Bisguanidinium-pyridoxal phosphate catalysed asymmetric reactions

• Main Author: Ang, Esther Cai Xia
• Other Authors: Tan Choon Hong
• Format: Thesis-Doctor of Philosophy
• Language: English
• Published: Nanyang Technological University 2024
• Subjects: Chemistry
• Online Access: https://hdl.handle.net/10356/174754
• Institution: Nanyang Technological University

Cofactors are essential non-protein molecules or ions that play a crucial role in facilitating the optimal functioning of enzymes. We are especially interested in pyridoxal 5'-phosphate (PLP), the active form of Vitamin B6, that serves as a versatile cofactor in numerous enzymatic reactions across diverse biological pathways. We propose to study biomimetic catalysis using ion pair catalysts derived from synthetic chiral cations and anionic pyridoxal 5'-phosphate. Chapter 1, an extensive background study on PLP is provided, elucidating its crucial roles in biological systems. The chapter delves into a comprehensive exploration of PLP's involvement in a diverse array of biological reactions. In addition, contemporary aldehyde catalysis were also studied. Furthermore, the pioneering work and the advancements that has been made over the years in our research group in the field of asymmetric ion pair catalysis, were also showcased. Chapter 2 presents the successful achievement of a highly enantioselective aza-Michael addition between free amines and ,-unsaturated carbonyl compounds using bisguanidinium PLP ion pair catalysis. The chapter focuses on the investigation and development of this innovative Bisguanidinium-PLP catalyzed enantioselective aza-Michael reaction, accompanied by a comprehensive discussion of the underlying reaction mechanism. Chapter 3 delves into the exploration of an aldol reaction between glycine and aldehydes utilizing a similar BG-PLP catalytic system. This chapter will comprehensively discuss the challenges encountered in designing this reaction, providing valuable insights into its intricacies. Finally, the chapter concludes with an outlook on future prospects and potential developments in this research area. Chapter 4, all experimental protocols including representative procedures and characterisation will be recorded. All supporting spectra (NMR and HPLC) will be attached at the end.