Myrcene oxidation

In several important cases, new synthetic strategies have been developed into new production schemes. An outstanding example of this is the production of an entire family of terpene derivatives from a-pinene (29), the major component of most turpentines, via linalool (3) (12). Many of these materials had been produced from P-pinene, a lesser component of turpentine, via pyrolysis to myrcene and further chemical processing. The newer method offers greater manufacturing dexibiUty and better economics, and is environmentally friendly in that catalytic air oxidation is used to introduce functionality. 

Sampling time 60 min extraction temperature 80°C. Monoterpenes a-pinene, p-myrcene, a-phellandreneand limonene sesquiterpenes a-cubebene, a-copaene, p-elemene, p-caryophyllene, a-humulene, y-muurolene, p-eudesmene and caryophyllene oxide diterpenes cembrene A and isoincensole acetate. 

The first observation is the similarity between the chemical compositions of both the Boswellia carteri and Boswellia sacra. For these three olibanum samples, a-pinene (2), (3-myrcene (8) and limonene (14) are the predominant monoterpenes. p-Caryophyllene (73) is the major sesquiterpene besides a-copaene (65), a-humulene (also called a-caryophyllene) (78) and caryophyllene oxide (95). The characteristic olibanum compounds isoincensole and isoincensole acetate (128) together with cembrene A (120) are the main diterpenes. 

Regioselective [4-1-2] cycloadditions to Cjq are also possible with 2,3-dimethyl-buta-1,3-diene (4) and with the monoterpene 7-methyl-3-methylideneocta-l,6-diene (5, myrcene) [22]. These monoadduct formations proceed under mild and controlled conditions. Most of these addition products of 1,3-butadiene derivatives (e.g. 4, 5, 8-12) are unstable against air and light [25]. The dihydrofuUerene moiety in the Diels-Alder adducts act as a 02-sensitizer and promotes the oxidation of the cyclohexene moiety to the hydroperoxide. Reduction of the hydroperoxide with PPhj yields the corresponding allylic alcohols [25]. 

Attempts to investigate boll weevil (Anthonomus grandis) pheromone biosynthesis have identified isomerization, dehydration, and oxidation of the pheromone alcohols, and anticipated allylic oxidation of myrcene and limonene, but no evidence for the cyclization of acyclic precursors. The aggregation pheromones of bark beetles have been reviewed. Ips calligraphus responds to ipsdienol only in the presence of the c/5-verbenol (32) large additional concentrations of the enantiomer (l/ ,4i ,5/ )-(32) reduce beetle response. 5-(-)-Ipsenol, the pheromone of Ips grandicollis, increases the response of /. avulsus to its own pheromone ipsdienol. ... 

Terpene = p-pinene, carvone, D-limonene, limonene oxide, myrcene... 

Among the other terpenes that have been used as substrate in the MTO-catalyzed oxidation reactions are the bicyclic monoterpenes carene and camphene, the acyclic monoterpene myrcene, fi-citronellene (the reduced form of myrcene), and the bicyclic sesquiterpene (i-caryophyllene (Fig. 6). 

With myrcene and p-citronellene, different results are obtained myrcene can be oxidized at the internal double bond with full conversion and good selectivity (90%), while p-citronellene is oxidized at the same bond with significantly inferior characteristics (72% conversion, 50% selectivity). The major side product in the latter case is the diepoxide, which does not occur in myrcene because of stabilization of this double bond via conjugation [52]. 

Simple transformations (hydrolysis of the pyrophosphate group to a hydroxy group, elimination, oxidation, etc.) convert geranyl pyrophosphate to monoterpenes such as geraniol, myrcene, and citronellal. 

Thevanmundi, Poonjaranmunda, Valiakaniak-kadan and Subhakara. Some of the newly developed cultivars are Panniyur-1, Panniyur-2, Panniyur-3 and Panniyur-4. By adopting GC and GC-MS techniques, researchers have identified over 55 compounds from the volatile oil of these pepper cultivars. The major compounds identified were a- and (3-pinene, sabinene, limonene, P-caryophyllene, myrcene, p-cymene and caryophellene oxide (Gopalakrishnan et al., 1993 Menon et al., 2000, 2002, 2003 Menon and Padmakumari, 2005). Table 2.7 illustrates this variability among different popular cultivars. 

Variety/ compound Limonene P-Pinene P-Caryophyllene Sabinene Caryophyllene oxide 8-3-Carene a-Pinene Myrcene p-Cymene Elemol... 

Floral volatiles could play many roles instead of or in addition to pollinator attraction. For example, many terpenes, including P-myrcene, ( )-P-ocimene, linalool, and ( )-P-caryophyllene, react readily with ozone and other reactive oxygen species (27). Thus, floral volatiles could function to protect the reproductive organs from oxidative damage. A variety of monoterpenes and sesquiterpenes is reported to have antimicrobial activity (28). Hence, floral terpenes could help defend floral organs, like the moist stigma, from bacterial or fungal infection. 

In the course of an examination of the autoxidation of terpene hydrocarbons, Bardyshev and Shavyrin have found, predictably, that those containing conjugated double bonds e.g. allo-ocimene, myrcene) are oxidized most rapidly, those with isolated double bonds or cyclopropane rings more slowly e.g. limon-ene, carene), and those with a single double bond slowest e.g. pinene). The effect of light, heat, and inhibitors was studied. ... 

Thus, the tricarbonyliron complex 1 of myrcene reacted with dichlorocarbene via cyclopropanation of the isolated uncomplexed double bond giving 2 and no cyclopropanation product of the diene system as observed with the free ligand. Liberation of the ligand failed with trimethylamine oxide but was successful with copper(II) chloride. 

The thioether 725, formally the addition product of myrcene (7) and thiophenol, was made from prenylmagnesium chloride (15, R = MgCl) and the chlorothioether 726. Formic acid caused cyclization of 725 to a mixture of double-bond isomers of ochtodene-l-thioethers, which were converted to the corresponding ochtoden-l-ols. The latter were oxidized to the aldehydes, which were equilibrated by base to the boll-weevil aldehydes 722 (R = CHO). ... 

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