Temperature-dependent molecular assembly governs the selective convergent dynamic covalent reactions on surfaces

Three highly ordered nanostructures consisting of different oligomers are exclusively obtained via a surface assembly-directed approach. It is suggested that this high selectivity is induced by the adsorption and assembly of specific oligomers at different temperatures, highlighting the self-sorting process in dynamic covalent reactions on surfaces.

Duplex-forming oligocarbamates with tunable nonbonding sites

In biopolymers such as proteins and nucleic acids, monomer sequence encodes for highly specific intra- and intermolecular interactions that direct self-assembly into complex architectures with high fidelity. This remarkable structural control translates into precise control over the properties of the biopolymer. Polymer scientists have sought to achieve similarly precise control over the structure and function of synthetic assemblies. A common strategy for achieving this goal has been to exploit existing biopolymers, known to associate with specific geometries and stoichiometries, for the assembly of synthetic building blocks. However, such systems are neither scalable nor amenable to the relatively harsh conditions required by various materials science applications, particularly those involving non-aqueous environments. To overcome these limitations, we have synthesized sequence-defined oligocarbamates (SeDOCs) that assemble into duplexes through complementary hydrogen bonds between thymine (T) and diaminotriazine (D) pendant groups. The SeDOC platform makes it simple to incorporate non-hydrogen-bonding sites into an oligomer's array of recognition motifs, thereby enabling an investigation into this unexplored handle for controlling the hybridization of complementary ligands. We successfully synthesized monovalent, divalent, and trivalent SeDOCs and characterized their self-assembly via diffusion ordered spectroscopy, 1H-NMR titration, and isothermal titration calorimetry. Our findings reveal that the binding strength of monovalent oligomers with complementary pendant groups is entropically driven and independent of monomer sequence. The results further show that the hybridization of multivalent oligomers is cooperative, that their binding enthalpy (ΔH) and entropy (TΔS) depend on monomer sequence, and that sequence-dependent changes in ΔH and TΔS occur in tandem to minimize the overall change in binding free energy.

The Rise of Boron-Containing Compounds: Advancements in Synthesis, Medicinal Chemistry, and Emerging Pharmacology

Boron-containing compounds (BCC) have emerged as important pharmacophores. To date, five BCC drugs (including boronic acids and boroles) have been approved by the FDA for the treatment of cancer, infections, and atopic dermatitis, while some natural BCC are included in dietary supplements. Boron's Lewis acidity facilitates a mechanism of action via formation of reversible covalent bonds within the active site of target proteins. Boron has also been employed in the development of fluorophores, such as BODIPY for imaging, and in carboranes that are potential neutron capture therapy agents as well as novel agents in diagnostics and therapy. The utility of natural and synthetic BCC has become multifaceted, and the breadth of their applications continues to expand. This review covers the many uses and targets of boron in medicinal chemistry.

Synthetically encoded complementary oligomers

Creating the next generation of advanced materials will require controlling molecular architecture to a degree typically achieved only in biopolymers. Sequence-defined polymers take inspiration from biology by using chain length and monomer sequence as handles for tuning structure and function. These sequence-defined polymers can assemble into discrete structures, such as molecular duplexes, via reversible interactions between functional groups. Selectivity can be attained by tuning the monomer sequence, thereby creating the need for chemical platforms that can produce sequence-defined polymers at scale. Developing sequence-defined polymers that are specific for their complementary sequence and achieve their desired binding strengths is critical for producing increasingly complex structures for new functional materials. In this Review Article, we discuss synthetic platforms that produce sequence-defined, duplex-forming oligomers of varying length, strength and association mode, and highlight several analytical techniques used to characterize their hybridization.

Peptide Macrocyclization Guided by Reversible Covalent Templating

The creation of complementary products via templating is a hallmark feature of nucleic acid replication. Outside of nucleic acid-like molecules, the templated synthesis of a hetero-complementary copy is still rare. Herein we describe one cycle of templated synthesis that creates homomeric macrocyclic peptides guided by linear instructing strands. This strategy utilizes hydrazone formation to pre-organize peptide oligomeric monomers along the template on a solid support resin, and microwave-assisted peptide synthesis to couple monomers and cyclize the strands. With a flexible templating strand, we can alter the size of the complementary macrocycle products by increasing the length and number of the binding peptide oligomers, showing the potential to precisely tune the size of macrocyclic products. For the smaller macrocyclic peptides, the products can be released via hydrolysis and characterized by ESI-MS.

Dynamic Fluorescent Patterning Based on Visible-Light-Responsive Diselenide Metathesis

A diselenide bond, as a dynamic covalent bond, is a versatile tool to construct smart interfaces, which can respond to visible light. In this work, we used microcontact printing (μCP) to construct diselenide patterns on quartz substrates. Fluorescent patterns were obtained on the modified surfaces via the visible-light-induced diselenide metathesis reaction, which allowed the patterning process to be fast, dynamically erasable, and compatible with different fluorescent molecules including rhodamine B and boron-dipyrromethene (BODIPY) used in this work. A variety of analytical methods offered comprehensive evidence for the success of the printing of diselenides here. We further printed diselenide and disulfide intersecting stripes on one single quartz substrate layer by layer and introduced rhodamine B and BODIPY to obtain a multicolored pattern simultaneously. By taking advantage of their responsiveness to different wavelengths, the composite pattern of disulfides and diselenides could be erased by two stepwise stages. The fluorescent images of the modified substrate showed a good agreement with the pattern of the poly(dimethylsiloxane) (PDMS) stamp, indicating the methodology with a potential application for information storage.

Systematic Approach to Mimic Phenolic Natural Polymers for Biofabrication

In nature, phenolic biopolymers are utilized as functional tools and molecular crosslinkers to control the mechanical properties of biomaterials. Of particular interest are phenolic proteins/polysaccharides from living organisms, which are rich in catechol and/or gallol groups. Their strong underwater adhesion is attributed to the representative phenolic molecule, catechol, which stimulates intermolecular and intramolecular crosslinking induced by oxidative polymerization. Significant efforts have been made to understand the underlying chemistries, and researchers have developed functional biomaterials by mimicking the systems. Owing to their unique biocompatibility and ability to transform their mechanical properties, phenolic polymers have revolutionized biotechnologies. In this review, we highlight the bottom-up approaches for mimicking polyphenolic materials in nature and recent advances in related biomedical applications. We expect that this review will contribute to the rational design and synthesis of polyphenolic functional biomaterials and facilitate the production of related applications.

Applications of Discrete Synthetic Macromolecules in Life and Materials Science: Recent and Future Trends

In the last decade, the field of sequence-defined polymers and related ultraprecise, monodisperse synthetic macromolecules has grown exponentially. In the early stage, mainly articles or reviews dedicated to the development of synthetic routes toward their preparation have been published. Nowadays, those synthetic methodologies, combined with the elucidation of the structure-property relationships, allow envisioning many promising applications. Consequently, in the past 3 years, application-oriented papers based on discrete synthetic macromolecules emerged. Hence, material science applications such as macromolecular data storage and encryption, self-assembly of discrete structures and foldamers have been the object of many fascinating studies. Moreover, in the area of life sciences, such structures have also been the focus of numerous research studies. Here, it is aimed to highlight these recent applications and to give the reader a critical overview of the future trends in this area of research.

Sequence-directed dynamic covalent assembly of base-4-encoded oligomers

As an information-bearing biomacromolecule, DNA is encoded in base-4, where each residue site can be occupied by any one of four nucleobases. Mimicking the information dense, sequence-selective hybridization of DNA, we demonstrate two orthogonal dynamic covalent interactions to effect the selective assembly of molecular ladders and grids from base-4-encoded oligo(peptoid)s.

Sequence-selective dynamic covalent assembly of information-bearing oligomers

Relatively robust dynamic covalent interactions have been employed extensively to mediate molecular self-assembly reactions; however, these assembly processes often do not converge to a thermodynamic equilibrium, instead yielding mixtures of kinetically-trapped species. Here, we report a dynamic covalent self-assembly process that mitigates kinetic trapping such that multiple unique oligomers bearing covalently coreactive pendant groups are able to undergo simultaneous, sequence-selective hybridization with their complementary strands to afford biomimetic, in-registry molecular ladders with covalent rungs. Analogous to the thermal cycling commonly employed for nucleic acid melting and annealing, this is achieved by raising and lowering the concentration of a multi-role reagent to effect quantitative dissociation and subsequently catalyze covalent bond rearrangement, affording selective assembly of the oligomeric sequences. The hybridization specificity afforded by this process further enabled information encoded in oligomers to be retrieved through selective hybridization with complementary, mass-labeled sequences.

Dynamic covalent interactions have been employed to mediate molecular self-assembly reactions but often do not converge to a thermodynamic equilibrium and yield a mixture of kinetically trapped species. Here, the authors show a sequence-selective, dynamic covalent self-assembly process that mitigates kinetic trapping to afford biomimetic molecular ladders with covalent rungs.

Temperature-mediated molecular ladder self-assembly employing Diels–Alder cycloaddition

Thermal annealing of sequence-defined, maleimide- and furan-bearing oligomers enables sequence-selective hybridization to afford molecular ladders incorporating Diels–Alder adduct-based rungs.

Discrete boronate ester ladders from the dynamic covalent self-assembly of oligo(phenylene ethynylene) derivatives and phenylenebis(boronic acid)

Reversible boronate ester chemistry enables the controlled, dynamic self-assembly of olig(phenylene ethynylene)s into highly conjugated ladder frameworks.

Solvent processable and recyclable covalent adaptable organogels based on dynamic trans-esterification chemistry: separation of toluene from azeotropic mixtures

New covalent adaptable networks (CANs) possessing processability and recyclability to monomers are desirable as an alternative to traditional plastics to address plastic waste-related issues.