Total synthese of (±)-cyclolaurene, (±)-epicylolaurene and (±)-β-cuparenones

Abstract

The first total synthesis of (±)-cyclolaurene (1̲) and (±)-epicyclolaurene (5̲), and a new route to (±)-β-cuparenone (4̲) are reported. Thus, orthoester Claisen rearrangement of the cinnamyl alcohol 8̲ furnished the eneester 10̲. Anhydrous CuSO, catalysed intramolecular cyclopropanation of the diazoketone derived from the ene-acid 7̲, generated a diastereoisomeric mixture of cyclopropyl ketone 6̲. The Huang-Minlon reduction of the ketones 6a̲ and 6b̲ furnished the cyclolaurene (1̲) and epicyclolaurene (5̲), whereas regiospecific ring cleavage using lithium in liquid ammonia furnished the β-cuparenone (4̲).