University of Otago, New Zealand

Chemistry

Te Tari Hua-Ruanuku

Dr Eng Wui Tan

contact photo
Dr Eng Wui Tan
Organic and bioorganic chemistry
Tel: (03) 479 7926
Location: Science II, 2n9
ewtan@chemistry.otago.ac.nz


Interactions of Molecules with Enzymes and Directing Effects of Substituents in Radical Reactions

Part of my research group is involved in the study of enzyme interactions with unusual molecules1. Various enzymes are under study, with families of synthetic molecules, in an attempt to correlate enzyme behavior with peculiar molecular structure and conformation. Transient and steady-state techniques are employed. It is our hope that this research will reveal unusual structural motifs that can be incorporated into the design of enzyme inhibitors and structural sensors. In collaboration with Dr. Keith Gordon, we are exploring the use of laser spectroscopy in some enzyme systems through diazo molecular probes2.

My research group is also interested in selective radical reactions as they allow the introduction of chemical functionality to otherwise featureless substructures for further manipulation. This technique is particularly applicable to chiral pool compounds as it simplifies the synthesis of enantiomerically pure molecules3-5. Selectivity in radical reactions can be achieved through the use of directing substituents which either activate or inactivate a particular position or stereochemical aspect. For example, the following reaction proceeds with >95% ee in quantitative yield4 via a bridged chlorine radical intermediate.

We are also trying to capture the imagination of students and the general public by representing molecular structure and function in exciting new ways. The benefits of graphics imaging in communicating concepts in Chemistry can be seen in 3D stylised computer generated reaction mechanisms, like the following two examples (in Quicktime 4 format). These represent two modes of nucleophilic displacement at a pentavalent phosphorus centre.

In-line displacement

Displacement via pseudo rotation

Research Group

Selected References

  1. Brevitt, S. E.; Tan, E. W. "Synthesis and In Vitro Evaluation of Two Progressive Series of Bifunctional Polyhydroxybenzamide Catechol-O-Methyltransferase Inhibitors", Journal of Medicinal Chemistry, 41, 2035-2039 (1997).
  2. Haghbeen, K.; Tan, E. W. "Facile Synthesis of Catechol Azo Dyes", Journal of Organic Chemistry, 63, 4503-4505 (1998).
  3. Wong, L. S.; Chan, B.; Tan, E. W. "Stereoselective Radical Bromination of alpha-Chloro Hydrocinnamic Acid Derivatives", Tetrahedron Lett., 41, 2671-2674 (2000).
  4. Shaw, J. P.; Tan, E. W. "Selective Bromination of alpha-Chloro and alpha-Bromo Carboxylic Acid Derivatives", Journal of Organic Chemistry, 61, 5635-5637, (1996).
  5. Shaw, J. P.; Tan , E. W.; Blackman, A. G. "Homochiral Methyl (2R, 3S)-3-Bromo-2-chloro-3-Phenylpropanoate" Acta Cryst. C51, 134-135 (1995).