Structural factors in the odor of alpha-santalol derivatives.

Alpha-Santalol is a sesquiterpene that is a major constituent of sandalwood (Santalum album L.), and is responsible for its distinctive woody odor. We replaced the polycyclic moiety and hydroxyl group of alpha-santalol with other moieties, and we compared the odors of the E/Z-isomers and their saturated analogues. Our previous study of the structure-odor relationships of alpha-santalols bearing hydroxyl, formyl, formyloxy, and acetoxy functional groups showed there was a similarity in odor between the Z-isomer and its saturated analogue. We synthesized alpha-santalols with a benzyl group in place of the hydroxyl group, because many benzyl compounds have strong characteristic odors. We found similar odors for the E-isomer and its saturated analogue. In contrast, the odors of the alpha-santalol derivatives with a hydroxyl, formyl, formyloxy, or acetoxy group were different. We also replaced the bulky polycyclic moiety with a linear alkyl chain. The polycyclic moiety was the most important structural factor in the characteristic sandalwood odor. The synthesis of derivatives and the evaluation of their odor allowed us to identify the key structural factors in the odor of alpha-santalol.