6-Selinene

The right half of the sesquiterpene (+)-p-selinene (as drawn below) includes (R)-(+)-limonene as a substructure. Retrosynthetic disconnection to (if)-(+)-limonene leads to the intermediate carbenium ions la and lb via 15-nor-ll-eudesmen-4-one (carbonyl alkenylation) and 15-nor-13-chloro-2-eudesmen-4-one (dehydrogenation, protective masking of the double bond in the side chain). These carbenium ions arise from (if)-9-chloro-p-menth-l-ene and the acylium ion Ic (synthone) originating from 3-butenoic acid as reagent (synthetic equivalent). (i )-/7-Menth-l-en-9-ol, on its part obtained by hydroboration and oxidation of (if)-(-l-)-limonene, turns out to be the precursor of the chloromenthene. 

the first step of a stereoselective synthesis of p-selinene reported by Mackenzie, Angelo and Wolinski involves hydroxylation of the C-8-C-9-double bond of (i )-(+)-limonene by hydroboration with diborane and subsequent 

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Many teipenes contain one or more rings, but these also can be viewed as collections of isoprene units. An exfflnple is a-selinene. Like fainesol, it is made up of three isoprene units linked head-to-tail. 

Selinene is a bicyclic sesquiterpene occurring in essential oil of celery. Its presence was first indicated by Ciamician and Silber who announced the isolation of a sesquiterpene boiling at 262° to 269°, but no characteristic derivatives were prepared. Schimmel Co. examined this sesquiterpene to which they assigned the name selinene. They prepared a solid dihydrochloride melting at 72° to 74° and ha-ving a specific rotation -h 18°. The pure sesquiterpene, regenerated from the dihydrochloride by means of sodium ethylate had the following characters —... 

The most recent work, however, on the sesquiterpene is that of fiemmler and Eisse. From the crude selinene, prepared hy fractional distillation, they prepared the crystalline dihydrochloride, Cj5H24.2HC1, melting at 72° to 74°, by passing a mixture of 1 part of dry hydrochloric acid gas with 3 parts of air, into the sesquiterpene dissolved in ether. This compound on digestion at very gentle heat, with a solution of caustic potash in methyl alcohol, yields selinene, which the authors conclude is a doubly unsaturated bicyclic compound. The characters of the selinene thus obtained are as follows —... 

By reducing selinene with sodium alcohol, tetrahydroselinene was... 

They have also carried out the oxidation of selinene by means of ozone and potassium permanganate and have thus been able to establish that the regenerated selinene is not absolutely identical with the natural selinene. They are the first to record the existence of a hemi-cyclic-sesquiterpene this compound is termed pseudo-()3)-selinene. By passing a current of ozone into a solution of natural selinene (pseudo-( 8)-selinene). in acetic acid, there is obtained a diketone, CjjHogOj, which is purified by treatment with permanganate in acetone solution. Its properties are as. follows —... 

The principal oxidation product of the selinene regenerated from the dihydrochloride is a diketocarboxylic acid, of the formula melting at 226°. 

Semmler deduces from these results that natural selinene is composed of a mixture containing principally the hemicyclic pseudo-(yS)-selinene, together with a small quantity of ortho-(a)-selinene. By passing through the dihydrochloride it is possible to convert the pseudo-(y8)-selinene into the ortho-(a)-selinene or regenerated selinene, which contains only a. small proportion of the (3 form. Both yield the same solid dihydrochloride. Selinene affords a typical example of the possibility of the displacement of the double bond from the side chain into the nucleus. 

The following structural formulae represent, according to Semmler, the constitutions of the two forms of selinene and illustrate how they both yield the same dihydrochloride and the same tetrahydroselinene. 

Selinene is still another case of unhappy nomenclature. The natural, body is first known as selinene. The regenerated sesquiterpene is termed ortho-tt-selinene, and because the natural, originally named selinene does, not agree with the artificial body, it is now called psewdo-selinene . 

Martin et al. (1974) collected specimens from 22 locations throughout the range of H. courbaril and identified a number of sesquiterpenes including caryophyllene [173], humulene [174], selinene isomers [175 is P-selinene], and other related compounds (see Eig. 2.48 for compounds 173-175). Caryophyllene and two selinene... 

Stylotelline (23) is a constituent of a Stylotella sp. collected offshore in New Caledonia. 13C NMR spectra involving 2D NMR techniques provided the bulk of information leading to its structure. The absolute configuration was demonstrated after the tertiary isocyano group was removed to yield the known conjugated diene, ( + )-d-selinene (24). Optical rotation and spectral data of the transformation product were identical in all respects to those of the corresponding product obtained from eudesmols [42], Although neither the isothiocyanato nor the formamido compounds were isolated, the latter was prepared, which allowed an nOe observation between the axial C-3 and the amide protons. 

The extrapolation of the vinylcyclopropane-cyclopentene rearrangement to a vinyl-cyclobutaiie-cyclohexene synthesis begins to create new insights into the synthesis of six membered ring natural products. The eudesmane sesquiterpene (—)-P-selinene, 217 illustrates such a strategy as summarized in Scheme 14 80). A suitable cyclohexene... 

The alkoxide generated by KH in THF was believed to be effective in accelerating the vinylcyclobutane ring expansion in the synthesis of 6-membered ring compounds 142). As an example, the cyclobutanol (416) reacted with KH and rearranged to (417), which upon subsequent oxidation, provided (418) 142) in 64.5% yield. The a,P-unsaturated ketone (418) was converted to (—)- 3-selinene (419)142). Similarly, furancyclohexanol (421) could be obtained from the cyclobutanol (420) 142). 

Steele CL, Crock J, Bohlmann J, Croteau R. (1998). Sesquiterpene synthases from grand fir Abies grandis). Comparison of constitutive and wound-induced activities, and cDNA isolation, characterization, and bacterial expression of delta-selinene synthase and gamma-humulene synthase./owrna/ of Biological Chemistry, 273,2078. 

Major mono- and sesquiterpene hydrocarbons in the oil are (+)-limonene (58-79%) and /3-selinene [17066-67-01], 5-20%. Its typical, long-lasting odor is caused primarily by two lactones, 3-butylphthalide [6066-49-5] and sedanenolide [62006-39-7] (1.5-11%) [328-334]. 

Celery seed Apium graveolens L. 3-Butylphthalide and sedaneno-lide (1.5-11), (+)-limonene (58-79), (3-selinene (5-20)... 

Cyperus brevifolius (Rottb.) Hassk. C. difformis L. C. glomeratus L. C. iria L. Sha Cao (rhizome) Allelopathic essential oils, terpenes, alpha-cyperone, beta-selinene, alpha-humulene.60197 198 A vermifuge, antidote, remedy for dysentery, alleviate stress, sedative. 

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