Organic Chemistry
http://rsc.anu.edu.au/research/easton.php
One theme of our research work involves the analysis of chemical reactions, particularly those occurring in biochemical systems. Results of these studies are being exploited to develop new synthetic methods and to produce physiologically active compounds with potential as pharmaceuticals. The other main field of research is in the area of supramolecular chemistry and molecular recognition, and involves the design and synthesis of molecular hosts tailored to form inclusion complexes with specific guests. Applications of this chemistry in the development of catalysts, molecular reactors, and photochemical and thermal switches are being pursued.
Highlights of our recent results include:
Personnel
highlights in 2002 include the submission of PhD theses by
C.K.Y.
Lee, G.J. Vuckovic, I. Walker, H. Onagi and S.B. McNabb. C.K.Y. Lee
was awarded a Ramsay Fellowship and S.B. McNabb a Japan Society for
the Promotion of Science Postdoctoral Fellowship, while B.J.W.
Barratt and H. Onagi were awarded prizes for their conference
presentations during the year.
Our early work in this area resulted in pharmaceutical formulations that are in everyday clinical use worldwide. In more recent studies modified cyclodextrins are being developed and exploited as molecular scaffolds for the construction of catalysts, molecular switches, and photochemical devices, and as templates to control the regio- and stereo-selectivity of reactions of included guest molecules. We have been able to design and prepare modified cyclodextrin hosts that display increased molecular recognition on binding of guest molecules. This has implications with respect to chemical separation technology (e.g. separation of isomers) through the incorporation of these materials into chromatography systems. By attaching reactive groups to cyclodextrins it has also been possible to produce catalysts with applications in chemical process technology. In this way we have been able to produce analogues of enzymes such as esterases, amidases and phosphatases. The latter have potential for application in soil and water bioremediation, to remove organophosphate pesticide residues. Another potential application of cyclodextrins in chemical process technology involves their use to control the assembly of the components of chemical reactions, to facilitate the reactions and alter the outcomes. The cyclodextrins thereby act as reaction vessels, but at the molecular level. In this regard, we have developed demonstration systems to alter by more than 4000 times the ratio of indigo and indirubin produced in competing condensation reactions and to reverse the regioselectivity of nitrile oxide cycloaddition processes. The latter reactions are also markedly accelerated compared to the analogous reactions in free solution. We have also been exploring the synthesis of cyclodextrin rotaxanes, catenanes and knots of various topologies. Where these have more than one ground state conformation, and the different states can be accessed using external stimuli, they form the basis of molecular devices such as ratchets and motors, temperature and light sensors, and photochemical frequency switches. Crystal structures of cyclodextrin host-guest complexes and rotaxanes show that these may be designed to exploit the cyclodextrins as insulators of molecular filaments formed by the guests. This has potential, for example, in the development of microelectronic systems, where the guests form conducting wires only in one direction. (with L. Barr, M.M. Cieslinski, P.G. Dumanski, J.B. Kelly, K. Lee, N.A. Lorimer, H. Onagi, M.-H. San, J.S. Simpson, and S.F. Lincoln, J.S. Locke, B.L. May [U. Adelaide], G.W. Simpson [CSIRO Molecular Science, Melbourne], R. Faulkner [Australian Vinyls Pty Ltd, Melbourne])
t = 0 min.
t = 5 min.
The Easton group investigates the time-dependence of seminar concentration