Total Synthesis of Danshenspiroketallactone

Described herein is the first synthesis of the monobenz­annulated 5,5-spiroketals danshenspiroketallactone and epi-danshen­spiroketallactone, two components of the traditional Chinese medicine Danshen. Key features of the synthesis include a directed metallation-lactonisation sequence to install the isobenzofuranone moiety and an oxidative radical cyclisation to afford the monobenz­annulated 5,5-spiroketal.