Spirovetivane sesquiterpenes

However, an efficient synthesis of the spirovetivane-sesquiterpene a-Vetispirene 392 was achieved initiating the cleavage of the silicon-cyclopropane carbon bond of 160 by fluoride ion. This was effected with anhydrous tetra-n-butyl ammonium fluoride in THF solution containing acetone at reflux temperature for 10 hr. The pentadienyl anion 387 thus generated experienced highly regioselective addition of acetone at the... 

The reaction between the sodium salt of an a-formylcycloalkanone and the phosphonium cyclopropane has been found to produce spiro compound 605, together with minor amounts of the dihydrofuran 606 (equation 215). This reaction sequence has been used in the synthesis of spirovetivane sesquiterpenes. ... 

The resulting spiro[4.5]decen-2-one (203) is not only a constituent of Vetiver oil of economical importance but also constitutes the key intermediate for the synthesis of other spirovetivane-sesquiterpenes ... 

A recently published synthesis of /3-vetivone (245) makes use of the hitherto rarely observed y-alkylation of a y-extended enolate anion [e.g. (244) — (245)]. As might be expected, deprotonation of (244) normally leads to the alternative a-alkylation product (246). However, by careful choice of experimental conditions which might be expected to bring about rapid equilibration of all possible enolate anions, the Curtin-Hammett principle is made to apply, and (245) is formed in high yield. Another route to the spirovetivane sesquiterpenes makes use of an acyloin condensation to construct the five-membered ring. ... 

Lumiproducts obtained by irradiation of q clohexadienones in neutral media can be transformed in several ways into useful synthetic intermediates (Scheme 26). For example add treatment of lumiproducts such as 147 gives spirocycHc compounds. This strategy has been used in the synthesis of spirovetivane sesquiterpenes such as ( )-P-vetivone (149). ... 

The alternative proposal for zizaane biogenesis (Scheme 22) involves a final cyclization of a spirovetivane intermediate e.g., a-iso-vetivene, 224) and subsequent ring expansion and elimination to zizaene (223) 294). The other members of the zizaane group could arise by rearrangements in the reverse direction to that indicated above. Although zizaene (223) does co-occur with spirovetivane sesquiterpenes... 

The spiro compound 347 constitutes the basic carbon framework found in sesquiterpenes of the spirovetivane and acorane class 184), which have been the target of many syntheses 185). The thermal C3 -> C5 ring expansion 111 -> 347 was of... 

However, a dispatch route to the [4.5]spirocyclic sesquiterpenes of the spirovetivane type has been recently reported from the readily available a-siloxycyclopropane-carboxaldehyde, via the stereospecific thermal ring enlargement of a silylated 1-vinylcyclopropanol (202) (equation... 

Vetispiranes (spirovetivanes). A group of sesquiterpenes with the skeleton (1). Important sources include vetiver oil [e.g., /S- vetivone and a-vetispirene (2)], a valuable fragrance substance for the perfume industry, and potatoes (Solanum tuberosum) [e.g., sola-vetivone (3), isolubimin (4), lubimin (5), and hydroxy lubimin (6)]. 

Irradiation of lumiproducts in aqueous acetic add with UV light above 300 nm brings about photorearrangement to SpirocycHc dienones. This type of transformation was used for the conversion of the nootkatane sesquiterpenes 3,4-dehydronootkatone (153) into the spirovetivane anhydro-P-rotunol (155) and in the synthesis of P-vetivone and 4-epi-P-vetivone from dehydro-P-vetivone. ... 

---