Shedding Light on Phytochemical Diversity: Photochromism of chromenes isolated from Piper kelleyi

Abstract

The following chapters are focused on understanding the photochromic behavior of naturally occurring chromenes and its role in the biosynthesis of a variety of natural product architectures. Ultimately, chromenes and ortho-quinonemethide derived natural products will be used to understand their role in anti-herbivore activity by exploring the molecular mechanism of photoxicity of chromenes and their synergistic activity with co-occurring natural products. Generation of natural ortho-quinonemethides in this manner for organic synthesis has never been explored before, nor has the role of this mode of reactivity in the composition of plant phytochemical diversity been established. Chapter 2 will establish the nature of the photochemical behavior of a common naturally occurring structural motif, which could be a light activated pharmacophore that could be responsible for its potent toxicity to herbivorous insects and perhaps the diversification of associated insects. This work shows a rapid means to access a large array of natural product scaffolds for the generation of libraries for high throughput screening. Moreover, the results from this study will shed light on the origins of nature’s method of generating natural products diversity and are likely to inspire new reaction discovery. The following work has resulted in the synthesis of a number of natural products, providing material for their full biological investigation. This material will be used to understand the synergistic action of these biosynthetically related and co-occurring natural products mixtures, which could result in a broad framework for discoveries in the health and agricultural sciences. The last chapter of the thesis will discuss work related to expanding the scope of reactivity of aza-oxyallyl cations. Previous work in our group sought interest in a modular strategy to prepare these motifs from a formal (3+2) cycloaddition of aza-oxyallylic cations. This work discussed here will focus on the cycloaddition with a carbonyl reactant to deliver 4-oxazoidinone motifs in a one-step pot from simple starting materials.