Use of transaminase enzymes for the synthesis of pharmaceutical intermediates

Chiral amines are highly valuable chemical species found in a broad spectrum of pharmaceutical, agrochemical and fine chemical products. The synthesis of some of these amines is often low yielding and convoluted (due to the use of protecting groups and chiral auxiliaries) or they have poor selectivities. The need for cleaner, more efficient and highly selective preparations of chiral amines therefore makes transaminases an attractive alternative to the classical chemical routes. Transaminases (TAms) are a group of enzymes that catalyse the conversion of aldehydes and prochiral ketones to primary amines and chiral secondary amines. Most TAms typically catalyse the conversion of α-ketoacids to α-amino acids. There is however one class of TAms (ω-TAms) that shows broad selectivity beyond ketoacids. The work in this thesis can be split in two halves: The first half is a discussion on the discovery, cloning and characterization of novel ω-TAms. Through BLAST sequence searches and phylogenetic matching to cloning, over-expressing and high through-put screening, a panel of 10 novel ω-TAms were discovered. The second half of this thesis discusses a novel transaminase-mediated chemoenzymatic intramolecular aza-Michael reaction. Three unsaturated ketoester substrates were screened against four of the 10 novel ω-TAms alongside three previously discovered ones. This reaction can potentially provide access to a myriad of natural product alkaloids containing a 2,6-piperidine or a 2,5-pyrrolidine core