Spiro decane skeleton

On the basis of both synthetic and degradative studies, Marshall and co-workers have shown that the structure of -vetivone based on a bicyclo-[5,3,0]decane skeleton is untenable and subsequent work dictated the structure (326) incorporating a spiro[4,5]decane skeleton, and this they have confirmed by total synthesis. The method employed was the selective introduction of an isopropylidene group in a stepwise fashion starting with the keto-olefin (327), which was obtained via photolysis of the known dienone (328). 

A new spiro sesquiterpene aldehyde, vitrenal, has been isolated from Lepidozia species and assigned structure (232) by a combination of chemical degradation (Scheme 28) and spectroscopic evidence (250). The absolute configuration of vitrenal (232) was established by X-ray crystallographic analysis of the di-/ -benzoate of (240) (250). Vitrenal is an enantiomeric sesquiterpene and has an unique spiro[4.5] decane skeleton which may be formed from the co-metabolites (230, 231). 

Another approach to the spiro[4-5] decane skeleton is illustrated by the exceptionally simple stereospecific synthesis of /3-vetivone based on a novel spiroannelation reaction of cyclic 1,3-diketone enol ethers developed at Columbia. ... 

DiBlasio, B., Fattorusso, E., Magno, S., Mayol, L., Pedone, C., Santocroce, C and Sica, D. 1976. Axisonitrile-3, axisothiocyanate-3, and axamide-3. Sesquiterpenes with a novel spiro[4,5] decane skeleton from the sponge Axinella cannabina. Tetrahedron 32 473-478. 

These compounds range through monocyclic (with a bisabolane framework), bicyclic (with an eudesmane, amorphane, axane, guaiane, isodaucane, or gorgonane framework), tricyclic (with an aromadendrane, cubenane, maaliane, pupukeanane, or trachyopsane framework), and spiro[4,5]decane carbon skeletons. 

An excellent review of the isolation, structural elucidation, total synthesis, and postulated biosynthesis of sesquiterpenoids based on the spiro[4,5]decane (vetis-pirane) skeleton has been published." Further studies on the development of alternative routes to the vetispirane sesquiterpenoids have been described. In one report100 the spirocyclic acetal (217), previously used as an intermediate in the synthesis of (—)-a-acorenol (218),101,102 has been converted into (—)-agarospirol (219) and (-)-/3-vetivone (220) by the reaction sequence outlined in Scheme 26. 

Connecting the bonds C-l-C-6 and C-6-C-10 in famesane formally produces the spiro[4,5]decane basic skeleton of acorane. The name of this class of sesquiterpenes stems from the Acorus species. (-)-4-Acoren-3-one, for example, has been isolated from Acorus calamus (Calamus, Araceae) and from the carrot Daucus carota (Umbelliferae). The oil of calamus (oil of sweet flag) from the rhizome of Acorus calamus with its warm and spicy odor and pleasant bitter taste is predominantly used in perfumery and as a minor (possibly carcinogenic) ingredient of vermouth, some flavored wines and liqueurs. (+)-3,7(ll)-Acoradiene is a constituent of juniper Juniperus rigida its enantiomer occurs in Chamaecyparis nootkatensis (Cupressaceae). 

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