Total Syntheses of the Resorcylic Acid Lactone Neocosmosin A and Its Enantiomer

A total synthesis of the structure, 1, assigned to
the recently reported resorcylic acid lactone (RAL) neocosmosin A
has been established. Olefin-cross metathesis, ring-closing metathesis,
palladium-catalyzed Meinwald rearrangement, and Mitsunobu esterification
reactions were used as key steps. A late-stage and simple modification
to the reaction sequence also provided compound ent-1 that, in fact, represents the true structure of the
natural product.