The conversion of natural (+)-aromadendrene into chiral synthons-I

(-)-Apoaromadendrone ( 3) can be obtained easily in large quantities from (+)-aromadendrene which is the main constituent in a commercially available distillation tail of the oil of Eucalyptus globules. Acid catalyzed selective cleavage of the C3-C4 bond of the cyclopropane ring in 3 gave (-)-isoapoaromadendrone( 9) in high yield. The regioselectivity of the cyclopropane ring opening was proved by NMR spectroscopy in combination with chemical transformations. Ozonolysis of 9 afforded the keto alcohol 14 which is a suitable chiral intermediate for the syntheses of guaianes and guaianolides.