Development of an Assay for a Diels-Alderase Enzyme

McAllister, Graeme Douglas (2000) Development of an Assay for a Diels-Alderase Enzyme. PhD thesis, University of Glasgow.

Abstract

We have been developing an assay for a Diels-Alderase enzyme. The assay is based on the proposed biosynthesis of chalcomoracin iv, a natural antifungal compound from the white mulberry Morus alba, which is thought to be formed by an enzyme-mediated Diels-Alder reaction between dienie ii and morachalcone A iii. Diene ii has never been isolated, but an analogue of ii, moracin C i has been isolated from M. alba and is thought to be a biological precursor to diene ii. We have developed the most efficient synthesis of moracin C i to date (10 steps, 12.3% overall), involving a 'one-pot' ester formation/intramolecular Wittig reaction, regioselective ortho-lithiation, and an unexpected but advantageous acid- induced acyl migration. Our route provides a general method for the synthesis of polyphenolic benzofurans. We have synthesised a sample of diene ii using a route similar to that of moracin C (12 steps). This synthesis included a regioselective carboxylation and an E- selective modified Julia olefination. The small sample of ii obtained was not fully characterised, due to instability during chromatography, but the structure was unequivocally confirmed by 1H NMR spectroscopy. We have prepared a series of protected morachalcone A iii precursors. These are easily prepared (3 steps), and while suitable deprotection conditions have not yet been found, this route can provide suitable intermediates for a biomimetic or total synthesis of chalcomoracin. Structural modifications were made to moracin C (see below), and in an attempt to probe the substrate specificity of the Diels-Alderase enzyme, two potential substrates v and vi, were fed to suspensions of M. alba cells. Initial analysis suggested that one of these compounds (v) was incorporated.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Adviser: Richard Hartley
• Keywords: Biochemistry, Organic chemistry
• Date of Award: 2000
• Depositing User: Enlighten Team
• Unique ID: glathesis:2000-75910
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Nov 2019 17:37
• Last Modified: 19 Nov 2019 17:37
• URI: https://theses.gla.ac.uk/id/eprint/75910