A 15-step synthesis of (+)-ryanodol

Rapid ryanodol route The plant-derived compound ryanodine and its hydrolyzed cousin ryanodol are biochemically interesting for their calcium-regulating capacity and chemically interesting for their dense tangle of carbon rings brimming with oxygen appendages. Chuang et al. report an efficient 15-step asymmetric synthesis of ryanodol from the structurally much simpler terpene pulegone (see the Perspective by Verdaguer). Key steps include a Pauson-Khand cyclization of a tethered alkene and alkyne with carbon monoxide to set the ring motifs, followed by an oxidation using selenium dioxide that delivers three different oxygen substituents in tandem. Science , this issue p. 912 ; see also p. 866