Strain-Promoted Alkyne-Nitrone Cycloadditions: Developing Bioorthogonal Labelling Strategies

Abstract

Chemical transformations that join two molecular components together rapidly while remaining highly efficient and selective are valued for their elegant simplicity and effectiveness in a myriad of applications. By applying the principles of ‘click’ chemistry to biology, information about molecular interactions in vivo can therefore be gained from minimally perturbing bioorthogonal coupling reactions. Developing bioorthogonal ‘click’ reactions – reactions that do not cross-react with biological components – provides new ways to accurately study biological systems at the molecular level. This thesis describes the development of such tools. Strain-promoted alkyne-nitrone cycloadditions (SPANC) represent rapid, efficient, selective, and tunable conjugation strategies that are applicable to biomolecular labelling experiments. Herein, SPANC reactions with bicyclo[6.1.0]nonyne are examined using physical organic methods to determine the stereoelectronic factors governing SPANC reactivity. Second-order rate constants (k2) of up to 1.49 M-1s-1 were measured and the resulting cycloadditions are applied to the design and synthesis of nitrone-based molecular probes. The first example of SPANC-mediated metabolic labelling in live-cell bacteria is reported, establishing SPANC as an efficient and bioorthogonal metabolic labelling strategy for cellular labelling.