P a-Phellandrene

Figure 9. Important odorants of dill herb A (3R,4S,8S)-3,9-epoxy-1-p-menthen, B (S)-a-phellandren, C methyl 2-methylbutanoate, D myristicin [33],

Black pepper Piper nigrum (Piperaceae) a- and p-pinene, phellandrene 

The major components of elemi oil are limonene (40-72%), a-phellandrene (10-24%), and the sesquiterpene alcohol elemol (1-25%) [488-491]. Both the resinoid and the oil have a fresh, citrus-like, peppery odor and are used predominantly in soap perfumes. (FCT 1976 (14) p. 755 [8023-89-0] (oil), [9000-74-2] (resin). 

Earlier workers established the presence of a-pinene, (3-pinene, 1-a-phellandrene, dl-limonene, piperonal, dihydrocarveol, a compound melting at 161°C, P-caryophyllene and a piperidine complex from the essential oil obtained by steam distillation of ground Malabar pepper. The above compounds were identified by the classical methods of derivatization and degradation. They also reported the presence of epoxy dihydrocary- 

MONOTERPENE HYDROCARBONS AND OXYGENATED COMPOUNDS There are 15 monoterpene hydrocarbons identified so far and they are camphene, 83-carene, p-cymene, limonene, myrcene, cis-ocimene, a-phellandrene, (3-phellandrene and a- and (3-pinenes, sabinene, a- and y-terpinenes, terpinolene and a-thujene. 

A pale olive green essential oil with a sharp, warm, woody spicy odour. Principal constituents are monoterpenes limonone (15-17%), sabinene (9-19%), (l-pinene (5-14%), a-pinene (2-11%), P-myrcene (1.5-2.5%), carene (0.2-14.0%), a-phellandrene (0.5-5.0%), sesquiterpenes P-caryphyllene (9-31%), P-bisabolene (0.1-5.1%) and p-farnescene (1-3%). Box 7.15 shows a chemical analysis and Box 7.16 is a material safety data sheet from a sup- 

Acylation of limonene at the disubstituted double bond is favoured by a factor of 2.3 over reaction at the trisubstituted double bond using acetyl hexachloroan-timonate. Mixed alkylcuprate alkylation of tricarbonylcyclohexadienyliron salts has been used to synthesize the a-phellandrene tricarbonyliron complex. Dichlorocarbene addition to limonene in the presence of 1,4-diazabicy-clo[2,2,2]octane is almost 100% stereoselective at the trisubstituted double bond (no yield given) (cf. Vol. 6, p. 31) in contrast to dibromocarbene addition to carvone (Vol. 7, p. 34), dichlorocarbene addition to the carveols is not regio-specific.  

Hydrogenation of thymoquinone (170) gives two of the menthane-2,5-diols [(171) and (172)]. All the diastereoisomeric 2,5-diols having the same chirality of the isopropyl group as ( —)-a-phellandrene (173) have been prepared, together with the four p-menth-l-ene-3,6-diols and the two (+ )-p-menthane-2,5-diones, and their interrelations and stereochemistries have been examined. 

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