Remarkably different selectivity can be obtained in the reaction of silicon enolates with α,β-unsaturated aldehydes by swapping the classically used Lewis acid catalysts for in situ-generated silicon Lewis acids, say Japanese scientists.
Read more about the conditions used by Takeo Taguchi and colleagues (Tokyo University of Pharmacy and Life Sciences) in their communication, free to access online until 22nd November.
Interactions that control the molecular ordering of fullerene are rare. This is a problem for scientists designing fullerene-based photovoltaic devices and field effect transistors, as the fullerenes must be ordered in the solid state to achieve high carrier mobility.
Now Eiichi Nakamura, at the University of Tokyo, Japan, and colleagues think they may have discovered an effective way to organise fullerene. They found that a perfluoro aromatic ring interacts face-to-face with fullerene resulting in close fullerene-fullerene contact. By attaching C6H5 groups to C60, they showed they could form an ordered crystalline arrangement of fullerenes in the solid state.
Nakamura tested the performance of the fullerenes in a thin film photovoltaic device and achieved a power conversion efficiency of 1.5 %. The group now plan to do detailed physical studies on the device performance.
Read more in Nakamura’s ChemComm communication, free to access until 22nd November.
Evidence that water came to Earth during its formation from cosmic dust, rather than following later in asteroids, has been shown by a group of international scientists.
The origin of the abundant levels of water on Earth has long been debated with the main differences in the theories being the nature of the material that carries the water, and whether the water came during or after planet formation.
Now, Nora de Leeuw at University College London, UK, and colleagues have used molecular-level calculations to prove that dissociative chemisorption of water onto the surface of olivine rich minerals, such as forsterite, is highly exothermic. And so when these mineral dust particles came together during Earth formation, gas-solid interactions could have resulted in water being adsorbed onto the surface of the dust particles. This means that water could have been part of the Earth from the very beginning.
Water could have been adsorbed onto minerals that created the Earth
‘Our calculations indicate that it is viable for water to become adsorbed at the surfaces of dust particles in the interstellar medium, where planets are formed. The water is thus trapped and becomes incorporated into the Earth,’ says de Leeuw.
De Leeuw’s work challenges the common assumption made by astronomers that the Earth’s water originated from bodies in the asteroid belt. ‘The work will be of tremendous interest to those modelling the geology and habitability of extrasolar terrestrial planets,’ comments Philip Armitage, an expert in astrophysical and planetary sciences at the University of Colorado, Boulder, US.
Rebecca Brodie
Find out more in de Leeuw’s communication. Are you sitting on results that are out of this world? Submit today to ChemComm and make an impact.
By replacing a single active-site amino acid residue in an aminomutase enzyme, scientists in the Netherlands have engineered a variant that can catalyse the formation of β-tyrosine, an important building block in bioactive compounds.
Phenylalanine aminomutase (PAM) is an enzyme that catalyses a chemically challenging α,β-amine shift, forming β-phenylalanine from β-phenylalanine. It can tolerate a wide variety of substituents on the aromatic ring of the substrate but not a para hydroxyl group and so it cannot be used to synthesis β-tyrosine. Although tyrosine aminomutase (TAM) catalyses the amine shift in α-tyrosine to generate β-tyrosine, it has a more limited substrate scope than PAM and has low enantioselectivity towards β-tyrosine.
So Dick Janssen and colleagues replaced a cysteine residue with serine in phenylalanine aminomutase to make an enzyme with both TAM and PAM activity and high enantioselectivity. This engineering enzyme can catalyse the formation of β-tyrosine from p-coumaric acid and may prove useful for synthesising enantiopure β-tyrosine and its derivatives, Janssen says.
For more details, read Janssen’s ChemComm communication, free to access until 12th November. This communication is part of the Enzymes and Proteins web theme issue.
13C NMR shifts can be used, alone or in combination with 1H NMR, to assign the absolute configuration of organic compounds, claim Spanish scientists.
Ricardo Riguera and colleagues at the University of Santiago de Compostela examined the 13C NMR data for a collection of chiral samples, including carboxylic acids and cyanohydrins, derivatised with common auxiliaries. In all cases they found a perfect correlation between the sign of ΔδRS (the difference in chemical shift for the protons around the asymmetric carbon in the R and S substrates) and the absolute configuration of the substrate.
The foundations of the method reside in the aromatic shielding effect produced by the auxiliary on the protons and carbons of the substrate, Riguera explains.
Read the full report in Riguera’s ChemComm communication, free to access until 12th November 2010. And if you enjoy the communication, you might also enjoy NMR methods for unravelling the spectra of complex mixtures, a review in Natural Product Reports by Riguera et al.
A new type hypervalent iodine reagent could enable more efficient and green catalytic oxidations, report Japanese chemists.
Hypervalent iodine reagents have emerged as promising organo-oxidants, replacing classical heavy metal oxidants such as lead and mercury. m-Chloroperbenzoic acid is commonly used as a stoichiometric reoxidant to regenerate the reactive iodine species, but scientists would like to use other, more environmentally friendly oxidants, such as peracetic acid, instead. Until now, however, no efficient iodine catalyst that works well with peracetic acid has been found.
Yasuyuki Kita, at Ritsumeikan University, Kusatsu, and colleagues discovered that their µ-oxo-bridged hypervalent iodine(III) compounds, in the presence of peracetic acid, could catalyse spirolactam formation. They also believe the compounds can catalyse other types of oxidation, such as phenolic oxidation, and, because they have a chiral structure, could have potential in asymmetric oxidative transformations.
Download the communication for free until 5th November 2011. And if you have some exciting research of your own to report, submit your manuscript to ChemComm today.
Depletion attraction forces can be used to assemble nanorod superlattices and branched nanocrystal networks, say Italian chemists. The nanostructures could be used in a variety of applications, including photovoltaics, they claim.
Liberato Manna and colleagues at the Italian Institute of Technology, Genova, discovered that in the presence of molecules such as oleic acid, nanorods assemble into superlattices. They also found that tetrapod-shaped nanocrystals form networks under similar conditions.
Want to find out how this works? Read the ChemComm article, which is free to access until 5th November, and add your comments on the work below.
Developing environmentally friendly, renewable energy is one of the challenges to society in the 21st century. One of the renewable energy technologies is solar energy conversion — a technology that directly converts daylight into electricity.
In their ChemComm Highlight in Chemistry, Dirk Guldi and Vito Sgobba survey recent breakthroughs in implementing carbon nanostructures — fullerenes, carbon nanotubes, carbon nanohorns and graphene — into solar energy conversion schemes, that is, bulk heterojunction and dye-sensitised solar cells. Read the article today and let us know what you think by leaving a comment.
2011 is the International Year of Chemistry (IYC 2011), a worldwide celebration of the achievements of chemistry and its contributions to the well-being of humankind. ChemComm is marking IYC 2011 by publishing a series of ‘Highlights in Chemistry’. For more information visit the the ChemComm and IYC 2011 website.
Japanese scientists have made a simple structural mimic of multipass transmembrane (MTM) proteins, one of the most common types of membrane protein.
Kazushi Kinbara, at Tohoku University, and colleagues made alternating amphiphilic multiblock molecules consisting of linearly connected hydrophilic and hydrophobic moieties. They found that the hydrophobic units stacked face-to-face to give folded structures, like those of MTM proteins.
Find out more in their ChemComm communication, free to download until 25th October. And why not mimic the authors and submit your best research to ChemComm?
Calcium plays a central role in many signalling pathways, including neuronal and sensory function. Now scientists in Germany have shown that surface plasmon resonance can be used to monitor Ca2+-induced conformational changes in a Ca2+-sensor protein immobilised on a chip.
Daniele Dell’Orco and colleagues at the University of Oldenburg, Germany describe their study in a recently published ChemComm communication. Download the article for free until 25th October.
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![Graphical abstract: Face-to-face C6F5–[60]fullerene interaction for ordering fullerene molecules and application to thin-film organic photovoltaics](http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=C0CC03028G "Face-to-face interactions")
