Research articles

Despite numerous potential applications, the development of light-responsive solid materials based on molecular photoswitches is impeded by the low efficiency of photoisomerization in the solid environment. Now a robust, solid porous material made from tetraphenylmethane and a photoswitchable overcrowded alkene exhibits nearly quantitative photoisomerization in the bulk and in photomodulation of gas uptake.

In contrast to the variety of stable carbonyl complexes of group 7–12 metals, few are known for group 3–5 metals; among those, cations have only been identified in the gas phase or by matrix isolation. Now, several unusual niobium and tantalum carbonyl compounds have been prepared as bulk crystalline compounds, including heptacarbonyl salts and the neutral ditantalum dodecacarbonyl.

The synthesis of chiral amino alcohols from simple alcohol starting materials can be achieved through a catalytic, asymmetric radical relay. Multiple catalysts work in concert to harness a H-atom transfer mechanism to enable enantio- and regioselective C–H amination by transient N-centred radicals.

Conventionally, urea is synthesized via two consecutive processes, N₂ + H₂ → NH₃ followed by NH₃ + CO₂. Now, an electrocatalyst consisting of PdCu alloy nanoparticles on TiO₂ nanosheets has been shown to directly couple N₂ and CO₂ in H₂O to produce urea under ambient conditions.

Single-atom catalysts maximize metal atom efficiency and exhibit properties that can be considerably different to their nanoparticle equivalent. Now a general host–guest strategy to make various single-atom catalysts on nitrogen-doped carbon has been developed; the iridium variant electrocatalyses the formic acid oxidation reaction with high mass activity and displays high tolerance to CO poisoning.

Site-selective functionalization of nearly identical C–H bonds has been a long-standing challenge. Now, a regioselective C–H amination has been achieved by [Cp^xIr(iii)] catalysis, which senses subtle electronic differences of allylic C–H bonds induced by remote electron-withdrawing groups. A linear correlation between Δ¹J_CH and ΔΔG^‡ is found, leading to predictable regioselectivities.

The mechanism of nucleation for α-synuclein (α-Syn) aggregation and amyloid formation in Parkinson’s disease is unclear. Now, α-Syn has been shown to undergo liquid–liquid phase separation and a liquid-to-solid-like transition leading to amyloid fibril formation. This raises the possibility that liquid–liquid phase separation is a key pathogenic mechanism behind α-Syn aggregation in Parkinson’s disease.

A ruthenium-catalysed multicomponent reaction provides rapid and tunable access to 1,3-dienyl-6-oxy polyketide motifs. An initial alkene–alkyne coupling produces unsymmetrical 3-boryl-1,4-dienes. Allylation of aldehydes and ketones with these products is highly diastereoselective and results in the formation of two carbon–carbon bonds, two stereodefined olefins and up to three contiguous sp³ stereocentres.

Despite the importance of C–H methylation in medicinal chemistry, the application to densely functionalized complex molecules remains a challenge. Now, a novel cobalt-catalysed method takes advantage of inherently present functional groups to guide the C–H activation and a boron-based methyl source enables the late stage C–H methylation of pharmaceutically relevant substrates.

Non-canonical amino acids (ncAAs) can be incorporated into proteins in cells using orthogonal aminaocyl–tRNA synthetase/tRNA pairs; the most widely adopted system is based on a pyrrolysyl–tRNA synthetase (PylRS)/tRNA pair. Now, three new PylRS/tRNA pairs have been developed that are mutually orthogonal and can be used together to site-specifically incorporate three distinct ncAAs into a single protein.

Proteins that interact with histone post-translational modifications have now been identified using an approach based on split-intein mediated histone semisynthesis. Histone modifications and disease-relevant mutations were installed into native chromatin with an adjacent photocross-linker to enable in situ cross-linking. This strategy enabled the determination of chromatin-relevant interactomes and represents a powerful tool for exploring epigenetic regulation and dysregulation at the molecular level.

A naturally occurring stand-alone and intermolecular Diels–Alderase, MaDA, has been identified from Morus alba cell cultures. MaDA is a FAD-dependent enzyme, which catalyses the intermolecular [4+2] cycloaddition via a concerted but asynchronous pericyclic pathway between morachalcone A and a diene generated from moracin C. Characterization revealed that MaDA possesses good substrate promiscuity towards both dienes and dienophiles.

Water plays an active role in modulating guest recognition by both artificial and biological hosts, but how this role can be controlled is unclear. Now, the de-wetting of the non-polar pockets of cavitands is shown to be affected by the orientation of methyl groups encircling the portal, which moderate the enthalpic and entropic contributions driving recognition.

Oxygen is a potent inhibitor of radical polymerization reactions, but the facultative bacterium Shewanella oneidensis has now been shown to facilitate aerobic radical polymerizations by first consuming dissolved oxygen and then directing extracellular electron flux to a metal catalyst. Aerobic polymerization activity is dependent on the S. oneidensis genotype and can be initiated using lyophilized or spent cells.

Scattering experiments in which two beams nearly co-propagate allow broadly tunable collision energies and can enable cold collisions. Now, such experiments have been combined with the preparation of NO molecules using stimulated emission to generate highly vibrationally excited states for state-to-state scattering studies, testing the theoretical gold standard in a regime not found in nature.

Metallacycles formed from two large, under-coordinated actinide M^IV cations and two rigid arene-bridged aryloxide ligands are capable of binding dinitrogen inside their cavity. These f-block complexes can catalyse the reduction and functionalization of dinitrogen as well as the catalytic conversion of molecular dinitrogen to a secondary silylamine.

The distortion of an amide group away from a planar conformation typically enhances its reactivity and such activation is usually achieved through the chemical synthesis of twisted amides. Now, it has been shown that a non-covalent activation strategy leading to accelerated hydrolysis can be achieved by binding a reactive twisted amide conformer inside a molecular cage.

The photoinduced dimerization of a prochiral anthracenecarboxylic acid occurs in an enantioselective fashion when the molecules are adsorbed on helical metal nanostructures. This enantiopreference arises mostly from the helicity of the silver and copper substrates—prepared using shear forces during the deposition process—and may also be influenced by chiroplasmonic effects.

Compounds of main-group elements rarely undergo direct carbonylation reactions. Now, an electron-rich silylene intermediate has been shown to readily react with CO to form a silylene carbonyl complex that is stable at room temperature. This complex engages in CO substitution as well as oxidative addition reactions.

Despite five decades of research, the alkaloid (+)-brevianamide A has remained an elusive target for chemical synthesis. Now, it has been shown that the total synthesis of (+)-brevianamide A can be achieved in seven steps and 7.2% overall yield to give 750 mg of the target compound.