Acorenols

The second chemotype (their Type 1) had, in addition to the Type 0 array, substantial amounts of a-longipinene [297] and an unidentified sesquiterpene alcohol. The third chemotype (their Type 2) was distinguished by the presence of, among other compounds, cedrene isomers, [a-cedrene is shown as 298], and large amounts of the isomeric sesquiterpene alcohols a-acorenol [294] and its P-isomer [295]. The acora-diene isomers [295 and 296] were also identified. Some geographic patterning was observed in the Type 0 chemotype when the data were subjected to numerical analysis a trend in the reduction of caryophyllene content was revealed in a west to east direction. The data sets for Types 1 and 2 were too small to allow for similar analysis. 

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. 

Shortly after these communications, the alcohol (127), named a-acorenol, was found to occur naturally in the wood of Juniperus rigida and Tomita and Hirose also demonstrated its facile cyclisation with formic acid to ( — )-(z-cedrene (123) in greater than 90% yield. The corresponding diene (132), a-acoradiene, which was also converted to (—)-a-cedrene, was found in the same source. Subsequently, Hirose et al. isolated four other related sesquiterpenes from the same species. These are j5-acoradiene (133), y-acoradiene (134), -acoradiene (135), and )3-acorenol (136). The above authors also reported a tricyclic alcohol... 

Tricho-acorenol (143), isolated from a T. koningii, has been claimed to be a new compound [129]. It is in fact identical to coccinol previously isolated from Fusidium coccineum in 1968 [208, 209]. In describing the evidence for structure 143, the authors report that MnC>2 oxidation of gave acorenone B [129] which is diastereomeric at the spiro-carbon, according to the reference quoted by the authors [210]. Aspects of the biosynthesis of coccinol have been studied [209] and the more pertinent details are presented in Scheme 22. 

Azo-dienophiles give more ene adduct than the corresponding substituted carbo-dienophile. The spirosesquiterpenoids ( )-jS-acorenol, ( )-/3-acoradiene, ( )-acorenone-B, and ( )-acorenone have all been synthesized from the ester (40). The key step, as previously described for the /8-acorenol synthesis, is the 100% endo-selective intramolecular ene reaction of the 1,6-diene (41) to a mixture of the epimers (42a and b). ... 

Braun N. et al., 2005, Santalum spicatum (R.Br) DC. Santalaceae)—Nor-helifolenal and acorenol isomers Isolation and biogenetic considerations. 15, 381-386. 

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... 

Acorenol is a spirocyclic sesquiterpene, isolated from the wood of juniperus rigida. The synthesis of racemic / -acorenol by Oppolzer is based on a stereocontroiied construction of five-membered ring systems using an intramolecular ene-reaction. 

Acetolactic acid, methyl ester, A33 Acetylaranotin, Y21 Acetylchloromalic acid, A1 Achillene, T1 Achillin, T22 Achromycin, Y28 Aconitine, K33 Acoradienes, T29, T5 Acoragermacrone, T22 Acorenols, T29 Acenaphthenes, A35 ... 

Tomita, B., and Y. Hirose Terpenoids. XXVI. Acoradiene and Acorenol, Key Intermediates of Cedrane Group Sesquiterpenoids, and Their Transformation into ( —)-a-Cedrene. Tetrahedron Letters 1970, 143. 

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