Volume 7 Issue 12, December 2015

The quantitative self-assembly of mechanically interlocked molecules in water, instead of organic solvents, opens up the possibility of such systems being used in a biological context where their functions can be interfaced with biomolecular systems.

Vision is initiated by photoisomerization of 11-cis retinal in the visual pigment rhodopsin — a fast and efficient process. Spectroscopic studies now demonstrate that the transition from the reactant photoexcited-state to the ground-state photoproduct, which mediates this important reaction, occurs on a sub-50-fs timescale and is vibrationally coherent.

Racemic or enantiomerically pure alcohols can be converted with high yield into enantiopure chiral amines in a one-pot redox-neutral cascade process by the clever combination of an alcohol dehydrogenase and an appropriate amine dehydrogenase.

Catalytic methods are among the most valuable tools for sustainable synthesis. Domino catalysis enables multiple reactions to be combined so that synthetic efficiency may begin to approach that of nature, but significant challenges remain before this promising approach can fulfil the needs of pharmaceutical and materials chemistry.

Synthetic vaccines offer one method to avoid the drawbacks associated with vaccines derived from whole organisms. This Perspective highlights the improvements and significant recent progress that has been achieved in developing well-defined synthetic vaccines using a variety of molecular antigens.

Uncertainty associated with solution-based electron-transfer studies of DNA–metal-complex systems has now been overcome by combining X-ray and time-resolved infrared data obtained for ruthenium polypyridyl–DNA crystals. Using these methods both the geometry of the reaction site and the kinetics of the reversible photo-induced one-electron oxidation of guanine have been determined.

Copper is a transition metal ion essential for the regulation of cellular oxidative stress and ATP production. Now, the inhibition of copper-trafficking proteins by a small molecule has been shown to significantly reduce proliferation of cancer cells. The results indicate that copper-trafficking proteins could represent new anti-tumour therapeutic targets.

The isomerization of the retinal chromophore of rhodopsin is the photochemical process that initiates the sense of vision. Now, heterodyne-detected transient grating spectroscopy has been used to resolve coherent vibrational dynamics during this process, helping to identify strictly local vibrational motions as the origin of the coherent surface crossing, which occurs on a sub-50-fs timescale.

A manganese catalyst is reported that aminates C–H bonds via a mechanism that lies between that of reactive noble metals (concerted) and chemoselective base metals (stepwise). Rather than exhibiting intermediate reactivity and selectivity, [Mn(^tBuPc)] is an outlier, and aminates all C(sp³)–H bonds, including 1°, while remaining tolerant of oxidizable π-functionality.

[Fe]-hydrogenase has an iron-guanylylpyridinol cofactor and catalyses the reversible hydrogenation of a methenyl-tetrahydromethanopterin. Now, [Fe]-hydrogenase has been reconstituted using synthetic cofactor mimics. The enzyme containing a mimic with a 2-hydroxy-pyridine group was active, whereas one containing a 2-methoxy-pyridine group was inactive. This result, together with DFT computations, supports a catalytic mechanism involving the deprotonated pyridinol hydroxy group as a proton acceptor.

Purely organic molecules with complex interlocked architectures have proved difficult to prepare in water. Now, a three-dimensional organic [2]catenane has been obtained in a weakly acidic aqueous solution, through an almost quantitative self-assembly process relying on dynamic hydrazone linkages. The catenane is kinetically stable in neutral and weakly basic environments.

The functionalization of primary amines by C–H activation is often hindered by their strong metal-coordinating properties. Now, a steric tethering approach — which temporarily converts amino alcohols into hindered secondary amines — has been developed. The approach allows these amino alcohols to be transformed into structurally complex and diverse products using palladium-catalysed aliphatic C–H activation.

Oxynitrides are garnering interest because of their variety of novel properties, but their synthesis has typically involved highly reducing conditions that put significant constraints on their composition, structure and properties. Now, the lability of H⁻ in perovskite oxyhydride BaTiO_3−xH_x has enabled H^–/N^3– exchange at a lower temperature, yielding a ferroelectric oxynitride BaTiO_3−xN_2x/3.

α-Substituted-β-hydroxy ketones are valuable intermediates, but their preparation by alkylation of enolates is difficult with hindered electrophiles. Now, a direct method for preparing α-substituted-β-hydroxy ketones — including those having α-quaternary centres — by addition of Grignard reagents to epoxyhydrazones has been developed, enabling the stereocontrolled incorporation of a wide range of carbon based substituents.

Impure glycerol is obtained as a significant by-product of biodiesel production. Now it is shown that this crude glycerol can be reacted with water over very simple basic or redox oxide catalysts to produce methanol in high yields, together with other useful chemicals, in a one-step low pressure process.

Iulia Georgescu explains why rubidium is atomic physicists' favourite chemical element.