Hemipterus

This method has been applied to the synthesis of (S)-2-methyl-4-octanol, an aggregation pheromone of Metamasius hemipterus.56... 

Attractive Compounds. The male-produced pheromones of sap beetles, known so far, show the rather stereotypic structures 125-147 (Scheme 15) methyl- and ethyl-branched hydrocarbons with three or four (T)-configured conjugated double bonds [4]. Up to now, 23 compounds could be identified, forming species specific mixtures. Major components in the bouquets are (2E,4E,6E)-5-ethyl-3-methyl-2,4,6-nonatriene, 128, in Carpophilus davidsoni [268] as well as in C.freemani [269], (2 ,4 ,6 )-4,6-dimethyl-2,4,6-nonatriene, 129,in C. truncatus [270], (3 ,5 ,7 )-5-ethyl-methyl-3,5,7-undecatetraene, 132, in C. mutillatus [271],(2 ,4 ,6 ,8 )-3,5,7-trimethyl-2,4,6,8-decatetraene, 134,in C. hemipterus [272] as well as C. brachypterus [273], (2 ,4 ,6 ,8 )-3,5,7-tri-... 

R) and (S)-3-octanol, (i )-2-dodecanol, (i )-2-methyl-4-heptanol and (i )-2-methyl-4-octanol, the pheromones of Myrmica scabrinodis, Crematogaster castanea, C. liengmei, C. auberti and Metamasius hemipterus were synthesized starting from nonracemic P-hydroxy sulfides. 

Malosse, C.P., Ramirez-Lucas, D., and Rochat, J.M. 1995. Solid phase mictroextraction, an alternative method for the study of airborne insect pheromones (Metamasius hemipterus, Coleop-tera, Curculionidae). J. High Resolut. Chromatogr. 18 669-700. 

Figure 6.6 Structures of 2,3-dihydro-2,3,5-trimethyl-6-(1 -methyl-2 -oxobutyl)-4H-pyran-4-one (stegobinone), pheromone of Stegobium paniceum (L.) (Anobiidae) (Kuwahara et al., 1978) and (2E,4E,6E,8E)-3,5,7-trimethyl-2,4,6,8-decatetraene, pheromone component of Carpophilus hemipterus (L.) (Nitidulidae) (Bartelt et al., 1991). The carbon skeletons are identical, and likely derived through similar pathways (see text).

Table 6.1 Biosynthesis of male-specific tetraenes of C. hemipterus through imperfect specificity. The simple acyl biosynthetic precursors of each tetraene are indicated acyl unit substitutions from the main incorporation pattern for tetraene 1 are indicated by an asterisk. Relative abundances and wind tunnel bioassay activities in C. hemipterus are also presented. Adapted from Bartelt (1999a) with permission... 

Bartelt R. J., Weisleder D., Dowd P. F. and Plattner R. D. (1992) Male-specific tetraene and triene hydrocarbons of Carpophilus hemipterus structure and pheromonal activity. J. Chem. Ecol. 18, 379 102. 

Petroski R. J. and Vaz R. (1995) Insect aggregation pheromone response synergized by host type volatiles. Molecular modeling evidence for close proximitiy binding of pheromone and coattractant in Carpophilus hemipterus (L.) (Coleoptera Nitidulidae). In Computer-Aided Molecular Design, eds C. H. Reynolds, M. K. Holloway and H. K. Cox, pp. 197-210. ACS Symposium Series 589, American Chemical Society, Washington, DC. 

Chapter 19 by Bartelt is devoted to the pheromonal role of short-chain hydrocarbons, especially short i n etli y l/etli y I - branched and unsaturated components in beetles. The most abundant components in Carpophilus hemipterus (Coleoptera, Nitidulidae) have been identified as (2/ ,4/ ,6/ ,8/ )-3,5,7-(rimc(hyl-2,4,6,8-decatetracnc and (2E,4E,6E,SE)-3,5,7-trimethyl-2,4,6,8-undecatetraene (Bartelt et al., 1990). Later studies showed that male C. hemipterus emit nine all-E tetraene hydrocarbons and one all-E triene hydrocarbon in addition to the two previously reported pheromonally active tetraenes (Bartelt et al., 1992). In their review of biologically active compounds in beetles, Francke and Dettner (2005) fisted only a few dozen of those pheromonal compounds, most of which were identified by Bartelt. 

The first evidence for long-range pheromones in nitidulids was for Ca. hemipterus and was obtained in a laboratory wind tunnel (Bartelt et al., 1990a). Flying beetles of both sexes were clearly more attracted to containers with males feeding on artificial diet than to containers with females on diet or to diet alone. This result was corroborated by tests with volatiles collected from feeding males and females onto porous-polymer filters. 

Monitoring the purification of the first pheromone (Ca. hemipterus) by wind-tunnel bioassay was complicated by a synergistic relationship with food odors. It was difficult to demonstrate the activity of the pheromone once it became chromatographically separated from the food scent that was also present in the volatile collections (Bartelt et al., 1990a). Consequently, food scent, or a synthetic version of this, was routinely added to each bioassay treatment, and the food scent itself became the control when pheromone activity was being evaluated. A variety of esters, alcohols, and other compounds were found to syner-gize the pheromone of Ca. hemipterus (Dowd and Bartelt, 1991). Synergistic effects were seen with all the species. 

Another biosynthetic issue is the origin of complex hydrocarbon blends, such as the 11 different tetraenes of Ca. hemipterus (Figure 19.3). While there could be separate biosynthetic systems for each of the Ca. hemipterus tetraenes, a more parsimonious explanation, which fits the data, is that a single biosynthetic system exists with imperfect selectivity for acyl units (Bartelt et al., 1992b). If the most abundant tetraene, 5, represents the normal product, then tetraenes 6,7,14, and 18 represent instances of one acyl substitution (or biosynthetic mistake ). There are six possible ways in which two of these substitutions could exist in one compound, and these are represented by 8,15,16,19,20, and 21. Occurrence of two substitutions would be rarer than just one, and the observed abundances reflected this expectation. Tetraenes with three or four substitutions would be even rarer, and these were not detected. Substitutions were never observed for the second acyl unit, which was unfailingly propionate. Related arguments can be made for the patterns of hydrocarbons in Ca. freemani and Ca. davidsoni (Bartelt et al., 1990b Bartelt and Weisleder, 1996). 

The functional pheromone of Ca. hemipterus appears to be a subset of the male-specific hydrocarbons (5-8 in Figure 19.3, Bartelt et al., 1992b). The compounds of Ca. hemipterus that were active had structural features in common as drawn in Figure 19.3, the left-hand portions of the active compounds were identical. Petroski and Vaz (1995) used computer-based molecular modeling to correlate molecular shape with biological activity. 

Figure 19.3 Biosynthesis of pheromone components from acyl precursors (upper) and conclusions regarding Ca. hemipterus tetraenes (lower). Abbreviations Ac = acetate, Pr = propionate, Bu = butyrate [X] is an unknown acyl carrier such as coenzyme A deviations from the main acyl incorporation pattern indicated by ( ).

Some of the observed cross-attraction may have been an artifact of unnaturally high pheromone releases from septa for example, the response threshold of Ca. mutilatus to the pheromone of Ca. hemipterus was at least ten times higher than to its own (Bartelt et al., 1994a). Furthermore, the ratios of components emitted from septa shifted somewhat over time (Bartelt and James, 1994) therefore, the preference for a species own blend may not have been as clear as possible, which would make cross-attraction appear relatively strong. 

Effects of pheromone dose on trap catch have been studied. The usual amount of pheromone per septum was 500 pg. In California, all doses of Ca. hemipterus pheromone from 15 to 15 000 pg per septum were significantly active in the field, and for Ca. mutilatus, all doses from 50 to 15 000 pg were active (Bartelt et al., 1994a). Attractiveness increased with pheromone dose throughout the range for both species. Similar trends were noted for these species in Australia when 500 - and 5000 -pg doses were compared (James et al., 1994). With Carpophilus beetles, high pheromone doses never became repellent. 

Bartelt, R. J., Dowd, P. F., Vetter, R. S., Shorey, H. H. and Baker, T. C. (1992a). Responses of Carpophilus hemipterus (Coleoptera Nitidulidae) and other sap beetles to the pheromone of C. hemipterus and host-related coattractants in California field tests. Environ. Entomol., 21,1143-1153. 

Dowd, P.F. and Bartelt, R. J. (1991). Host-derived volatiles as attractants and pheromone synergists for driedfruit beetle, Carpophilus hemipterus. J. Chem. Ecol., 17, 285-308. 

Petroski, R. J. and Vaz, R. (1995). Insect aggregation pheromone response synergized by host-type volatiles molecular modeling evidence for close proximity binding of pheromone and coattractant in Carpophilus hemipterus (L.)... 

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