Synthetic efforts towards the synthesis of the complex diterpene providencin

Gaich, Tanja; Weinstabl, Harald; Mulzer, Johann.   

Synlett  (2009),   (9),  1357-1366.

Providencin is a novel, highly oxygenated marine furanocembranolide featuring a cyclobutane ring and a highly strained 7,8-trans-epoxide. Various approaches to the total synthesis of this compound are reported. The cyclobutane moiety is generated via [2+2] cycloaddition and the furan ring is constructed via a Wipf ­palladium-catalyzed alkynone cyclization. The macrocyclic ring is closed via a Horner-Wadsworth-Emmons olefination or ring-­closing metathesis. The latter reaction, however, produces the undesired 7,8-Z-olefin exclusively, and the conversion into the E-isomer has been, thus far, unsuccessful.