Asymmetric syntheses of ent-callilongisins B and C

Callilongisin B, isolated in 2012, is a 3,4- seco -abietane-type diterpenoid having four stereocenters, whereas callilongisin C has an aromatic ring structure. Total syntheses of ent -callilongisins B and C were accomplished via a common intermediate in 19 steps and 22 steps, respectively. The key feature for the synthesis of ent -callilongisin B is an oxidative dearomatization accompanied by δ -lactonization and the synthetic method of ent -callilongisin C includes Suzuki coupling for installation of a carbon unit and Mukaiyama hydration.