Curcumenes

The sesquiterpenoid hydrocarbons (5)-a-curcumene (59) and (5)-xanthorrhizol (60) were prepared by asymmetric conjugate addition of the appropriate aryllithium reagent to unsaturated oxazoline 56 to afford alcohols 57 (66% yield, 96% ee) and 58 (57% yield, 96% ee) upon hydrolysis and reduction. The chiral alcohols were subsequently converted to the desired natural products. ... 

In addition to these studies, the Harmata group also successfully achieved the total synthesis (+)-curcumene 208 and curcuphenol 209 utilizing the 2,1-benzothiazine chemistry <03TL7261>. The synthesis of (+)-curcuphenol was accomplished by reduction of benzothiazine 94, followed by protection, desulfurization, reductive deamination and deprotection to give diol 223 in good yield. The latter was then converted into (+)-curcuphenol 209 (Scheme 63). The total synthesis of (+)-curcumene involved a similar approach to that of (+)-cucurphenol. 

Almost simultaneously with the identification of 2E, 4 , 6Z- 10 COOMe, a thermally unstable stereoisomer, 2E, 4Z, 6Z- 10 COOMe 118, was found to be a key component of the male-produced sex pheromone of Thyanta pallidovirens> along with the sesquiterpenes (+)-a-curcumene, (-)-P-sesquiphellandrene, and (-)-zingiberene 119 [10,25]. 2E, 4Z, 6Z-10 COOMe was an essential component of the attractive blend, whereas any one, any two, or all three of the sesquiterpene components were equally effective as the other portion of the blend. None of the components were active alone. Pheromone blends attracted only females in both laboratory and field bioassays [10]. The same compounds are also produced by the congener T. custator [10] and other Thyanta spp. (J.G. Millar, unpublished data). 

The male produced sex pheromone of the red-shouldered stink bug, Thyantapallidovirens Stal (Hemiptera Pentatomidae), was shown to consist of a blend of methyl ( "2, Z 4,. Z6)-decatrienoate and the sesquiterpenes (+)-a-curcumene, (—)-zingiberene and (—)-P-sesquiphellandrene. In laboratory bioassays, sexually mature males attracted sexually mature females but not males, and females did not attract either sex. Pheromone... 

The sequence, addition of one equivalent of MeLi to a solution of dithioester (1) and (2) in THF at -78°C, led, after allowing the temperature to rise slowly to 20°C and the usual work up, to dithioacetal (3) in a 79% yield [333]. Dithioacetalization and a Wittig reaction yielded dehydro-ar-curcumene (4). 

Such routes have been used for the synthesis of natural products terpenes such as egomaketone (3-(4-methyl-3-pentenoyl)furan, perillene, ar-turmerone and iso-ar-turmerone [341], ar-curcumene [152], artemisia and isoartemisia ketones [342, 343], damascone [344], macrolides such as maysine [345], and pheromones with the sex attractant of the pine saw-fly [346],... 

An example of practical application of the asymmetric cross-coupling, enantioselective synthesis of a-curcumene (19), is shown in Scheme 8F.6 [21]. The compound was synthesized with 66% ee through Ni/(S)-(/ )-PPFA (lOa)-catalyzed cross-coupling of 1 -(p-tolyl)ethylmag-nesium chloride (17) and vinyl bromide (4b). 

This coupling reaction was used in a synthesis of (R)-(—)-curcumene (2) in 66% optical yield, (equation II).3... 

Table I shows the quantitative comparison of selective compounds in the hydrocarbon fraction. The total amount of monoterpenes in the steam distilled sample was less than that in the liquid carbon dioxide extract. These compounds could have been lost during distillation. The significant decrease in zingiberene and the concomitant increase in ar-curcumene confirmed that zingiberene was converted to ar-curcumene (16). g-Sesquiphelladrene, another compound which could be converted to ar-curcumene, decreased slightly. The scheme of oxidative conversion of zingiberene and B-sesquiphel-...

Figure 3. Oxidative conversion of zingiberene and B-sesquiphel-landrene into ar-curcumene.

Ginger oil displays considerable compositional diversity but is typically characterized by a high content of sesquiterpene hydrocarbons, including zingiberene, ar-curcumene, (3-bisabolene and (S-sesquiphellandrene. 

The essential oil obtained from the rhizomes of Z. officinale from Cuba contained ar-curcumene (22.1%), zingiberene (11.7%), (3-bisabolene (11.2%) and cadina-1,4-diene (12.5%) (Pino et al., 2004). 

The chemical composition of the essential oils obtained from the hydrodistillation of the rhizomes of the common ginger (Z. officinale) grown in Mauritius was analysed by Fakim et al. (2002). The oil was characterized by the presence of geranial (16.3%), neral (10.3%), zingiberene (9.5%), (3-sesquiphellan-drene (6.3%) and ar-curcumene (5.1%). 

Composition of ginger oil prepared from fresh ginger rhizomes was determined by gas chromatography (GC) and GC-MS techniques. The main sesquiterpene hydrocarbons identified were a-zingiberene (27-30%), a-curcumene... 

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