Revitalizing the aromatic aza-Claisen rearrangement: implications for the mechanism of ‘on-water’ catalysis
Kaitlin D. Beare and Christopher S. P. McErlean
DOI: 10.1039/C3OB40118A   

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Reversible protein affinity-labelling using bromomaleimide-based reagents
Ramiz I. Nathani, Vijay Chudasama, Chris P. Ryan, Paul R. Moody, Rachel E. Morgan, Richard J. Fitzmaurice, Mark E. B. Smith, James R. Baker and Stephen Caddick
DOI: 10.1039/C3OB40239H 

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In this HOT article, Rao and co-workers report a novel Rh(II) and Ru(II) catalysed regio- and chemoselective C-H oxygenation for the facile synthesis of a variety of functionalised phenols from easily accessible arenes. The reaction demonstrates excellent reactivity, ortho-selectivity, good functional group tolerance and high yields. This practical method allowed the synthesis of a few 2-acylphenols in gram-scale and its utility has been well exemplified in further applications in heterocycle synthesis and direct modification of drug Fenofibrate.

Broadening the catalyst and reaction scope of region- and chemoselective C–H oxygenation: a convenient and scalable approach to 2-acylphenols by intriguing Rh(II) and Ru(II) catalysis
Gang Shan, Xuesong Han, Yun Lin, Shanyou Yu and Yu Rao
DOI: 10.1039/C3OB27457H

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In this HOT paper, Blagg and coworkers at the Institute of Cancer Research, Sutton, report an efficient C2-functionalisation via direct C–H arylation for N3-MEM-protected imidazo[4,5-b]pyridines. The imidazo[4,5-b]pyridine heterocycle is a versatile purine isostere and important ring system which has seen a recent growth in medicinal chemistry application of potential therapeutic benefit; for example in protein kinase inhibitors for the treatment of cancer, inflammatory disease and diabetes. This methodology allows easy access to 2,7- and 2,6-disubstituted derivatives from common intermediates in an approach amenable to the divergent synthesis of analogues and which is applicable to rapid medicinal chemistry exploration of this emerging purine isostere.

Regioselective C2-arylation of imidazo[4,5-b]pyridines
Jonathan Macdonald, Victoria Oldfield, Vassilios Bavetsias and Julian Blagg
DOI: 10.1039/C3OB27477B

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In this HOT paper, Marder, Whiting, Przyborski and co-workers investigate the ability of thiazole-containing small molecules to induce the differentiation of human pluripotent stem cells and their derivatives. Understanding how the structure of molecules relates to their function and biological activity is essential in the development of new analogues with targeted activity. This is especially relevant in mediating developmental processes in mammalian cells and the regulation of stem cell differentiation. This study provides further insight into the complexity of compound design in terms of developing small molecules with specific biological activities to control the development and differentiation of mammalian cells.

Synthesis and applications of 2,4-disubstituted thiazole derivatives as small molecule modulators of cellular development
Garr-Layy Zhou, Daniel M. Tams, Todd B. Marder, Roy Valentine, Andrew Whiting and Stefan A. Przyborski
DOI: 10.1039/C3OB00005B

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These articles are HOT as recommended by the referees. And we’ve made them free to access for 4 weeks.

Host–guest complexation driven dynamic supramolecular self-assembly 
Huacheng Zhang, Kim Truc Nguyen, Xing Ma, Hong Yan, Junfei Guo, Liangliang Zhu and Yanli Zhao

Org. Biomol. Chem., 2013, DOI: 10.1039/C2OB27340C

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Modular synthesis of polyene side chain analogues of the potent macrolide antibiotic etnangien by a flexible coupling strategy based on hetero-bis-metallated alkenes 

Mario Altendorfer, Aruna Raja, Florenz Sasse, Herbert Irschik and Dirk Menche

Org. Biomol. Chem., 2013, DOI: 10.1039/C2OB26906F

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Synthesis and binding studies of novel di-substituted phenanthroline compounds with genomic promoter and human telomeric DNA G-quadruplexes
Chunying Wei, Yanbo Wang, Meiying Zhang
DOI: 10.1039/C3OB27426H

Researchers in China have developed a series of phenanthroline molecules that interact with human telomeric DNA G-quadruplexes, which are promising targets in anti-cancer drug discovery.

G-quadruplexes are guanine-rich nucleic acid sequences. The guanine bases can hydrogen bond to form tetrads, and these tetrads can then stack up to form a G-quadruplex. They are significant in telomeres as their formation inhibits the telomerase enzyme, which is implicated in the onset of around 85% of cancers.

G-quadruplexes are also increasingly being found in non-telomeric parts of the chromatid, such as genomic promoter regions. Their presence and purpose is still not fully understood although they have also been implicated in cell aging and the formation of cancerous cells. For these reasons, G-quadruplexes are pretty promising targets for drug discovery.

Phenanthrolines can stabilise telomeric G-quadruplexes, and some have shown excellent inhibition of the telomerase enzyme. Before now, interactions between phenanthrolines and promoter G-quadruplexes have been relatively unstudied.

In this HOT article, Chunying Wei and co-workers at the Key Laboratory of Chemical Biology and Molecular Engineering at Shanxi University have synthesised six novel di-substituted phenanthroline molecules. They have also probed their interaction with human telomere and promoter G-quadruplexes. They have found that the compounds significantly inhibit the telomerase enzyme at low micromolar concentrations.

It is hoped that these molecules will aid and inspire the design of new anti-cancer drugs.

Annabella Newton is an organic chemist based in Melbourne, Australia. Until recently, she was a postdoctoral researcher and she has just started work as a trainee patent attorney with Phillips Ormonde Fitzpatrick.

In this HOT article Carsten Schmuck and co-workers report the synthesis and evaluation of a series of four-armed peptide ligands that can inhibit β-tryptase. These tetravalent ligands are made up of 2 sets of arms incorporating the artificial arginine analogue guanidiniocarbonyl pyrrole cation and can inhibit β-tryptase in a reversible and non-competitive way by binding to anionic hotspots on the surface of the enzyme.

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A new approach to inhibit human β-tryptase by protein surface binding of four-armed peptide ligands with two different sets of arms
Qian-Qian Jiang, Lina Bartsch, Wilhelm Sicking, Peter R. Wich, Dominik Heider, Daniel Hoffmann and Carsten Schmuck
DOI: 10.1039/C3OB27302D

Over the past few decades a lot of interest has been given to macrocycles with a twisted structure that has a preferred direction and show an optical chirality due to their possible uses in many areas such as in materials for chiral recognition.

In this HOT paper Eiji Yashima and colleagues from Nagoya University report the design and synthesis of three helically twisted [1 + 1]macrocycles, whose chirality can be controlled by acid–base interactions and zinc coordination.

Yashima et al. connect the twisted [1 + 1]macrocycles using via o-, m-, and p-linkages and use chiral amidinium–carboxylate salt bridges as a versatile structural motif to control the twisting motion of the macrocycles.

Find out all of the details of this study by downloading this paper. It’s free to access for 4 weeks.

Synthesis of helically twisted [1 + 1]macrocycles assisted by amidinium–carboxylate salt bridges and control of their chiroptical properties
Yuji Nakatani, Yoshio Furusho and Eiji Yashima
DOI: 10.1039/C2OB27054D

In this HOT communication, Yanli Zhao and co-workers from Nanyang Technological University report the construction of a series of dynamic supramolecular self-assemblies based on covalently linked pillar[5]arene trimers. These trimers have three binding sites, each capable of interacting with a bivilogen bipyridinium functionality. In solution these molecules assemble into complex structures.

Zhao et al. use techniques including dynamic light scattering, scanning electron microscopy and transmission electron microscopy to permit the detailed examination of these elegant supramolecular assemblies.

Acetone mixtures of the two components produce small building blocks at concentrations of 0.5 mM, with expanding aggregates rolling into hollow nanospheres when concentrations approach 1 mM. Beyond this concentration large flat layers are created, which stack at concentrations in excess of 2 mM. In essence the system demonstrates a reversible multidimensional transformation from 0D to 3D, and is an example of controlled dynamic self-assembly.  This represents a novel method for developing new functional materials with a switchable morphology control.

Published on behalf of Steve Moore, Organic & Biomolecular Chemistry web science writer.