Journal zyxwvutsr of Natural Products zyxwvutsrq Vol. 52, No. I, pp. 75-80,Jan-Feb I989 75 CHEMOTAXONOMY OF THE AUSTRALIAN DOLICHODERINAE: VOLATILE CONSTITUENTS OF lRlDOM YRMEX DlSCORS MARLENE F. COX, JOSEPH J. BROPHY, and ROBERTF. ToIA*.' Department of Organic Chemistry. University of Nm South Wales. P.O. Box I, Kensington. N.S.W. 2033. Australia ABsTRACT.-Fifteen components have been identified in the CH,C1, extract of Irido- mynnex discors by combined gc-ms techniques. Ten of these zyxw (6-methylhept-S-en-2-one, ac- tinidine, the two cis. trans- and the two trans. cis-isomers of iridodial, 1,3,3-trimethyl-2,7- dioxabicyclo{2.2.1 )heptane, 24 3-methylcyclopentyl)propional, 2-acetyl-3-methylcyclopen- tene, and isodihydronepetalactone) have been noted in other species of Iridomyrmex. A further component has been tentatively identified as an isomer of I ,3,3-trimethyl-2,7-dioxabicyclo- {2.2.l)heptane. The remaining four components (I-methycyclopentene, 1-methyl-2-ethylcy- clopenrane, 2-methylcyclopenr- I-ene-carboxaldehyde, and geranylacetone), which were con- firmed by co-injection with authentic samples prepared by unambigious syntheses, have not been reported previously from insect sources. Ants of the genus Iridomymzex (Dolichoderinae)are the dominant arthropods of the soil in all climatic zones of Australia (1). Chemical interest in this genus was sparked in 1950 when the antibiotic and insecticidal activities of iridomyrmecin, a terpenoid iso- lated from Iridomymex humilis (Mayr), were reported (2). Since then, a wide variety of compounds, including hydrocarbons, fatty acids, iridoids, other terpenoids, and pyrazines have been reported from Iridomyrmex conifw (Florel) zyx (3), zyxw 1. humilis (3-lo), Iridomyrmex myrmecodiae (Emery) zyxwv ( 1 l), Iridomyrmex nitidiceps (5,11,12), Iridomymzex nitidus (Mayr) (3, 11-13), ldiomyrmex purpureus (=detectus) (3,5,11,14,15), and ldiomymex rufoniger (Lowne) ( 1 1). It is noteworthy that specimens of worker ants of 1. purpureus collected over a wide area of southeastern Australia possessed similar chemical profiles (15). Terpenoid constituents have also been noted, but not identified, in Idiomyrmex gracilis var. rubriceps (Forel), ldiomyrmex gracilis (Lowne), and 1. rufoniger (11). From the point of view of biological activity, several of the compounds noted above have been shown to elicit behavioral responses in ants. For example, 9-hexadecenal, the lipid fraction, and the exocrine gland constituents of 1. humilis are all involved in the trailing behavior ofthis species (4,10,16,17), and isovaleric acid and iridodial form the basis of the defensive secretion of 1. nitidiceps (12). As part of our continuing interest in the chemotaxonomy of Australian ants, we now report our results from examination of the volatiles from the CH,CI, extract of two collections of Idiomymzex discors (Forel), one collected from New South Wales and the other from Western Australia. RESULTS AND DISCUSSION A representative glc trace of the volatile constituents of the CH,CI, extract ofl. dis- cors collected in New South Wales is presented in Figure 1, and the peak identifications are given in Table 1. Assignments were made by comparison of gc-ms data and reten- tion times with those from reference compounds. The two major components are the commonly occurring 6-methyhept-5-en-2-one (peak 6) and the various cis, trans- and trans, cis-iridodials (three isomers are accounted for by peak 9 and the fourth isomer by 'Present address: Pesticide Chemistry and Toxicology Laboratory, 20 1 Wellman Hall, University of California, Berkeley, CA 94720.