Sandalwood essential oil, which can be obtained by steam distillation from Santalum trees (e.g. Santalum album), may be described as having a sweet woody scent.
From a chemical point of view, sandalwood essential oil is composed of sesquiterpenes, unsaturated alcohols, aldehydes and polycyclic ketones. Santalol (CAS# 11031-45-1) is the main component responsible for the characteristic sandalwood smell. While the material can be obtained from sandalwood essential oil, the method is highly demanding and economically inconvenient (preparation from sandalwood yields 4.0-6.5%).
Sandalore and santalol are not only important in the fragrance industry, but in the last decades, their specific use in medicine has also been reported. For example, these materials have been explored as an agonist of the cutaneous receptor (influencing human hair growth), and as an influencer of the central nervous system and transdermal absorption.5-8
With enormous interest in sandalwood surrogates it was discovered that synthetic compounds with similar fragrant characteristics can be prepared, including trimethyl(cyclopentenyl)alkenols, or alkanols. One of most widely used is sandalore (3-methyl-5-(2,2,3-trimethylcyclopent-3-en-1-yl)pentan-2-ol; F-1).1-4
F-1. Chemical structures of santalol (a,b) and sandalore (c)
F-3. Catalysts tested in 3-methyl-5-(2,2,3-trimethylcyclopent-3-en-1-yl)pent-3-en-2-one hydrogenation
F-2. Reaction scheme of sandalore synthesis
F-4. Reaction course using 30% sodium hydroxide as catalyst, room temperature*
F-5. Reaction course using 10% potassium hydroxide as catalyst, room temperature, molar ratio campholenic aldehyde:solvent = 1:32, (CA: campholenic aldehyde; BA: butan-2-one; MeOH: methanol); *ethanol, **propan-2-ol
F-6. Possible 3-methyl-5-(2,2,3-trimethylcyclopent-3-en-1-yl)pent-3-en-2-one hydrogenation products*
F-7. Hydrogenation product concentration using T-4466 catalyst at different temperatures*
F-8. Hydrogenation product concentration using chosen types of Adkins catalysts*
For the full article, please check out the Perfumer & Flavorist+ March 2021 issue.