January 2011 – Organic & Biomolecular Chemistry Blog

Archive for January, 2011

HOT: Tetra-substituted furans in one pot? No problem!

26 Jan 2011

When a referee calls a paper outstanding you know you are onto a good thing!
Pirali et al. from Università degli Studi del Piemonte Orientale “A. Avogadro” have documented a straightforward synthesis of dialkyl 2-acyl-5-aminofuran-3,4-dicarboxylates, displaying four points of diversity and an unprecedented substitution pattern. The products are easily isolated and the functional groups are ripe for further derivatisation, making this a reaction which is both mechanistically interesting and also has practical value for synthetic and medicinal chemists.

Both reviewers thought this HOT article would be of wide interest in the organic community and it is now free to access until 18th February.

Read it today in OBC.

A novel α-isocyanoacetamide-based three-component reaction for the synthesis of dialkyl 2-acyl-5-aminofuran-3,4-dicarboxylates
Riccardo Mossetti, Diego Caprioglio, Giampiero Colombano, Gian Cesare Tron and Tracey Pirali
Org. Biomol. Chem., 2011, Advance Article
DOI: 10.1039/C0OB00979B

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HOT: Two-faced nucleosides combat RNA viruses

25 Jan 2011

Ribavirin is a nucleoside drug used to treat RNA viral infections such as Hepaptitis C, which interferes with RNA metabolism required for viral replication. But its efficiency is relatively low, so in a HOT article just published, Yang He and colleagues at Sichuan University report the synthesis of two new nucleosides and their improved anti-viral activity.

He’s nucelosides contain structural features of two naturally occurring components of RNA (guanine and cytosine). This unique feature allows it to interfere with the RNA virus via hydrogen bond pairing with either guanine or cytosine, as well as allowing it to be recognised by viral enzymes more efficiently than ribavirin.

If you want to find out more about these interesting bio-active nucleosides download the article now! It’s free to access until the 18th February.

Synthesis of Janus type nucleoside analogues and their preliminary bioactivity
Hao-Zhe Yang, Mei-Ying Pan, Da-Wei Jiang and Yang He
Org. Biomol. Chem., 2011, DOI: 10.1039/C0OB00495B

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HOT: Understanding chorismate mutase catalysis – a QM/MM study

25 Jan 2011

This latest contribution to the debate over the origin of catalysis in the chorismate mutase enzyme may bring an end to the controversy surrounding the nature of its transition state.

Adrian Mulholland and collaborators at the University of Bristol have used quantum and molecular mechanics to model the rearrangement of chorismate to prephenate in Bacillus subtilis chorismate mutase and aqueous solution. The chorismate mutase enzyme is a favourite model for theories of biological catalysis, but there is still disagreement on exactly how it occurs.

The team found that a slightly different reaction path was followed in each environment and that there were differences in the transition state structures between water and the enzyme. A significantly more stable transition state was formed in the enzyme. These results are in opposition to previously published work which suggested that catalysis in the enzyme does not involve transition state stabilisation at all, but rather is due to the formation of a reactive conformation of the substrate.

The referees were impressed with the careful and thorough nature of this study – read the full article online here, it’s free until the end of February.

Analysis of chorismate mutase catalysis by QM/MM modelling of enzyme-catalysed and uncatalysed reactions
Frederik Claeyssens, Kara E. Ranaghan, Narin Lawan, Stephen J. Macrae, Frederick R. Manby, Jeremy N. Harvey and Adrian J. Mulholland
Org. Biomol. Chem., 2011, Advance Article
DOI: 10.1039/C0OB00691B

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Review: Copper catalysis in the construction of indole and benzo[b]furan rings

24 Jan 2011

The impact of copper chemistry on indole and benzo[b]furan synthesis in the last years has been extraordinary. Heterocycles are very important structural motifs due to their presence in natural products, drug discovery and chemical comodities. Therefore, the search of suitable methods for the synthesis of heterocycles is a very important topic nowadays.

Copper is a relatively cheap metal with great catalytic properties. Copper catalysis has received a great deal of attention in organic synthesis recently and and a variety of new practical and efficient methods based on copper-catalyzed reactions have been developed.

In this review, Sandro Cacchi and colleagues at University of Rome highlight the many methods for indole and benzofuran construction by copper catalysis that has been described in recent years.

‘We believe that this brief summary can provide the reader with a helpful overview of the copper chemistry in this area and can be of value to chemists planning the construction of specific indole and benzo[b]furan derivatives’

At the editorial office we also believe that the reader will find this review very constructive and informative. Read it here.

Copper catalysis in the construction of indole and benzo[b]furan rings
Sandro Cacchi, Giancarlo Fabrizi and Antonella Goggiamani
Org. Biomol. Chem., 2011, 9, 641-652
DOI: 10.1039/C0OB00501K

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Reliable DFT transition structures – Cover Issue 3

21 Jan 2011

Are you concerned about your choice of functional? Losing sleep over computing costs? Then look no further than OBC!

This article by Jonathan Goodman and Luis Simón, highlighted on the cover of OBC Issue 3, discusses the relative merits of twelve different DFT functionals for the geometry optimisation of organic transition state structures.

They concluded that despite more sophisticated (and therefore costly) functionals being available, B3LYP and related functionals are still capable of predicting transition states with an acceptable level of accuracy.

The full article is currently free to access until March – download it today for an end to your functional troubles!

How reliable are DFT transition structures? Comparison of GGA, hybrid-meta-GGA and meta-GGA functionals
Luis Simón and Jonathan M. Goodman
Org. Biomol. Chem., 2011, 9, 689-700
DOI: 10.1039/C0OB00477D, Paper

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HOT: Enantioselectivity in aridization reactions

12 Jan 2011

This HOT paper by Graham Hutchings and co-workers describes a cautionary tale of solubility, as the group discovered a systematic error in HPLC measurements of the enantiomeric excess of N-arene-sulfonyl-2-phenylaziridines.

They showed that the heterogeneous or homogeneous copper-catalysed synthesis of N-arene-sulfonyl-2-phenlaziridines mainly yields the R enantiomer. However previous reports significantly over-estimate the percentage enantiomeric excess when hexane was used as the HPLC injection solvent, due to the formation of an insoluble racemic phase.

The group has improved their analytical procedure to afford the correct value, but advise that previous reports on the
enantioselectivity of copper-catalysed aziridination reactions ‘should be regarded with caution if the analytical
procedure involved HPLC’.

Both reviewers thought this well-presented study is of importance to the field. Download it today – it’s now free to access until 8th February.

On the enantioselectivity of aziridination of styrene catalysed by copper triflate and copper-exchanged zeolite Y: consequences of the phase behaviour of enantiomeric mixtures of N-arene-sulfonyl-2-phenylaziridines

Laura Jeffs, Damien Arquier, Benson Kariuki, Donald Bethell, Philip C. Bulman Page and Graham J. Hutchings

Org. Biomol. Chem., 2011, Advance Article
DOI: 10.1039/C0OB00724B, Paper

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HOT: Double-headed nucleosides by the CuAAC reaction

11 Jan 2011

Poul Nielsen and his group at University of Southern Denmark describe the synthesis of new double-headed nucleosides, using the CuAAC reaction, and their influence on the stability of the hybridization of oligonucleotides.

In this HOT paper they describe a new type of nucleosides that are able to stabilize three-way junctions. If you want to find out more about these interesting stabilising contacts download the article, which is free to access until the 8th February.

The synthesis of double-headed nucleosides by the CuAAC reaction and their effect in secondary nucleic acid structures
Anna S. Jørgensen, Khalil I. Shaikh, Gerald Enderlin, Elise Ivarsen, Surender Kumar and Poul Nielsen
Org. Biomol. Chem., 2011, Advance Article
DOI: 10.1039/C0OB00438C

To give you a better overview on Nielsen’s previous research, we have outlined below a collection of their latest OBC published papers. Enjoy!

Stabilisation of nucleic acid secondary structures by oligonucleotides with an additional nucleobase; synthesis and incorporation of 2′-deoxy-2′-C-(2-(thymine-1-yl)ethyl)uridine
Søren Ljungberg Pedersen and Poul Nielsen
Org. Biomol. Chem., 2005, 3, 3570-3575
DOI: 10.1039/B510167K

Synthesis and modelling of DNA junction and minor groove zipper motifs incorporating the double-headed nucleoside 5′(S)–C-(thymine-1-ylmethyl)thymidine
Mikkel S. Christensen, Charlotte M. Madsen and Poul Nielsen
Org. Biomol. Chem., 2007, 5, 1586-1594
DOI: 10.1039/B700852J

Nucleic acid secondary structures containing the double-headed nucleoside 5′(S)-C-(2-(thymin-1-yl)ethyl)thymidine
Charlotte Andersen, Pawan K. Sharma, Mikkel S. Christensen, Signe I. Steffansen, Charlotte M. Madsen and Poul Nielsen
Org. Biomol. Chem., 2008, 6, 3983-3988
DOI: 10.1039/B810930C

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HOT: Studying the scope of the 1,2-sulfone rearrangement

11 Jan 2011

Adrien Quintard and Alexandre Alexakis from the University of Geneva report a systematic study on the application and scope of the 1,2-sulfone rearrangement and notably on its asymmetric variant.

A wide variety of nucleophiles can be used to yield highly functionalised substrates, with some demonstrating excellent enantioselectivities of up to 94% ee. This 1,2-sulfone rearrangement constitutes an alternative to the use of expensive 1,1-bis(phenylsulfonyl)ethene and leads to a formal alkylation of the nucleophile.

Both reviewers thought this HOT article would be of very wide interest in the organic community and it is now free to access until 8th February.

1,2-Sulfone rearrangement in organocatalytic reactions
Adrien Quintard and Alexandre Alexakis
Org. Biomol. Chem., 2011, Advance Article
DOI: 10.1039/C0OB00818D

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Organic & Biomolecular Chemistry Blog

Archive for January, 2011

Top ten most accessed articles in December

HOT: Tetra-substituted furans in one pot? No problem!

HOT: Two-faced nucleosides combat RNA viruses

HOT: Understanding chorismate mutase catalysis – a QM/MM study

Review: Copper catalysis in the construction of indole and benzo[b]furan rings

Reliable DFT transition structures – Cover Issue 3

Top ten most accessed articles in November

HOT: Enantioselectivity in aridization reactions

HOT: Double-headed nucleosides by the CuAAC reaction

HOT: Studying the scope of the 1,2-sulfone rearrangement

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