The Construction of a Complex Carbon Skeleton

—Total Syntheses of Ryanodol—

Abstract

Ryanodine is a ryanodane diterpene isolated from Ryania speciosa in 1948. This compound has an agonist activity for ryanodine receptor (RyR) as the calcium channel. Moreover, ryanodol is known as the hydrolysis analogue of ryanodine. The structural features of these compounds are a unique complex ring system with highly oxygenated carbon skeleton. Thus, it is important to construct pentacyclic rings and introduce oxygen functions efficiently for the synthesis. In this review, the total syntheses of ryanodol reported by three groups are described.