Terminating catalytic asymmetric Heck cyclizations by stereoselective intramolecular capture of η3-allylpalladium intermediates: total synthesis of (-)-spirotryprostatin B and three stereoisomers

A catalytic intramolecular Heck reaction, followed by capture of the resulting eta(3)-allylpalladium intermediate by a tethered diketopiperazine, is the central step in a concise synthetic route to (-)-spirotryprostatin B and three stereoisomers. This study demonstrates that an acyclic, chiral eta(3)-allylpalladium fragment generated in a catalytic asymmetric Heck cyclization can be trapped by even a weakly nucleophilic diketopiperazine more rapidly than it undergoes diastereomeric equilibration. (C) 2010 Elsevier Ltd. All rights reserved.