Alcohol geraniol

The conversion of isopentenyl diphosphate (IPP) to terpenoids begins with its isomerization to dimethylallyl diphosphate, abbreviated DMAPP and formerly called dimethylallyl pyrophosphate. These two C5 building blocks then combine to give the C10 unit geranyl diphosphate (GPP). The corresponding alcohol, geraniol, is itself a fragrant terpenoid that occurs in rose oil. 

Ru(II)-BINAP complexes (1) can effect enantioselective hydrogenation of pro-chiral ally lie and homoallylic alcohols, without hydrogenation of other double bonds in the same substrate.1 The alcohols geraniol (2) and nerol (3) can be reduced to either (R)- or (S)-citronellol (4) by choice of either (R)- or (S)-l. Thus the stereochemical outcome depends on the geometry of the double bond and the chirality... 

Figure 11.2 Oxidation of the monoterpene alcohol geraniol to geranial by CPO in the presence of hydrogen peroxide and absence of halide ions.

Allylic P-unsaturated,alcohols (geraniol, 3-phenyl-2-propenol) were efficiently oxidised to the aldehydes by fran.y-Ru(0)2(TMP)/(lutidine-iV-oxide)/CgHg [586]. As fran.y-Ru(0)2(TMP)/(Cl2pyN0)/CgHy24h it oxidised cyclohexanol to cyclohexanone [587]. 

Chiral Mo02(acac)(L ) complexes, where L is a chiral bidentate 0,0-ligand derived from (L)-frans-4-hydroxyproline bearing a Si(OEt)3 moiety, have been successfully heterogenised on zeolite-Y and tested for the epoxidation of allylic alcohols (geraniol and nerol) with TBHP (Scheme 4) [18]. 

In particular, substrates like terpene alcohols are often used with Candida rugosa with very high enantiomeric excesses and at high yields. Lee et al. could increase significantly the maximum reaction velocity of this lipase in AOT-based reverse micelles and obtained conversions up to 70% during the esterification of diterpenes alcohols (geraniol, menthol, citronellol) [130]. 

However, the lower fatty acid esters (particularly the acetates) of the acyclic terpene alcohols geraniol, linalool, and citronellol are extremely important both as fragrance and as flavor substances. The acetates occur in many essential oils, sometimes in rather high amounts. Formates, propionates, and butyrates occur less frequently. As a result of the development of large-scale production processes for terpenes, the esters of acyclic terpene alcohols are nearly always made synthetically. All acyclic terpene esters that are used as fragrance and flavor materials can be prepared by direct esterification of the appropriate alcohols. However, special precautions are required for the esterification of linalool. 

These regular monoterpenes constitute a small class which includes the trienes myrcene 4 and ocimenes (5-7) and the alcohols geraniol 15, nerol 16, citronel-lol 17, linalool 18, etc (Structure 4.5). 

A great profusion of oxygen-containing isoprenoid compounds are known. Of particular importance in the acyclic series are the alcohols geraniol, nerol, and linalool, and the aldehydes geranial (citral a), neral (citral b), and citronellal ... 

Fig. 7 Monoterpene alcohols geraniol, linalool, nerol, and a-terpineol and sesquiterpene alcohols guaiol and carotol...

Examples of monoterpenes include the linear aldehyde citral, which is found in many essential oils, and the (cis) alcohol geraniol, a major component of oil of geranium. Cyclic monoterpenes include limonene, menthol, pinene, camphor, and carvone, major components of lemon oil, mint oil, turpentine, camphor oil, and caraway oil, respectively. Sesquiterpenes include farnesol, a component of rose oil, and bisabolene, a component of Bisabol myrrh. The diterpenes include phytol, a component of chlorophyll, and vita-... 

SYNS 2,6-DIMETHYL-trans-2,6-OCTADIEN-8-OL 3,7-DIMETHYL-trans-2,6-OCTADIEN-l-OL FEMA No. 2507 GERANIOL (FCC) GERANIOL ALCOHOL GERANIOL EXTRA GERANYL ALCOHOL GUANIOL LEMONOL... 

Geranial.—Corresponding to the higher ethene alcohol geraniol (p. 167) is the aldehyde derived from it and known as geranial. It has the constitution... 

CIC The basic Muscat note is produced from linalool, balanced with further terpene alcohols, geraniol and linalool oxides. The catty odour of the concord grape is based on methyl anthranilate, combined with ethyl-3-mercapto propionate, benzaldehyde adds the touch of a seedy character. 

The alcohols geraniol-nerol, linalool, citronellol and their esters are the largest tonnage materials of this class. Their syntheses are described in detail above and no further explanation is necessary here. The chemical stability of these materials is limited by the unsaturation in them. To improve stability, particularly in oxidative media such as bleaches and laundry powders, various hydrogenated analogues have been developed. In some, one of the double bonds is reduced, in others both are. 

The 1,2,4-trioxane ring system is the key structural subunit in a number of substances with promising anti-malarial activity, and has been constructed by a number of groups using a photooxygenation approach. Thus the readily available allylic alcohol geraniol reacts with O2 to give a mixture of mono- and... 

The acyclic terpene alcohols geraniol, linalool, and citronellol are the most important terpene alcohols used as fragrance and flavor substances. Geraniol and linalool are, in addition to nerol and lavandulol, primary products in terpene biosynthesis. The fully saturated alcohols tetrahydrogeraniol and tetrahydrolinalool are also... 

The alcohols geraniol/nerol, linalool, citronellol and their esters are the largest tonnage materials of this class. (People in the fragrance industry tend to use nomenclature rather loosely. For example, to the chemist,... 

Figure 10.8 shows three monoterpenoid alcohols geraniol (10.16), citronellol (10.21) and linalool (10.22) all of which have been mentioned earlier as being key fragrance ingredients which can be obtained from natural sources. Geraniol is one of the character impact components of rose but it is only present in rose oils to the extent of about 30%. Much... 

Epoxy-methylsulphonates (158) have been used as intermediates in a stereoselective 1,3-transportation reaction of the allylic alcohols geraniol (157 R = H) and farnesol (157 R = Me2C=CHCH2) to linalool and nerolidol, respectively (Scheme 9). ""... 

The performances of bimetallic Rh-Ge/Si02 and Rh-Ge/Al203 catalysts prepared by catalytic reduction were measured for another a,p-unsaturated aldehyde, namely citral (Fig. 9.7). The addition of Ge to Rh by the surface redox reaction promoted the hydrogenation of citral to the unsaturated alcohols (geraniol/nerol), while the saturated aldehyde (dtroneUal) was the main product on the monometallic Rh catalyst [41]. 

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