Zizaane

Ramage et have suggested that hinesol (282) can serve as a precursor to the zizaane-type sesquiterpenes [e., (342)] by cyclisation to the secondary cation (336) followed by a Wagner-Meerwein shift to the tricyclic cation (337). This last step finds a laboratory precedent in the solvolysis of the mono-mesylate (338) to the tricyclic ketone (339). Although this proposal explains the gross structure... 

In a study of the hydrocarbons from Reunion vetiver oil, a compound of the structure (ii) has been isolated, referred to as prezizaene. Zizaene (iii) can be detected in the acid-catalysed isomerisation of prezizaene, both of which are finally isomerised to three new hydrocarbons. The biogenesis of the zizaane-type sesquiterpenes is considered to involve cyclisation of (+)-v-curcumene (i) as shown. Personal communication from Professor... 

Cuparane, Thujopsane, Chamigrane, Acorane, Alaskane, Cedrane, Zizaane, and Trichothecane... 

Undoubtedly one of the major highlights in the sesquiterpenoid field this year has been the very interesting results concerning the co-occurrence patterns and in vitro conversions of sesquiterpenes within the farnesane,bisabolane,curcumane, acorane, alaskane, cedrane, and zizaane groups. For instance, Kaiser and... 

Bonds between C-2 and C-11, C-6 and C-10 as well as C-6 and C-15 of famesane formally link up the tricyclic sesquiterpene skeleton prezizaane, which converts into zizaane by methyl shift. 

The oil of vetiver with its aromatic to harsh, woody odor, steam-distilled for perfumery from roots of vetiver grass Vetiveria zizanoides (Poaceae) which is grown chiefly in Haiti, India, and Java, contains some prezizaanes and zizaanes such as (+)-prezizaene, (-)-7-prezizaanol, (-l-)-6(13)-zizaene and (-l-)-6(13)-zizaen-12-ol, also known as khusimol. 

The intramolecular variant of the de Mayo reaction has been applied in the synthesis of -bulnesene (21), epiprecapnelladiene (22), and of the zizaane carbon skeleton (23). Coates et have described a variant of this general strategy for ring synthesis whereby but-2-enolides are used as one of the TT-components in the photocycloaddition. 

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... 

Andersen has recently reported the isolation and identification of allocedrol having the absolute configuration corresponding to the zizaane family (i.e. enantiomer of 227-OH) from vetiver oil (298a). Pyrolysis of the methanesulfonate at 100° affords (4-)-prezizaene (221) in 64% yield. 

Kido, F., H. Uda, and A. Yoshikoshi Synthetic Study of Zizaane-type Sesquiterpe-noids. J. Chem. Soc. Perkin I 1972, 1755. 

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