Sesquiterpene acorone

Alternatively, trialkylstannylcesium compounds can be prepared by fluoride ion-induced desilylation. Treatment of (trimethysilyl)tributylstannane with cesium fluoride affords a tributylstanyl anion. The anion reacts with a C-I bond to form a vinyl anion that promotes intramolecular cyclization [6]. The spiro ketone obtained is converted into a natural sesquiterpene acorone (Scheme 2.3). 

It is clear from these and previous results obtained over the past two or three years that the spiro-sesquiterpenes provide an important link between certain monocyclic and tricyclic sesquiterpenes. This is further exemplified by the recent work of Andersen and SyrdaP who have now reappraised the absolute stereochemistries of (-)-a- (137) and (- )-/3-alaskene (138). It now appears that 5-acoradiene, isolated by Hirose et is, in fact, (-I-)- -alaskene. Andersen and Syrdal also made the interesting observation that phthalic anhydride dehydration of the diols derived from iso-acorone (139) gave rise to small amounts of (-f )-a-cedrene (126 R = Me) and (— )-2-epi-a-cedrene (136). Subsequently these authors found that (-t- )-nerolidol (140) and a number of its derivatives undergo acid-catalysed cyclization to a mixture of a- and -bisabolenes (141), of which the... 

Acorone (166), a sesquiterpene diketone isolated from the essential oil of roots of Acorus calamus, was the first spirosesquiterpenoid to be characterized, with the carbon skeleton of cation 158. At present several compounds of this class are known and an extensive review has been published (267). Hydrocarbons (e.g., y-acoradiene = a-alaskene, 167) and alcohols (e.g., a-acorenol, 168) directly derivable from the spiro-cation 159 have been isolated from wood of Juniperus... 

Marx JN, Norman LR. Synthesis of (—)-acorone and related spirocyclic sesquiterpenes. J. Org. Chem. 1975 40 1602-1606. 

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