Odors of sandalwood

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). 

Properties Extracted from Amryris balsamifera L. (Fam. Rutaceae). Clear, pale yellow viscous liquid odor of sandalwood. Sol in mineral oil, propylene glycol insol in glycerin. 

Properties Colorless hquid light odor of sandalwood. D 0.982-0.985, refr index 1.487-1.492. 

Epoxy-a-pinene, produced by epoxidation of (+)-a-pinene, rearranges in the presence of Lewis acids to (-)-campholenealdehyde which is not only one of the constituents of various juniper species, but also the starting reagent for the synthesis of fragrances with the odor of sandalwood. Sandalore, for example, is produced by Knoevenagel aUcenylation of campholenealdehyde with propanal followed by reduction of the aldehyde function with sodium borohydride... 

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). 

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. 

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 odor of ambergris, urine, sandalwood, and musk are believed to be related to their distinct structures, and small structural modifications can influence decisively the odor quality and potency. There are three different classes of musk that are not related in structure ... 

The odor of a freshly crushed mint leaf, like many plant odors, is due to the presence in the plant of volatile C10 and Ci5 compounds, which are called terpenes. Isolation of these substances from the various parts of plants, even from the wood in some cases, by steam distillation or ether extraction gives what are known as essential oils. These are widely used in perfumery, as food flavorings and medicines, and as solvents. Among the typical essential oils are those obtained from cloves, roses, lavender, citronella, eucalyptus, peppermint, camphor, sandalwood, cedar, and turpentine. Such substances are of interest to us here because, as was pointed out by Wallach in 1887 and reemphasized by Ruzicka in 1935, the components of the essential oils can be regarded as derived from isoprene ... 

Amyris Oil, West Indian Type, occurs as a clear, pale yellow, viscous liquid having a distinct odor suggestive of sandalwood. It is the volatile oil obtained by steam distillation from the wood of Amyris balsamifera L. (Fam. Rutaceae). It is soluble in most fixed oils and usually in mineral oil. It is soluble in an equal volume of propylene glycol, the solution often becoming opalescent on further dilution. It is practically insoluble in glycerin. 

Neumann A,Weiss P, Wolschann P. A comparison of the molecular surfaces of sandalwood odorous molecules. Conformational calculations on sandalwood odor Vlll. J. Mol. Struct. 1993 296 145-152. 

Properties Colorless hquid odor of oil of sandalwood. D 0.971-0.973, refr index 1.504-1.508, bp 300C. Soluble in three parts of 70% alcohol insoluble in water. Combustible. 

Bajgrowicz JA, Frater G. Chiral recognition of sandalwood odorants. Enantiomer 2000 5 225-234. 

Typically, the oil will contain 45-47% of the a-isomer and 20-30% of the (3-isomer. Both isomers contribute to the distinctive woody odour of the oil. The (3-isomer is more intense and also contributes to the slightly animalic, urinous character of the oil. It is interesting to note that the odours of sandalwood and urine are closely related. One of the commonest parosmias (where an odorant is perceived differently by different subjects) is that of sandalwood and urine. Similarly, when a secondary alcohol with a sandalwood character is oxidised to the corresponding ketone, there is a high probability that the ketone will smell urinous. There are many other components in sandalwood oil, particularly sesquiterpenoids alcohols, aldehydes and hydrocarbons. Some of these make important contributions to the overall odour effect. 

In connection with structure activity relationship studies, Chapuis [40] prepared a series of sandalwood odorant alcohols. In this context, alcohol 181 has been prepared from (+)-trans-pinocarveol 179 in two steps. Accordingly, orthoester rearrangement of alcohol 179 afforded ester 180 which, after the Grignard reaction, gave tertiary alcohol 181 (Scheme 6.27). 

As to influences of the familiarity of or experience with fragrances, Kawano (2001) reported that the odors of lemon, lavender, patchouli, marjoram, rosemary, and sandalwood increased a activity over occipital electrode sites in subjects to whom these fragrances were well known. On the... 

Camphene is the starting material for the synthesis of camphor and of isobornyl acetate (Fig. 10.1.10). Condensation of camphene with phenolic compounds followed by hydrogenation gives a mixture of isobornyl cyclohexanol isomers, which have the odor of (costly) sandalwood. Methoxyeugenol, another com-... 

Generic term for the odor of wood, e.g., cedarwood, sandalwood... 

Sandalwood oil is obtained by distillation of the wood of the parasitic tree Santalum album. The isomeric alcohols a-santalol [115-71-9] (255) and (3-santalol [115-71-9] (256) account for 90% of the oil. Over-harvesting has taken the species to the brink of being endangered and supply is, consequently, now very short. Fortunately, the odor can be recreated using synthetic materials, such as the isobornylcyclohexanols (see under camphene in section Bicyclic Monoterpeniod Hydrocarbons) and the campholenic aldehyde derivatives described in Section 8.4.4. Details of sandalwood chemistry can be found in Chapter 6 of the book by Sell (323). 

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. 

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. 

Many cyclic sesquiterpene alcohols are key odor components in essential oils, for example, cedrol in cedarwood oil, the vetiverols in vetiver oil, and the santalols in sandalwood oil. Since these alcohols have not yet been synthesized on an industrial scale, they are described under the oil in which they occur (Chapter 3). Some of their derivatives, however, are discussed in this section. 

The oil is sometimes incorrectly called West Indian sandalwood oil. However, its composition and odor are different from those of the oils obtained from sandalwood species. The major components of amyris oil are sesquiterpenoids such as elemol [639-99-6], /3-eudesmol [473-15-4], and epi-7-eudesmol [15051-81-7] [241-244]. 

Sandalwood oil. East Indian is obtained by steam distillation of the heartwood of Santalum album L. (Santalaceae). It is a slightly viscous, almost colorless to yellow liquid with a characteristic, sweet, woody, long-lasting odor. 

East Indian sandalwood oil consists almost exclusively of closely related sesquiterpenoids by far the main constituents are the alcohols a-santalol [115-71-9], 45-55%, and /3-santalol [77-42-9], 18-24%. Mainly responsible for the odor is /3-santalol. [261, 764-769]. 

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