Volume 15 Issue 11, November 2023

Fluorination strategies are important in assisting the synthesis of pharmaceuticals. Iodine(I/III) catalysis has become particularly useful for installing gem-difluoro groups but is limited to styrenes. Now, the hypervalent iodane-catalysed difluorination of enynes has enabled access to diverse homopropargylic difluorides.

Site-specific modification of RNA in cells is crucial for analysis and functional investigations. Natural enzymes that promote RNA methylation using S-adenosyl-l-methionine (SAM) exist, but leveraging these proteins for RNA modification is limited by cell permeability, stability and specificity of their substrates. Now, a de novo ribozyme that acts on a stabilized and cell-permeable SAM analogue enables site-specific RNA modification with a click handle in living cells.

Gas bubble accumulation at interfaces is a barrier to achieving more efficient electrochemical devices. A clever model system to understand bubble formation during electrochemical hydrogen evolution now reveals similarities between the forces at play during their detachment from the catalyst surface and those involved in wine climbing up a glass.

Open-shell organic molecules with properties that can be modulated by external stimuli are of interest for spintronics applications. Now, an overcrowded alkene with open-shell tetraradical character has been synthesized in which the interaction between the π-conjugated subunits depends on the charge and spin state.

Organic chemists meet biennially to present exciting developments in the realm of synthesis. Thomas Barber discusses the standout themes of this year’s international synthesis in organic chemistry symposium.

An infrared laser-induced temperature jump provides a rapid and broadly applicable perturbation to protein dynamics. Temperature-jump crystallography was paired with time-resolved X-ray crystallography to study the dynamic enzyme lysozyme. Measurements with and without a functional inhibitor revealed different patterns in the propagation of motion throughout the enzyme.

Experimental and computational studies establish the operation of Fe(iii)-based metalloradical catalysis for the asymmetric cyclopropanation of alkenes with different classes of diazo compounds. The reaction proceeds through a stepwise radical mechanism involving α-Fe(iv)-alkyl and γ-Fe(iv)-alkyl radical intermediates. This work provides a future direction for the development of metalloradical catalysis.

Aromatic oligoamide macrocycles have been developed in which the constrained backbone enforces hydrogen-bond donors to orient towards the macrocycle centre, forming a highly electropositive cavity. These macrocycles show strong binding for various anions and can partition into biomembranes to facilitate selective transmembrane anion transport.

Wavepacket dynamics around conical intersections are influenced by geometric phase, which can affect chemical reaction outcomes but has only been observed through indirect signatures. Now, by engineering a controllable conical intersection in a trapped-ion quantum simulator, the destructive wavepacket interference caused by a geometric phase has been observed.

Geometric phase interference has been predicted to appear around conical intersections but has been experimentally illusive owing to competing effects in molecular systems. Now, this effect has been demonstrated in chains of trapped ions using state-of-the-art quantum simulation and read-out techniques.

Hypervalent iodine catalysis remains a powerful method to enable geminal difluoromethylenation of alkenes. However, the scope is mainly limited to styrene derivatives. Now, enynes have been validated as competent substrates where a formal 1,2-shift of the alkyne occurs, thereby enabling highly versatile homopropargylic difluorides to be generated.

Ribozyme-mediated post-transcriptional RNA modification is a powerful method for site-specific RNA labelling and analysis of RNA functions. Now, an alkyltransferase ribozyme—termed SAMURI—has been shown to catalyse the transfer of a propargyl group from a stabilized synthetic S-adenosylmethionine analogue to a specific adenosine on the target RNA within cells.

Although gas bubble dynamics during electrochemical processes dramatically affect performance, the fundamental understanding and manipulation of such dynamics have been limited. Now, electrolyte composition is found to be a key factor in inducing a solutal Marangoni instability that impacts both H₂ gas detachment and coalescence between H₂ microbubbles.

Tetrafluorenofulvalene (TFF) defies conventional rules of bond strength in organic chemistry. In particular, the central alkene bond of TFF becomes stronger in the quintet state and in the tetraanion. These changes arise from the unusual interplay between the twist, aromaticity and spin pairing in the π-electron system of TFF.

Shifts in temperature alter the structure and dynamics of macromolecules. Now, infra-red laser-induced temperature jump is combined with X-ray crystallography to observe protein structural dynamics in real time. Using this method, motions related to the catalytic cycle of lysozyme, a model enzyme, are visualized at atomic resolution and across broad timescales.

Effective synthetic anion receptors are challenging to design. Now, star-shaped macrocycles, with a cavity defined by multiple convergent amide NH and phenyl CH groups, have been synthesized in one pot from their monomeric building blocks. These macrocycles strongly bind a variety of anions, selectively transport chloride across cell membranes and restore the function of cystic fibrosis cells.

Cobalt(II) complexes of porphyrins have dominated the development of metalloradical catalysts. Now it has been shown that five-coordinate iron(III) complexes of porphyrins with an axial ligand are also potent metalloradical catalysts for olefin cyclopropanation. They are shown to react with different classes of diazo compounds via a stepwise radical mechanism.

While chiral hybrid organic–inorganic perovskites are promising materials for optoelectronic applications, the synthesis of three-dimensional single crystals has proven challenging. Now, a general strategy has been shown to synthesize chiral, three-dimensional perovskites by heterogeneous nucleation. The single-crystalline materials contain no chiral component; their chiroptical activity arises from supercells formed by chiral patterns of the A-site cations.

Allostery produces concerted functions of protein complexes by orchestrating the cooperative work between the constituent subunits. By restoring functions of pseudo-active sites that have been lost through evolution, allosteric sites have now been designed into a rotary molecular motor, V₁-ATPase, resulting in its rotation being boosted allosterically.

Scandium is challenging and expensive to isolate in pure form using conventional solvent extraction. Now a covalent organic framework (COF) has been synthesized that can incorporate scandium coordination complexes; subsequent removal of the scandium ions generates open coordination sites, and the resulting ‘metal-imprinted’ COF can be used for highly selective, cyclable scandium capture.

Pump–probe measurements conventionally achieve femtosecond time resolution for X-ray crystallography of reactive processes, but the measured structural dynamics are complex. Using coherent control techniques, we show that the ultrafast crystallographic differences of a fluorescent protein are dominated by ground-state vibrational processes that are unconnected to the photoisomerization reaction of the chromophore.

Most chemoproteomic screening approaches are indirect. Now, a chemoproteomic platform based on chiral sulfonyl fluoride probes has been developed for the direct identification of probe-modified tyrosines and lysines in live cells. Stereoselective modification by structurally diverse probes was observed for 634 tyrosines and lysines across functionally diverse protein sites.

Bicyclic lactones are valuable motifs for the synthesis of natural products and bioactive molecules. Now, a palladium-catalysed protocol has been developed to access unsaturated bicyclic lactones in one step from corresponding carboxylic acids. The method demonstrates reverse site selectivity for C(sp³)–H activation to form diverse bicyclic cores.

Three-protein conjugates, which have so far been produced using protein-engineering strategies, can now be generated using a chemical approach that enables the addition of small-molecule functionality. Checkpoint inhibitory T cell engagers (CiTEs) were assembled and shown to have enhanced in vitro potency compared to a traditional T cell engager.

Didier Astruc surveys the numerous applications of ferrocene, from catalysis to materials and redox-related devices including biosensors and nanomedicine.