13-santalene

Two distinct sesquiterpenes exist in the essential oil of Santalum album, known as a-santalene and /3-santalene. 8-santalene is probably a bicyclic and a-santalene a tricyclic sesquiterpene. These sesquiterpenes were discovered by Guerbet. From the method of their preparation it is doubtful whether they have been obtained in a state of purity, so that the characters assigned to them must be accepted with some reserve, and as probably being only approximate. 

No crystalline hydrochlorides eould be obtained from either santalene. tt-Santalene forms a liquid dihydrochloride of optical rotation -n 6°, when dry hydrochloric acid is passed through its ethereal solution. It also forms a crystalline nitrosochloride melting with decomposition at 122°, and a nitrol-piperidide melting at 108° to 109°. /3-santalene forms corresponding compounds, the dihydrochloride having a rotatory power -H 8°. It forms, however, two isomeric nitrosochlorides, CigHj NOCl. They may be separated by fractional crystallisation from alcohol. One melts at 106°, the other at 152°. The corresponding nitrol-piperidides melt at 105° and 101° respectively. 

Further studies on the biosynthesis of ovalicin (57) have demonstrated the use of deuterium magnetic resonance in biosynthetic studies. Compounds (59)—(62), structurally related to (-)-a-santalene (58), have been isolated from the essential oil of Lavandula ojficinalis and L. hybrida " An alternative synthesis of a-santalol... 

Santalum album L. S. myrtifolium Roxb. S. verum L. Tan Xian (Sandalwood) (heartwood) Alpha-santalol, beta-santalol, alpha-santalene, beta-santalene, santene, alpha-santenone, alpha-santenol, santalone, santalic acid, teresantalic, isovaleraldehyde, teresantalol, tricycloekasantal, santalin, deoxysantalin, sinapyl aldehyde, caniferyl aldehyde, syringic aldehyde.33 Treat stomachache. 

Suggest a synthesis of /8-santalene from the following ketone. (Do not worry about stereochemistry.)... 

As an example, when phenylpotassium is allowed to react with 8-bromonortricyclene, a-santalene is produced which is then submitted again to metallation with LIC-KOR followed by borylation and oxidation.76 The allowance for torsional equilibration produces the (Z)-a-santalol, one of the main constituents of the highly prized sandalwood oil, with no trace of the (A l-isomcr. The entire sequence can also be contracted to a one-flask protocol still giving quite acceptable yields.76... 

The thermal reactions of l-oxa-l,3-butadienes such as acroleine 2-78 with alkenes such as 2-79 usually need relatively harsh conditions (150°C-250°C) [120]. As a side reaction polymerisation of the a,/l-unsaturated carbonyl compound can take place addition of radical inhibitors such as hydroquinone or 2,6-di-ferf-butyl-4-methylphenol can be helpful in avoiding this unwanted transformation. In the described hetero Diels-Alder reaction the cycloadduct 2-80 was obtained which was then transformed into racemic-/3-santalene 2-81 (Fig. 2-22). 

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