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Biocatalysis: an article collection

05 Oct 2012

Beers, wines and cheeses are enjoyed around the world today and have been for millennia. In fact the practices of brewing and cheese-making pre-date recorded history so it is difficult to accurately determine when we first started using naturally occurring enzymes and microorganisms to create valuable (and in this case, tastier!) products.

Biocatalysts are of course used in far more diverse applications than the creation of food-stuffs, including in many organic syntheses and in the generation of fine chemicals. Due to their natural design, they can offer superior selectivity for particular products and have a far lower environmental impact than many traditional catalysts. Our knowledge and understanding of biocatalysts has increased dramatically in the last few decades, which has allowed us to develop biologically modified and biomimetic catalysts for a range of applications.

To keep you up to date with the latest advances in this rapidly expanding field we have collected together these high impact articles and made them free to access until the 31^st October!

Click here for the full list of free articles

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Molecular fossils: new compounds from 4900-year-old wood

28 Sep 2012

If you dug up a wooden artefact, how could you tell what type of tree it came from? French chemists have identified unique molecules from an ancient piece of oak that could hold the key.

Pierre Adam and co-workers from the University of Strasbourg, France, used gas chromatography-mass spectrometry to identify triterpenoid molecules, which appear to be related to the natural product oleanane, in a 4900-year-old wood sample collected from river sediments. The discovered triterpenoids are unusual as they only have an oxygen-containing functional group at the C-2 position, while triterpenoids from living trees either have this at C-3 or both C-2 and C-3. This crucial difference could be due to chemical breakdown of the molecules by micro-organisms in the environment where the wood is buried.

The transformation is important, as the structure of the molecules identified today can be directly traced back to the natural molecules that existed in the living wood, so they can be linked.

Read the full article in Chemistry World

And read the OBC paper, highlighted as being HOT by the referees, for free here:
Triterpenoids functionalized at C-2 as diagenetic transformation products of 2,3-dioxygenated triterpenoids from higher plants in buried wood
Gilles Schnell, Philippe Schaeffer, Estelle Motsch and Pierre Adam
DOI: 10.1039/C2OB26191J

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OBC issue 40 now online!

27 Sep 2012

The cover of this week’s issue of OBC highlights the work of Florian Hollfelder and colleagues at University of Cambridge. This HOT paper from Hollfelder et al. presents kinetic and computational evidence that hydrolytic reactions of sulfonate esters proceed with a two-step mechanism involving a pentavalent intermediate for poorer leaving groups.

Kinetic and computational evidence for an intermediate in the hydrolysis of sulfonate esters
Ann C. Babtie, Marcelo F. Lima, Anthony J. Kirby and Florian Hollfelder
DOI: 10.1039/C2OB25699A

The inside cover features the work of Lechosław Latos-Grażyński and co-workers showing that a N-confused porphyrin undergoes controlled regionselective phosphorylations at the inner, outer or both carbon atoms of the inverted pyrrole ring.

Regioselective phosphorylation and thiophosphorylation of N-confused porphyrin: a route to hybrid carbaporphyrinoids
Norbert Grzegorzek, Lechosław Latos-Grażyński and Ludmiła Szterenberg
DOI: 10.1039/C2OB26019K

Both covers are free to access for the next 6 weeks.

Also featuring in this issue are 2 more articles marked as being HOT be the referees:

Metal-free reactions of alkynes via electrophilic iodocarbocyclizations
Adeline Palisse and Stefan F. Kirsch
DOI: 10.1039/C2OB26508G

Highly enantioselective synthesis of Warfarin and its analogs catalysed by primary amine–phosphinamide bifunctional catalysts
Juan Dong and Da-Ming Du
DOI: 10.1039/C2OB26334C

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Highly enantioselective synthesis of Warfarin by primary amine–phosphinamide bifunctional catalysts

26 Sep 2012

In this HOT article Juan Dong and Da-Ming Du, Beijing Institute of Technology, present a new organocatalytic enantioselective Michael addition of 4-hydroxycoumarin to α,β-unsaturated ketones.

The article features a new kind of bifunctional primary amine–phophinamide catalyst, which when applied to catalyze the Michael reaction of 4-hydroxycoumarin to α,β-unsaturated ketones lead to the synthesis of the important pharmaceutical product Warfarin.

Highly enantioselective synthesis of Warfarin and its analogs catalysed by primary amine–phosphinamide bifunctional catalysts
Juan Dong and Da-Ming Du
DOI: 10.1039/C2OB26334C

This article features as part of OBC‘s organocatalysis collection. If you liked this article why not have a look at the collection for other articles on organocatalysis….

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Metal-free reactions of alkynes via electrophilic iodocarbocyclizations

25 Sep 2012

Electrophilic cyclisations is an area of chemistry that is continually and rapidly growing and expanding. This Emerging area from Adeline Palisse and Stefan F. Kirsch, University of Wuppertal, highlights the recent progress in C–C bond-forming halocyclisations allowing the reaction of alkynes with carbon-nucleophiles.

Palisse and Kirsch focus on iodine electrophiles, and aim to show that these iodocyclisations with alkynes have become a very useful strategy to construct structures. The review is roughly split into three major categories:
1)   malonates as nucleophilic
2)   arene nucleophiles
3)   olefins as nucleophiles

Read this Emerging Area today! Download it free by following the link below…

Metal-free reactions of alkynes via electrophilic iodocarbocyclizations
Adeline Palisse and Stefan F. Kirsch
DOI: 10.1039/C2OB26508G

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OBC issue 39 out now

21 Sep 2012

On the front cover of this issue of OBC Chun Liu and colleagues, at Dalian University of Technology, report a fast and efficient ligand-free protocol for the synthesis of N-heteroaryl substituted 9-arylcarbazolyl derivatives under aerobic and aqueous conditions using a palladium catalyst.

A highly efficient and aerobic protocol for the synthesis of N-heteroaryl substituted 9-arylcarbazolyl derivatives via a palladium-catalyzed ligand-free Suzuki reaction
Xiaofeng Rao, Chun Liu, Jieshan Qiu and Zilin Jin

The inside cover features the work of James D. White and co-workers, Oregon State University, describing the total synthesis of phorboxazole A, one of the most potent antitumor marine macrolide natural products with a challenging structure.

Total synthesis of the marine toxin phorboxazole A using palladium(II)-mediated intramolecular alkoxycarbonylation for tetrahydropyran synthesis
Punlop Kuntiyong, Tae Hee Lee, Christian L. Kranemann and James D. White

Also featuring in this issue are 4 Communications:

Rationally-designed fluorescent lysine riboswitch probes
Pradeep Budhathoki, Lina F. Bernal-Perez, Onofrio Annunziata and Youngha Ryu

A novel copper-catalyzed reductive coupling of N-tosylhydrazones with H-phosphorus oxides
Lei Wu, Xiǎo Zhang, Qing-Qing Chen and An-Kun Zhou

Rapid synthesis of substituted pyrrolines and pyrrolidines by nucleophilic ring closure at activated oximes
Nandkishor Chandan, Amber L. Thompson and Mark G. Moloney

KI-catalyzed imidation of sp3 C–H bond adjacent to amide nitrogen atom
Zhi-Qi Lao, Wen-He Zhong, Qing-Hua Lou, Zhong-Jun Li and Xiang-Bao Meng

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Small molecule control of bacterial biofilms – a must read review by Christian Melander

18 Sep 2012

This HOT review from Christian Melander and colleagues at North Carolina State University presents a comprehensive overview of development of small molecules targeting bacterial biofilms through non-microbicidal mechanisms. Melander et al. discuss the varied approaches that are applied to the discovery of lead small molecules that mediate the development of biofilms. These are grouped as:

Compounds that modulate biofilms by targeting bacterial signalling pathways
Chemical library screening
Natural products and natural product analogues that possess anti-biofilm activity

This review is very timely and covers an important topic in addressing bacterial infections, as antibiotic resistance is an issue of ever increasing concern, and has been described as a must read.

Download it today by following the link below; it’s free to access for 4 weeks

Small molecule control of bacterial biofilms
Roberta J. Worthington, Justin J. Richards and Christian Melander
DOI: 10.1039/C2OB25835H

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OBC issue 38 online now: Kulinkovich cyclopropanation, organozinc halides and much, much more

13 Sep 2012

Featuring on this week’s front cover is a review from Margaret A. Brimble summarising the application of the Kulinkovich cyclopropanation in the transformation of esters with diisopropoxytitanacyclopropane derivatives into cyclopropanols in the total synthesis of natural biologically active compounds.

The Kulinkovich hydroxycyclopropanation reaction in natural product synthesis
Isabell Haym and Margaret A. Brimble

On the inside cover is a HOT communication from Ying Fu et al. presenting a general procedure for the nucleophilic addition of organozinc halides to nitrones using trimethylsilyl chloride as a promoter and as a good protection reagent for the sensitive N-hydroxylamine group.

Trimethylsilyl chloride promoted synthesis of α-branched amines by nucleophilic addition of organozinc halides to nitrones
Ying Fu, Yanhua Liu, Yaojuan Chen, Helmut M. Hügel, Minzhu Wang, Danfeng Huang and Yulai Hu

Both articles are free to access for 6 weeks

Also in this issue:

3 more HOT articles:

Catalytic asymmetric synthesis of butane diacetal-protected (4S,5S)-dihydroxycyclohexen-1-one and use in natural product synthesis
David J. Burns, Shuji Hachisu, Peter O’Brien and Richard J. K. Taylor
DOI: 10.1039/C2OB26406D

An alternative one-pot gold-catalyzed approach to the assembly of 11H-indolo[3,2-c]quinolines
Giorgio Abbiati, Antonio Arcadi, Marco Chiarini, Fabio Marinelli, Emanuela Pietropaolo and Elisabetta Rossi
DOI: 10.1039/C2OB26380G

Steric effects on the catalytic activities of zinc(II) complexes containing [12]aneN₃ ligating units in the cleavage of the RNA and DNA model phosphates
Yang Song, Ju Zan, Hao Yan, Zhong-Lin Lu and Ruibing Wang
DOI: 10.1039/C2OB25624J

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Catalytic asymmetric synthesis of butane diacetal-protected (4S,5S)-dihydroxycyclohexen-1-one and use in natural product synthesis

12 Sep 2012

In this Communication Peter O’Brien and colleagues from the University of York describe a short and efficient asymmetric synthesis of a chiral cyclohexenone derivative ((4S,5S)-dihydroxycyclohexen-1-one ). This derivative is a very useful synthon for a variety of natural products, as shown by O’Brien et al., who prepare 2 cyclohexenone natural products isolated from the mycelia of Lasiodiplodia theobromae.

The approach presented has been described as being ‘elegant chemistry which uses symmetry breaking reactions to quickly reach a synthetic goal.’

Find out more by downloading the Communication now….

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An alternative one-pot gold-catalyzed approach to the assembly of 11H-indolo[3,2-c]quinolines

12 Sep 2012

In this HOT paper Antonio Arcadi, Università degli Studi di L’Aquila, and colleagues present a newly developed one-pot gold-catalysed approach to the assembly of 11H-indolo[3,2-c]quinolines from readily available unprotected 2-[2-(2-aminophenyl)ethynyl]anilines and aldehydes.

Arcadi et al. use the clever idea of first using a fast regio-selective intramolecular reaction, followed by a slower intermolecular condensation and subsequent cyclisation and final hydrogen transfer nicely provides a fast, synthetically efficient and elegant access to indolo[3,2-c]quinolines. With its broad scope, mild conditions and high regioselectivity this could be a valuable alternative to protocols previously described in the literature.

Find out more by downloading this paper today. It’s free to access for 4 weeks so grab it whilst you can.

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