Total synthesis of Bassiatin and its stereoisomers: Novel divergent behavior of substrates in Mitsunobu cyclizations

Total syntheses of the morpholine-2,5-dione, Bassiatin, and its stereoisomers, is completed with a key step in the syntheses, the Mitsunobu cyclization of hydroxyacid acyclic precursors. The hydroxyacid precursors are hindered alcohols and two substrates underwent Mitsunobu cyclization with retention of configuration, whereas the other two substrates underwent Mitsunobu cyclization with either retention or inversion of configuration depending on reaction conditions.