Species monoterpenes

In order to expand the chemical sampling of this species to its entire range and to investigate xylem terpenoids in detail, Zavarin et al. (1990) collected wood samples from 191 trees from 20 areas, isolated the monoterpene fractions, and subjected them to GLC analysis. The major component was identified as a-pinene, with P-pinene, 3-carene, and limonene as lesser, but stiU important, components. Minor... 

The second example features R cartilagineum, a cold-water species that enjoys a wide distribution (Gabrielson and Scagel, 1989). Patterns of variation for halogenated monoterpenes have been reported for this species collected from several locations that include Atlantic, Pacific, and Antarctic waters. Both cyclic and acyclic... 

Pureswaran, D. S., R. Gries and J. H. Borden. 2004. Quantitative variation in monoterpenes in four species of conifers. Biochem. Syst. Ecol. 32 1109-1136. 

Evidence for de novo synthesis of pheromone components was obtained by showing that labeled acetate and mevalonate were incorporated into ipsdienol by male Ips pini [103,104]. Similarly, labeled acetate and other labeled intermediates were shown to be incorporated into frontalin in a number of Dendroctonus species [105]. Possible precursors to frontalin include 6-methyl-6-hep-ten-2-one, which was incorporated into frontalin by D. ruffipennis [106]. The precursor 6-methyl-6-hepten-2-one also was shown to be converted to bre-vicomin in the bark beetle, Dendroctonus ponderosae [107]. In addition, the expression patterns of HMG-CoA reductase and HMG-CoA synthase are tightly correlated with frontalin production in Dendroctonus jeffreyi [108, 109]. A geranyl diphosphate synthase cDNA from I. pini was also isolated, functionally expressed, and modeled [110]. These data indicate that the de novo isoprenoid biosynthetic pathway is present in bark beetles. A variety of other monoterpene alcohols such as myrcenol, pityol, and sulcitol are probably synthesized through similar pathways [111]... 

Whereas some species oxidize host terpenes more randomly, producing an array of rather unspecific volatiles with little information, others use highly selective enzyme systems for the production of unique olfactory signals. However, apart from transformations of monoterpene hydrocarbons of host trees, oxygenated monoterpenes may well be biosynthesized de novo by the beetles (see below). 

None of the monoterpene pheromones of bark beetles is represented by a specific compound per se however, species specificity of the signal is accomplished by qualitatively and quantitatively fine-tuned mixtures including enantiomeric proportions. 

While earlier it was generally thought that the acyclic monoterpene alcohols 242-245 are derived from the host tree s oleoresin component, myreene [453], more recent results clearly show that at least in some species they are produced denovo [454-456]. 

Oxygenated monoterpenes which are found in almost every bark beetle species attacking coniferous trees, include czs-verbenol 246, frans-verbenol 247, and myrtenol 248, representing primary products of allylic oxidation of the host terpene a-pinene 45. Further oxidation of 247 or 248 leads to the... 

The western grey kangaroo (Macropusfuliginosus), the major indigenous herbivore in southwestern Australia, avoids plants of the family Myrtaceae (which include Eucalyptus spp. cloves, and guava), which includes 3500 species on that continent. Essential oils characterize the Myrtaceae many species contain two to nine of these. In one experiment, seven Myrtaceae species were not browsed, while comparable species of other families were. All seven species contained the monoterpene 2,5-dimethyl-3-methylene 1,5-heptadine. The kangaroos also browsed one non-Myrtaceae species (Sollya heterophylla, Pittosporaceae) very little. This species contained the same monoterpene (Jones etal, 2003). 

Mule deer, Odocoikus hmionus hemionus, prefer juniper (Juniperus spp.) that contains lower amounts of volatile oils (i.e. oxygenated monoterpenes). Of three species tested, alligator juniper (J. deppeana) had the lowest level of volatile oils and was preferred, while Utah juniper (j. osteosperma) and Rocky Mountain juniper (J. scopulorum) ranked higher in volatile oil content and lower in preference by deer (Schwartz etal, 1980). 

Piperitone, with its fresh minty camphor4ike odor, is present in various leaf essential oils. Among Mentha and Eucalyptus genera, there are piperi tone-rich species which are considered common sources of this natural monoterpene ketone. The (45) (-f)- enantiomer was reported to be... 

In a similar approach, Shishido et al. (241) used oxime 215 [derived from the monoterpene (+)-citronellal (214)] for the synthesis of (—)-mintlactone (218) and (+)-isomintlactone (219), sweet compounds isolated from some Mentha species (Scheme 6.89). Bicyclic isoxazoline 216 was obtained in good yield from the cycloaddition. As expected, the product possessing tra i-l,4-substimtion prevailed. Reductive hydrolysis of the major isomer of 216 using hydrogen-Raney Ni-trimethyl borate provided p-hydroxyketone 217. This compound was dehydrated to give an enone and this was followed by carbonyl reduction-lactonization to complete the synthesis of both lactones 218 and 219 (241). 

Herz, W., Pethtel, K.D., and Raulais, D. Isoflavones, a sesquiterpene lactone-monoterpene adduct and other constituents of Gaillardia species. Phytochemistry, 30, 1273, 1991. 

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