Lewis acid-mediated skeleton transformation of Euphorbia diterpenes: From lathyrane to euphoractane and myrsinane.

Natural euphoractane and myrsinane diterpene skeletons, together with an unnatural 5/7/7/4 fused-ring diterpene skeleton were furnished via BF3·Et2O-mediated transformation of lathyrane-type diterpene, Euphorbia factor L1. The skeleton transformation process was mainly involved in the cascade oxirane-opening (cyclopropane-opening)/oxe-Micheal addition reaction. The structures of three diterpenes were confirmed by comprehensive spectra analysis and single crystals X-ray diffraction. Current results proved the biogenesis pathway between lathyrane with euphoractane and myrsinane by chemical transformation for the first time.