Utilisation of novel marine biocatalysts in enantioselective synthesis

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Murphy, Edel J.
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University College Cork
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This project focuses on the utilisation of hydrolases and transaminases as biocatalysts in asymmetric synthesis. The primary aim of this work is the investigation of the synthetic utility of marine biocatalysts, which were isolated from a saltwater lake in West Cork, in enantioselective synthesis. Chapter 1 provides a literature overview focussing on the substrate scope of transaminases, highlighting the applicability of wild-type and engineered transaminases in enantioselective synthesis of primary amines. Chapter 2 describes the use of a novel marine esterase, esterase 26D, for the kinetic resolution of various ester substrates. In particular, it was found that the substrate scope of esterase 26D is complementary to the substrate scope of a number of commercially available hydrolases. The distinctive substrate scope of the marine esterase resulted in improved activity towards substrates which could not be readily resolved in a synthetically useful manner using commercially available enzymes. Thus, this biocatalyst was employed to provide highly enantioenriched carboxylic acids and alcohols where the stereogenic centre was not at the reacting site, but one or two carbons away. Chapter 3 describes the investigation of the substrate scope and synthetic utility of marine transaminases, building on earlier work carried out in the group. Two marine whole cell transaminases, P-ω-TA and P-ω-TAad2, were utilised in the kinetic resolution of various racemic primary amines, such as 1-aminotetralins and 1-aminoindanes. Once again, the work focused in particular on the resolution of amines which contained an additional stereogenic centre, two or three carbons removed from the amino substituent. The activity, enantioselectivity and remote diastereoselectivity of the marine transaminases were compared to that of known transaminase Cv-ω-TA. Most significantly, across the substrate screen, marine transaminases P-ω-TA and P-ω-TAad2 display remote diastereoselectivity, which is not seen with Cv-ω-TA. In this chapter the genome sequence alignment and molecular modeling information were used to rationalize the observed similarities and differences in the activity and selectivity of the three transaminases, P-ω-TA, P-ω-TAad2 and Cv-ω-TA. Chapter 4 summarises the investigation of the use of purified and immobilised transaminases, Cv-ω-TA and P-ω-TA, in the kinetic resolution process, with the ultimate objective of use of the immobilised transaminases in a continuous flow process. Chapter 5 details the overall conclusions of this thesis and future work. Lastly, chapter 6 contains the full experimental details and spectroscopic characterisation of the compounds synthesised in this work.
Biocatalysis , Hydrolases , Organic chemistry , Synthesis , Enantioselective , Stereochemistry , Esterase , Transaminase , Metagenomic , Biotransformation , Stereoselective , Kinetic resolution , Asymmetric synthesis , Enantioselective synthesis , Marine biocatalysts , Biocatalyst , Genome mining , Transamination
Murphy, E. J. 2022. Utilisation of novel marine biocatalysts in enantioselective synthesis. PhD Thesis, University College Cork.