Pheromones structure elucidation

The nature of functional groups in a pheromone can be determined by chemical modification coupled with a sensitive bioassay of the converted material. For example, if a pheromone loses activity after saponification and regains it upon acetylation it likely contains an acetate group. Loss of activity after hydrogenation indicates unsaturation. Inscoe and Beroza (IS) tabulated many of the typical functional group tests that can be used in pheromone structure elucidation. These tests need not be restricted to purified material they can be employed on crude extracts as well and the results may suggest purification methods to be used (or avoided). 

Whereas the role of olfaction in chemical ecology is gaining increased attention, new bioanalytical methodologies and instrumentation provide unprecedented opportunities besides the structural elucidation of pheromones and other chemosignals,... 

Fig. 4 Gas chromatographic traces of extracts from females of the pale brown chafer Phyl-lopertha diversa monitored by a conventional detector, flame-ionization detector (FID), and a biosensor, electroantennographic detector (EAD), using a male antenna as the sensing element. Although the peak of the sex pheromone (arrow) is hardly seen in the FID trace, its pheromonal activity was initially indicated by the strong EAD peak. Structural elucidation, followed by synthesis and behavioral studies lead to the identification of an unusual sex pheromone, l,3-dimethyl-2,4-(lff,3ff)-quinazolinedione [124]. It is unlikely that this minor compound would be fished out by a bioassay-oriented isolation procedure...

Abstract This chapter reviews chemical structures of biologically active, volatile compounds in beetles. Techniques used for structure elucidation are briefly discussed as well as facts and speculations on the biosynthesis of target compounds. Syntheses of selected substances are cursorily presented. The order of sections follows taxonomic classifications. Depending on the biological significance of relevant compounds in certain taxa, the corresponding sections are again subdivided into attractive compounds (mostly intraspecifically active pheromones) and defensive compounds (mostly interspecifically active allomones). 

Keywords Beetles Attractive compounds Pheromones Defensive compounds Biosynthesis Identification techniques Structure elucidation... 

Structure elucidation of semiochemicals by modern NMR-techniques (including HPLC/NMR) is often hampered by the very small amounts of available material and problems in the isolation of pure compounds from the complex mixtures they are embedded in. Thus, the combination of gas chromatography and mass spectrometry, GC/MS, is frequently the method of choice. Determination of the molecular mass of the target compound (by chemical ionisation) and its atomic composition (by high resolution mass spectrometry) as well as a careful use of MS-Ubraries (mass spectra of beetle pheromones and their fragmentation pattern have been described [27]) and gas chromatographic retention indices will certainly facihtate the identification procedure. In addition, the combination of gas chromatography with Fourier-transform infrared spec-... 

Attractive Compounds. Though the first report on the identification of a pheromone from a scarabaeid beetle dates back more than 30 years - phenol as an attractant for males of the gras grub beetle Costelytra zealandica [135] which turned out to be produced by beetle associated bacteria [136] - most of the pheromone structures known today have been elucidated during the last decade [3,137,138]. 

Structure elucidation of the female-produced sex pheromones of Trogo-derma spp. has a rather confused history. Extracts of females of T. inclusum were shown to contain (Z)-14-methyl-8-hexadecenol and the methyl ester of the respective carboxylic acid [215]. The corresponding compounds showing (E)-configuration were shown to be present and behaviourally active in T. inclusum [216]. Finally, investigations of head space collections, obtained with live females, revealed the presence of 14-methyl-8-hexadecenal, an aldehyde... 

In some flea beetles, Phyllotreta and Aphthona spp., species specific, male produced blends of himachalene derivatives like 201,202, and 203 were identified. Structure elucidation was carefully carried out on the basis of spectroscopic methods, micro reactions, and independent syntheses [370,371]. Compounds 201,202,203 are perceived by both male and female antennae, as would be expected for an aggregation pheromone. Investigations on the behaviour mediating capacity of the compounds are ongoing. 

Aggregation arrestant pheromone of the German cockroach, Blattella germanica (L.) (Dictyoptera Blattellidae). Isolation and structural elucidation of blattellastanoside-A and -B. Journal of Chemical Ecology 19 2521-2541. 

Persoons, C. J., Verwiel, P. E. J., Talman, E. and Ritter, F. J. (1979). Sex pheromone of the American cockroach, Periplaneta americana isolation and structure elucidation of periplanone-B. Journal of Chemical Ecology 5 221-236. 

A few years ago the complete structure of periplanone-B, apart from its stereochemistry, was elucidated and published by our research team (32,33,34) with Persoons as the principal investigator, who included this work in his doctoral thesis (35), and shared the Royal Dutch Shell Prize for 1978 with Ritter for this work and the structure elucidation of faranal, the trail pheromone of the Pharaoh s ant, Monomorium pharaonis (36,37). 

Persoons, C.J. "Structure elucidation of some insect pheromones a contribution to the development of selective pest control agents" Thesis, Wageningen, 1977. 

Prior to delving into the details, this overview briefly summarizes the recent progress made as follows (1) progress in structure elucidation, (2) complexity of the multicomponent pheromone, (3) stereochemical aspects of chemical ecology, (4) dual roles of semiochemicals such as pheromones and kairomones, and (5) new trends in mammalian chemical ecology. 

The first example of chemical communication in low-GC Gram-positive bacteria was discovered in 1978 by Dunny, Clewell and their colleagues.93 It was found that conjugative plasmid transfer of Enterococcus faecalis was induced by a chemical substance, termed sex pheromone, which is secreted from plasmid-free recipient cells. Several years later, the structure of the sex pheromone was elucidated to be an oligopeptide by Suzuki et al Since this discovery, a variety of cell-to-cell communication events in Gram-positive bacteria have been found to be mediated by peptidic substances.95-97... 

Structure elucidation of pheromones in nanogram quantities 88AG(E)460. 

In the 1960s, structure elucidation of insect pheromones was a very difficult task due to the scarcity of the sample available from the insects. As shown in Table 7.2, Jacobson et al. in the USA published three incorrect structures of pheromones. 

The isolation, structural elucidation, and total synthesis of insect pheromones continue to be a very active area of natural product research (c/. Vol. 8, pp. 66, 102). A recent paper in this area describes the identification of ancistrodial (36) and ancistrofuran (37) as components of the defence secretion of termite soldiers Ancistrotermes cavithorax). 

As in previous Reports, pyrrolidine compounds of other than plant origin will not be discussed. However, attention is drawn to the structural elucidation of ikarugamycin (1) from Streptomyces phaeochromogenes var. ikaruganensis, to new synthetic work on pyrrolnitrin (2) from Pseudomonas pyrocinia, and to structural analogues of the male butterfly sex pheromone (3). ... 

---