A modular synthesis of the lamellarins: Total synthesis of lamellarin G trimethyl ether

A modular synthesis of the lamellarin family of natural products has been developed that is based on the application of three iterative halogenation/cross-coupling reaction sequences. The ability to halogenate the pyrrole core in a regioselective fashion, even in the presence of highly electron-rich aryl substituents, has been established. The compatibility of Suzuki coupling conditions with free alcohols and phenols in the boronic acids has been employed to reduce the number of protection/deprotection steps. Indeed, the presence of a free phenol on boronic acid 3 has been determined to be critical for the successful final coupling in route to lamellarin G trimethyl ether, since protected versions fail to undergo coupling.