| Popis: |
This thesis is concerned with the total synthesis of two related macrocyclic natural products, cavicularin and riccardin C. Cavicularin is particularly noteworthy owing to its interesting structure: its 14-membered macrocyclic core imparts sufficient strain on the system to force one of the arenes in this paracycophane to adopt a boat-shaped conformation, deviating from planarity. The natural product also exhibits optical activity despite containing no chiral centres, this being due to axial and planar chirality in the molecule. Herein, routes to these two natural products are presented. Key steps include a highly chemoselective hydrogenation and a Wittig macrocyclisation and, in the case of cavicularin, regioselective halogenation and radical induced transannular ring contraction. This work also furnished a number of highly strained macrocycles as precursors to the natural products. These structures were found to contain boat-shaped aromatic rings, in addition to twisted olefin functionalities. A discussion of these features is presented in Chapter 6, with full crystallographic data provided in the Appendix. A review of these and related bisbibenzyl natural products is presented in Chapter 1, including their isolation, characterisation, an overview of their biological activity and previous synthetic work. Experimental procedures and characterisation data are provided in Chapter 7 |
