Volume 10 Issue 7, July 2018

Michelle Francl dusts off Pauling’s notes on bonding to explore the illusory link between electron promotion and hybridization.

Ghotas Evindar, Chemistry Group Leader at GlaxoSmithKline, talks with Nature Chemistry about the advantages of using encoded libraries in drug discovery and the challenges these technologies present.

Certain drug targets have been deemed undruggable because of the difficulty in finding pharmacologically useful inhibitors. Now, two teams have developed exciting technologies for the creation of diverse collections of macrocyclic molecules and have demonstrated their usefulness for discovering macrocyclic inhibitors.

Sodium chloride phases with unconventional non-1:1 stoichiometries are known to exist under high-pressure conditions. Now, Na₂Cl and Na₃Cl two-dimensional crystals have been obtained under ambient conditions, on graphene surfaces, from dilute solutions.

Amino acids have now been used as chemical inputs to provide control over self-assembly in semiconducting structures. This approach enables temporal control over the formation of nanostructures and consequently control over their transient electronic conductivity.

A second-generation DNA-templated library of 256,000 small-molecule macrocycles has been developed. The improved method was created by streamlining and integrating multiple aspects of DNA-encoded and DNA-templated library synthesis methodology. In vitro selection of the macrocycle library against insulin-degrading enzyme enabled the discovery of potent inhibitors.

Crosslinking within peptides containing two pairs of cysteines to form chemical bridges has now been shown to provide rapid access to thousands of different macrocyclic scaffolds in libraries that are easy to synthesize, screen and decode. Applying this strategy to phage-encoded libraries yielded binders with remarkable affinities despite the small molecular mass.

Nearly two decades after its discovery, the Ru(II)-catalysed C–H arylation of N-chelating aromatics with aryl halides was reinvestigated and a new key reaction intermediate was uncovered. A thorough mechanistic elucidation has now led to the development of a new class of catalysts with unique efficacy towards late-stage arylation of ‘real-world’ compounds.

Living systems rely on externally tuneable and stimuli-responsive conformational changes of proteins and protein assemblies for a wide range of essential functions. A combination of experimental and computational analyses has now enabled the fabrication of a rationally designed, synthetic, stimuli-responsive protein assembly through modulation of its free-energy landscape.

Biominerals feature unique and potentially useful three-dimensional structures but are often difficult to transform into functional materials. Now, a two-step ion exchange/insertion reaction has been shown to convert synthetic carbonate salts and calcium carbonate biominerals into lead halide perovskites with tunable optoelectronic properties while preserving the shapes and microstructures of the precursors.

Gene expression profiling remains cost-prohibitive and challenging to implement in a clinical setting. Now, a molecular computation strategy for classifying complex gene expression signatures has been developed. Classification occurs through a series of molecular interactions between RNA inputs and engineered DNA probes designed to implement a relevant linear classification model.

Metal-catalysed enantioselective fluorination of C(sp³)–H bonds is an attractive method for preparing chiral organofluorines, but the challenge of achieving both enantioselectivity and reductive elimination selectivity remains unsolved. Now, it has been demonstrated that a chiral amino amide transient directing group can serve as a ligand for a palladium catalyst that promotes both enantioselective C(sp³)–H insertion and C(sp³)–F-selective reductive elimination.

Multi-electron redox reactions are kinetically sluggish; however, plasmonic nanoparticles have shown promise as multi-electron reduction catalysts. Now, the principles that govern the harvesting of multiple electron–hole pairs from plasmonically excited gold nanoparticle photocatalysts are elucidated, providing a general foundation for the plasmonic catalysis of challenging multi-electron, multi-proton chemistry, such as N₂ fixation and CO₂ reduction.

Enzymes are powerful catalysts for chemical synthesis because they are capable of providing unparalleled levels of selectivity; however, in nature they only catalyse a limited collection of reactions. Now, it has been shown that non-natural reactions that proceed via free-radical intermediates can be catalysed with high selectivity by using an exogenous photoredox catalyst in conjunction with enzymes.

The common form of salt has a 1:1 ratio of Na⁺ and Cl⁻; however, species that deviate from this can be found under extreme conditions, such as high pressure. Now, as a result of cation–π interactions that promote ion–surface adsorption, Na₂Cl and Na₃Cl have been observed as two-dimensional crystals on graphene at ambient conditions.

The implications of coherence signals for the transfer of energy within the Fenna–Matthews–Olson complex of photosynthetic green sulfur bacteria is a well debated topic. Now, polarization-controlled 2D spectroscopy — aided by vibronic exciton modelling — has enabled the characterization of all such coherences and determination of their physical origins; while electronic coherences dephase extremely rapidly, ground- and excited-state vibrational coherences dominate.

A new concept for targeted drug delivery based on enrichment triggered prodrug activation has been developed. Without enrichment, the activation reaction is sluggish; however, following enrichment, the increased concentration enhances the activation reaction rate, thereby leading to the release of the payload. The same approach can be used in antibody–drug conjugate applications.

Kit Chapman explores the voyage to the discovery of element 118, the pioneer chemist it is named after, and false claims made along the way.