Sesquiterpenes modhephene

Turning now to the intriguing propellane sesquiterpene modhephene (308), Karpf and Dreiding159 have provided full details of their original synthesis. Hot... 

Intrtimolecular exocyclic transannular cycloaddition of TMM can provide a viable route to propel-lanes, such as the sesquiterpene modhephene (144). This methodology is demonstrated in an efficient synthesis of a [3.3.3]propellane (145) (equation 149). The methylenecycloptt ane approach is preferred in this case because it works well with dialkyl-substituted systems. 

Four syntheses of the related sesquiterpene, modhephene (9) have also been reported. " One of these also proceeds via a [2 + 2]photocycloaddition route to give (7) followed by an acid-catalysed Cargill rearrangement to (8), which was converted to modhephene (9) by conventional methods. The bulk of the work in this area continues to be directed at the synthesis of sesquiterpenes of the hirsutane group. Details have appeared of the previously reported synthesis... 

Uyehara, X, Murayama, X, Sakai, K., Onda, K., Ueno, M., and Sato, X., Rearrangement approaches to cyclic skeletons. XIII. Total synthesis of triquinane sesquiterpenes, ( )-modhephene and ( )-isocomene, on the basis of formal substitution at both bridgeheads of a bicyclo[2.2.2]oct-5-en-2-one. Bull. Chem. Soc. Jpn., 71, 231, 1998. 

Oppolzer has designed two approaches to modhephene, both of which are based on the high level of stereochemical control attainable in intramolecular thermal ene reactions. In the first (Scheme XCIV), a, jJ-unsaturated ketone 793 is obtained by aldol methodology and heated at 250 °C in toluene to produce 794 A methyl group and double bond are next introduced in standard fashion prior to arrival at the final sesquiterpene stage. 

Cuprate conjugate additions. One step in a recent synthesis of (-t-)-modhephene (3). a natural sesquiterpene with a (3.3.3)propellane skeleton, involved conjugate addition of lithium dimethylcuprate to 1. The desired reaction proved difficult... 

The formal synthesis of the propellane sesquiterpene natural product modhephene (168) was... 

The pentalenone 6 is an intermediate in the synthesis of 3.3.3. propellane sesquiterpenes like modhephene. But, again, poor yields were observed by Paquette in the multi-step synthesis of by acylation of cyclopentene or 1-trimethylsilylcyclopentene and cyclization of the corresponding divinyl-ketone. 41,42 Moreover, two isomeric pentalenones were obtained and it was necessary to isomerize with rhodium trichloride. 

Mehta, G. and Subrahmanyam, D., Photochemical oxa-di-Jt-methane rearrangement approach to [3.3.3]propellanes. Total synthesis of sesquiterpene hydrocarbon ( )-modhephene,/. Chem. Soc., Perkin Trans. 1, 395, 1991. 

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