Volume 11 Issue 10, October 2019

Chemistry’s lack of visibility in relation to other disciplines, such as astronomy and life sciences, means it is in danger of becoming the forgotten science. How can chemists discuss their work with the public so that we retain our position as the central science for future generations?

Michelle Francl wonders if there is a risk to making yourself at home in the lab.

Frank–Kasper phases are topologically close-packed structures typically found in ordered mixtures of ‘hard particles’ such as metallic alloys. Now, a shape amphiphile has been shown to self-assemble into a Frank–Kasper Z phase, which had so far remained elusive in soft materials.

The biosynthetic pathway that produces the structurally uncharacterized gut bacterial genotoxin colibactin can produce unstable, macrocyclic products; however, the extent to which these structures contribute to colibactin’s biological activities is not yet fully understood. Now, two recent studies have provided new insights and reached distinct conclusions regarding their potential mechanisms of action and relevance for genotoxicity.

To celebrate the centenary of the International Union of Pure and Applied Chemistry in July 2019, the 47th IUPAC World Chemistry Congress took place in Paris. Its programme reflected how chemistry can help to address today and tomorrow’s most challenging issues, in particular, those relevant to human well-being and sustainable development.

The shape complementarity between the active site of a catalyst and a substrate influences how effectively a reaction can be catalysed. Computational tools can be used to visualize the shape around the active centre of a range of catalysts and the application of such approaches to rationalize the behaviour of known catalysts — and to design new ones — is discussed.

Colibactin is produced by human enterobacteria and assumed to be a gut bacterial genotoxin. Now, colibactin-645 has been identified as a macrocyclic colibactin metabolite that contains a C-terminal 5-hydroxy-4-oxazolecarboxylic acid moiety and induces DNA double-strand breaks in vitro and in human cell cultures via a unique copper-mediated oxidative mechanism.

Precolibactin 886 is a complex microbiome-derived metabolite implicated in colorectal cancer and produced by the clb gene cluster. A chemical synthesis and analysis of precolibactin 886 is reported which shows that its biosynthetic precursor degrades to other known clb metabolites. The data also provide insights into the structures and reactivity of advanced clb products.

The Z phase, one of three fundamental Frank–Kasper phases—topologically close-packed structures commonly found in metal alloys—is associated with a relatively large volume ratio between its constituents. This means it is typically not formed in single-component soft materials. Now, a shape amphiphile has been shown to self-assemble in a variety of unconventional structures, including the Z phase.

Enacyloxin IIa is an antibiotic, assembled by a modular polyketide synthase, with promising activity against the Gram-negative bacterium Acinetobacter baumannii. Now, it has been shown that the enacyloxin IIa polyketide chain is released via transfer to a separately encoded carrier protein by a non-elongating ketosynthase domain, followed by condensation with 3,4-dihydroxycyclohexane carboxylic acid by a non-ribosomal peptide synthetase condensation domain.

The antibiotic enacyloxin IIa is assembled by a modular polyketide synthase, and released from it by condensation of the enacyloxin acyl chain with 3,4-dihydroxycyclohexane carboxylic acid. A multipronged approach shows the structural basis for recognition between the peptidyl carrier protein domain that bears the acyl chain and the non-ribosomal peptide synthetase condensation domain that ligates it with the carboxylic acid.

Polyacetylene is an ideal system to probe to gain a better understanding of the nature of charge transport in conducting polymers. Now, individual atomically precise polyacetylene chains have been synthesized on a copper surface and characterized using a range of techniques, revealing a doping-induced semiconductor-to-metal transition.

Polytheonamides are potently cytotoxic hypermodified ribosomal peptides that are produced by an uncultivated bacterium. Now, a bioinformatic mining strategy has enabled the development of a bacterial production host that can be cultivated in a laboratory. The host generates polytheonamide-like compounds within 2 days, and can efficiently introduce multiple d-amino acids, asparagine N-methylations and C-methyl groups into various peptides.

Previous methods for functionalizing hydrocarbons with CO₂ to form carboxylic acid derivatives have required stoichiometric energy-intensive reagents such as strong bases or electrophilic activators. Now, a simple solid base has been developed that transforms aromatic hydrocarbons, CO₂ and methanol into aromatic esters via a two-step cycle requiring no additional reagents.

Difluorocarbene transfer is mostly limited to reactions that utilize its intrinsic electrophilicity. Now, a controllable palladium-catalysed difluorocarbene transfer reaction is reported that involves nucleophilic and electrophilic palladium difluorocarbene species. The selective reactions between arylboronic acids and the difluorocarbene precursor BrCF₂PO(OEt)₂ give four different products—difluoromethylated and tetrafluoroethylated arenes and their corresponding fluoroalkylated ketones.

Asymmetric autocatalysis—such as that observed experimentally in the Soai reaction—may have been responsible for the origin of biological homochirality. The magnitude of the energy imbalance required to induce directed symmetry breaking and asymmetric amplification in the Soai reaction has now been identified and compared to the parity violation energy difference.