Organic Synthesis on Strigolactones Chemistry

Abstract

Strigolactones (SLs) are carotene-derived natural products that play important roles as phytohormones (within plants), as seed germinators of parasitic weeds (between plants), and as chemical communicators between plants and fungi (between kingdoms). A subset of these molecules, called non-canonical SLs, exhibit highly diverse structures that present significant challenges to the synthetic chemist.

The research topic of this thesis is focusing on developing novel synthesis routes from commercially available ionones to two strigolactone molecules: carlactone (CL) and avenaol. Based on the knowledge gained en route to CL, further research was conducted towards CL derivatives which shared the same carbon skeleton as CL.

The choice of which non-canonical SLs to target for synthesis was not random. As the biosynthetic precursor of all SLs, and a natural product in its own right, the importance of CL is self-evident. However, total synthesis routes to this molecule remains relatively under-explored. There is still no large-scale preparation that can produce enough CL to enable further biological research. Therefore, inventing a cost-effective and chemoselective synthetic route is necessary.

Avenaol is perhaps the most synthetically challenging non-canonical SL, possessing a unique fused cyclopropane unit that is incredibly sterically congested. We have designed a novel synthetic strategy that intercepts an intermediate in the only reported synthesis of avenaol. We aimed at significantly simplifying the total synthesis of avenaol, thereby facilitating material access for further studies into its potential biological or therapeutic properties.