Volume 12 Issue 2, February 2020

Bruce C. Gibb takes a look at the dark side of academia and considers a multitude of sins.

It is crucial to replace fossil fuel-based plastics with biodegradable ones that are made from renewable sources. Now, a new generation of bioplastics has been prepared through the stereoselective polymerization of diastereomeric monomers — a synthetic approach that allows tuning of the materials’ toughness, ductility and melting point.

Meroterpenoids are mixed terpenoid–polyketide natural products with a variety of biological activities. Now, a synthetic approach that combines biocatalytic oxidation with a range of other radical-based reactions enables the divergent synthesis of eight oxidized meroterpenoid natural products and one analogue.

Monoclonal antibodies have shown tremendous success in cancer treatment; however, humanization for clinical applications is expensive and not straightforward. Now, molecularly imprinted polymer nanogels have been developed that can block cell-surface proteins and disrupt tumour spheroids.

Synthetic organic chemistry is increasingly automated, data rich and intelligent. At the Automated Synthesis Forum, industry and academia showcased their recent progress towards this augmented future.

Growing polymers directly on surfaces has emerged as a powerful tool because it can provide a route to otherwise inaccessible structures such as defect-free linear chains, graphene nanoribbons and two-dimensional networks. This Review Article describes general principles and key aspects of this method from the perspectives of surface science and polymer chemistry.

High electrical conductivities in metal–organic frameworks—attractive for applications in sensing and energy storage—typically arise in layered MOFs from metal–ligand bonds with strong covalent character. Now, lanthanide-based MOFs have shown high out-of-plane conductivities originating instead from the π-stacking of organic ligands.

Quantum dots functionalized with energy-accepting dyes hold promise for converting low-energy photons into higher-energy visible light for bioimaging, catalysis and solar energy harvesting. Now, it has been shown that non-toxic silicon quantum dots can be used in these systems; the transfer of spin-triplet excitons to molecules at their surface has been observed.

Screening commercial kinase inhibitors for antibacterial activity identified the anticancer drug sorafenib as a major hit. Subsequent structure–activity optimization created a new antibacterial analogue with high potency against methicillin-resistant Staphylococcus aureus, including challenging persisters and biofilms, as well as demonstrating efficacy in an in vivo mouse model. The mode of action involves stimulation of protein secretion and inhibition of menaquinone biosynthesis.

The broad infrared spectrum of water in the OH stretching region shows how significantly a water molecule is distorted when within a hydrogen-bonding network; it also raises the question of what the spectrum of a single OH oscillator would be. Now, the spectral signatures of isolated OH oscillators embedded in cold water cages have been measured using vibrational spectroscopy.

It is difficult to develop suitable fluorescent probes for live-cell nanoscopy, but a general strategy is now reported that can transform regular fluorophores into fluorogenic probes with excellent cell permeability and low unspecific background signals. Using this approach, probes in a variety of colours were developed for different cellular targets and used for wash-free, multicolour, live-cell confocal and STED microscopy.

Meroterpenoids are mixed terpenoid–polyketide natural products that exhibit a range of biological activities. A hybrid synthetic strategy that combines biocatalytic and radical-based methods has now been developed and it enables eight different oxidized meroterpenoids to be made in just 7–12 steps from commercially available materials.

Homogeneous photocatalysts for the conversion and storage of solar energy typically feature separate sensitizer–catalyst assemblies, whereas previous examples of single-chromophore single-molecule photocatalysts are inefficient and do not use significant portions of the visible spectrum. Now a dirhodium single-chromophore single-molecule catalyst has been developed that generates hydrogen using low-energy light through a previously unobserved mechanism.

A stable zinc-based metal–organic framework known to retain its porosity and crystallinity after exposure to moisture has been shown to undergo structural changes at the molecular level on adsorbing water. This dynamic and reversible response to the presence of water, including the rearrangement of bonds, is suggested to be the reason for the hydrolytic stability of this particular metal–organic framework.

The Varkud satellite ribozyme, which catalyses site-specific RNA cleavage and ligation, is an important model to understand RNA catalysis. Now, a combination of theoretical and experimental work has revealed new details about its catalytic mechanism. Mg²⁺ is shown to play an important role in organizing the active site, and the proton transfers in the transition state have also been identified.

Carbon capture technologies are poised to play an important role in reducing CO₂ emissions to mitigate global warming, but their cost prevents their extensive use. Now, CO₂ capture and utilization have been combined using a triple-level dynamic combinatorial approach. CO₂ was spontaneously captured by industrial polyamines to create libraries of ligands that can be used for the separation and recovery of metals.

Gaining a better understanding of the complex electronic structure of single-molecule magnets is essential for their design and development. The 4f-electron density distribution of a dysprosium single-molecule magnet has now been experimentally determined using synchrotron diffraction data interpreted with a multipole model. The magnetic easy axes were recovered by analysis of the 4f-electron density shape, which is clearly oblate.