Synthetic Studies toward Communesins

Communesins A-H are a growing family of natural products isolated from a marine fungal strain of Penicillium species. Preliminary biological evaluation has revealed that these compounds possess insecticidal activity and cytotoxicity against several tumor cell lines. Their interesting biological activities and unique structures have attracted considerable attention of synthetic chemists worldwide. To date, several elegant protocols for assembling the core structure of these indole alkaloids have been described, including intermolecular Diels-Alder reaction of methylated aurantioclavine with quinine methide imine and intramolecular hetero Diels-Alder reaction of the azaortho-xylylene intermediates. Recently, three completed total syntheses for communesin F have been disclosed, in which the crucial vicinal quaternary stereogenic centers were constructed by employing an intramolecular cyclopropanation; an intramolecular Heck reaction of a tetrasubstituted alkene, or an oxidative coupling of a 3-substituted indole, as the key step. Accompanying the total synthesis, the absolute configuration of natural communesin F was established as 6R, 7R, 8R, 9S, 11R. However, total syntheses of other members of communesin family that contain an epoxide moiety have not been achieved, which will stimulate more synthetic studies.