Organic & Biomolecular Chemistry Blog

Computational tools for predicting the viability of reactions are invaluable for making synthetic chemists’ lives easier, and this latest study makes another valuable addition to the metaphorical toolbox.

It is assumed that microwave irradiation assists organic reactions, such as Diels-Alder reactions, by rapid heating of the reactants.  However, to date there are no computational studies which explain the role of microwaves on the course of these reactions.

Now, Maria Pilar Prieto and co-workers from the University of Castilla-La Mancha have used DFT to rationalise the activation of intramolecular Diels-Alder cycloaddition reactions under microwave conditions.  They  found that the activation energy of the reaction and the polarity of the stationary points on the reaction surface are good indicators of whether or not a reaction can be improved by microwave irradiation.

Read the full details of their findings online – the article is free to access for four weeks:

“In silico” mechanistic studies as predictive tools in microwave-assisted organic synthesis
A. M. Rodriguez, P. Prieto, A. de la Hoz and A. Díaz-Ortiz
Org. Biomol. Chem., 2011, Advance Article
DOI: 10.1039/C0OB01037E

Deazapurines are bicyclic heterocycles derived from purine where one nitrogen atom is replaced by a carbon. Although they have been widely studied in recent years, the mechanistic understanding of the biosynthesis of 7-deazapurines has always been intriguing.

There is a question that inevitably arise when looking at the biosynthetic pathway of deazapurines: Where does N-7 go? 

Now, Professor Moody and his group at University of Nottingham have solved this mystery by using a doubly labelled purine-adenine and following it up by NMR spectroscopy and mass spectrometry.
Their conclusions are supported and support a recent study published in Biochemistry.

If you want to find out more about the fate of this nitrogen and the mechanistic understanding of the biosynthesis of deazapurines, read this HOT paper which is free to access until 16th March.

7-Deazapurine biosynthesis: NMR study of toyocamycin biosynthesis in Streptomyces rimosus using 2-13C-7-15N-adenine
Ugo Battaglia, Jed E. Long, Mark S. Searle and Christopher J. Moody
Org. Biomol. Chem., 2011
DOI: 10.1039/C0OB01054E

Lantibiotics (and there is no spelling mistake) are a potential new class of antibiotics for clinical applications and food preservation. Their drawback is however their inability to penetrate the outer membranes of Gram-negative bacteria.

John Vederas and colleagues, at University of Alberta in Canada, try to overcome this problem by developing new ‘siderophores – transporters’ able to deliver lantibiotics to the targeted bacteria.

If you want to find out more about what happened next and the scope and limitation of siderophore-mediated drug transport for the development of new antibiotics download this HOT article which is free to access until 8th March.

Chemical synthesis and biological evaluation of gallidermin-siderophore conjugates
Sabesan Yoganathan, Clarissa S. Sit and John C. Vederas
Org. Biomol. Chem., 2011
DOI: 10.1039/C0OB00846J

Nature has been giving organic chemists inferiority complexes for many, many years, so it is always good to see a neat piece of synthesis for a tricky natural product.

The structure of viridenomycin – an antibiotic with anti-tumor activity – has been known for 20 years, but attempts to synthesise it thus far have failed due to its complex structure and inherent instability. Now, Andy Whiting and colleagues from Durham University have synthesised fragments suitable for constructing a particularly unstable part of viridenomycin via a series of cross-coupling reactions.

They focused on the northern polyene fragment, synthesising several analogues with better isometric ratios and increased stability towards photoisomerisation than the original tetraene fragment.  The authors hope that their method may help to achieve the total synthesis of this valuable complex molecule.

Read how they did it online – the article is free to access for 4 weeks!

Studies towards the synthesis of the northern polyene of viridenomycin and synthesis of Z-double bond analogues
Jonathan P. Knowles, Victoria E. O′Connor and Andrew Whiting
Org. Biomol. Chem., 2011, Advance Article
DOI: 10.1039/C0OB00977F

Organic azides are considered to be amongst the most hazardous chemicals and therefore not amongst the most popular within  synthetic chemistry communities. In organic chemistry they are commonly used as a way to introduce an amine group, which makes them key compounds for synthetic chemists.

Steven Ley, Ian Baxendale and their group at University of Cambridge, describe in these back to back papers the development of a flow process for the synthesis of alkyl and aryl azides in high conversions. One of the key features of this flow procedure is the introduction of a new monolithic triphenylphosphine reagent that allows the use of triphenylphosphine in flow to provide high purity products without the need of further purification steps.

They also describe a general protocol for the in-line purification of the intermediates. They incorporate the azide synthesis and purification process into a multistep flow sequence to generate a collection of aminocyanotriazoles in a fully automated fashion.

Now you can read these very interesting and HOT papers which are free to access until the 8th March.

Download both papers here.

Flow synthesis of organic azides and the multistep synthesis of imines and amines using a new monolithic triphenylphosphine reagent
Catherine J. Smith, Christopher D. Smith, Nikzad Nikbin, Steven V. Ley and Ian R. Baxendale
Org. Biomol. Chem., 2011
DOI: 10.1039/C0OB00813C

A fully automated, multistep flow synthesis of 5-amino-4-cyano-1,2,3-triazoles
Catherine J. Smith, Nikzad Nikbin, Steven V. Ley, Heiko Lange and Ian R. Baxendale
Org. Biomol. Chem., 2011
DOI: 10.1039/C0OB00815J