Volume 6 Issue 6, June 2014

Nature assembles complex natural products using bifunctional building blocks and a mere handful of reaction types. Mimicry of this method seeks to revolutionize natural product and small-molecule synthesis.

Many of the rate parameters used in models of tropospheric chemistry are obtained through laboratory ozonolysis experiments. Now, results on the self-reaction of an important, but long-elusive, intermediate could alter many of those inferences.

The controlled synthesis of two-dimensional carbon nanomaterials enables their properties to be tailored for potential device applications. Functionalized graphene-like nanosheets with controlled thickness have now been obtained by irradiating monolayers of carbon-rich molecular precursors at room temperature.

The lomaiviticins are exceedingly potent antibiotic agents, but the mechanism responsible for this activity has so far been unclear. Now, efficient generation of double-strand breaks in DNA by lomaiviticin A has been linked to the remarkable cytotoxicity of these diazobenzofluorene-containg natural products.

Borinium ions are difficult to isolate due to the extreme electron deficiency of the boron atom. Now, a unique two-coordinate linear dimesitylborinium cation has been synthesized that impresses with extraordinary Lewis acidity and oxophilicity.

Carbonization of a self-assembled monolayer of a hexayne amphiphile at the air/water interface at room temperature results in the formation of functional carbon nanosheets. The nanosheets exhibit a molecularly defined thickness, are mechanically self-supporting over several micrometres, and have macroscopic lateral dimensions on the order of centimetres.

Criegee intermediates play an important role in atmospheric chemistry but their direct study has proved difficult. Transient infrared absorption spectroscopy has now been used to probe the decay kinetics of the Criegee intermediate CH₂OO directly, revealing that its self-reaction is extremely rapid. This may have important consequences for the interpretation of previous laboratory experiments.

Polyene motifs are found in a large number of natural products. Now, by applying a general retrosynthetic algorithm, it has been shown that the polyene motifs found in >75% of these compounds can be synthesized using just 12 bifunctional haloalkenyl MIDA boronate building blocks and one coupling reaction.

Understanding the process of exciton fission, which occurs in certain organic materials, could lead to the development of more efficient photovoltaic devices. Here, an expression derived from first principles is used to accurately characterize the singlet fission rate of a wide array of materials, reproducing a transition from weak to strong coupling as a function of molecular separation.

Borinium ions are two-coordinate boron cations that contain only four valence electrons on boron, and are difficult to isolate without electron donation from adjacent heteroatoms. Now, diarylborinium salts with no lone-pair donation from heteroatoms have been isolated, characterized and found to participate in an unusual reaction with CO₂.

(−)-Lomaiviticin A inhibits the growth of cancer cells at nanomolar to picomolar concentrations; however, the basis for this potent cytotoxicity is not known. This natural product has now been shown to induce production of DNA double-strand breaks at nanomolar concentrations. Evidence demonstrates that strand cleavage proceeds via reactive carbon-centred free radical intermediates.

Soft materials that can undergo a macroscopic change in response to external stimuli may prove useful for a range of biological applications. Now, it has been shown that hydrogels encapsulating active enzymes can undergo a gel–sol transition in the presence of a range of small-molecule triggers and can potentially be used as sensors or drug-delivery systems.

Controlling the self-assembly of small molecules within living animals is complicated because of the complex and dynamic nature of the physiological environment. Here, a strategy for directing in situ self-assembly of small molecules into fluorescent nano-aggregates in living mice is demonstrated. The nano-aggregates can be used for imaging caspase-3/7 activity in human tumour xenograft mouse models.

A hybrid protocell model is described in which a fatty acid membrane spontaneously assembles on the surface of coacervate microdroplets with molecularly crowded interiors. The membrane-enclosed protocells exhibit uptake and exclusion properties that differ from the uncoated droplets. The internal structure can be disassembled at high ionic strength without loss of membrane integrity. This model may help to reconcile alternative mechanisms of prebiotic compartmentalization.

Colloidal inverse bicontinuous cubic mesophases have now been formed by self-assembly of amphiphilic dendritic-linear block copolymers in solution. The internal networks of water channels provide a high surface area with tunable functional groups that can serve as anchoring points for macromolecular guests such as proteins and enzymes.

The biosynthesis of lipid mediators has not previously been identified in mitochondria. Here, polyunsaturated cardiolipins are shown to be oxidized in the mitochondria by cytochrome c. Subsequent hydrolysis of these oxygenated species generates a variety of oxygenated fatty acids as well as non-oxygenated and oxygenated lyso-cardiolipins. These reactions represent a new biosynthetic pathway for the production of lipid mediators.

John Arnold, Thomas L. Gianetti and Yannai Kashtan look back on thorium's chemistry, and look forward to harnessing its nuclear potential.