Atta Pheromones

The reductive cleavage of the alkylcobalamine is facilitated by light irradiation and can then proceed at a much more positive potential. A demonstration photoelec-trochemical reactor for the Bij-catalyzed photoelectrochemical synthesis of Michael adduct 17, the alarm pheromone of the ant atta texana (Scheme 9) has been constructed where the complete device is driven solely by solar energy . Hopefully, mediated photoelectrochemical reactions of this type will also be realized at chemically modified electrodes. 

The Barton-Zard pyrrole synthesis has now been extensively applied to synthesis of natural and unnatural products containing pyrrole units. Methyl 4-methylpyrrole-2-carboxylate is the trail-maker pheromone of the Texas leaf-cutting ant Atta texana.24 It is readily prepared by the Barton Zard method in 60% yield (Eq. 10.22).22... 

Atta texana W- Antennal response of previously identified trail pheromone component Methyl 4-methylpyrrole-2-carboxylate 64 [164]... 

S)-4-methyl-3-heptanone (146), the alarm pheromone of the leafcutting ant Atta texarta is about 400 times more active than its optical isomer. This acyclic ketone (146) could be prepared by simply starting from diethyl ketone and propyliodide. 

The title ketone (S)-4, which is 400 times more active than its optical antipode,6 is the principal alarm pheromone of the leaf cutting ant Atta texana. (S)-4 has also been identified as an alarm pheromone 1n three other ant genera of the subfamily Mymioinae,6 9 as a component of the defensive... 

Trail Pheromones. Tumlinson et al. (133) identified methyl 4-methyl pyrrole-2-carboxylate (XXXVT as the major trail pheromone of the ant, Atta texana. Another poison gland product, 3-butyl-5-methyloctahydroindolizine (XXXVI) has been reported to be the dominant releaser of trail following for workers of Monomorium pharaonls (134).In contrast to these cyclic releasers... 

Riley et aK (157) identified S-(+)-4-methyl-3-heptanone as the alarm pheromone of Atta texana and reported that it was 100X more active as an alarm releaser than the unnatural (-)-enantiomer. Similarly, Benthuysen and Blum (158) demonstrated that workers of Pogonomyrmexbadius were more sensitive to the S(+) enantiomer than to the R-(-) enantiomer of this compound, which is the primary alarm pheromone of this species. 

Methyl 4-methylpyrrole-2-carboxylate (Ar7) was the first trail pheromone identified in ants. It is used by Atta texana,231 Atta cephalotes232 and Acromyrmex octospinosus233 Two Metapone ant species use the unsubstituted derivative Ar40 as the trail pheromone.234 Methyl nicotinate (Ar41) is the minor component of the trail pheromone of an Aenictus sp.196... 

The synthetic utility of the SAMP/RAMP hydrazone method is demonstrated in particular in the stereoselective alkylation of aldehyde and ketone SAMP/RAMP hydrazones. A great number of natural products have been synthesized using this method, like the principal alarm pheromone of the leaf cutting ant Atta texana (eq 1), the C(l)-C(15) segment of FK 506 (eq 2) the amino acid MeBMT (eq 3), and (-)-methyl kolavenate (eq 4). ... 

Most social insects use alarm and trail pheromones. Their specificity is not so important, but fast release and dispersal are important. They tend to be small volatile substances for instance, (S)-4-methyl-3-heptanone is an alarm pheromone in the leaf-cutting ant, Atta textata. 

CgHigO, Mr 128.21, bp. 63-67°C, (5.33 kPa) [a] ° -t-21.7° [(45)-enantiomer, hexane]. A widely distributed alarm pheromone in leaf-cutting ants, e.g. Atta texana. M. was the first pheromone in which the significance of the absolute configuration for the biological activity became apparent. Only the (4S)-enan-tiomer is active. 

Some ant species (Formicidae) use nitrogen heterocycles as trail pheromones others however use hydrocarbons or alcohols (Fig. 8.62). In the rectal glands of a few Lasius and Formica species, 3,4-dihydroisocoumarins have been identified. The scents are emitted by exocrine glands like the poison apparatus or the sternal gland. The trail pheromone of the leafcutter ant (Atta texana) is effective at extremely low concentrations of 80 fg/cm (If = 10" ). One milligram of methyl 3-methylpyrrole-2-carboxylate is sufficient to lay a trail three times around the Earth. 

Insects detect pheromones in surprisingly small amounts. Thus, male Bombyx mori begin to react when air contains as little as 100 molecules of the female sex pheromone per cm 210). The trail pheromone of the leaf cutting ant Atta texana, methyl-4-methyl-pyrrole-2-carboxyl-ate (46) is perceived at a concentration of 0,08 pg/cm, that is 3.48 molecules/cm 240), about the same as that recorded for the trail pheromone cw-3-cw-6-/ran5-8-dodecatrien-l-ol of Reticulitermes virgin-icus termite workers (47) 241). 

Trail pheromone of leaf cutting ants Atta sp.)... 

Jaffe, K., Bazire-Benazet, M. and Howse, P. E. (1979) An integumentary pheromone-secreting gland in Atta sp territorial marking with a colony-specific pheromone in Atta cephalotes. J. Insect Physiol., 25, 833-9. 

Several conclusions can be drawn from this equation, as applied to the alarm pheromone of Atta texana. The first is that as the amount of chemical emitted increases (i.e., Q increases), so at any one time the radii of the active spaces increase, and so does the total duration of the signal, given by the equation, derived from that above... 

Jaffe and Howse, 1979). The first scouts to find leaf material recruit other workers exclusively, and do not join in leaf-cutting for up to an hour. Scouts recruit nest-mates both by the traU pheromone and by tactile displays. As in Solenopsis, the degree of recruitment is modulated by the strength of the trail, but in the case of Atta this is not dependent on the number of recruiting ants, so that individuals apparently regulate the amount of trail pheromone they deposit, based upon the information they have about the quality and quantity of food available. 

Fig. 15.10 Trail pheromones identified from myrmicine ants, indicating the diversity of structures encountered. ( l) Atta texana (Tumlinson et al., 1972) andcephalotes (Riley et al.y 1974b) (b) A. sexdens rubropilosa (Cross et aL, 1979) and Myrmica spp. (Ever-shed et al., 1981) (c) Lasius fuliginosus (Huwyler et al., 1975) (d) Monomorium pharaonis (Ritter et al., 1977) (e) Solenopsis invicta (Williams et a/., 1981 Vandermeer etal., 1981).

Bradshaw, J. W. S., Howse, P. E. and Baker, R. (1984) A novel pheromone regulating chain transport of leaves in Atta cephalotes. Animal Behaviour (in press). 

Riley, R. G., Silverstein, R. M., Carroll, B. and Carrol, R. (1974b) Methyl 4-methyl-pyrrole-2-carboxylate a volatile trail pheromone from the leaf-cutting ant, Atta cephalotes. J. Insect Physiol., 20, 651-4. 

Methylpyrrole-2-carboxylic acid (compound B) is the trail pheromone of the ant species Atta texana. A third of a milligram has been estimated to be sufficient to mark a path around Earth, and each ant carries only 3.3 ng (10 g). Propose a s3mthesis starting from 3-methylcyclobutene-1-carboxyUc acid (conqtound A). (Hint What dione is the retros3mthetic precursor to compound B, and how can you make it from compound A )... 

Methyl-3-heptanone (386a, Scheme 68), the alarm pheromone of the Texas leaf-cutting ant (Atta texana) was synthesized by Riley et al 173, 174) and required resolution of the intermediate, racemic 2-methyl-4-pentenoic acid (384). A convenient synthesis of methyl 4-methylpyrrole-2-carboxylate (392), the trail pheromone of A. texana, has been reported by Sonnet (775) (Scheme 69). Formylation of ester (390) with CUCHOMe and AICI3 gave predominantly the desired 4-formyl derivative (391). 

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