Archive for October, 2011

The lightest rotaxane

Rotaxanes are dumbbell-shaped molecules that are threaded through a separate macrocylic molecule. The two molecules are not chemically bonded to one another but instead are mechanically interlocked – a feature that can be exploited for molecular switches in molecular electronics, actuators and controlled drug release.

In a quest to understand the spatial requirements of these molecules, Suvankar Dasgupta and Jishan Wu from the National University of Singapore have discovered the lightest rotaxane to date. The rotaxanes in question were composed of a dibenzylammonium ion which was threaded through crown ether molecules of various sizes. As a result of their investigations, Dasgupta and Wu found that a [20]crown ether was capable of encompassing the dibenzylammonium dumbbell.

To find out more about this research, download the Chemical Science article today.

Also of interest…

Visit the ChemComm Supramolecular web theme issue for lots more on Rotaxane structures.

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The next generation of photoactive zeolites

A hybrid photocatalytic system, coupling a zeolite with graphene, has been developed by teams in the UK, India and Germany. This new system could have implications for important applications such as water and air purification, dye degradation, self-cleaning and anti-bacterial surfaces as well as various technical photosynthetic processes.

Dominik Eder at the University of Münster and colleagues at the University of Cambridge, used a titanosilicate zeolite (TS-1) with graphene incorporated, at varying concentrations, in its pores.  TS-1 was chosen becasue of its good photocatalytic properties and graphene was chosen for its exceptional electrical and optical properties, along with its ability to accept electrons via photoexcitation.

The team found that the photocatalytic activity was greater when compared to TS-1 hybrids with carbon nanotubes.

Reference:
Hybridizing photoactive zeolites with graphene: a powerful strategy towards superior photocatalytic properties
Z Ren, E Kim, S W Pattinson, K S Subrahmanyam, C N R Rao, A K Cheetham nd D Eder, Chem. Sci., 2011
DOI:10.1039/c1sc00511a

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Targeted drug delivery to cancer cells

By building methotrexate – a potent leukaemia drug – into nanoscale coordination polymers as bridging ligands, scientists have achieved high drug loadings of 79 wt% and selective delivery to cancer cells, where the drug is released. The polymers have superior in vitro efficacy to the free drug and the toxic side effects of the free drug are avoided.

 

Reference:
Lipid-Coated Nanoscale Coordination Polymers for Targeted Delivery of Antifolates to Cancer Cells

R C Huxford, K E deKrafft, W S Boyle, D Liu and W Lin, Chem. Sci., 2011
DOI
: 10.1039/c1sc00499a

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Top ten most accessed articles in September

This month sees the following articles in Chemical Science that are in the top ten most accessed:-

Why not take a look at the articles today and blog your thoughts and comments below.

A general approach to the enantioselective a-oxidation of aldehydes via synergistic catalysis
Scott P. Simonovich, Jeffrey F. Van Humbeck and David W. C. MacMillan
Chem. Sci., 2011, Advance Article, DOI: 10.1039/C1SC00556A

A robust and scalable synthesis of the potent neuroprotective agent (-)-huperzine A
Maung Kyaw Moe Tun, Daniel-Joachim Wüstmann and Seth B. Herzon
Chem. Sci., 2011, Advance Article, DOI: 10.1039/C1SC00455G

Palladium(0)-catalyzed cyclopropane C–H bond functionalization: synthesis of quinoline and tetrahydroquinoline derivatives
Sophie Rousseaux, Benoît Liégault and Keith Fagnou
Chem. Sci., 2011, Advance Article, DOI: 10.1039/C1SC00458A

Asymmetric synthesis of highly functionalized cyclopentanes by a rhodium- and scandium-catalyzed five-step domino sequence
Brendan T. Parr, Zhanjie Li and Huw M. L. Davies
Chem. Sci., 2011, Advance Article, DOI: 10.1039/C1SC00434D

Use of precatalysts greatly facilitate palladium-catalyzed alkynylations in batch and continuous-flow conditions
Wei Shu and Stephen L. Buchwald
Chem. Sci., 2011, Advance Article, DOI: 10.1039/C1SC00409C

Asymmetric dearomatization of pyrroles via Ir-catalyzed allylic substitution reaction: enantioselective synthesis of spiro-2H-pyrroles
Chun-Xiang Zhuo, Wen-Bo Liu, Qing-Feng Wu and Shu-Li You
Chem. Sci., 2011, Advance Article, DOI: 10.1039/C1SC00517K

Tracking gold acetylides in gold(i)-catalyzed cycloisomerization reactions of enynes
Antoine Simonneau, Florian Jaroschik, Denis Lesage, Magdalena Karanik, Régis Guillot, Max Malacria, Jean-Claude Tabet, Jean-Philippe Goddard, Louis Fensterbank, Vincent Gandon and Yves Gimbert
Chem. Sci., 2011, Advance Article, DOI: 10.1039/C1SC00478F

Enantioselective rhodium-catalyzed arylation of electron-deficient alkenylarenes
Aakarsh Saxena and Hon Wai Lam
Chem. Sci., 2011, Advance Article, DOI: 10.1039/C1SC00521A

Reactivity of NHC Au(i)–C s-bonds with electrophiles. An investigation of their possible involvement in catalytic C–C bond formation
Magnus T. Johnson, J. Marthinus Janse van Rensburg, Martin Axelsson, Mårten S. G. Ahlquist and Ola F. Wendt
Chem. Sci., 2011, Advance Article, DOI: 10.1039/C1SC00428J

Nickel-catalyzed cross coupling of non-activated alkyl halides: a mechanistic perspective
Xile Hu
Chem. Sci., 2011, 2, 1867-1886, DOI: 10.1039/C1SC00368B

Fancy submitting an article to Chemical Science? Then why not submit to us today or alternatively contact us your suggestions.

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A way of life – chemistry meets biology in Chemical Science

Chemical techniques are critical for studying and manipulating biological systems. Here at Chemical Science, we’ve published a host of great articles at the interface of chemistry and biology. Below is a selection of some of the recent ones. Sign up for our e-alerts and browse our issues to keep up-to-date with the latest exceptional research in this fascinating field.

Ultrafast infrared chemical imaging of live cells
Hemmel Amrania, Andrew P. McCrow, Mary R. Matthews, Sergei G. Kazarian, Marina K. Kuimova and Chris C. Phillips, Chem. Sci., 2011, 2, 107-111

Clickable, photoreactive inhibitors to probe the active site microenvironment of fatty acid amide hydrolase
Susanna M. Saario, Michele K. McKinney, Anna E. Speers, Chu Wang and Benjamin F. Cravatt, Chem. Sci., 2011, DOI: 10.1039/C1SC00336D

Molecular recognition of cytochrome c by designed receptors for generation of in vivo and in vitro functions
Satoshi Shinoda and Hiroshi Tsukube, Chem. Sci., 2011, DOI: 10.1039/C1SC00162K

Diversity in natural product families is governed by more than enzyme promiscuity alone: establishing control of the pacidamycin portfolio
Sabine Grüschow, Emma J. Rackham and Rebecca J. M. Goss, Chem. Sci., 2011, 2, 2182-2186

1H NMR metabolomics combined with gene expression analysis for the determination of major metabolic differences between subtypes of breast cell lines
Miroslava Cuperlovic-Culf, Ian C. Chute, Adrian S. Culf, Mohamed Touaibia, Anirban Ghosh, Steve Griffiths, Dan Tulpan, Serge Léger, Anissa Belkaid, Marc E. Surette and Rodney J. Ouellette, Chem. Sci., 2011, 2, 2263-2270

Rapid fluorescence imaging of miRNAs in human cells using templated Staudinger reaction
Katarzyna Gorska, Ioanna Keklikoglou, Ulrich Tschulena and Nicolas Winssinger, Chem. Sci., 2011, 2, 1969-1975

Methods for converting cysteine to dehydroalanine on peptides and proteins
Justin M. Chalker, Smita B. Gunnoo, Omar Boutureira, Stefanie C. Gerstberger, Marta Fernández-González, Gonçalo J. L. Bernardes, Laura Griffin, Hanna Hailu, Christopher J. Schofield and Benjamin G. Davis, Chem. Sci., 2011, 2, 1666-1676

Engineering DNA aptamers for novel analytical and biomedical applications
Mingxu You, Yan Chen, Lu Peng, Da Han, Bincheng Yin, Bangce Ye and Weihong Tan, Chem. Sci., 2011, 2, 1003-1010

Submit your own hot research to our chemical biology and bioorganic Associate Editors: Benjamin Cravatt and Thomas Carrell.

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A cheaper way to catalyse the oxidative annulation of alkynes

The first ruthenium-catalysed oxidative annulation of alkynes with air as an oxidant has been done by scientists in Germany.

The team used an inexpensive ruthenium catalyst for aerobic C-H bond functionalisations, providing novel access to structural motifs of bioactive alkaloids.

Oxidative annulations reactions of alkynes by C-H bond cleavages provides a route to polycyclic heteroarenes. Ruthenium-catalysed methods use stoichiometric amount of copper(II) or silver(II) salts, but these lead to heavy metal by-products. Rhodium-catalysed methods are known but this ruthenium method is cheaper with improved scope and chemoselectivity.

 

Reference:
Ruthenium-catalyzed aerobic oxidative coupling of alkynes with 2-aryl-substituted pyrroles

L Ackermann, L Wang and A V Lygin, Chem. Sci., 2011,
DOI
: 10.1039/c1sc00619c

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Interview with Chemical Science Editor-in-Chief David MacMillan

David MacMillan David MacMillan is the A Barton Hepburn chair, director of the Merck Center for Catalysis and department chair of chemistry at Princeton University, US. His research focuses on organic chemistry and catalysis.

Why did you decide to become a chemist?   

It’s a funny story. I originally went to Glasgow to study physics but the physics lecture theatre was really cold and the chemistry lecture theatre was much warmer so I switched degree. That makes it sound trivial – I obviously liked the subject too. 

What’s going on in your lab at the moment?   

Something I’m really excited about is synergistic catalysis. Instead of using one catalyst to do one reaction (i.e. one activation mode), can you strategically carry out two activation modes in the same reaction such that you find two activating molecules that will react with each other. There are a whole host of different bond connections that can fly out of that – new reactions, new bond formations, high levels of selectivity and enantioselectivity. It is something that nature does but chemists rarely do and so the area is completely wide open.   

Another thing we’re looking at is collective total synthesis: how do you think of ways to strategically build molecules that allow you to build lots of families of natural products as opposed to just one natural product? That would allow you to systematically make things with much higher levels of efficiency. When it comes to using natural products, collective total synthesis makes much more sense, in the same way that a medicinal chemist would much prefer to make a late stage molecule that can be diversified at the end rather than making a different single molecule every single time.   

Aside from your own research, what’s hot in organic chemistry right now?   

The work of Eric Jacobsen is exceptionally interesting – the whole idea of using small numbers of interactions to stabilise transition states, allowing you to go after different ways of activating molecules, for example counter-ion catalysis, which his group does.   

I also find Steve Buchwald’s work amazing because it is chemistry that has a massive impact on a day-to-day basis. To me, that is exceptionally exciting.   

C-H bond activation is one of the great frontiers of the field and there are some really fantastic people doing it – Christina White, Melanie Sanford, Jin-Quan Yu, to name a few. 

You are Editor-in-Chief of Chemical Science. What are the most exciting parts of this role? 

This is unbelievably exciting. People might say ‘does the world need another journal?’ I would argue that the world might not need just another journal but what we do massively need is quality, excellent journals. In my opinion, there are simply not enough of them. A lot of the other journals out there are heterogeneous in quality. With Chemical Science, we’ve found a society publishing group that has really got behind the idea of doing something different and is fully supporting it, both financially and in terms of resources and effort. I was given the chance to put together what I think is the best editorial board in the world. It is an unbelievable group of people – the quality is not surpassed. I believe that if you get great people together with great resources, it thermodynamically has to play out to be this great thing. 

You have received numerous awards throughout your career, including the 2011 ACS award for creative work in synthetic organic chemistry. What do awards mean to you?   

People like me are always cynical about awards and say they don’t mean anything to us until we receive one and then we are exceptionally happy. It makes you feel like you are being recognised by the greater community and that is a superb feeling. You are doing something that you care about and it is nice to know that the community also thinks it is valuable.   

What are the main challenges facing chemists and chemistry?   

There are the big societal challenges that everyone is aware of, such as energy and scarce natural resources. Another challenge is being able to make any molecule we want efficiently and selectively.   

One major thing chemists need to work on is their ability to promote their work to other scientists and the public. This is something we are really not good at in general and if we improved, it would really open doors for us and improve society’s perception of chemistry and its impact.   

You are a consultant for a number of pharmaceutical companies. Can you comment on the current state of the industry and the recent high profile redundancies?   

Pharma is obviously in a state of flux right now.  We are seeing fewer drugs being approved on a yearly basis and there is a constant question as to why. I suspect the real reason is a combination of factors including: (i) the FDA (US Food and Drug Administration) setting unrealistic bars and guidelines for when drug approval is possible, (ii) the push towards company mergers, which leads to fewer approaches towards developing drugs for any given target for society, as well as a net reduction in the number of scientists gainfully employed in the practice of making drugs on a world-wide basis, and (iii) the impact of Wall Street on pharma and the constant push for quarterly short term success at the price of long term success, which is the eight year cycle to produce drugs. The latter has resulted in a lot of lay-offs to save money by cutting R&D. The problem is this is setting the stage for more disappointment in the long term (or killing the goose that lays the golden egg). 

I think there are two bright sides in this gloomy picture. The first is that smart people (and chemists are very smart) will always find a way towards using their talents and to success. This will most likely play out in the form of small companies being built by chemists and biologists who are being pushed out of big pharma. These people will continually push innovation, determination and they will have a buy-in for the companies they form, as opposed to being continually distracted by the fear of losing their job at a larger company. These companies will grow and will provide jobs in the US and Europe for the future. It will take a while, but it will happen. 

The second is that many big pharma companies are in trouble. However, it is my view that the best ones will make it and the not so successful ones will not. The ones that will make it through will prosper and they will see re-growth in the future. As to where these companies will be located, I still see Europe, Japan and the US as the major locales for these companies for many years to come. 

What advice would you give young scientists starting out in their career?   

Follow your dream. Don’t get bogged down by the small, incremental things even if someone tells you you should be doing them. Concentrate on what you really want to achieve. 

What do you do in your spare time?   

I hang out with my family. I have a five year old daughter and an amazing wife. Because of my job, time is limited so I try to spend as much of my free time with them as possible. I am always playing or watching football with my daughter and we go to libraries and go cycling. My favourite thing is quality time with my family. 

What would you be if you weren’t a chemist?   

I’d like to have been a professional football player but I am absolutely terrible at it so there is no way that would ever have happened. Perhaps something in design but it is a really difficult question – chemistry has been my focus for such a long time.

Read some of Professor MacMillan’s latest research in Chemical Science:

The intramolecular asymmetric allylation of aldehydes via organo-SOMO catalysis: A novel approach to ring construction
Phong V. Pham, Kate Ashton and David W. C. MacMillan, Chem. Sci., 2011, 2, 1470

A general approach to the enantioselective -oxidation of aldehydes via synergistic catalysis
Scott P. Simonovich, Jeffrey F. Van Humbeck and David W. C. MacMillan, Chem. Sci., 2011, DOI: 10.1039/c1sc00556a

Also of interest

Diamine ligands in copper-catalyzed reactions
David S. Surry and Stephen L. Buchwald, Chem. Sci., 2010, 1, 13-31

Dialkylbiaryl phosphines in Pd-catalyzed amination: a user’s guide
David S. Surry and Stephen L. Buchwald, Chem. Sci., 2011, 2, 27-50

Hydroxyl-directed C–H carbonylation enabled by mono-N-protected amino acid ligands: An expedient route to 1-isochromanones
Yi Lu, Dasheng Leow, Xisheng Wang, Keary M. Engle and Jin-Quan Yu, Chem. Sci., 2011, 2, 967-971

This interview was also published in Chemistry World.

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Mechanically locked capsule captures oppositely charged guests

By combining hydrogen bonding and mechanical bonding, scientists in Spain have made a mechanically locked capsule that can encapsulate two oppositely charged ions. 

molecular capsule

Pablo Ballester and Marco Chas, at the Institute of Chemical Research of Catalonia, Tarragona, made the capsule’s two hemispheres out of a calix[4]pyrrole and a calix[4]arene. The calix[4]pyrrole uses hydrogen bond interactions to recognise anions or N-oxide  guests while the calix[4]arene provides efficient cation-π and CH-π interactions for co-encapsulated guests. The capsule can fit two neutral or oppositely charged guests and the encapsulation is reversible. 

If this has captured your attention, download Ballester’s Chemical Science Edge article for free and read more.

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Promising therapeutics for heart failure

Complexes for future nitroxyl (HNO) therapies have been made by scientists in the US, South Africa and Norway. HNO donors have been used as anti-alcoholism agents and are proving to be promising therapeutics for heart failure. 

The team made ferric nitric oxide complexes and described the first insight into the electronic structure, reactivity and potential fate of these {FeNO}8 complexes in biology. The researchers say that {FeNO}8 could be used as a nitroxyl donor at ambient temperature and physiological pH.

 

Reference:
A thermally stable {FeNO}8 complex: properties and biological reactivity of reduced MNO systems
A K Patra, K S Dube, B C Sanders, G C Papaefthymiou, J Conradie, A Ghosh and T C Harrop, Chem. Sci., 2011
DOI:
10.1039/c1sc00582k

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Cleaner gases for industrial energy applications

Japanese scientists have improved the gas separation efficiencies of porous materials by precisely tuning the framework’s flexibility. Separating gas mixtures is important for generating cleaner gases for industrial energy applications. For example, carbon dioxide needs to be removed from biogas and ethane from natural gas to increase the methane content.

Porous coordination polymers are promising candidates for gas separation and this new study show that specific design of them can contribute to improved industrial separation processes.

Reference:
A solid solution approach to 2D coordination polymers for CH4/CO2 and CH4/C2H6 gas separation: equilibrium and kinetic studies
S Horike, Y Inubushi, T Hori, T Fukushima and S Kitagawa, Chem. Sci., 2011
DOI: 10.1039/c1sc00591
j

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