Frank Schröder

Semiochemicals from bark beetles: New results, remarks, and reflections

A brief survey is given about recent results in the identification of semiochemicals in bark beetles: Males ofIps sexdentatus (Boern.), stressed by the attack on resinous trees produce large amounts of 3(S)-1-methyl-5-(1-hydroxyl-1-methylethyl)-cyclohexa-1,3-diene. The compound appears to be derived from Δ3-carene and acts as a repellent. Males ofIps typographus (L.), stressed through the attack on unsuitable host material release 3-methyl-7-methylene-1,3(E), 8-nonatriene, which seems to act as a repellent. The odor bouquet of three species ofPityogenes is described. The occurrence of (+)-grandisol and other compounds related to weevil pheromones points to a close relation between Scolytidae and Curculionidae. Females ofDendroctonus simplex (Le Conte) use (−)-frontalin as the main pheromone. 6-Methyl-6-hepten-2-one, a minor component among the volatile compounds released by the females, is regarded as a possible precursor of frontalin. Similarly, (2R,5S)-2(1-hydroxyl-1-methylethyl)-5-methyltetrahydrofuran, pityol, a pheromone ofPityophthorus spp., is regarded to at least share a common biogenetic precursor with 6-methyl-5-hepten-2-ol, sulcatol. A new bicylic acetal, 2-ethyl-1,5-dimethyl-6,8-dioxabicyclo[3.2.1]octane, is described as an aggregation pheromone of the beech bark beetle,Taphrorychus bicolor (Herbst). Structural relationships between bark beetle pheromones and plant volatiles are discussed.

A new family of tricyclic alkaloids from Myrmicaria ants

Abstract The poison gland secretion of the African ant, Myrmicaria opaciventris , contains three families of new alkaloids. These alkaloids are represented by a “monomeric” type with 15 carbon atoms in a row forming derivatives of indolizines, while the two other families are “dimers” and “trimers” with 30 and 45 carbon atoms, respectively. The major constituents of the low molecular weight alkaloids are identified to be pyrrolo[2,1,5-cd]indolizines, highly dominated by l-ethyl-3,4,41,5,6,7-hexahydro-2-((1 Z )-1-propenyl)-pyrrolo[2,1,5-cd]indolizine, myrmicarin 215A . The higher molecular weight components show complex oligocyclic structures, which are closely related to the pyrroloindolizines. The alkaloid pattern shows a high degree of intraspecific variation.

The male pheromone of the old house borerHylotrupes bajulus (L.) (Coleoptera: Cerambycidae): Identification and female response

We report here the identification of the long-range, male-produced sex pheromone of the Old house borerHylotrupes bajulus. Chemical analysis of hexane extracts obtained by surface extraction from dissected prothoracic glands and from headspace samples of the two sexes, revealed male-specific compounds: (3R)-3-hydroxy-2-hexanone, 2-hydroxy-3-hexanone, the diastereomeric diols (2R, 3R)-2,3-hexanediol and (2S, 3R)-2,3-hexanediol, 2,3-hexanedione, as well as 1-butanol. In wind tunnel bioassays we tested the influence of these male-specific compounds from the prothoracal glands on the behaviour of unmated and mated females. Specific behavioural sequences of the tested females (activity, running behaviour, searching, cleaning, flying, extension of ovipositor) were recorded. Unmated females were attracted by male beetles, headspace extracts of males, synthetic blends of the major pheromone compounds as well as by the components (3R)-3-hydroxy-2-hexanone, and the diastereomeric diols. Hexane, female beetles and 2,3-hexanedione did not attract unmated females. The reactions of mated females to male beetles and headspace samples did not differ significantly from those of the controls. The results of the bioassays show that the two-stage premating behaviour is initiated by emission of a long-range sex pheromone from the male prothoracal glands, which functions as an activator, attractant, and possibly aphrodisiac for unmated females.

3,4-β-Epoxy-8-deoxycumambrin B, A sesquiterpene lactone from Tanacetum parthenium

From feverfew, Tanacetum parthenium, collected in South America, the guaianolide 3,4-epoxy-8-deoxycumambrin B and the eudesmanolide epoxysantamarine were isolated. The structures were derived by means of spectroscopic methods. The relative stereochemistry of 3,4-epoxy-8-deoxycumambrin B was established by chemical conversion and NOESY experiments.

Sex Pheromone of Female Vine Bud Moth, Theresimima ampellophaga Comprises (2S)-Butyl (7Z)-Tetradecenoate

The sex pheromone of the vine bud moth, Theresimima ampellophaga, released at the 3rd–5th abdominal tergites, was identified by coupled GC-EAG, GC-MS, and synthesis as (2S)-butyl (7Z)-tetradecenoate. For the first time, full stereochemistry is unambiguously defined for the sex pheromone of a member of the Zygaenidae. The synthetic compound caught significant numbers of males in field-trapping experiments.