Volume 15 Issue 6, June 2023

Dipolar cycloadditions are excellent processes for generating heterocyclic systems from simple starting materials, but arenes as dipolarophiles have not been extensively explored. Now, the intramolecular dipolar cycloaddition of aromatic rings has been achieved using in situ generated diazoalkenes to produce bicyclic or tricyclic heterocycles.

Constructing aptamers with desired target-binding affinities may lead to new applications but is challenging. Now, a new method using a high-dimensional microfluidic approach enables quantitative isolation of aptamers with programable binding affinities.

From humans designing machines, to machines designing biology, deep learning is turning the tables for assisted exploration of biologically active and diverse protein designs. Now, a deep-learning-based strategy has been used to design artificial enzymes that catalyse a light-emitting reaction.

Complexity is a hallmark of biological systems, but scientific experiments are typically conducted in simplified conditions. Now, diverse polymers that mimic the local environments of complex biological mixtures have been shown to improve protein folding, stability and function.

Catenanes that are chiral owing to the relative orientation of their rings have always been referred to as ‘topologically chiral’. It is now shown that although in specific cases the stereochemistry is a topological property of the structure, the underlying stereogenic unit itself is not inherently topological in nature.

Bioresponsive hyperpolarized probes contain magnetic resonance signals that can be many orders of magnitude larger than those of common, thermally polarized probes. This Perspective discusses how bioresponsive hyperpolarized probes can be directly linked to biological events to give functional information, enabling the mapping of physiological processes and diseases in real time using magnetic resonance.

1,3-Dipolar cycloadditions are well-known transformations in organic synthesis. However, the reactivity of benzene rings in these processes is underexplored. In situ-generated diazoalkenes have now been shown to undergo intramolecular 1,3-dipolar cycloadditions with aromatic rings. The transformation results in an unaromatized benzene ring that enables the synthesis of functionalized heterocycles.

Generating aptamers for use as affinity reagents in analytical applications is important, but SELEX, the standard method for aptamer generation, is unable to select for pre-defined binding affinities. Now, by combining efficient particle display, high-performance microfluidic sorting and high-content bioinformatics, the method ‘Pro-SELEX’ can afford the quantitative generation of aptamers with programmable binding affinities.

Catenanes are topologically non-trivial and, perhaps for this reason, molecules composed of two oriented rings have always simply been referred to as ‘topologically chiral’. Now it has been shown that the same stereogenic unit can arise in systems whose stereochemistry is Euclidean, suggesting a need to rethink this fundamental form of mechanical chirality.

Indole-5,6-quinone (IQ) is a long-sought intermediate and structural subunit of eumelanin pigments whose instability has precluded isolation and characterization. It has now been shown that a sterically shielded derivative of IQ exhibits hallmark eumelanin properties, including near-infrared absorption, ultrafast nonradiative decay and a persistent semiquinone radical formed by comproportionation.

Photochemical reduction of CO₂ is a significant challenge and many existing methods use catalysts containing rare metals. Now a metal-free version of this reaction—with high selectivity for formate generation over H₂ or CO—has been achieved that features a combination of carbazole photosensitizer and organohydride catalyst.

Precise analysis of DNA–protein interactions can help to better understand various biological processes. Now, the ‘light-induced lysine (K) enabled crosslinking’ strategy (shortened to ‘LIKE-XL’) has been developed for spatiotemporal and global profiling of DNA–protein interactions, affording the discovery of low-affinity interactions between transcription factors and DNA using sequence-specific DNA baits.

Methods for the direct construction of 1,3-disubstituted planar chiral ferrocenes are elusive. Now, a modular platform enables the construction of planar chirality in 1,3-disubstituted ferrocenes/ruthenocenes via enantioselective relay remote C–H arylation. The strategy involves an initial enantiodetermining ortho-C‒H activation enabled by a Pd(II)/chiral amino-acid ligand, followed by relay to the remote meta-position by a bridgehead-substituted norbornene mediator.

The synthesis of two-dimensional nanostructures with controlled dimensions from polymeric precursors remains challenging. Now, two-dimensional nanoparticles with chemically different spatially defined cores have been fabricated through seeded growth and are shown to undergo a programmable degradation process.

Large biomolecules cannot be loaded into conventional Janus nanoparticles with small mesopores, preventing the establishment of efficient logic-gate systems in single Janus nanoparticles. Now, an emulsion-oriented assembly approach has been shown to fabricate Janus double-spherical nanoparticles with dual-tunable mesopores, enabling the design of various single-particle-level logic systems.

Covalent organic frameworks (COFs) have remained difficult to grow as single crystals. Now, amphiphilic amino-acid derivatives that assemble in micelles in aqueous solutions have been shown to promote the growth of a variety of imine-bridged COFs into single crystals, in a step-by-step fashion, within their hydrophobic compartment.

Continuous-rotation 3D electron diffraction is a powerful technique to determine structures from nanocrystals. A data treatment method that takes into account dynamical diffraction effects has now been shown to lead to more accurate structure models, better sensitivity to weak signals and a reliable determination of absolute configuration—even for materials containing only light atoms.

Polyhydroxyalkanoates are potential substitutes for non-degradable polyolefin plastics. Now, it has been shown that structurally related methylated polyhydroxybutyrates, synthesized from carbon monoxide and 2-butenes, can provide a full suite of polyolefin-like polymers. These materials can be recycled or upcycled, and their properties can be easily tuned by varying the cis/trans ratio of the starting materials.

Functionalization of unsymmetrical internal alkenes usually takes place with low regioselectivity, giving a mixture of isomers. Now, a highly regio- and enantioselective remote 1,n-dioxygenation of internal alkenes using a palladium catalyst has been developed for the synthesis of chiral 1,n-diols. Regioselectivity tuning was demonstrated by altering the rate-determining step, enabled by the phenyl-substituted Pyox ligand.

A simple and general enantioselective method for the synthesis of non-fused lower carbo[n]helicenes (n = 4–6) is reported. The helicene scaffold is constructed with high enantioselectivity by Pd⁰-catalysed C–H arylation with aryl bromides. A bifunctional ligand provides a precise chiral environment that allows fine control of the enantioselectivity.

Rajeev K. Dubey and Frank Würthner discuss the colourful character of perylene bisimides and the impact of aggregation on their functional properties.