(–)-Probetaenone I (1) has been synthesized by an intramolecular Diels–Alder reaction and, thereby, its structure has been clearly confirmed; in the biosynthesis of betaenoneB (2) the stereochemistry of the C-8 hydroxylation of (1) was proved to involve retention of configuration.
Stereoselective synthesis of (−)-betaenone Cthrough intramolecular Diels-Alderreaction has made possible to provide pertinent intermediates for the biosynthetic study of betaenones.