Volume 6 Issue 12, December 2014

Rotaxanes with cyclodextrin end groups have been used as a platform to investigate anion binding in water, revealing that halogen bonding can serve as the basis for molecular recognition in aqueous solvents, which may have implications in medicinal chemistry and beyond.

Oxidation of 5-methylcytosine has been proposed to mediate active and passive DNA demethylation. Tracking the history of DNA modifications has now provided the first solid evidence that 5-hydroxymethylcytosine is a stable epigenetic modification.

Molecular simulations have the potential to give valuable insights into experimental results, but can be limited by the time- and length-scales they can simulate. Now, reactive chemistry can be driven through a novel simulation approach, which could have ramifications for many research areas, including astrobiology and the origins of life.

Lignin is an abundant renewable resource, but its intrinsic recalcitrant nature has so far hampered its conversion into higher value chemicals. Now, a two-step strategy, oxidation followed by bond cleavage, has been shown to deconstruct lignin into high yields of low-molecular-weight aromatics.

Enhancing the structural diversity of peptide natural products relies on synthetic modifications that are typically not chemo- or regioselective. A nonribosomal peptide synthetase has now been engineered to incorporate a non-natural amino acid containing a reactive bio-orthogonal handle.

The ability to achieve strong molecular recognition in water is a key challenge for supramolecular chemistry. Now, halogen bonding — the attractive interaction between an electron-deficient halogen atom and a Lewis base — has been shown to be superior to hydrogen bonding for strong anion binding in water. Ripple image: © PhotoDisc/Getty Images.

Computational chemistry is traditionally used to interpret experimental findings. Now its use in reaction discovery is described with the development of the ab initio nanoreactor — a highly accelerated, first-principles molecular dynamics simulation of chemical reactions that discovers new molecules and mechanisms without preordained reaction coordinates or elementary steps.

Reduction of 5-hydroxymethylcytosine (hmC) levels in DNA often occurs in cancers. Using isotope tracing experiments, this epigenetic DNA modification, which was thought to be an intermediate of demethylation, is now shown to be stable. A delay in the generation of hmC on newly synthesized DNA is responsible for the reduction of hmC levels in cancers.

Kinetic, X-ray crystallographic and computational studies have enabled the formulation of a comprehensive mechanistic picture of the enantioselective sulfenofunctionalization reaction of alkenes and a stereochemical model for the origin of the enantioselectivity. The experiments resulted in the development of 2,6-dialkylaryl sulfenylating agents, improving the enantioselectivity of the reaction to >99:1 for γ-alkenols.

A protein has been engineered so that 24 identical copies self-assemble into a cube-shaped hollow cage 23 nm in diameter and containing a 130-Å-diameter inner cavity. This represents the largest and most porous structure of its type so far.

Natural products provide a rich source of leads for drug discovery. Now, a computational method is available that can be used to identify the macromolecular targets of these compounds. Much like medicinal chemists' reasoning, the software infers target information by comparing the substructures with those of drugs and other natural products with known targets.

Transferring molecular motion to macroscopic shape change of a crystal has potential application in actuators, or ‘artificial muscles’. Now, a single crystal of a Ni complex has been shown to exhibit a large, abrupt, temperature-induced crystal expansion/contraction near room temperature. The crystal deformation is induced by a collective 90° rotation of oxalate anions in the complex.

The use of β-lactam antibiotics is severely threatened by metallo-β-lactamases (MBLs), which contribute to the development of resistance. Now, crystallographic and solution studies reveal that recently reported MBL inhibition with a rhodanine can be attributed to fragmentation and complex formation with the resulting thioenolate.

The mechanism of O₂ reduction in aprotic solvents is important for the operation of Li–O₂ batteries but is not well understood. A single unified mechanism is now described that regards previous models as limiting cases. It shows that the solubility of the intermediate LiO₂ is a critical factor that dictates the mechanism, emphasizing the importance of the solvent.

Selective pyridine dearomatization processes traditionally use precious metal catalysts with reagents in stoichiometric excess, and are not well-understood mechanistically. Now, efficient 1,2-regioselective pyridine dearomatization is achieved using equimolar pinacolborane and an earth-abundant lanthanide catalyst. Mechanistic and theoretical studies elucidate the reaction mechanism and explain observed reactivity trends.

Trick cutlery and mobile phones have one peculiar element in common, as Marshall Brennan explains.