Fragrance compounds

Uses ndReactions. Camphene is used for preparing a number of fragrance compounds. Condensation with acids such as acetic, propionic, isobutyric, and isovaleric produce usehil isobomyl esters. Isobomyl acetate (41) has the greatest usage as a piae fragrance (81). The isobomyl esters of acryhc and methacrylic acids are also usehil ia preparing acryUc polymers. 

Aluminum alkyls react by the Ziegler reaction with the least substituted double bond to give the tricitroneUyl aluminum compound. Oxidation of the iatermediate compound then produces the tricitroneUyl aluminate, which is easily hydroly2ed with water to give citroneUol (112,113). If the citroneUene is opticaUy active, opticaUy active citroneUol can be obtained (114). The (—)-citroneUol is a more valuable fragrance compound than the ( )-citroneUol. 

Hydrogenation of a-terpineol gives dihydroterpineol [498-81-7] a mixture of cis- and trans-compounds (120). Dihydroterpinyl acetate [80-25-1] produced from the mixture is also a useful fragrance compound. 

Uses ndReactions. The main use for citroneUol is for use in soaps, detergents, and other household products. It is also important as an intermediate in the synthesis of other important fragrance compounds, such as citroneUyl acetate and other esters, citroneUal, hydroxycitroneUal, and menthol. 

Cinnamaldehyde, [14371-10-9] CgH CH=CHCHO (bp, 253°C at 101.3 kPa), produced by the alkaline condensation of benzaldehyde and acetaldehyde is the main ingredient in cassia oil. It is used in soap perfumes and as an intermediate in the production of other flavor and fragrance compounds. 

Samuel, C., Davis, J.M. (2002). Statistical-overlap theory of column switching in gas chromatography application to flavor and fragrance compounds. Anal. Chem. 74, 2293. 

P., Bughbauer, G., Tropsha, A. Combinatorial QSAR of ambergris fragrance compounds./. Chem. Inf. Comput. Sci. 2004, 44, 582-595. 

Werkhoff P, Brennecke S, Bretschneider W, Progress in the chirospecific analysis of naturally occurring flavour and fragrance compounds, Chem Mikrobiol Technol Lebebsm 13 129-152, 1991. 

Scheme 2.2.7.8 Synthesis of lactone (R) -16, a natural fragrance compound occurring in the essential oil of labdanum resin [30].

Dihydroxy esters of the type 5a can easily be lactonized with concomitant elimination of water to give the corresponding a, 3-unsaturated lactones. Therefore, hydroxy keto ester (R)-2c, obtained by recLBADH-catalyzed reduction of Ic, was reduced with NaBH4 prior to acid-catalyzed lactonization for the synthesis of labdanum fragrance compound (R)-16 (Scheme 2.2.7.8) [12]. 

The oils are used in many perfume and aroma compositions, because of their spicy clove odor. A small amount is used as an antiseptic, mainly in dentistry. The leaf oil, in particular, is also used as a raw material for the production of eugenol, which is the starting material for further commercially important fragrance compounds, such as isoeugenol and eugenyl esters. 

Terpenes important for both fragrances and flavours can be prepared from citral, such as citronellol, linalool, nerolidol, geraniol, farnesol and bisabolol. Citral is also an important starting material for the synthesis of vitamins A and E, carotenoids and other flavour and fragrance compounds like ionones. Most of the /3-ionone synthesised is probably used for vitamin A synthesis. 

In plants the 13-hydroperoxide produced from linolenic acid by lipoxygenase (Sect. 23.4.1.2) can be converted to the allene oxide by allene oxide synthase followed by cyclisation, reduction and -oxidation to form jasmonic acid, an important plant growth factor the corresponding methyl jasmonate is a valuable flavour and fragrance compound that imparts a sweet-floral, jasmine-like note... 

Esters are widespread in fruits and especially those with a relatively low molecular weight usually impart a characteristic fruity note to many foods, e.g. fermented beverages [49]. From the industrial viewpoint, esterases and lipases play an important role in synthetic chemistry, especially for stereoselective ester formations and kinetic resolutions of racemic alcohols [78]. These enzymes are very often easily available as cheap bulk reagents and usually remain active in organic reaction media. Therefore they are the preferred biocatalysts for the production of natural flavour esters, e.g. from short-chain aliphatic and terpenyl alcohols [7, 8], but also to provide enantiopure novel flavour and fragrance compounds for analytical and sensory evaluation purposes [12]. Enantioselectivity is an impor-... 

Ambergris oxide (Ambrox ) is one of the most important ambergris fragrance compounds and is a key compound of ambra, a secretion product of the... 

Scheme 23.16 Microbial pathways from triterpene and tetraterpene (carotenoid) precursors to valuable flavour and fragrance compounds. 1 Carotenoid-cleaving peroxidase-containing supernatant of certain fungal cultures, e.g. Lepista irina 2 Serratia liquefaciens, Botrytis sp.

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... 

Fig. 5.1. A sample of floral scent compounds. (1) Substituted methyl esters of benzoic acid. The ester smells unpleasantly sweet when R = H (methyl benzoate), of wintergreen when R = OH (methyl salicylate), and of concord grape when R = NH2 (methyl anthranylate). Odorants with unusual origins and biological functions include the homoterpene 4,8-dimethyl-1,3,7-nonatriene (2) and the wet-earth compound geosmin (3). Some ubiquitous fragrance compounds are ben-zaldehyde (4), benzyl alcohol (5), indole (6), (S)-linalool (7), ( )-/ -ocimene (8), and of-farnesene (9).

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