Dr G.N. Sheldrake
B.Sc. (University of Leeds), 1981
Ph.D. (University Glasgow), 1984
Senior Lecturer in Environmental Chemistry
Tel: + 44 (0) 28 9097 4593
Fax: + 44 (0) 28 9097 6524
The enzyme-catalysed oxidation of organic substrates using microorganisms and molecular oxygen is widely utilised as a clean oxidation technique. The selectivity of these biological catalysts enables oxidations to be carried out which are impossible or difficult with “conventional” synthetic reactions. In the example shown in Figure 1 we have combined enantioselective biological oxidation with diastereoselective synthesis and a novel reductive ring contraction to produce highly-functionalised enantiopure carbocycles which have potential as intermediates to antiviral agents.
In Figure 2 we show the enantiocomplementary synthesis of both enantiomers of 1-pyridylalkanols using two different enzymes in the same organism under different biotransformation conditions. An alcohol dehydrogenase enzyme (ADH) under oxygen-limited conditions catalyses asymmetric pyridyl ketone reductions and a toluene dioxygenase enzyme (TDO) under oxygen-rich conditions enantioselectively hydroxylates alkyl pyridines. The chiral pyridyl alkanol bioproducts are useful ligands and chiral auxiliaries for asymmetric catalysis.
We have interests in many areas of cleaner oxidation chemistry, one current example being the preparation of solid-supported dioxiranes. Dioxiranes are powerful oxygen-transfer reagents and are used widely in synthetic organic chemistry. Although these reagents also have environmental benefits compared with many traditional transition metal oxidants, dioxiranes have not been used in industrial manufacture because of problems associated with handling and scale-up. We are currently preparing a range of both achiral and chiral ketones attached to insoluble organic and inorganic supports which will be used to produce dioxiranes either stoichiometrically or catalytically in oxidation reactions. By supporting the reagents recovery and regeneration will be simplified resulting in fewer environmental and safety problems for industrial processes.