Farnesol

Farnesol pyrophosphate is an immediate precursor of squalene, the key intermediate in steroid and triterpenoid biogenesis, which arises from the coupling of two farnesol pyrophosphate molecules or of C,s units derived therefrom. The numerous types of sesquiter-penoid carbon skeletons represent various modes of cyclization of farnesol (sometimes with rearrangement) and it is probable that farnesol pyrophosphate is also the source of these compounds. 

Farnesol derivatives also have juvenile hormone activity. 

Although the term terpene once referred only to hydrocarbons current usage includes functionally substituted derivatives as well grouped together under the general term isoprenoids Figure 26 6 (page 1086) presents the structural formulas for a number of representative examples The isoprene units m some of these are relatively easy to identify The three isoprene units m the sesquiterpene farnesol, for example are mdi cated as follows m color They are joined m a head to tail fashion... 

Many terpenes contain one or more rings but these also can be viewed as collec tions of isoprene units An example is a selmene Like farnesol it is made up of three isoprene units linked head to tail... 

Hydrolysis of the pyrophosphate ester group converts farnesyl pyrophosphate to the corresponding alcohol farnesol (see Figure 26 6 for the structure of farnesol)... 

The enzyme catalyzed reactions that lead to geraniol and farnesol (as their pyrophosphate esters) are mechanistically related to the acid catalyzed dimerization of alkenes discussed m Section 6 21 The reaction of an allylic pyrophosphate or a carbo cation with a source of rr electrons is a recurring theme m terpene biosynthesis and is invoked to explain the origin of more complicated structural types Consider for exam pie the formation of cyclic monoterpenes Neryl pyrophosphate formed by an enzyme catalyzed isomerization of the E double bond m geranyl pyrophosphate has the proper geometry to form a six membered ring via intramolecular attack of the double bond on the allylic pyrophosphate unit... 

Nerolidol and Farnesol. The alcohols nerohdol [7212-44-4] (96) and famesol [4602-84-0] (97) are isomeric and are both important perfumery products. Nerohdol has been isolated from neroH oil, jasmine, citroneUa oil, and pepper oil. It has a mild and woody-floral, slightly green odor with excellent tenacity and good blending and fixative properties (190). 

Unsymmetrical trans vinyl halides have been prepared from acetylenic alcohols by Corey and co-workers (as illustrated in the accompanying formulation) in connection with their synthesis of farnesol and Gecropia juvenile hormone. Several syntheses of vinyl halides (with... 

Stereospecific Synthesis of Trisubstituted Olefins from Acetylenes or Aldehydes Applications to the Total Synthesis of Cecropia Juvenile Hormones (JH) and Farnesol... 

The next group of alcoholic bodies to be studied are those which, although open-chaini alcohols, show considerable tendency to easily pass into closed-chain compounds, so that they occupy a definite position of their own, midway between the ordinary aliphatic series and the closed-chain series. The principal members of this important group are geraniol, nerol, linalol, and citronellol, together with the so-called aliphatic sesquiterpene alcohols, farnesol and nerolidol. 

Farnesol, CjsH gO, is an aliphatic sesquiterpene alcohol, which occurs in ambrette seed oil, and flower oils of the type of acacia, lime flowers, mignonette, and lilac flowers. 

Oxidation of farnesol with chromic acid mixture gives rise to the aldehyde farnesal, which has the following characters —... 

Farnesal forms a semi-carbazone, which crystallises from acetic ether in fine flakes, which melt at 133° to 135°. This body is particularly useful for the identification of farnesol. 

Farnesol forms an acetate, farnesyl acetate, which is a nearly odourless oil, boiling at 169° to 170° at 10 mm. 

When dehydrated with potassium hydrogen sulpnate, farnesol yields a sesquiterpene, which has been named farnesene, and is a colourless oil having the following characters —... 

Kerschbaum has carried out a series of experiments in order to determine the constitution of farnesol. 

In order to establish the primary character of farnesol, farnesenic acid was prepared from farnesal oxime and the corresponding nitrile. Saponification of the farnesene-nitrile with caustic soda solution yields farnesenic acid and acetic acid, and also a ketone which was identified as a dihydropsewdoionone. The semi-carbazone melts between 95° and 96°. The dihydropmtdoionone from farnesene nitrile proved to be... 

It is evident from these reactions that farnesol has the constitution of an aliphatic sesquiterpene alcohol with three double bonds, and that-its formula is—... 

The above constitution of farnesol has been confirmed by the oxidation experiments of Harries and Haarmann. ... 

A solution of 45 mmols of 1-bromo-3,7,11-trlmethyl-2,6,10-dodecatriene (obtained from synthetic farnesol, commercially available and containing four isomers) in 10 ml of benzene was added dropwise at 0 to a stirred solution of 45 mmols of piperonylpiperazine in 60 ml of benzene containing 5 g of triethyiamine. The mixture was stirred for 2 hours and then the precipitated triethyiammonium bromide was fiitered off. The benzene soiution was washed first with water and then with K2CO3 soiution and finaliy dried (K2CO3). Removal of ben-... 

The intramolecular Hiyama reaction is excellently suited for the construction of carbocyclic and heterocyclic ring systems of different size. In most examples, problems of induced diastereoselectivity are involved (Sections 1.3.3.3.9.2.2. and D.2.3.). In the total synthesis of the antitumor germacranolide ( )-costunolide from ( ,.E)-farnesol, the correctly substituted ( , )-cyclodecadiene moiety was constructed by an intramolecular Hiyama reaction22. 

The carbon skeleton of helminthosporal can be accounted for from three isoprene units (XVI), but they cannot be formed by cyclization of a farnesol precursor, as the three units are not joined head to tail. There is the possibility that the aldehyde carbons were joined in the early stages of biosynthesis to form helminthosporane (XVII, XX) as an intermediate, followed by later oxidation to yield the dialdehydes. As a test of this hypothesis the actively growing fungus was fed mevalonic acid labeled with carbon-14 in the 2-position (mevalonic acid being a precursor of isoprene units) (2). Thus, three units of radioactivity should be incorporated, one being the... 

Farnesol was obtained from Fluka AG (Buchs, CH9470, Switzerland) as a mixture of 65% (E), (E)- and 35% (Z), (E)- isomers. It is also available from the Aldrich Chemical Company, Inc. This procedure works equally well with pure (E), (F)-famesol, which may be obtained from the above mixture by careful distillation, at reduced pressure, through a Nester-Faust Teflon spinning-band column. 

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