Articles in 2017

Chlorodifluoromethane (ClCF₂H), an inexpensive and abundant industrial raw material, represents an ideal and straightforward reagent for introducing the difluoromethyl group. However, efficient approaches for activation of the typically inert ClCF₂H are limited. Now, ClCF₂H is employed via a difluorocarbene pathway for palladium-catalysed difluoromethylation of arylboronic acids with broad substrate scope.

Ligand development underlies many advances in Pd-catalysed cross coupling but has seen limited application in the growing field of Ni catalysis. Now, a phosphine framework is shown to enable Ni-catalysed Suzuki coupling of acetals. Parameterization studies provide structural insight into ligand success and a quantitative model to facilitate further ligand design.

Lysine-rich peptides from the ribosomal core and derived homolysine decapeptides of either L-, D- or mixed chirality have now been shown to enhance RNA polymerase ribozyme activity at low magnesium concentrations, accelerate ribozyme evolution and enable templated RNA synthesis within membranous protocells.

A dynamic foldamer scaffold has now been ligated to a water-compatible, metal-centred binding site and a conformationally responsive fluorophore to form a receptor mimic that inserts into the membrane of artificial vesicles. Binding of specific carboxylate ligands induces a global conformational change that depends on the structure of the ligand, and can be detected via fluorescence.

Converting oxygen-rich biomass into fuels requires the removal of oxygen groups through hydrodeoxygenation. MoS₂ monolayer sheets decorated with isolated Co atoms bound to sulfur vacancies in the basal plane have now been synthesized that exhibit superior catalytic activity, selectivity and stability for the hydrodeoxygenation of 4-methylphenol to toluene when compared to conventionally prepared materials.

The biomimetic syntheses of bipleiophylline, one of the most complex monoterpene indole alkaloids, and voacalgine A, its biosynthetic precursor, have been achieved from pleiocarpamine starting material. The development of a divergent oxidative coupling for the formation of the benzofuro[2,3-b]indolenine and isochromano[3,4-b]indolenine moieties was key to this accomplishment.

Di- and tripeptide building blocks in which the C-terminus has been converted into an aldehyde are shown to form dynamic chemical networks through imine condensation followed by the formation of cyclic N,N-acetals. The networks exhibit multi-phase growth of prion-like assemblies that template the formation of chain-length-specific peptide-like oligomers.

The development of methods for the site-selective modification of natural products is a topic of contemporary investigation and importance. Now, it has been shown that benzynes produced by the hexadehydro-Diels–­Alder (HDDA) reaction react with many secondary metabolites, with a substantial preference for one of several potential pathways.

Simple peptides are shown to assemble into well-defined amyloid phases with paracrystalline surfaces that can catalyse reactions in an enantioselective manner. Modifying individual amino acids in the building blocks enables the structure of the assembled aggregates, and the reactions that they can catalyse, to be controlled predictably.

Synthetic heterodimers provide a platform to demonstrate molecular design principles of vibronic coupling. Now, it has been shown that quantum beating caused by vibronic coupling can be controlled by packing a structurally flexible heterodimer on single-walled carbon nanotubes. This quantum beating requires a vibration to be resonant with the energy gap between excited states and structural rigidity.

Many properties of polymers are dictated by topology. However, the topology of a macromolecule is typically a static feature after synthesis. Now, an approach to dynamic and transformable macromolecular architecture has been developed. When triggered by an external stimulus, macromolecular topology can be triggered to transform via thermodynamic control.

Electron-transfer-mediated decay (ETMD) is a recently discovered type of electronic relaxation that involves the refilling of a core hole by an electron from a neighbouring species. It has now been observed in LiCl solution, when previously it had only been seen in rare-gas clusters. Spectra generated during ETMD are observed to be sensitive to the immediate environment of the initially ionized ion.

The analysis of complex (bio)molecules by NMR spectroscopy is often complicated by limitations in sensitivity. Now, it has been shown that ¹³C NMR signals are strongly enhanced in solution by resonant microwave irradiation of a nitroxide polarizer. This method exhibits up to one-thousand-fold improvements in sensitivity, which stands to greatly improve the detail with which small molecules and metabolites can be studied.

Cation–π interactions are critical for the adhesion proteins of marine organisms, yet the energetics of cation–π interactions in underwater environments remains uncharted. Nanoscale force measurements and NMR spectroscopy reveal that interfacial confinement fundamentally alters the energetics of cation–π mediated assembly.

The properties of discrete species can sometimes be improved by fixing them into extended materials. This strategy has now been applied to silver(I) chalcogenide/chalcogenolate clusters, resulting in a metal–organic framework with enhanced stability and fluorescent sensing capabilities. Crystallographic analysis allows precise structural determination of guest binding, which is responsible for both emission turn-off and multicoloured turn-on.

A scalable, one-pot, solution-based protocol for the controlled synthesis of uniform non-spherical block copolymer micelles is a desirable but challenging target. Now, a polymerization-induced crystallization-driven self-assembly process has been developed that offers facile access to 1D and platelet micelle morphologies and to near monodisperse cylinders of controlled length.

The secondary and tertiary structure of a protein has profound implications on function and catalysis. Now, both the secondary and tertiary structures of a synthetic polymer have been utilized to catalyse the polymerization of N-carboxyanhydrides. Both the folding of the resulting polypeptides into α-helices and their macromolecular organization dramatically enhance the polymerization rate.

Radical SAM enzymes are versatile enzymes catalysing chemically challenging reactions. Now, a radical SAM enzyme that post-translationally modifies ribosomally synthesized peptides to contain D-amino acids has been discovered in Bacillus subtilis, and its mechanism has been deciphered. These peptides, called epipeptides, efficiently inhibit bacterial growth.

Helium is generally recognized as being chemically inert. A thermodynamically stable compound of helium and sodium, Na₂He, has been predicted computationally and then synthesized at high pressure. It exists as an electride, where strongly localized electrons serve as anions located at the centre of Na₈ cubes.

Photoreceptors play an essential role in determining the fate of subsequent biological reactions, however, tracking their structural evolution on ultrafast timescales has been challenging. Now, photoactive yellow protein has been studied using time-domain Raman spectroscopy with sub-7-femtosecond pulses, revealing the ultrafast rearrangement of its hydrogen-bonding structure and also the structure of the first photocycle intermediate.