Enantioselective synthesis of (-)-platensimycin oxatetracyclic core by using an intramolecular Diels-Alder reaction.

An enantioselective route to the oxatetracyclic core of (-)-platensimycin (1) has been investigated by using an intramolecular Diels-Alder reaction as the key step. The thermal reaction of E/Z mixture (1:1) provided oxatetracyclic core 2 from the E-diene and the Z-diene was recovered unchanged. The Diels-Alder substrate was conveniently assembled in optically active form with use of (S)-carvone as the starting material.