium-Catalyzed Synthesis of Chiral 1,2,3-Triazoles Units and Precise Construction of Stereocontrolled Oligomers

Iridium-catalyzed azide-thioalkyne cycloaddition reaction (IrAAC) has proved to be a powerful tool for the synthesis of fully substituted 1,2,3-triazole compounds with exclusive regioselectivity. Here we report its successful use in the precise construction of stereocontrolled oligomers that have great potential in diverse applications. Starting with the azide derived from L-prolinol and different functionalized thioalkynes, chiral 1,2,3-triazole units were fabricated with high efficiency under the IrAAC condition, which were further assembled into stereocontrolled oligotriazoles through metal-free exponential growth strategies. The structure and uniformity of these oligomers were well identified by ¹H NMR, size-exclusion chromatography, and mass spectrometry, the stereoregularity of which were studied through circular dichroism and circular polarized luminescence analysis.

Leveraging blockchain concepts as watermarkers of plastics for sustainable waste management in progressing circular economy

Blockchain-integrated waste management and circular economy are emergent concepts that target minimising waste generation and fluctuations of resource commodity. Blockchain can support a circular economy and green principles by enabling information transparency, reliability and automation. Redesigning plastics by molecular tagging is the way forward to ensure synthetic plastics are kept in an infinite loop and support closed-loop recycling. The involvement of major corporations in product development and blockchain-integrated closed-loop recycling has resulted in several successful green chemical approaches toward circular plastic economy projects. Government policies and legislations are progressively supporting plastic redesigning for improving the plastic circular economy. Nevertheless, a systematic approach is required in addressing blockchain technology and plastic redesigning to effectively leverage circular economy initiatives.

Synthesis of High Performance Thiophene-Aromatic Polyesters from Bio-Sourced Organic Acids and Polysaccharide-Derived Diol: Characterization and Degradability Studies

In this work, the feasibility of replacing petroleum-based poly(ethylene terephthalate) (PET) with fully bio-based copolyesters derived from dimethyl 2,5-thiophenedicarboxylate (DMTD), dimethyl 2,5-dimethoxyterephthalate (DMDMT), and polysaccharide-derived 1,6-hexanediol (HDO) was investigated. A systematic study of structure-property relationship revealed that the properties of these poly(thiophene-aromatic) copolyesters (PHS(20-90)) can be tailored by varying the ratio of diester monomers in the reaction, whereby an increase in DMTD content noticeably shortened the reaction time in the transesterification step due to its higher reactivity as compared with DMDMT. The copolyesters had weight-average molar masses (Mw) between 27,500 and 38,800 g/mol, and dispersity Đ of 2.0-2.5. The different polarity and stability of heterocyclic DMTD provided an efficient mean to tailor the crystallization ability of the copolyesters, which in turn affected the thermal and mechanical performance. The glass transition temperature (Tg) could be tuned from 70-100 °C, while the tensile strength was in a range of 23-80 MPa. The obtained results confirmed that the co-monomers were successfully inserted into the copolyester chains. As compared with commercial poly(ethylene terephthalate), the copolyesters displayed not only enhanced susceptibility to hydrolysis, but also appreciable biodegradability by lipases, with weight losses of up to 16% by weight after 28 weeks of incubation.

Discrete oligourethanes of sequence-regulated properties – impact of stereocontrol

Properties and functions of natural biopolymers such as proteins are strongly dependent on the sequence of amino acid monomers. The regulation of the properties of synthetic polymers by controlling monomer...

Discrete, self-immolative N-substituted oligourethanes and their use as molecular tags

The depolymerization of N-substituted oligourethanes via an intramolecular cyclization event was studied in-depth, while the applicability of these macromolecules as anti-counterfeiting tags was demonstrated by labeling a polyurethane material.

Metabolic engineering strategy for synthetizing trans-4-hydroxy-L-proline in microorganisms

Trans-4-hydroxy-L-proline is an important amino acid that is widely used in medicinal and industrial applications, particularly as a valuable chiral building block for the organic synthesis of pharmaceuticals. Traditionally, trans-4-hydroxy-L-proline is produced by the acidic hydrolysis of collagen, but this process has serious drawbacks, such as low productivity, a complex process and heavy environmental pollution. Presently, trans-4-hydroxy-L-proline is mainly produced via fermentative production by microorganisms. Some recently published advances in metabolic engineering have been used to effectively construct microbial cell factories that have improved the trans-4-hydroxy-L-proline biosynthetic pathway. To probe the potential of microorganisms for trans-4-hydroxy-L-proline production, new strategies and tools must be proposed. In this review, we provide a comprehensive understanding of trans-4-hydroxy-L-proline, including its biosynthetic pathway, proline hydroxylases and production by metabolic engineering, with a focus on improving its production.

Protecting-Group-Free Iterative Exponential Growth Method for Synthesizing Sequence-Defined Polymers

As a main synthetic strategy for monodisperse sequence-defined polymers, the known iterative exponential growth (IEG) methods were all developed on protecting-group chemistry, where the additional deprotection reactions increased their synthetic steps and decreased their atom economy. In this study, we developed a protecting-group-free IEG method for the formation of sequence-defined polymers by combining three orthogonal click reactions of copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC), sulfur-fluoride exchange reaction (SuFEx), and Ugi four-component reaction (Ugi-4CR). In this approach, oligomer synthesis began with three parallel CuAAC, SuFEx, and Ugi-4CR couplings among three monomers each with two orthogonal clickable end groups. By iteratively applying parallel CuAAC, SuFEx, and Ugi-4CR to couple three resultant oligomers, each having two orthogonal clickable terminals, this approach could exponentially grow three different sequence-defined polymers simultaneously with high efficiency, requiring no protecting-group chemistry. Additionally, each Ugi-4CR coupling reaction could introduce two external side groups to provide the molecular variation and side-chain functionalization for the resultant sequence-defined polymers.

Stimulus-cleavable chemistry in the field of controlled drug delivery

This review comprehensively summarises stimulus-cleavable linkers from various research areas and their cleavage mechanisms, thus provides an insightful guideline to extend their potential applications to controlled drug release from nanomaterials.

Insights into the structure-performance relationships of extraction materials in sample preparation for chromatography

Sample preparation is one of the most crucial steps in analytical processes. Commonly used methods, including solid-phase extraction, dispersive solid-phase extraction, dispersive magnetic solid-phase extraction, and solid-phase microextraction, greatly depend on the extraction materials. In recent decades, a vast number of materials have been studied and used in sample preparation for chromatography. Due to the unique structural properties, extraction materials significantly improve the performance of extraction devices. Endowing extraction materials with suitable structural properties can shorten the pretreatment process and improve the extraction efficiency and selectivity. To understand the structure-performance relationships of extraction materials, this review systematically summarizes the structural properties, including the pore size, pore shape, pore volume, accessibility of active sites, specific surface area, functional groups and physicochemical properties. The mechanisms by which the structural properties influence the extraction performance are also elucidated in detail. Finally, three principles for the design and synthesis of extraction materials are summarized. This review can provide systematic guidelines for synthesizing extraction materials and preparing extraction devices.

High-throughput preparation of radioprotective polymers via Hantzsch's reaction for in vivo X-ray damage determination

Radioprotectors for acute injuries caused by large doses of ionizing radiation are vital to national security, public health and future development of humankind. Here, we develop a strategy to explore safe and efficient radioprotectors by combining Hantzsch's reaction, high-throughput methods and polymer chemistry. A water-soluble polymer with low-cytotoxicity and an excellent anti-radiation capability has been achieved. In in vivo experiments, this polymer is even better than amifostine, which is the only approved radioprotector for clinical applications, in effectively protecting zebrafish embryos from fatally large doses of ionizing radiation (80 Gy X-ray). A mechanistic study also reveals that the radioprotective ability of this polymer originates from its ability to efficiently prevent DNA damage due to high doses of radiation. This is an initial attempt to explore polymer radioprotectors via a multi-component reaction. It allows exploiting functional polymers and provides the underlying insights to guide the design of radioprotective polymers.

Damage and Repair in Informational Poly(N-substituted urethane)s

The degradation and repair of uniform sequence-defined poly(N-substituted urethane)s was studied. Polymers containing an ω-OH end-group and only ethyl carbamate main-chain repeat units rapidly degrade in NaOH solution through an ω→α depolymerization mechanism with no apparent sign of random chain cleavage. The degradation mechanism is not notably affected by the nature of the side-chain N-substituents and took place for all studied sequences. On the other hand, depolymerization is significantly influenced by the molecular structure of the main-chain repeat units. For instance, hexyl carbamate main-chain motifs block unzipping and can therefore be used to control the degradation of specific sequence sections. Interestingly, the partially degraded polymers can also be repaired; for example by using a combination of N,N'-disuccinimidyl carbonate with a secondary amine building-block. Overall, these findings open up interesting new avenues for chain-healing and sequence editing.

Polyurethanes and Polyallophanates via Sequence-Selective Copolymerization of Epoxides and Isocyanates

Aryl isocyanates are introduced as comonomers for ring-opening copolymerization (ROCOP) with epoxides. Informed by studies of reaction kinetics, we show that divergent sequence selectivity for AB- and ABB-type copolymers can be achieved with a single dimagnesium catalyst. The resulting materials respectively constitute a new class of polyurethanes (PUs) and a new class of materials featuring an unprecedented backbone structure, the polyallophanates (PAs). The successful use of isocyanate comonomers in this way marks a new direction for the field of ROCOP while providing distinct opportunities for expansion of PU structural diversity. Specifically, the methodology reported herein delivers PUs featuring fully substituted (tertiary) carbamyl nitrogen atoms, a structural motif that is almost inaccessible via extant polymerization strategies. Thus, in one step from commercially available comonomers, our methodology expands the scope of ROCOP and gives access to diverse materials featuring both privileged (PU) and unexplored (PA) microstructures.

Efficient Protocol for the Synthesis of "N-Coded" Oligo- and Poly(N-Substituted Urethanes)

Sequence-defined poly(N-substituted urethanes) were synthesized via a solid-phase iterative protocol including two successive orthogonal coupling steps: the formation of an activated carbonate and its chemoselective reaction with the secondary amine group of amino alcohol building blocks. This simple method was used to write binary information on the formed polymers using four-coded molecules, 2-(methylamino)ethanol, 2-(ethylamino)ethanol, 2-(propylamino)ethanol, and 2-(butylamino)ethanol, symbolizing binary dyads 00, 01, 10, and 11, respectively. The method is fast and allows synthesis of uniform oligomers and polymers with controlled lengths (4-mer to 28-mer) and digital information sequences. Furthermore, the coded poly(N-substituted urethanes) were easily characterized by electrospray mass spectrometry and decoded by tandem mass spectrometry. Overall, these digital macromolecules offer interesting advantages over conventional sequence-coded polyurethanes, i.e., synthesis of longer chains, reduced synthesis times, and better solubility and processing in common organic solvents.

A New Class of Materials: Sequence-Defined Macromolecules and Their Emerging Applications

Emerging applications of a new class of materials, sequence-defined macromolecules, are explored. Such molecularly highly defined macromolecules require stringent synthesis and purification procedures, yet offer unprecedented application possibilities. The first examples of molecular data storage and related technologies are already starting to emerge today. From a more fundamental point of view, such macromolecules offer a unique opportunity to determine quantitative structure-property relationships (QSPR), which critically aids in designing materials with applications ranging from catalysis to artificial enzymes.

Tunable biomaterials from synthetic, sequence-controlled polymers

Polymeric biomaterials have many applications including therapeutic delivery vehicles, medical implants and devices, and tissue engineering scaffolds. Both naturally-derived and synthetic materials have successfully been used for these applications in the clinic. However, the increasing complexity of these applications requires materials with advanced properties, especially customizable or tunable materials with bioactivity. To address this issue, there have been recent efforts to better recapitulate the properties of natural materials using synthetic biomaterials composed of sequence-controlled polymers. Sequence control mimics the primary structure found in biopolymers, and in many cases, provides an extra handle for functionality in synthetic polymers. Here, we first review the advances in synthetic methods that have enabled sequence-controlled biomaterials on a relevant scale, and discuss strategies for choosing functional sequences from a biomaterials engineering context. Then, we highlight several recent studies that show strong impact of sequence control on biomaterial properties, including in vitro and in vivo behavior, in the areas of hydrogels, therapeutic materials, and novel applications such as molecular barcodes for medical devices. The role of sequence control in biomaterials properties is an emerging research area, and there remain many opportunities for investigation. Further study of this topic may significantly advance our understanding of bioactive or smart materials, as well as contribute design rules to guide the development of synthetic biomaterials for future applications in tissue engineering and regenerative medicine.

A versatile strategy for the synthesis of sequence-defined peptoids with side-chain and backbone diversity via amino acid building blocks

Designing artificial macromolecules with absolute sequence order is still a long-term challenge in polymer chemistry as opposed to natural biopolymers with perfectly defined sequences like proteins and DNA. Herein, we combined amino acid building blocks and iterative Ugi reactions for the de novo design and synthesis of sequence-defined peptoids. The highly efficient strategy provided excellent yields and enables multigram-scale synthesis of perfectly defined peptoids. This new strategy furnishes the broad structural diversity of side chains, as well as backbones. Importantly, the overall hydrophobicity and lower critical solution temperature (LCST) behaviours of these precisely defined peptoids can be logically altered by variation of the sequence. By following the same Ugi chemistry, these peptoids are also conjugated to DNA in a simple way, facilitating the development of novel therapeutics.

Sequence-defined non-natural polymers: synthesis and applications

Sequence-defined polymer: A promising gateway for the next generation polymeric materials and vast opportunities for new synthetic strategies, functional diversity and its material and biomedical applications.

Direct comparison of solution and solid phase synthesis of sequence-defined macromolecules

Sequence-defined macromolecules of high molecular weight are synthesised by the combination of click chemistry with multicomponent reactions. The synthesis is performed on solid phase as well as in solution to directly compare the two approaches.

Sequence-definition in stiff conjugated oligomers

The concept of sequence-definition in the sense of polymer chemistry is introduced to conjugated, rod-like oligo(phenylene ethynylene)s via an iterative synthesis procedure. Specifically, monodisperse sequence-defined trimers and pentamers were prepared via iterative Sonogashira cross-coupling and deprotection. The reaction procedure was extended to tetra- and pentamers for the first time yielding a monodisperse pentamer with 18% and a sequence-defined pentamer with 3.2% overall yield. Furthermore, three novel trimers with a 9H-fluorene building block at predefined positions within the phenylene ethynylene chain were synthesised in 23–52% overall yields. Hence, it was confirmed that a functionality of interest can be incorporated selectively at a pre-defined position of these monodisperse oligomers. All respective intermediate structures were fully characterised by proton and carbon NMR, mass spectrometry, size-exclusion chromatography, and IR spectroscopy. Additionally, thermal and optical transitions are reported for the different oligomers.

Green Tea Catechin Dramatically Promotes RNAi Mediated by Low-Molecular-Weight Polymers

Cytosolic delivery is the major challenge that limits the clinical translation of siRNA-based therapeutics. Although thousands of polymers have been developed for siRNA delivery, the efficiency-toxicity correlation is unsatisfactory. Here, we report a facile strategy to fabricate core-shell-structured nanoparticles with robust siRNA delivery efficiency. The nanoparticle is prepared by entropy-driven complexation of siRNA with a green tea catechin to yield a negatively charged core, followed by coating low-molecular-weight polymers to form the shell. This supramolecular strategy facilitates the polymers condensing siRNA into uniform nanoparticles. The nanoparticle specifically down-regulates target genes in vitro and in vivo, and efficiently attenuates chronic intestinal inflammation in an inflammatory bowel disease model. Notably, the highly efficient nanoparticles are applicable for various polymers with different topologies and chemical compositions, providing a versatile technique to break down the efficiency-toxicity correlation of cationic polymers. The proposed strategy in this study permits the development of a promising platform for polymer-mediated siRNA delivery.

Dual Sequence Control of Uniform Macromolecules through Consecutive Single Addition by Selective Passerini Reaction

The selective Passerini reactions of 4-formylbenzoic acid and 4-isocyanobenzoic acid with aliphatic isocyanides and aldehydes were utilized to synthesize sequence-defined uniform macromolecules. Our strategy does not involve any protecting groups or reactive group transformation steps and allows direct and consecutive propagation of sequence in each step. Introduction of diverse side groups by using different aliphatic components provided a range of sequence-defined uniform macromolecules in high yield and gram scale. The strategy also allows further Passerini self-coupling or cross-coupling of the formed sequences with other small molecules, affording polymers with up to 5098.3 Da and 20 side groups. Thus, this strategy will show promise for more efficient synthesis of new sequence-defined macromolecules.

Click and Click-Inspired Chemistry for the Design of Sequence-Controlled Polymers

During the previous decade, many popular chemical reactions used in the area of "click" chemistry and similarly efficient "click-inspired" reactions have been applied for the design of sequence-defined and, more generally, sequence-controlled structures. This combination of topics has already made quite a significant impact on scientific research to date and has enabled the synthesis of highly functionalized and complex oligomeric and polymeric structures, which offer the prospect of many exciting further developments and applications in the near future. This minireview highlights the fruitful combination of these two topics for the preparation of sequence-controlled oligomeric and macromolecular structures and showcases the vast number of publications in this field within a relatively short span of time. It is divided into three sections according to the click-(inspired) reaction that has been applied: copper-catalyzed azide-alkyne cycloaddition, thiol-X, and related thiolactone-based reactions, and finally Diels-Alder-chemistry-based routes are outlined, respectively.