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1,5-(H, RO, RS) shift/6π-electrocyclic ring closure tandem processes

19 Nov 2012

In this HOT paper Angel Vidal and co-workers at Universidad de Murcia discuss the conversion of N-(2-Substituted)aryl ketenimines into 3,4- dihydroquinolines. The reaction involves a 1,5-migration of a hydride or alkoxyl group, followed by a subsequent 6pi-electrocyclic ring closure.

Vidal et al. perform a detailed experimental study on the relative migratory aptitudes and activating effects of the 1,5- (H, RO, RS) shift / 6p-electrocyclic ring closure, and provide new interesting insights into the formation of highly substituted quinolones.

Want to know what the relative migratory aptitudes are? Or what has the best activating effect? Download the paper for free for the next 4 weeks!

1,5-(H, RO, RS) shift/6π-electrocyclic ring closure tandem processes on N-[(α-heterosubstituted)-2-tolyl]ketenimines: a case study of relative migratory aptitudes and activating effects
Mateo Alajarín, Baltasar Bonillo, Raúl-Angel Orenes, María-Mar Ortín and Angel Vidal
DOI: 10.1039/C2OB27010B

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Stereospecific total synthesis of (+)-myrrhanol C achieved

16 Nov 2012

Spanish chemists have completed the stereospecific total synthesis of (+)-myrrhanol C.

(+)-Myrrhanol C is a natural triterpene isolated from mastic gum (the resin of Pistacia lentiscus), a substance well known for its medicinal properties as well as use in various cuisines. The compound itself was used to embalm corpses in ancient Egypt. More recently, it has been recognised as a promising anti-prostate cancer lead. However, before a molecule can be used to develop drugs, a successful synthesis must be developed.

Mastic gum (from Pistacia lentiscus, pictured) has been used for many applications, from treating snakebites to tooth whiteners. © Science Photo Library

Alejandro Barrero and his group at the University of Granada have done just that. Their synthesis starts with (–)-sclareol, a bicyclic diterpene alcohol isolated from clary sage (Salvia sclarea). It then proceeds through a key C–H oxidation step, which is achieved with cytochrome P450 enzyme catalysis by incubating a reaction intermediate with the fungus Mucor plumbeus.

By cultivating clary sage, Barrero can sustainably produce (–)-sclareol, meaning (+)-myrrhanol C can be made on a large scale that is also environmentally friendly.

Read the full story in Chemistry World

And read the OBC paper, highlighted as being HOT by the referees, for free here:
First synthesis of (+)-myrrhanol C, an anti-prostate cancer lead
Victoriano Domingo, Lidia Lorenzo, José F. Quilez del Moral and Alejandro F. Barrero
DOI: 10.1039/C2OB26947C

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Supramolecular chemistry: synthetic ion channels

16 Nov 2012

Researchers in Canada have developed the first benzimidazolium-based synthetic ion channel and shown that it can cause damage to bacterial cells walls.

The movement of ions through cell walls is essential for a host of biological processes. The vast majority of this transportation occurs through ion channels or pores in the cell membrane. Man-made versions of these intracellular transport systems have been the subject of investigation by the supramolecular chemistry community for many years.

In this HOT paper, the Schmitzer group at the Université de Montréal are particularly interested in the transport of chloride ions in epithelial cells through calcium activated ion channels. They hope to mediate the concentrations of both calcium and chloride ions using synthetic ionophores.

Building on their research into imidazolium amphiphiles, they have developed a benzimidazolium-based compound that increases chloride flux in a variety of lipid bilayer systems, and increases bacterial cell wall permeability to calcium ions.

This compound will hopefully inspire new drugs to treat cystic fibrosis, which is caused by mutation of a chloride-ion channel known as the cystic fibrosis transmembrane conductance regulator protein (CFTR). They may also aid in the development of new antibiotics to combat resistant strains of bacteria.

Want to find out more? Read this paper FREE for the next 4 weeks.

Benzimidazolium-based synthetic chloride and calcium transporters in bacterial membranes
Claude-Rosny Elie, Audrey Hébert, Mathieu Charbonneau, Adam Haiun and Andreea R. Schmitzer
DOI: 10.1039/C2OB26966J

Published on behalf of Annabella Newton, Organic & Biomolecular Chemistry web science writer. Annabella Newton is a postdoctoral researcher based in Melbourne, Australia.

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C-H activation: an article collection

14 Nov 2012

One of the simplest and most utilised chemical reactions is the burning of hydrocarbons and while combustion is an excellent way to exploit the energy content of this naturally occurring resource, there is a lot more we can do with the ‘inert’ C-H bond.

C-H activation allows us to convert cheaper hydrocarbon starting materials into more valuable and versatile products; leading to the development of a wide range of reagents and catalysts that activate C-H bonds. To keep you up to date with the latest developments in the field we have created this article collection, where all articles are free to download until 15^th December.

Click here for the full list of free articles

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Hypervalent iodine-mediated spirocyclization – unexpected formation of δ-spirolactones

13 Nov 2012

In this HOT communication Boris J. Nachtsheim and colleagues at Eberhard Karls University present preliminary results towards a fast and efficient synthetic approach of γ-spirolactams based on an iodine(III)-mediated oxidative spirocyclization of 2-(4-hydroxybenzamido)-acrylates.

In addition Nachtsheim et al. discuss the discovery of an unexpected side reaction, a rare iodine(III)-mediated spirocyclization that gave δ-spirolactones. With fluorinated solvents and modified reaction conditions this side reaction was able to produce δ-spirolactones in yields up to 70%.

Interested? Find out more about these reactions and their mechanisms by downloading this Communication for FREE.

A hypervalent iodine-mediated spirocyclization of 2-(4-hydroxybenzamido)acrylates – unexpected formation of δ-spirolactones
Christian Hempel, Nicole M. Weckenmann, C. Maichle-Moessmer and Boris J. Nachtsheim
DOI: 10.1039/C2OB26815A

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Organic & Biomolecular Chemistry issue 46: achiral supramolecular stacks & heteroaromatic α-hydroxy esters

08 Nov 2012

Guess what…. yes you got it, it’s Organic & Biomolecular Chemistry time! This week’s issue has 1 Perspective, 5 Communications and 17 Papers for your reading pleasure.

Front cover:

Put your hands together for this very nice image highlighting the work of David B. Amabilino and colleagues. Amabilino et al. use the induction of chirality in achiral aggregates of an oligo(p-phenylenevinylene) to detect the enantiomeric excess in acids used in the resolution of chiral compounds. These achiral supramolecular stacks can detect the enantiomeric excess of substoichiometric amounts different organic acids.

Sensitive detection of enantiomeric excess in different acids through chiral induction in an oligo(p-phenylenevinylene) aggregate
François Riobé, Albertus P. H. J. Schenning and David B. Amabilino
DOI: 10.1039/C2OB26411K

Inside cover:

This image of seaside chemistry is courtesy of Ming-Hua Xu and co-workers at Shanghai Institute of Materia Medica. Xu et al. present their work on developing a highly efficient and enantioselective route to quaternary carbon-containing heteroaromatic α-hydroxy esters. Xu et al. employ the catalytic asymmetric 1,2-addition of arylboronic acids to obtain these heteroaryl α-ketoesters.

Rhodium-catalyzed enantioselective 1,2-addition of arylboronic acids to heteroaryl α-ketoesters for synthesis of heteroaromatic α-hydroxy esters
Hui Wang, Ting-Shun Zhu and Ming-Hua Xu
DOI: 10.1039/C2OB26316E

Hot articles in this issue:

Reduction of metal ions by boranephosphonate DNA
Subhadeep Roy, Magdalena Olesiak, Petra Padar, Heather McCuen and Marvin H. Caruthers

The bacterial second messenger c-di-GMP: probing interactions with protein and RNA binding partners using cyclic dinucleotide analogs
Carly A. Shanahan and Scott A. Strobel

As always the articles featured on the covers are free to access for 6 weeks, and the HOT articles are free for 4!

For all this and much, much more take a look at the issue online today!

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Reduction of metal ions by boranephosphonate DNA

07 Nov 2012

In this HOT communication Marvin H. Caruthers and co-workers from the University of Colorado show that oligodeoxyribonucleotides bearing boranephosphonate linkages (bpDNA) are able to reduce a variety of metal ions whilst producing nanoparticles. Carauthers et al. discovered that during the reduction of metal ions in protic solvents, the B–P bond undergoes solvolysis and generates phosphate diesters (in water) or triesters (in alcohols).

To highlight the utility of this reaction Caruthers et al. synthesised an oligomer containing an O-methyl phosphate triester linkage, which cannot be prepared via usual methods of DNA synthesis as such triesters are base labile.

Caruthers et al. believe that, in addition to bpDNA‘s potential applications in the construction of DNA templated metallic nanostructures, the new reactivity of boranephosphonates shown can be exploited as a general method for the introduction of a variety of functionalities onto the DNA backbone via phosphate triesters.

Intrigued? Read this Communication for free for the next 4 weeks to find out more!

This Communication is part of the Nucleic acids: new life, new materials collection. Why not take a look at similar work and let us know what you think here on the blog or on Twitter.

Reduction of metal ions by boranephosphonate DNA
Subhadeep Roy, Magdalena Olesiak, Petra Padar, Heather McCuen and Marvin H. Caruthers
DOI: 10.1039/C2OB26661J

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The bacterial second messenger c-di-GMP: probing interactions with protein and RNA binding partners using cyclic dinucleotide analogs – a HOT review

02 Nov 2012

One of the essential capabilities of bacteria for their continued survival is the ability to adapt and change to reflect the changing environment in which they reside. One way in which they achieve this is through the second messenger signalling molecule bis-(3′–5′)-cyclic dimeric guanosine monophosphate (c-di-GMP), which facilitates behaviour adaptions.

c-di-GMP is found throughout the bacterial domain and plays a vital role in regulating the transition between the motile planktonic lifestyle and the sessile biofilm forming state. It also controls the virulence response of pathogenic organisms and is thought to be connected to quorum sensing, the process by which bacteria communicate with each other.

This HOT review from Scott A. Strobel and Carly A. Shanahan, Yale University, summarises the current state of knowledge and understanding of c-di-GMP signalling in bacteria with a focus on protein and RNA binding partners of the second messenger. Efforts towards the synthesis of c-di-GMP and its analogues are discussed as well as studies aimed at targeting these binding partners with synthetic dinucleotide analogues.

To find out more about this messenger molecule read this review taken from our Nucleic acids: new life, new materials collection.

Enjoy free access for 4 weeks, so download it today.

The bacterial second messenger c-di-GMP: probing interactions with protein and RNA binding partners using cyclic dinucleotide analogs
Carly A. Shanahan and Scott A. Strobel
DOI: 10.1039/C2OB26724A

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Organic & Biomolecular Chemistry issue 45: poisonous frogs, spirocyclic alkaloids & cycloadditions

31 Oct 2012

Issue 45 of Organic & Biomolecular Chemistry is now online, so hop to it and take a cheeky peek….

Featuring in the issue this week:

Leaping on to the front cover is this image (right) from Andrew B. Holmes, Annabella F. Newton and colleagues. The cover highlights the work of Holmes et al. exploring the synthesis of the histrionicotoxin family, which includes some interesting investigations into the intriguing observed regioselectivity of the dipolar cycloaddition during the key cascade hydroxylamine-alkyne cyclisation/nitrone cycloaddition to form the azaspirocyclic core.

Intramolecular nitrone dipolar cycloadditions: control of regioselectivity and synthesis of naturally-occurring spirocyclic alkaloids
Alastair J. Hodges, Joseph P. Adams, Andrew D. Bond, Andrew B. Holmes, Neil J. Press, Stephen D. Roughley, John H. Ryan, Simon Saubern, Catherine J. Smith, Michael D. Turnbull and Annabella F. Newton
DOI: 10.1039/C2OB26333E

The inside cover of this week’s issue (left) features the work of Feng Shi and co-workers from Henan University. Shi et al. re-examine the use of the Kobayashi benzyne precursor in the [3 + 2] cycloaddition of arynes with 3-oxidopyridinium species, for the first time in 16 years, expanding investigations further than ever before.

Aryne cycloaddition with 3-oxidopyridinium species
Hailong Ren, Chunrui Wu, Xiuxiu Ding, Xiaoge Chen and Feng Shi
DOI: 10.1039/C2OB26519B

Both of these papers have been highlighted as being HOT chemistry by the reviewers, and they are both FREE to access for the next 6 weeks, so enjoy!

Also in this issue: 6 Communications and a further 14 papers full of great content.

Read the complete issue now…

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Organic & Biomolecular Chemistry issue 44 online now

29 Oct 2012

Welcome to issue 44 of OBC…..

Featuring on the front cover is a paper from Günter Haufe and colleagues, described by the reviewers as being an important contribution to the field of organofluorine chemistry. Haufe et al. present results of the reactions of β-alkoxyvinyl polyfluoroalkyl ketones with ethyl isocyanoacetate and potassium tert-butoxide, which are strongly dependent on the structure of the starting enones, and the application of this reaction to the synthesis of new fluorinated pyrroles.

Reactions of β-alkoxyvinyl polyfluoroalkyl ketones with ethyl isocyanoacetate and its use for the synthesis of new polyfluoroalkyl pyrroles and pyrrolidines
Ivan S. Kondratov, Violetta G. Dolovanyuk, Nataliya A. Tolmachova, Igor I. Gerus, Klaus Bergander, Roland Fröhlich and Günter Haufe
DOI: 10.1039/C2OB26176F

This bright image on the inside cover is courtesy of Kristin Bowman-James and co-workers at the University of Kansas. Bowman-James et al. summarise results from previous studies on the stability and reactivity of the sulfur mustard and its surrogates toward hydrolysis and nucleophilic attack, and add results of their own on the reactivity of this class of molecules with simple nucleophiles in non-polar solvents, assessing their behaviour in the absence of competing solvation effects.

Sulfur, oxygen, and nitrogen mustards: stability and reactivity
Qi-Qiang Wang, Rowshan Ara Begum, Victor W. Day and Kristin Bowman-James
DOI: 10.1039/C2OB26482J

Read the entire issue on our webpage, and don’t forget that the articles featuring on the covers are free for you to download for the next 6 weeks.

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