Fragrances sandalwood

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. 

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). 

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). 

Some oils consist almost entirely of esters for example, those of Oaultheria procumhens and Betula lenta contain about 99 per cent, of methyl salicylate. Bergamot and lavender owe the greater part of their perfume value to esters of linalol, of which the acetate predominates. Geranium oil owes its fragrance chiefly to geranyl esters, of which the tiglate is the chief. On the other hand, oils such as spike lavender, sandalwood, lemon-grass, and citronella contain but small quantities of esters, and owe their perfume value to entirely different types of compounds. 

Another opportunity to combine two reaction steps towards a one pot synthesis is the epoxidation of a-pinene and the isomerization of the epoxide to campho-lenic aldehyde (Scheme 5.6). Zeolite Ti-Beta seems adequate to deal with both steps as a catalyst [24]. Campholenic aldehyde is the starting material for several sandalwood fragrances. 

Some alicyclic alcohols are important as synthetic sandalwood fragrances. A few alicyclic aldehydes are valuable perfume materials and are obtained by Diels Alder reactions using terpenes and acrolein. Esters derived from hydrogenated aromatic compounds, such as /cr/-butylcyclohexyl and decahydro-/3-naphthyl acetates, are also used in large amounts as fragrance materials. 

When camphene reacts with guaiacol (2-methoxyphenol), a mixture of terpenyl phenols is formed. Hydrogenation of the mixture results in hydrogenolysis of the methoxy group and gives a complex mixture of terpenyl cydohexanols (eg, 3-(2-isocamphyl) cyclohexanol [70955-714] (45)), which after fractional distillation produces a useful sandalwood fragrance product (85). A similar process has also been developed using catechol and camphene (86). 

Campholenic Aldehyde Manufacture. Campholenic aldehyde is readily obtained by the Lewis-acid-catalyzed rearrangement of a-pinene oxide. It has become an important intermediate for the synthesis of a wide range of sandalwood fragrance compounds. Epoxidation of (+)- Ct-pinene (8) also gives the (+)-o -a-pinene epoxide [1686-14-2] (80) and rearrangement with zinc bromide is highly stereospecific and gives (-)-campholenic aldehyde... 

Sesquiterpenic alcohols used in perfumery are mainly of natural origin. Three alcohols of this type are shown in Figure 8. Cedrol is the main alcohol constituent of cedarwood oil. Alpha-santalol constitutes about 80% of sandalwood oil and about 30% patchouli alcohol is found in patchouli oil, a very popular woody-earthy fragrance material. 

This overview of monohydric alcohols covered the major products used by the industry. The one exception was Sandalore which was introduced only recently. It was included as an example of the continuing search for new fragrance materials to replace natural products,in this case, expensive and scarce sandalwood oil. 

Although we have described the perfumes in this family as being based on Hedione, in Coriandre the material used is Magnolione, a closely related material with a very similar though rather more jasminic olfactory character. This makes up some 20% of the formula with 10% of patchouli. Methyl ionone, vetiveryl acetate, cedryl acetate, Vertofix, and sandalwood make up the woody aspect of the fragrance, with a small amount of Galaxolide as the musk. 

E.-J. Brunke E. Klein, Chemistry of Sandalwood Fragrance. In Fragrance Chemistry The Science of the Sense of Smell ... 

Alpha-Pinene oxide 9 (Eq. 15.2.5) is known as a reactive molecule which rearranges easily under the influence of an acid catalyst (6, 7). Thereby many products can be formed. For example compounds such as the isomeric campholenic aldehyde 11, trans-carveol 12, trans-sobrerol 13, p-cymene 14 or isopinocamphone 15 are observed as main by-products. At temperatures higher than 200°C more than 200 products can be formed. The industrially most desired compound among these is campholenic aldehyde 10. It is the key molecule for the synthesis of various highly intense sandalwood-like fragrance chemicals (7, 8). 

For example, rearrangement of a-pinene oxide produces, among the ten or so major products, campholenic aldehyde, the precursor of the sandalwood fragrance santalol. The conventional process employs stoichiometric quantities of zinc chloride but excellent results have been obtained with a variety of solid acid catalysts (see Fig. 2.23), including a modified H-USY [70] and the Lewis acid Ti-Beta [71]. The latter afforded campholenic aldehyde in selectivities up to 89% in the liquid phase and 94% in the vapor phase. 

Endo-exo selectivity typically ranges from 20 1 to 45 1 with a maximum of 97.5 2.5 diastereoselection. Prepara-tively convenient reaction conditions are employed (CH2CI2, CH2Cl2/cyclohexane temp, approx. 0°C ca. 0.3 M concentration and 0.1-1.0 molar equiv of Lewis acid). Products are typically crystalline and brought to high optical purity by recrystallization. Epimerization-free hydrolysis is effected with LiOH in THF/water. This procedure has been successfully applied in a nine-step synthesis of cyclosarkomycin in 17% overall yield (eq 2), and to syntheses of the sandalwood fragrances. ... 

Since the dawn of civilization, say, 5000 years ago perfumes and perfumery chemicals encompassing flavors and fragrances and even pleasant food additives attracted attention in India and were used in temples, religious rites and even for personal sophistication. The earliest reference to such materials was to he found in the Vedas, say, during 2000-2500 BC. In particular, sandalwood, camphor, saffron, etc. were mentioned in connection with certain rites. 

The mixture is used as such in large amounts as a fixative with sandalwood odor in a broad range of fragrances. 

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