Of insect juvenile hormone

Esterases of the Juvenile Hormone of Insects Many works have been dedicated to the inhibition of esterases of the juvenile hormone of insects. The purpose of these works is to control insect populations by ehminating their metamorphosis. Among the numerous trifluoromethyl ketones that have been synthesized, thioalkyl derivatives of trifluoroacetone have been shown to be the most active ones. Curiously, the corresponding alcohols are also excellent inhibitors. Trifluoromethyl ketones can also inhibit other insect esterases antenna esterases and esterases that are involved in the release of pheromones (Figure 7.33). The inhibition of these latter ones can also be interesting for insect control purposes. 

Phvtoluvenolds. Wigglesworth (JL) demonstrated that a hormone secreted by the insect corpora allata was responsible for the control of differentiation in immature insects and reproduction in adult female insects. Williams (3) prepared an active extract of this hormone from adult male cecropia moths and called it "juvenile hormone". We were able to derive sufficient knowledge of the chemistry of the juvenile hormone from the study of the active cecropia extract to synthesize JH III Q). Seven years later its presence as a natural hormone in the tobacco hornworm was confirmed Ci). Three other analogous juvenile hormones (JH 0, I, II) have been found to occur only in lepidoptera (5, ., 2.) (Figure 1). Juvenile hormone III is the principal juvenile hormone of insects and has been demonstrated in all of the insect taxa investigated. 

Interestingly, the leaves of seme trees, such as hemlock, make a chemical similar to the juvenile hormones of insects. When larvae (caterpillars) feed on these leaves, they cannot metamorphose into the adult form. Aj arently, this is a chemical defense mechanian seme trees use to prevent leaf-feeding insects from reaching sexual maturity. 

As in insects, a complex interaction of hormones in the amphibian larva precipitates metamorphosis. Ultimately, two major classes of hormones act together to control amphibian metamorphosis the thyroid hormones (made by the thyroid gland) and prolactin (made by the pituitary gland). Thyroid hormones function somewhat like the molting hormones of insects, in that an increase of their concentration relative to prolactin leads to metamorphosis of the larva into the adult. Prolactin functions somewhat like the juvenile hormones of insects, in that it tempers the action of the thyroid hormones. In most species, thyroid hormones increase dramatically in concentration during metamorphosis and this stimulates resorption of certain larval organs and differentiation of new adult organs. 

Epoxidation of the following compound in a laboratory synthesis gives a 40% yield of the juvenile hormone of insects. Explain why only a 40% yield is obtained. 

The hormone that inhibits molting is methyl famesoate, which is very similar to the juvenile hormone of insects it inhibits the functioning of the Y organ between two successive molts. In insects this second hormone is... 

Juvenile hormones are insect hormones that keep the insect in the juvenile, (larval) stage. They are famesoic acids, acids of the sesquiterpene alcohol farnesol. 

An interesting review of the biosynthesis and transport of juvenile hormones in insects has appeared.17 The syntheses of the juvenile hormones JHI—JHIII (25)—... 

No prediction can be made as yet on the future role of anti-juvenile hormones in insect control. However, the results obtained hitherto demonstrate the possibility of developing anti-insect agents acting to disrupt rather than mimic endocrine function. 

The juvenile hormones of many insects are sesquiterpenes (Bowers, 1991,1992 Fraga, 1991 Law, 1983 Menn and Beroza, 1972). 

For early history of the topic see Trost, B. M. The Juvenile Hormone of Hyalophoria Cecropia Acc. Chem. Res. 1970, 3, 120 and references cited therein. See also, Rees, H. H. Goodwin, T. W. Molting Hormones Biochem. Soc. Trans. 1974, 2,1027-1032. Karlson, P. Sekeris, C. E. Ecdysone, an Insect Steroid Hormone, and its Mode of Action Recent Progress in Hormone Research 1966, 22, 473 95. 

Figure 16.2 shows examples of naturally occurring, physiologically active cyclic ethers. Tetrahydrocannabinol (THC), the principal active ingredient in marijuana, includes a six-membered ring ether. Morphine contains a five-membered ring ether. Three-membered cyclic ethers (epoxides) are rare in nature. The juvenile hormone of some insects contains a cir-substituted epoxide. This hormone controls the rate insect maturation. 

The juvenile development of insects proceeds through a series of moltings (molting of larvae among the holometabola also molting of pupae) to result eventually in the adult insect. The most familiar example is the development caterpillar-pupa-butterfly. The process of molting involves three hormones, as shown in Fig. 56. 

Cinnamyl—sesamol ethers, eg (35), are useful as insect chemosterilants (111). 3,4-Methylenedioxyphenyl-3-halo-2-propynyl ethers (36, X = halogen) are synergists for carbamate insecticides (112). HaloaLkyl or haloalkenyl ethers, eg (37), show acaricidal and insect juvenile hormone activity (113). The first total synthesis of gibbereUic acid was from 2-methoxy-6-aLkoxyethyl-l,4-benzoquinone, a derivative of hydroxyhydroquinone (114). 

The use of polylactides for delivery of insect hormone analogs and other veterinary compounds (115,116) has been studied. Microspheres, pellets, and reservoir devices based on polyglycolide, poly-(DL-Iactide), poly(L-lactide), and various copolymers have been used to deliver methoprene and a number of juvenile hormone analogs. ... 

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