Sandalwoods

Sandalwood oil is obtained by distillation of the parasitic tree Santa-lum album. The major components of the oil are the santalols (27, 28). Many syntheses of these and related chemicals have been reported but, elegant as they are, none compete economically with the oil itself. The synthetic sandalwood materials fall into two main classes, the so-called terpenophenols and the materials derived from campholenic aldehyde. 

Rearrangement of a-pinene oxide, catalysed by zinc chloride or bromide, gives a product known as a-campholenic aldehyde. Aldol condensation of this with a second aldehyde or a ketone gives an a, (3-unsaturated carbonyl compound that can then be reduced to an 

---

C. The only lerpene-like natural hydrocarbon containing nine C atoms. It is found in East Indian sandalwood oil and also in Siberian, German and Swedish pine-needle oils. It has a rather unpleasant smell, resinifies easily and is difficult to obtain pure. 

East Indian sandalwood oil contains a hydrocarbon given the name santene (C9H14) Ozona tion of santene followed by hydrolysis gives compound A What is the structure of santene" ... 

PYES, APPLICATION AND EVALUATION] (Vol 8) 1 sandalwood oil [OILS, ESSENTIAL] (Vol 17)... 

Whatever the physiology of odor perception may be, the sense of smell is keener than that of taste (22). If flavors are classed into odors and tastes as is common practice in science, it can be calculated that there are probably more than 10 possible sensations of odor and only a few, perhaps five, sensations of taste (13,21,35—37). Just as a hereditary or genetic factor may cause taste variations between individuals toward phenylthiourea, a similar factor may be in operation with odor. The odor of the steroid androsterone, found in many foods and human sweat, may eflcit different responses from different individuals. Some are very sensitive to it and find it unpleasant. To others, who are less sensitive to it, it has a musk or sandalwood-like smell. Approximately 50% of the adults tested cannot detect any odor even at extremely high concentrations. It is befleved that this abiUty is genetically determined (38). 

Sometimes a skilled peifumei detects a sandalwood-musky note in authentic Bulgarian otto of rose. This note has been identified (11) as the trace iagredient, 7-methoxy-3,7-dimethyl-2-octanol [41890-92-0] (17), which has been commercially available for some time as Ossyrol (trademark of Bush, Boake, Aken Inc). This compound had never before been identified ia nature, but demonstrates how, sometimes, synthetic fragrance chemists can anticipate nature. 

Sandalwood Oil, East Indian. The use of sandalwood oil for its perfumery value is ancient, probably extending back some 4000 years. Oil from the powdered wood and roots of the tree Santalum album L. is produced primarily in India, under government control. Good quaUty oil is a pale yellow to yellow viscous Hquid characterized by an extremely soft, sweet—woody, almost ariimal—balsarnic odor. The extreme tenacity of the aroma makes it an ideal blender—fixative for woody-Oriental—floral fragrance bases. It also finds extensive use for the codistillation of other essential oils, such as rose, especially in India. There the so-called attars are made with sandalwood oil distilled over the flowers or by distillation of these flowers into sandalwood oil. The principal constituents of sandalwood oil are shown in Table 11 (37) and Figure 2. 

The piincipal component, t7t-a-santalol (65), has contioveisial odoi piopeities t7t-P-santalol (66) contributes most to the odor of sandalwood. A number of trace constituents have been characterized, two of which (76) [59300-43-5J and (77) [63569-02-8] ate worthy of mention for their very clean sandalwood notes (38). 

Amyris Oil. Obtained by steam distillation of the wood of y m hakamijera L., the so-called West Indian sandalwood which is indigenous to northern South America, Central America, and the West Indies, amyris oil [8015-65-4] is a pale yellow to brownish yellow viscous oil with a slightly oily-sweet and occasionally peppery balsamic woody note. It finds use as a blender and fixative for soap fragrances. The volatile constituents, which are primarily hydrocarbon and oxygenated sesquiterpenes, are shown in Table 22 and Figure 5 (63). 

The Prins reaction with formaldehyde, acetic acid, acetic anhydride, and camphene gives the useful alcohol, 8-acetoxymethyl camphene, which has a patchouli-like odor (83). Oxidation of the alcohol to the corresponding aldehyde also gives a useful iatermediate compound, which is used to synthesize the sandalwood compound dihydo- P-santalol. 

Myrcene with its conjugated diene system readily undergoes Diels-Alder reactions with a number of dienophiles. For example, reaction with 3-meth.5i-3-pentene-2-one with a catalytic amount of AlCl gives an intermediate monocyclic ketone, which when cyclized with 85% phosphoric acid produces the bicycHc ketone known as Iso E Super [54464-57-2] (49). The product is useful in providing sandalwood-like and cedarwood-like fragrance ingredients (91). 

Aldol reaction of the campholenic aldehyde with 2-butanone gives the intermediate ketones from condensation at both the methyl group and methylene group of 2-butanone (Fig. 6). Hydrogenation results in only one of the two products formed as having a typical sandalwood odor (160). 

Aldol reaction of campholenic aldehyde with propionic aldehyde yields the intermediate conjugated aldehyde, which can be selectively reduced to the saturated alcohol with a sandalwood odor. If the double bond in the cyclopentene ring is also reduced, the resulting product does not have a sandalwood odor (161). Reaction of campholenic aldehyde with -butyraldehyde followed by reduction of the aldehyde group gives the aHyUc alcohol known commercially by one manufacturer as Bacdanol [28219-61 -6] (82). 

When the a,P-unsaturated ketone is hydrogenated to the alcohol, a product with an intense sandalwood odor is produced (162). Many other examples of useful products have been made by condensation of campholenic aldehyde with ketones such as cyclopentanone and cyclohexanone. 

OC-Santalol. Sandalwood oil is comprised of mainly (90%) a- and P-santalol, which gives the oil the woody, tenacious sandalwood odor. An impure a-santalol [115-71 -9] (100) can be isolated by the distillation of the oil. P-Santalol [77-42-9] (101) is also isolated but ia much smaller amounts. The price of sandalwood oil, E. Indian, ia 1995 was 286/kg, and the oil from Indonesia was 187/kg (69). The high price of these oils has created the need to synthesize new materials with the sandalwood odor. The terpenophenols are manufactured by condensation of camphene with phenoHc compounds followed by hydrogenation to the cycloaUphatic alcohols (194). 

The wood of llarAi.f ia t-tiMmamii, a ZaDzlhar tren, yields about 0-G pereLiiL.ot essential oil, havina ao odour recalling that of sandalwood oil. lls chaiueL rs are as tollriws... 

In addition to the above-described terpenes proper, there are a few other hydrocarbons which may be conveniently dealt with here. These are salvene, the so-called olefinic terpenes, myrcene and ocimene, the terpene homologues, cantharene, santene, and a hydrocarbon of the formula CjjHjg found in sandalwood oil, and the diterpene phyllocladene. 

Santene has also been examined by Aschan. The following are the characters of the purest specimens which have been isolated from sandalwood and Siberian nine oils —... 

Schimmel Co. have isolated a hydrocarbon of the formula CjjHj from sandalwood oil. This body is completely saturated and is unaffected by potassium permanganate at ordinary temperatures. 

---