Total Synthesis of (−)-Spirotryprostatin B: Synthesis and Related Studies

The total synthesis of spirotryprostatin B, a cytostatic spiro[pyrrolidine-3,3‘-oxindole] alkaloid, is
described. The key step of the synthetic approach consists of the application of the MgI2-mediated ring-expansion reaction of a spiro[cyclopropane-1,3‘-oxindole] with an aldimine, leading to rapid assembly of
the spirotryprostatin core. The route documents the installation of the prenyl side chain by Julia−Kocieński
olefination of a key aldehyde precursor, a transformation that ultimately allows for facile synthesis of
analogues and facilitates structure−activity relationships studies