Chemical Science Blog

The RSC Macrocylic and Supramolecular Chemistry meeting (MASC-11) is taking place on the 19^th and 20^th December 2011 at the University of Bath, UK.

A number of high profile authors will be speaking at the meeting including Chem Soc Rev Associate Editor, Professor Phil Gale, and Professor Kay Severin who is giving the Chemical Science sponsored lecture. To find out more about Professor Severin’s research, download his latest Chemical Science articles:

• Dative boron–nitrogen bonds in structural supramolecular chemistry: multicomponent assembly of prismatic organic cages
• Constitutionally selective amplification of multicomponent 84-membered macrocyclic hosts for (−)-cytidine•H⁺

Dr Jonathan Nitschke will be delivering the Dalton Transactions lecture as a result of being awarded the 2011 Dalton Transactions European/African Lectureship earlier on this year. Jonathan has also recently been awarded the ChemComm 2012 Cram Lehn Pedersen award.

Read more about Jonathan’s research by downloading his Chemical Science articles: 

• Selective anion binding by a “Chameleon” capsule with a dynamically reconfigurable exterior 
• Reactivity modulation in container molecules.

ChemComm, Chemical Science and Chem Soc Rev Deputy Editor, Joanne Thomson, will be attending the event. If you would like to arrange a meeting with Joanne, please email her at the Editorial Office.

To attend MASC-11, register before the 12^th December 2011. The deadline for poster abstract submissions is 1^st December.

Researchers from the University of Reading have designed an organocatalysed cascade reaction for the construction of nitrocyclohexanes 4.

This elegant domino reaction enables the union of two achiral reagents to generate products containing up to five contiguous stereocentres in excellent levels of enantio- and diastereoselectivity.

André Cobb’s group employed a thiourea catalyst 3 to initiate a Michael-Michael cascade reaction between nitro-esters 1 and nitro-styrenes 2. The catalyst is thought to first coordinate to the nitro-ester prior to intramolecular deprotonation at the α-position to generate a nitronate. Synchronous coordination with nitrostyrene enables the first stereoselective Michael addition to generate a second nitronate primed for cyclisation onto the conjugated ester.

This cascade process demonstrates the power of organocatalysis for the asymmetric assembly of complex molecular architecture from simple starting materials.

Read more – download Cobb’s Edge article.

A DNA-based computational device with variable input has been developed by scientists led by Nadrian Seeman in the US. Previous examples of DNA-based computers have used fixed systems, but here they used the same system with different settings. This means that the system could be reusable, unlike other systems that perform one computation and then can’t be used again.

The readout of the system is obtained by algorithmically assembling gold nanoparticles. Although arranging gold nanoparticles by DNA self-assembly has been reported, this is the first time such an arrangement of nanoparticles has been obtained as the result of a computation.  The system may be considered as a first step in an assembly of a programmed array incorporating nanomechanical devices or other varieties of biochemical, chemical or materials systems that can be organised as the result of a simple computation.

Reference:
A Programmable Transducer Self-Assembled from DNA
B Chakraborty, N Jonoska and N C Seeman, Chem. Sci., 2011
DOI: 10.1039/c1sc00523e

Rotaxanes are dumbbell-shaped molecules that are threaded through a separate macrocylic molecule. The two molecules are not chemically bonded to one another but instead are mechanically interlocked – a feature that can be exploited for molecular switches in molecular electronics, actuators and controlled drug release.

In a quest to understand the spatial requirements of these molecules, Suvankar Dasgupta and Jishan Wu from the National University of Singapore have discovered the lightest rotaxane to date. The rotaxanes in question were composed of a dibenzylammonium ion which was threaded through crown ether molecules of various sizes. As a result of their investigations, Dasgupta and Wu found that a [20]crown ether was capable of encompassing the dibenzylammonium dumbbell.

To find out more about this research, download the Chemical Science article today.

Also of interest…

Visit the ChemComm Supramolecular web theme issue for lots more on Rotaxane structures.

A hybrid photocatalytic system, coupling a zeolite with graphene, has been developed by teams in the UK, India and Germany. This new system could have implications for important applications such as water and air purification, dye degradation, self-cleaning and anti-bacterial surfaces as well as various technical photosynthetic processes.

Dominik Eder at the University of Münster and colleagues at the University of Cambridge, used a titanosilicate zeolite (TS-1) with graphene incorporated, at varying concentrations, in its pores.  TS-1 was chosen becasue of its good photocatalytic properties and graphene was chosen for its exceptional electrical and optical properties, along with its ability to accept electrons via photoexcitation.

The team found that the photocatalytic activity was greater when compared to TS-1 hybrids with carbon nanotubes.

Reference:
Hybridizing photoactive zeolites with graphene: a powerful strategy towards superior photocatalytic properties
Z Ren, E Kim, S W Pattinson, K S Subrahmanyam, C N R Rao, A K Cheetham nd D Eder, Chem. Sci., 2011
DOI:10.1039/c1sc00511a

By building methotrexate – a potent leukaemia drug – into nanoscale coordination polymers as bridging ligands, scientists have achieved high drug loadings of 79 wt% and selective delivery to cancer cells, where the drug is released. The polymers have superior in vitro efficacy to the free drug and the toxic side effects of the free drug are avoided.

Reference:
Lipid-Coated Nanoscale Coordination Polymers for Targeted Delivery of Antifolates to Cancer Cells
R C Huxford, K E deKrafft, W S Boyle, D Liu and W Lin, Chem. Sci., 2011
DOI : 10.1039/c1sc00499a

Chemical techniques are critical for studying and manipulating biological systems. Here at Chemical Science, we’ve published a host of great articles at the interface of chemistry and biology. Below is a selection of some of the recent ones. Sign up for our e-alerts and browse our issues to keep up-to-date with the latest exceptional research in this fascinating field.

Ultrafast infrared chemical imaging of live cells
Hemmel Amrania, Andrew P. McCrow, Mary R. Matthews, Sergei G. Kazarian, Marina K. Kuimova and Chris C. Phillips, Chem. Sci., 2011, 2, 107-111

Clickable, photoreactive inhibitors to probe the active site microenvironment of fatty acid amide hydrolase
Susanna M. Saario, Michele K. McKinney, Anna E. Speers, Chu Wang and Benjamin F. Cravatt, Chem. Sci., 2011, DOI: 10.1039/C1SC00336D

Molecular recognition of cytochrome c by designed receptors for generation of in vivo and in vitro functions
Satoshi Shinoda and Hiroshi Tsukube, Chem. Sci., 2011, DOI: 10.1039/C1SC00162K

Diversity in natural product families is governed by more than enzyme promiscuity alone: establishing control of the pacidamycin portfolio
Sabine Grüschow, Emma J. Rackham and Rebecca J. M. Goss, Chem. Sci., 2011, 2, 2182-2186

¹H NMR metabolomics combined with gene expression analysis for the determination of major metabolic differences between subtypes of breast cell lines
Miroslava Cuperlovic-Culf, Ian C. Chute, Adrian S. Culf, Mohamed Touaibia, Anirban Ghosh, Steve Griffiths, Dan Tulpan, Serge Léger, Anissa Belkaid, Marc E. Surette and Rodney J. Ouellette, Chem. Sci., 2011, 2, 2263-2270

Rapid fluorescence imaging of miRNAs in human cells using templated Staudinger reaction
Katarzyna Gorska, Ioanna Keklikoglou, Ulrich Tschulena and Nicolas Winssinger, Chem. Sci., 2011, 2, 1969-1975

Methods for converting cysteine to dehydroalanine on peptides and proteins
Justin M. Chalker, Smita B. Gunnoo, Omar Boutureira, Stefanie C. Gerstberger, Marta Fernández-González, Gonçalo J. L. Bernardes, Laura Griffin, Hanna Hailu, Christopher J. Schofield and Benjamin G. Davis, Chem. Sci., 2011, 2, 1666-1676

Engineering DNA aptamers for novel analytical and biomedical applications
Mingxu You, Yan Chen, Lu Peng, Da Han, Bincheng Yin, Bangce Ye and Weihong Tan, Chem. Sci., 2011, 2, 1003-1010

Submit your own hot research to our chemical biology and bioorganic Associate Editors: Benjamin Cravatt and Thomas Carrell.

The first ruthenium-catalysed oxidative annulation of alkynes with air as an oxidant has been done by scientists in Germany.

The team used an inexpensive ruthenium catalyst for aerobic C-H bond functionalisations, providing novel access to structural motifs of bioactive alkaloids.

Oxidative annulations reactions of alkynes by C-H bond cleavages provides a route to polycyclic heteroarenes. Ruthenium-catalysed methods use stoichiometric amount of copper(II) or silver(II) salts, but these lead to heavy metal by-products. Rhodium-catalysed methods are known but this ruthenium method is cheaper with improved scope and chemoselectivity.

Reference:
Ruthenium-catalyzed aerobic oxidative coupling of alkynes with 2-aryl-substituted pyrroles
L Ackermann, L Wang and A V Lygin, Chem. Sci., 2011,
DOI: 10.1039/c1sc00619c