Synthetic studies toward ryanodol, ryanodine, and related insecticidal natural products

Abstract

(+)-Ryanodine was first identified in 1948 by Folkers and coworkers as part of an effort to identify the insecticidal constituents of Ryania speciosa Vahl, a shrub native to Central and South America. In fact, the crude ext. from the shrub was marketed as Ryanex, a non-specific insecticide. However, this product was later removed from the market and efforts to make improved ryanodine-derived insecticides have been thwarted by challenging synthetic chem. In this seminar, we will describe a synthetic strategy that provides access to (+)-ryanodine and the related natural product (+)- 20-deoxyspiganthine in 18 and 19 steps, resp. A key feature of this strategy is the reductive cyclization of an epoxide intermediate that possesses the crit. pyrrole-2-carboxylate ester. We will also describe recent efforts to prep. the antifeedant isoryanoid natural product perseanol.