Archive for the ‘Reviews’ Category

Don’t underestimate the power of the dark side

Electrophilicity - the dark side of indole reactivity

In this PERSPECTIVE article, Marco Bandini presents an overview of indole electrophilicity, illustrated with a range of pertinent examples of this “dark-side” of indole reactivity.

Indoles are one of the most common heterocyclic motifs found in nature. These bicyclic arenes have had a profound impact on drug discovery, materials science, catalysis and many other areas of chemistry.

Professor Marco Bandini and his research group at the Università di Bologna specialise in indole “decoration” and the development of new methodology for the chemical manipulation of this functional group.

The indolyl core is, as Bandini explains, “spectacularly nucleophilic” and this accounts for a large proportion of the literature contributions. There is, however, also a relatively undeveloped side of their reactivity: “electrophilic” indoles.

While there are many examples of this type of reactivity, some of which date back to the 1960s, it remains in the shadow of the well-understood and established chemistry that explores the indole core’s innate nucleophilicity. The opportunities to expand the chemical portfolio of indole decoration, via nucleophilic substitutions and additions, are still largely unexplored.

The ubiquity of this core means that new ways to functionalise and manipulate indoles will always be a welcome addition to the organic chemist’s toolbox. As Bandini discusses, exploitation of the umpolung chemistry of these functional groups provides access to a wide diversity of chemical structures.

This Perspective article elegantly documents the electrophilic nature of indoles, and highlights some of the important discoveries and developments in this field. It is a must-read for anyone interested in these intriguing molecules.

Give yourself to the dark side and check out the article here.

Electrophilicity: the “dark-side” of indole chemistry
Marco Bandini
DOI: 10.1039/C3OB40735G

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PERSPECTIVE – A Brief History of Molecular Sensors

In this HOT article, Julius Rebek Jr presents a fascinating insight into the design of molecules which can detect and destroy organophosphorus compounds.

Organophosphorus (OP) compounds are primarily used as pesticides, and can be a useful alternative to more traditional chlorinated hydrocarbon-based pesticides. However, due to OP compounds’ ability to inhibit acetylcholine esterase (AChE), they can be extremely toxic to humans and they have therefore found use as nerve agents and chemical weapons. For these reasons, their toxicity is an area of intense research focus and new methods for their detection and treatment are always welcome.

Rebek and his research group at The Scripps Research Institute have been looking into molecular sensors for OPs for several years, and this paper highlights some of the significant developments in the field. Their interest in the area was sparked by a carefully crafted pyridine structure discovered by Swager, which upon reaction with an OP undergoes a subsequent cyclisation reaction to create a fluorescent dye. This is a useful premise for the sensing of OPs. The Rebek group have expanded upon this premise and developed a series of molecular sensors that employ similar mechanisms. They have used their established expertise in cavitand chemistry to develop specially-tailored vase-shaped molecules, which are able to fold around OP-based nerve agents and isolate them from the surrounding medium. This paper provides a whistle-stop tour of an exciting and important area of organic chemistry.

Chemical approaches for detection and destruction

Chemical approaches for detection and destruction of nerve agents
Dariush Ajami and Julius Rebek, Jr.
DOI: 10.1039/c3ob40324f

Free to access for 4 weeks

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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

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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Taking a look at this week’s issue of Organic & Biomolecular Chemistry

Organic & Biomolecular Chemistry issue 42

On the front cover:

We have this HOT article from Marcos N. Eberlin and colleagues studying corrole isomers using traveling wave ion mobility mass spectrometry and collision induced dissociation experiments. The isomers had subtle structural changes, promoted by exchange of nitrogen and carbon atoms in the corrole ring, and significant differences in the shapes and charge distributions of the protonated molecules were found to lead to contrasting gas phase mobilities.

Corrole isomers: intrinsic gas-phase shapes via traveling wave ion mobility mass spectrometry and dissociation chemistries via tandem mass spectrometry
Maíra Fasciotti, Alexandre F. Gomes, Fabio C. Gozzo, Bernardo A. Iglesias, Gilberto F. de Sá, Romeu J. Daroda, Motoki Toganoh, Hiroyuki Furuta, Koiti Araki and Marcos N. Eberlin
DOI: 10.1039/C2OB26209F

On the inside cover:

A Perspective by Xuefeng Jiang, Jason S. Chen and colleagues, on the thermodynamic driving force of many synthetic transformations – gas extrusion. The review focuses on gas expulsion in key reactions within natural products total syntheses, selected from the past two decades. Included are transformations that generate sulfur dioxide, carbon dioxide, carbonyl sulfide, or nitrogen through polar, radical, pericyclic, photochemical, or organometallic mechanisms.

Gas extrusion in natural products total synthesis
Xuefeng Jiang, Lei Shi, Hui Liu, Akbar H. Khan and Jason S. Chen
DOI: 10.1039/C2OB26152A

There is also:

Another HOT article on the efficient synthesis of N-(buta-2,3-dienyl) amides from terminal N-propargyl amides and their synthetic potential towards oxazoline derivatives by Shengming Ma et al., 1 Communication and 16 more Papers… read them all in OBC issue 42 – it’s online now.

And don’t forget, the cover articles will be free to access for the next 6 weeks!

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Metal-free reactions of alkynes via electrophilic iodocarbocyclizations

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

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 36 online now!

It’s all getting a bit fruity on the cover of this week’s issue of OBC thanks to the work of Sungwoo Hong and co-workers from Korea Advanced Institute of Science and Technology. Hong et al. present the impressive catalytic effects of Fe(OTf)3 in the Pd(II)-catalyzed conjugate addition of arylboronic acids to chromones to give a variety of flavanones, which exclusively yield flavone analogs when of catalytic amounts of DDQ and KNO2 are added.

Synthetic approach to flavanones and flavones via ligand-free palladium(II)-catalyzed conjugate addition of arylboronic acids to chromones
Donghee Kim, Kyungrok Ham and Sungwoo Hong

The inside cover highlights the work of Alexander V. Butin and colleagues, who have developed a simple method for the transformation of furfural, a large-scale product from the processing of agricultural and forestry wastes, into the  potent pharmacologically active compounds indolo[3,2-c]quinolines and isocryptolepines.

From biomass to medicines. A simple synthesis of indolo[3,2-c]quinolines, antimalarial alkaloid isocryptolepine, and its derivatives
Maxim G. Uchuskin, Arkady S. Pilipenko, Olga V. Serdyuk, Igor V. Trushkov and Alexander V. Butin

Both of these cover articles will be free to access for the next 6 weeks.

Also of interest in this issue is the review:

Organic fluorine as a polypeptide building element: in vivo expression of fluorinated peptides, proteins and proteomes

from L. Merkel and N. Budisa who present the most recent advances in the field of protein biosynthesis using fluorinated amino acids.

Read the entire issue HERE today!

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OBC issue 34 now online

Forget the pot of gold at the end of the rainbow, this week it’s all about getting you hands on issue 34 of Organic & Biomolecular Chemistry and its technicoloured covers.

On the front cover Hidemitsu Uno, Ehime University, and colleagues have prepared potential selective near-infrared (NIR) dyes by the fusion of boron-dipyrromethene (BODIPY) chromophores. Uno et al. designed these π-fused bis-BODIPY chromophores to show intensive absorption and strong fluorescence in the near-infrared region and not to have any strong absorption in the visible region.

π-Fused bis-BODIPY as a candidate for NIR dyes
Mitsunori Nakamura, Hiroyuki Tahara, Kohtaro Takahashi, Toshi Nagata, Hiroki Uoyama, Daiki Kuzuhara, Shigeki Mori, Tetsuo Okujima, Hiroko Yamada and Hidemitsu Uno

The inside cover from Xin-Dong Jiang, Henan University, and co-workers demonstrates the synthesis of a novel BODIPY from a 3,4,4a-trihydroxanthene-fused pyrrole, that is non-cytotoxic and so is suited to the labeling of living cells in the NIR region.

A NIR BODIPY dye bearing 3,4,4a-trihydroxanthene moieties
Xin-Dong Jiang, Ruina Gao, Yi Yue, Guo-Tao Sun and Weili Zhao

Also in this issue is a review by Liqun Jin and Aiwen Lei which presents insights into the elementary steps in Negishi coupling through kinetic investigations.

Read the complete issue here…. and as always the cover articles will be free to access for the next 6 weeks!

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Issue 32 now published: Lythracea alkaloids and core-substituted naphthalenediimides on the covers

Issue 32 is now published, read it here today!

The front cover of this issue (right) highlights the work of E. Peter Kündig et al. who present the total syntheses of the Lythracea alkaloids (+)-vertine and (+)-lythrine, which is the first reported total synthesis of (+)-lythrine.

Asymmetric synthesis of (+)-vertine and (+)-lythrine
Laëtitia Chausset-Boissarie, Roman Àrvai, Graham R. Cumming, Laure Guénée and E. Peter Kündig
DOI: 10.1039/C2OB25880C

The inside cover (left) is courtesy of Sheshanath V. Bhosale et al. whose Emerging area review provides an update on the progress in the field of core-substituted naphthalenediimides from 2010, covering supramolecular chemistry, sensors, photo-induced electron transport in artificial photosystems, and solar cell applications.

Recent progress of core-substituted naphthalenediimides: highlights from 2010
Sheshanath V. Bhosale,  Sidhanath V. Bhosale and Suresh K. Bhargava
DOI: 10.1039/C2OB25798J

Both of these articles will free to access for the next 6 weeks so take a look and let us know your thoughts by commenting below.

Missed our 10th anniversary themed issue for OBC? Well after reading this week’s issue have a look at the 68 articles that made up our 10th birthday issue here….
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Issue 31 online now, complete with mutant lipases & cyclic di-oxoguanidines

Organic & Biomolecular Chemistry issue 31, it’s here and waiting to be read!

Secondary alcohols having bulky substituents on both sides of the hydroxy group are inherently poor substrates for most lipases. In a paper by Tadashi Ema et al., highlighted on this week’s front cover of OBC (right), the detailed rational design and creation of mutant lipases that display remarkably enhanced catalytic activity and enantioselectivity for poor substrates bearing bulky substituents on both sides of the hydroxy group is presented.

Redesign of enzyme for improving catalytic activity and enantioselectivity toward poor substrates: manipulation of the transition state
Tadashi Ema, Yasuko Nakano, Daiki Yoshida, Shusuke Kamata and Takashi Sakai
DOI: 10.1039/C2OB25614B

The inside front cover (left) highlights the Communication of Wen-Xiong Zhang and Zhenfeng Xi et al., presenting the first metal-free one-pot sequential coupling of various amines, carbodiimides and acyl dichlorides, providing a simple and straightforward path to cyclic di-oxoguanidines via an unexpected 2,2-dichloroimidazolidindione intermediate.

Metal-free synthesis of cyclic di-oxoguanidines via one-pot sequential transformation of amines, carbodiimides and acyl dichlorides
Fei Zhao, Yang Wang, Wen-Xiong Zhang and Zhenfeng Xi
DOI: 10.1039/C2OB25799H

Both of these featured articles are FREE to access for the next 6 weeks, why not have a read and let us know your thoughts by commenting below.

 

Also in this issue:

Emerging Area
Transition metal-catalyzed fluorination of multi carbon–carbon bonds: new strategies for fluorinated heterocycles
Guosheng Liu
DOI: 10.1039/C2OB25702E

Perspective
Discovery, application and protein engineering of Baeyer–Villiger monooxygenases for organic synthesis
Kathleen Balke, Maria Kadow, Hendrik Mallin, Stefan Saß and Uwe T. Bornscheuer
DOI: 10.1039/C2OB25704A

View the complete issue online now……

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