Catalytic asymmetric synthesis of palmerolide A via organoboron methodology.

A catalytic enantioselective synthesis of the antimelanoma marine natural product (-)-palmerolide A was accomplished using a longest sequence of 21 steps and without resorting to stoichiometric chiral auxiliaries or the chiral pool. The right half was constructed with a new variant of the Claisen-Ireland rearrangement exploiting an alkenylboronate as a masked hydroxyl. The left half featured the first application of a diol.SnCl(4)-catalyzed enantioselective crotylboration in the context of a complex target. This distinct strategy could pave the way to the design of simplified analogues of palmerolide.