Syntheses and odor of "bulky group"-modified sandalwood odorants: isophorono-beta-santalol analogues.

Three osmophoric points have been found to be necessary for the scent of sandalwood odorants. One of these points is the bulky group in a certain distance from the osmophoric hydroxyl group. Such a hydrophobic moiety is part of the trimethylcyclopentenyl derivatives, the so called campholenals, among them many are known to exert a strong and long lasting sandalwood odor. In continuation of our SAR-studies of sandalwood odorants four isophorone analogues of beta-santalol have been synthesized. The hydrophobic region of these new isophorone derivatives is now a trimethylcyclohexene nucleus, so to speak an extension of the cyclopentene part of the campholenals by one methylene group. This modification changes the sandalwood odor drastically to woody odor notes, reminiscent only to sandalwood odor. The environs of the crowded trimethylcyclohexene nucleus demonstrate the sensitivity of sandalwood odor on the shape of the hydrophobic, bulky part of beta-santalol analogues.