Eudesmol synthesis

Similar strategies were used by Booker-Milburn et al. in approaches toward the synthesis of dictyol C and a-eudesmol [215], and by Blake et al. in approaches toward the synthesis of ophiobolin F and fusicoccin A [216]. 

The protic reaction on occasion is a useful method of alkene formation, but is far from general because the cation intermediate tends to undergo rearrangements.Further, even for cases in which elimination to an alkene is the predominant pathway, the regioselectivity of the process is often mediocre. A key step in the synthesis of (+)-a-eudesmol and (-)-a-selinene exemplifies this point (Scheme 60). There are, however, isolated examples of excellent selectivity, such as the reaction of a 3-ketotetrahydrofuran tosyl-hydrazone salt to give the corresponding cyclic enol ether as the major product (Scheme 61), the intro-... 

The structure of eudalene, C14H16, a degradation product of eudesmol (a terpene found in eucalyptus oil), was first established by the following synthesis ... 

The protic Bamford-Stevens reaction has been successfully utilized in the asymmetric synthesis of the naturally occurring sesquiterpenes (+)-a-eudesmol and (-)-a-selinene. Here, the more-substituted alkene was formed preferentially (equation 4,1). ... 

This method was used in a synthesis of (—)-modhephene (78% ee) which incorporates a [3.3.3]propellane skeleton65. Enantioselective syntheses of (7 )-muscone (>95% ee)66, (+ )-/ -eudesmol (75% ee)67, and (—)-chokol A (80 % ee)68 also make use of this asymmetric cyclo-propanation, employing chiral dioxolanes as inductors. 

In an analogous way, Darzens and Levy have synthesized isopropylmethylnaphthalene (eudaline) 26, which contains a dehydrogenated sesquiterpene eudesmol motif. The reaction is applicable for the synthesis of methyl derivatives of phenanthrene such as 27. ... 

Homologation of Carbonyl Compounds. Methoxy(phenyl-thio)trimethylsilylmethyllithium (1), an acyl anion equivalent, is generated by treating methoxy(phenylthio)trimethylsilylmethane with butyllithium at —80 °C in THF. This anion adds to carbonyl compounds in 1,2-fashion, providing ketene 0,5-acetals via Peterson alkenation (eq 1). The ketene 0,5-acetals thus obtained are converted to methyl esters by methanolysis in the presence of hydrogen chloride and mercury(II) chloride This procedure was applied to the synthesis of (=E)-/8-eudesmol (eq 2)M... 

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