Multifidene synthesis

Boland, W. Jaenicke,L. 1979, Synthesis of multifidene , Journal of Organic Chemistry, 44,4819-24. 

The fact that the unsymmetrical product dominates in the cross-metathesis of a cyclic olefin and a terminal olefin is an advantage for the efficient synthesis of the brown algae pheromones multifidene (yield 31%) and viridiene (yield 30%) via the cross-metathesis between bicyclo[3.2.0]hepta-2,6-diene and but-l-ene or butadiene, respectively (molar ratio 1/2), in the presence of lmol% of Ru(=CHCH=CPh2)(Cl)2(PCy3)2 Scheme 15.1 (Randall 1995). 

Selenium.— The past decade has seen a vast increase in the use of selenium reagents, to the extent that they now play an important role in many synthetic schemes. For example, a recently reported synthetic study of prostacyclins utilizes the propensity for selenium to induce intramolecular cyclizations onto a double bond, i.e, (188) - (189). The reagent of choice here is phenylselenyl chloride, which has also been used in the synthesis of ( )-multifidene. Important elements of this latter synthesis are the stereocontrolled introduction of the phenylselenyl group, from PhSeCl, a to the masked aldehyde functionality in (190). This is followed by a selenium-induced and stereocontrolled addition of ethylmagnesium bromide with subsequent elimination of PhSe to give the epoxide (191) from which multihdene is prepared by deoxygenation. 

Allyl vinyl ethers (66) undergo [l,3]rearrangements to give cyclopentanones (67) when heated with Pd° catalysts,in vivid contrast to the uncatalysed thermal rearrangement of compounds such as (66), which results in the formation of cycloheptenones. The recently developed oxyanionic Cope rearrangement of cyclononatrienols has been used by Paquette and Crouse as the key step in a brief synthesis of ( )-multifidene (68)/ Highly substituted alkylcyclopentenes may be prepared by [3 + 2]cycloadditions between allyl cations and olefins/ ... 

Lebreton J, Alphand V, Furstoss R. A short chemoenzymatic synthesis of (+)-multifidene and (+)-viridiene. Tetrahedron Lett. 1996 37 1011-1014. 

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