Chemical strategies to probe biological systems using cyclopropenones and phosphines

Bioorthogonal chemistries are powerful tools to investigate biomolecules in their native environments and provide a holistic understanding of cellular functions. These transformations can be performed in complex physiological settings without disturbing endogenous activity (i.e., they are “bioorthogonal”). While the spectrum of bioorthogonal reactions has grown over the last two decades, few reactions can be deployed in cells. Additionally, the majority of cell-compatible chemistries cannot be used together due to cross reactivity issues, largely prohibiting multi-component studies. Most applications have thus been restricted to detecting a single biological target, which is informative but cannot provide a complete picture of cellular function. A more holistic understanding may be possible via the development of compatible reactions to monitor multiple biomolecules simultaneously. Additionally, new methods to visualize biomolecule dynamics and identify biomolecule interaction networks would enable new biological pursuits. To address these limitations, I developed new chemical strategies to probe biomolecule targets in live cells using bioorthogonal cyclopropenone and phosphine reagents.Overall, this thesis focuses on the development of new chemical reactions for applications in cellular systems. In Chapter 1, I introduce the utilities and characteristics of a popular reagent for bioorthogonal applications, phosphines. I summarize the broad types of bioorthogonal chemistries of phosphine probes and their applications. In Chapter 2, I describe a new class of biocompatible reagents: cyclopropeniminium compounds. These probes are stable in aqueous solution and react with phosphines via a distinct mechanism. Due to reactivity differences, these probes were compatible with other existing transformations for multicomponent applications. In Chapter 3, I describe a fluorescence “turn-on” (i.e. fluorogenic) reaction of cyclopropenones and phosphines for deployment in live ce