Chemical Communications Blog

This ChemComm Feature Article by Chuo Chen’s group, based at the Southwestern Medical Center, University of Texas focuses on biosynthesis and total synthesis of cyclic pyrrole-imidazole dimers. Pyrrole-imidazole alkaloids are secondary metabolites which are found exclusively in marine sponges. They have very unique structures and attractive biological properties. Part of what makes these molecules so interesting is the fact that they contain many functional groups and are highly populated with nitrogen atoms. Pyrrole-imidazole alkaloids often have polycyclic skeletons which make them ideal platforms to work on in the development of new synthetic ideas and methodologies.

Many pyrrole-imidazole alkaloids have been tested and determined to have promising biological properties such as anticancer, antimicrobial, antiviral or immunosuppressive activities. Although this is the case, much work still needs to be carried out to determine the full biological profile of pyrrole-imidazole alkaloids.

Another aspect of pyrrole-imidazole alkaloids which still contains unknowns is the biosynthetic pathway; a range of biosynthetic pathways have been suggested but the complete route has not yet been fully determined. It is agreed that the main stages of the biosynthesis are catalysed by cyclases and oxidases but the exact enzymes have not been identified. A number of interesting hypotheses are highlighted and discussed in this review including work from Faulkner and Clardy who isolated the first dimeric pyrrole-imidazole alkaloid, sceptrin, in 1981.

As well as summarising different biosynthetic routes to these intriguing compounds the authors also discuss synthetic strategies. Numerous groups have successfully synthesised different pyrrole-imidazole dimers and highlights of this section include Baran’s work synthesising a number of different dimers and Chen’s own work which involves developing a biomimetic approach for the synthesis of ageliferins. Chen’s synthesis contains an oxidative radical cyclisation as the key step to give the ageliferin core skeleton. The group have successfully synthesised a range of ageliferins using this adaptable approach.

To download the full article for free* click the link below:

Dimeric pyrrole-imidazole alkaloids: synthetic approaches and biosynthetic hypotheses
Xiao Wang, Zhiqiang Ma, Xiaolei Wang, Saptarshi De, Yuyong Ma and Chuo Chen
DOI: 10.1039/c4cc02290d

*Access is free until the 12.07.14 through a registered RSC account – click here to register

A compound that kills bacteria and cleaves their DNA to prevent them passing on drug-resistant genes has been designed by researchers in India.

The increasing ineffectiveness of antibiotics and the absence of suitable new ones are problems long recognised by the medical community. Bacteria can mutate and adapt to become resistant so the stock of effective antibiotics is diminishing. In a recent report, the UK’s Chief Medical Officer stated that increasingly resistant microbes represent a global threat that in the next 20 years could see many more deaths associated with what were routine and safe surgeries.

Read the full article in Chemistry World»

Read the original journal article in ChemComm – it’s free to download until 11th July:
A prospective antibacterial for drug-resistant pathogens: a dual warhead amphiphile designed to track interactions and kill pathogenic bacteria by membrane damage and cellular DNA cleavage
Durairaj Thiyagarajan, Sudeep Goswami, Chirantan Kar, Gopal Das and Aiyagari Ramesh
Chem. Commun., 2014, Advance Article, DOI: 10.1039/C4CC02354D, Communication

Due to their low volatility, favourable solvent properties and tunable phase behaviour, ionic liquid (IL) technology continues to attract interest in a wide variety of applications. Over the last few decades, the term ‘task specific ionic liquid’ (TSIL) has appeared, the meaning of which is that the application has been considered more carefully in the design and structure of one or both of the constituent IL ions.

In this ChemComm communciation, researchers from the Los Alamos National Laboratory, New Mexico, USA, describe advances in the application of ILs in the area of nuclear fuel reprocessing. The authors describe how neptunium may exist in solution in +III, +IV, +V and + VI oxidation states. The pentavalent state is the most stable and common, but interestingly, usually the most reluctant to coordinate with ligands, or take part in ion exchange processes.

Ionic liquid molecular structure and stabilizing behaviour towards Np(V) in aqueous solution

In aqeuous solution, in the presence of the ionic liquid betaine bistriflimide, the lifetime of the Np(IV) solution species is significantly increased. This is followed by the presence of a characteristic electronic adsorption at 970nm. Without the IL, an anti-oxidant is required to keep the metal from converting to its +V form. Np(V) has a rich and complex coordination chemistry at room temperature, so the authors repeated experiments with sources of  Np(V) at 60^oC. After 3 days, 90% of the starting neptunium compound had been converted to the betaine complexed form, compared with a 15% conversion at room temperature. Again the material was stable in solution, not resulting in Np(IV) species unless a reducing agent such as hydrazine was deliberately added.

With this detailed study, the authors significantly add to the body of knowledge of competitive coordination chemistry of actinides in aqueous solutions of ionic liquids. This should, in turn, enable new separation technology R&D for the important task of nuclear fuel reprocessing.

Read this ChemComm communication for free* today!

Unusual redox stability of neptunium in the ionic liquid [Hbet][Tf₂N]
Kristy Long, George Goff and Wolfgang Runde
DOI: 10.1039/C4CC01835D

*Access is free untill Friday 6th June through a registered RSC account – click here to register

All of the referee-recommended articles below are free to access until 2nd June 2014

Surprising acidity of hydrated lithium cations in organic solvents
Haiqiang Deng, Pekka Peljo, T. Jane Stockmann, Liang Qiao, Tuomas Vainikka, Kyösti Kontturi, Marcin Opallo and Hubert H. Girault 
Chem. Commun., 2014,50, 5554-5557
DOI: 10.1039/C4CC01892C, Communication

In situ generation of sulfoxides with predetermined chirality via a structural template with a chiral-at-metal ruthenium complex
Zheng-Zheng Li, Su-Yang Yao, Jin-Ji Wu and Bao-Hui Ye 
Chem. Commun., 2014,50, 5644-5647
DOI: 10.1039/C4CC01907E, Communication

A triple-channel lab-on-a-molecule for triple-anion quantification using an iridium(III)–imidazolium conjugate
Kun Chen and Michael Schmittel 
Chem. Commun., 2014,50, 5756-5759
DOI: 10.1039/C4CC01421A, Communication

A bromine-radical mediated three-component reaction comprising allenes, electron-deficient alkenes and allyl bromides: facile synthesis of 2-bromo-1,7-dienes
Takashi Kippo and Ilhyong Ryu 
Chem. Commun., 2014, Advance Article
DOI: 10.1039/C4CC01597E, Communication

Photocatalytic CO2 reduction using a molecular cobalt complex deposited on TiO2 nanoparticles
Tong Jin, Chao Liu and Gonghu Li 
Chem. Commun., 2014, Advance Article
DOI: 10.1039/C4CC00503A, Communication

Simulation of the self-assembly of simple molecular bricks into Sierpiński triangles
Pawel Szabelski and Damian Nieckarz 
Chem. Commun., 2014, Accepted Manuscript
DOI: 10.1039/C4CC01344A, Communication
From themed collection Systems Chemistry

Graphene nanoribbons (GNRs) are ultra-thin strips of graphene which exhibit technologically relevant optical, electronic and magnetic properties. How well these properties can be defined, understood and exploited depends on how precisely these ‘GNRs’ can be prepared. Top-down approaches to realise these materials from, for example, graphite, graphene or carbon nanotubes have been developed over recent years. However, the resultant  materials are typically non-uniform, being wide, (relatively speaking) with a large amount of disorder.

In this ChemComm communication, Alexander Sinitskii and co-workers from the University of Nebraska and collaborators from the University of Puerto Rico report an elegant, controlled, bottom-up solution synthesis of well defined nitrogen doped graphene nano-ribbons. Though the materials produced are extremely insoluble, they have been extensively characterised via a range of surface analytical techniques.

The synthesis itself centres around the 3 step preparation of a multi-aryl containing dibromo pyrimidine monomer which is polymerised via a Yamamoto coupling using a nickel catalyst. The desired graphene  structure is delivered via a cyclodehydrogenation Scholl reaction using ferric chloride. The molecular control from this route yields a very well defined structure. The only disorder introduced is a symmetrical one due to alternate possible sites for the  four constituent nitrogen atoms present in each unit cell.

Synthetic route to well defined nitrogen doped graphene nanoribbons (4N-GNRs)

The 4N-GNR materials were deposited on a variety of supports to enable microscopic and surface analytics such as AFM, STM, TEM, XPS, EDX and Raman spectroscopy. The materials were observed to take on a ‘nanobelt’ conformation on deposition from sonicated dispersions. Particularly striking is the improvement in the fine structure reported in the Raman spectra, compared with typical signals for less well defined carbon materials, confirming the structural quality of the 4N-GNRs produced.

This communication will doubtless prove important to the development of sustainable synthetic routes to well defined graphene nanoribbons, enabling  further study of the fascinating properties of these exciting new materials.

Read this RSC Chemical Communication today – access is free* for a limited time only!

Bottom-up solution synthesis of narrow nitrgoen-doped graphene nanoribbons
Chem. Commun., 2014,50, 4172-4174
DOI: 10.1039/C4CC00885E

*Access is free untill the 19th May through a registered RSC account – click here to register

All of the articles below are free to access until 14th May

Oxamato-based coordination polymers: recent advances in multifunctional magnetic materials
Thais Grancha, Jesús Ferrando-Soria, María Castellano, Miguel Julve, Jorge Pasán, Donatella Armentano and Emilio Pardo  
Chem. Commun., 2014, Advance Article
DOI: 10.1039/C4CC01734J, Feature Article

Applying a multitarget rational drug design strategy: the first set of modulators with potent and balanced activity toward dopamine D3 receptor and fatty acid amide hydrolase
Alessio De Simone, Gian Filippo Ruda, Clara Albani, Glauco Tarozzo, Tiziano Bandiera, Daniele Piomelli, Andrea Cavalli and Giovanni Bottegoni  
Chem. Commun., 2014, Advance Article
DOI: 10.1039/C4CC00967C, Communication

Stability, durability and regeneration ability of a novel Ag-based photocatalyst Ag2Nb4O11
Hongjun Dong, Gang Chen, Jingxue Sun, Yujie Feng, Chunmei Li and Chade Lv  
Chem. Commun., 2014, Accepted Manuscript
DOI: 10.1039/C4CC01183J, Communication

Tunable light emission from co-assembled structures of benzothiadiazole molecules
Kaushik Balakrishnan, Wei-Liang Hsu, Shuntaro Mataka and Stanley Pau  
Chem. Commun., 2014, Advance Article
DOI: 10.1039/C4CC01685H, Communication

Biomolecular Logic Gate for Analysis of the New Delhi Metallo-β-Lactamase (NDM)-Coding Gene with Concurrent Determination of Its Drug Resistance-Encoding Fragments
Yu-Hsuan Lai, Yu-Chieh Liao, Jung-Jung Mu, Tsui-Ming Kuo, Yuan-Hao Hsu and Min-Chieh Chuang  
Chem. Commun., 2014, Accepted Manuscript
DOI: 10.1039/C4CC01108B, Communication

A gram-scale route to phlegmarine alkaloids: rapid total synthesis of (−)-cermizine B
Ben Bradshaw, Carlos Luque-Corredera and Josep Bonjoch  
Chem. Commun., 2014, Advance Article
DOI: 10.1039/C4CC01708K, Communication

Useful small molecules with potential applications in the cosmetics and fine chemical industries have been recovered from waste plastics by scientists in the US.

Petroleum based polymers such as polyesters and polycarbonates make up a significant proportion of the 100 million tonnes of plastic waste generated globally every year, of which only between 5–30% is recycled. Traditional recycling commonly leads to new plastics with inferior properties that frequently find use in lower grade applications, such as fibres or carpeting.

The pincer catalyst hydrogenates the ester linked backbone of the polymer, unzipping it into small molecules

Read the full article in Chemistry World»

Read the original journal article in ChemComm – it’s free to download until 2^nd May:
Controlled hydrogenative depolymerization of polyesters and polycarbonates catalyzed by ruthenium(II) PNN pincer complexes
Eric M. Krall, Tyler W. Klein, Ryan J. Andersen, Alex J. Nett, Ryley W. Glasgow, Diana S. Reader, Brian C. Dauphinais, Sean P. Mc Ilrath, Anne A. Fischer, Michael J. Carney, Dylan J. Hudson and Nicholas J. Robertson  
Chem. Commun., 2014, Advance Article, DOI: 10.1039/C4CC00541D

Here are this month’s referee-recommended hot articles – all free to download until 13th April:  

High gas storage capacities and stepwise adsorption in a UiO type metal–organic framework incorporating Lewis basic bipyridyl sites
Liangjun Li, Sifu Tang, Chao Wang, Xiaoxia Lv, Min Jiang, Huaizhi Wu and Xuebo Zhao  
Chem. Commun., 2014,50, 2304-2307
DOI: 10.1039/C3CC48275H, Communication  

Hydrosilylation catalysis by an earth alkaline metal silyl: synthesis, characterization, and reactivity of bis(triphenylsilyl)calcium
Valeri Leich, Thomas P. Spaniol, Laurent Maron and Jun Okuda  
Chem. Commun., 2014,50, 2311-2314
DOI: 10.1039/C3CC49308C, Communication  

Nano-sized heterometallic macrocycles based on 4-pyridinylboron-capped iron(II) clathrochelates: syntheses, structures and properties
Ying-Ying Zhang, Yue-Jian Lin and Guo-Xin Jin  
Chem. Commun., 2014,50, 2327-2329
DOI: 10.1039/C3CC49038F, Communication  

Structural analysis and reactivity of unusual tetrahedral intermediates enabled by SmI2-mediated reduction of barbituric acids: vinylogous N-acyliminium additions to α-hydroxy-N-acyl-carbamides
Michal Szostak, Brice Sautier and David J. Procter  
Chem. Commun., 2014,50, 2518-2521
DOI: 10.1039/C3CC48932A, Communication  

The genesis of a heterogeneous catalyst: in situ observation of a transition metal complex adsorbing onto an oxide surface in solution
Antoine Hervier, Juliette Blanchard, Guylène Costentin, John Regalbuto, Catherine Louis and Souhir Boujday  
Chem. Commun., 2014,50, 2409-2411
DOI: 10.1039/C3CC48838A, Communication  

Click here to see more hot ChemComm articles for March

Anchoring aspirin onto cisplatin could create a cancer treatment capable of overcoming drug resistance in cisplatin resistant cells, new research shows.

Cisplatin, along with other chemotherapeutic drugs, is used to treat various types of cancer, including testicular, ovarian, lung and bladder cancer. However, clinical use of cisplatin is limited by developing resistance, earning it the nickname the ‘penicillin of cancer’. Resistance mechanisms to cisplatin are well defined, but there are still no treatments available to surmount or reverse it.

Upon cellular uptake, asplatin is reduced by ascorbic acid to give cisplatin and aspirin

Read the full article in Chemistry World»

Read the original journal article in ChemComm – it’s free to access until 22nd April:
The Ligation of Aspirin to Cisplatin Demonstrates Significantly Synergistic Effect to Tumor Cells
Qinqin Cheng, Hongdong Shi, Hong-Xia Wang, Yuanzeng Min, Jun Wang and Yangzhong Liu  
Chem. Commun., 2014, Accepted Manuscript, DOI: 10.1039/C4CC00419A