<i>RS</i>-a<i>-</i>Amino acids bearing a b- or g-substituent have been prepared using standard methods for a-amino acid synthesis. The deracemisation of <i>RS</i>-a-amino acids, using D-amino acid oxidase (DAAO) from <i>Trigonopsis variabilis</i> and hydride reducing agents, has been investigated. The enzyme has been shown to tolerate the b- and g-substituted a-amino acids as substrates. The use of NaCNBH<sub>3</sub> for the deracemisation of acyclic a-amino acids has been demonstrated for the first time. Screening of a random library of organisms was undertaken to identify novel oxidase enzymes for use in the deracemisation reaction. The screen revealed five organisms that were able to oxidase L-phenylalanine to phenylpyruvic acid, indicating possible L-amino acid oxidase activity. In the screening for monoamine oxidase the assay methods employed lacked the sensitivity to identify conversion of benzylamine to benzaldehyde. For the first time the cyclic oxidation-reduction sequence used for the deracemisation of <i>RS</i>-a-amino acids has been extended to encompass the deracemisation of racemic amines. The deracemisation of <i>RS</i>-a-methylbenzylamine, using an enantioselective monoamine oxidase and ammonia:borane as reducing agent, has been shown to proceed with moderate yields and high selectivity.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:650028 |
| Date | January 2001 |
| Creators | Enright, Alexis |
| Publisher | University of Edinburgh |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://hdl.handle.net/1842/13802 |
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