Juvenile hormones I and

Plant secondary metabolites which mimic JH activity appear to be active on a narrow range of host species. What account(s) for this effect The majority of bioassays used last larval instars of P. apterus, O. fasciatus and pupae of T. molitor to test for activity of the juvenoids. Are these the most sensitive insects Six JHs have been identified to date different homologs have been isolated from specific insect orders. Juvenile hormone III appears to be ubiquitous [12, 13] and, in most species, is the only JH present. Juvenile hormone I and II are important in the regulation of metamorphosis and ovarian maturation in Lepidoptera [5] and the bis-epoxide appears to be the principle JH in higher Diptera [20]. Therefore, the nature of the JH in the test insect and the role that it plays in development must be considered in the selection of the bioassay a compound which mimics the action of JH in P. apterus (Hemiptera) is unlikely to be active in a Lepidopteran insect. 

Allelochemicals may also be released into the environment as a defence against phytoparasitic nematodes [173]. Juvenile hormones have been shown to affect the development of nematodes [174]. Juvenile hormone I and MF inhibited hatching of the eggs of Haemonchus contortus [175] and application of JH III (3.4 mM) to third-stage larval females of the rodent hookworm, Nippostrongylus brasiliensis, resulted in a 50% reduction in egg production [176]. The biosynthetic precursor of JH III, famesol, inhibits development of larvae of the nematode Trichinella spiralis [177]. However, in the few studies done, these compounds do not appear to have an effect on plant parasitic nematodes [175, 178]. 

The juvenile hormones I and II (Table 40) are isoprenoid-like compounds which contain one or two more C-atoms then juvenile hormone III, a true sesquiterpene (D 6.2). They are formed and act as molting hormones (E 3.1) in the majority of insects. 

In the juvenile hormones I and II propionate is incorporated in contrast to the juvenile hormone III. It is, therefore, expected that with propionyl Co A (D 4) as the starter molecule, homoisopentenyl pyrophosphate is built in a pathway similar to that of isopentenyl pyrophosphate biosynthesis (Fig. 142). The different juvenile hormones may derive from homoisopentenyl pyrophosphate and isopentenyl pyrophosphate in the relations shown in Table 40. 

Homoterpenoids Juvenile hormones I and II (D 7) Insects (Corpora allata) Determination of the outcome of molts... 

Much interest has been shown in the biosynthesis of insect juvenile hormones (62 R1, R2 = Me or Et). In adult male moths, [l-14C]propionate was specifically incorporated into juvenile hormone I [JH-1, (62 R1 = R2 = Et)], and tracer was only found at, and equally distributed between, C-7 and C-ll.90 Application of [2-14C]-and [3-14C]-propionate led to extensive randomization of label, which suggests that C-2 and C-3 formed in propionate catabolism can be re-used as smaller fragments, whilst C-l is either removed from propionate in a metabolically active form or is highly diluted. Ternary complexes of brain, corpora cardiaca, and corpora allata from the tobacco budworm Heliothis virescens produced labelled JH-I and JH-II (62 R1 = Et, R2 = Me) when incubated with L-[Me-14C]methionine or sodium [l-l4C]propionate.91 Partial degradation of the juvenile hormones showed that in JH-I portions a and /3 (62) had incorporated one atom of tracer from each propionate, whereas fraction y was unlabelled, and in JH-II only fraction a was... 

Juvenile hormone I is the vital hormone that regulates the metamorphosis of insects. Its unique structure stimulated a number of synthetic efforts to devise methods for controlling double-bond stereochemistry and the enantioselectivity of the epoxide. Propose a synthesis of juvenile hormone I as a single enantiomer and compare your approach with those reported by Imai, K., Marumo, S., Ohtaki, T. Tetrahedron Lett. 1976, 1211 and Mori, K., Fujiwhara, M. Tetrahedron 1988, 44, 343. 

Solomon, K.R., Bowl ns, S.B., Meicalf, R.I.. and Katzencllcnhogen, J.A. (1973). The efleet of PBO and triorthocresyl phosphate on llie activity of juvenile hormone mimics and their sulphur isosteres in Tenehrio mnfinir T,. and Owopetlus fitseiaius (Dallas). Life Sci. 13, 733-742. 

In the Lepidoptera, four other homologs have been isolated in addition to JH III. The ethyl branched homologs, juvenile hormone I (JH I), methyl-10/ , 1 l-epoxy-7-ethyl-3,l 1-dimethyl-2,6-tridecadienoate, and juvenile hormone II, methyl-10/ , 1 l-epoxy-3,7,11-trimethyl-2,6-tridecadienoate, and their corresponding acids predominate in this order [14, 15, 16]. Two additional homologs, juvenile hormone 0 (JH 0), 10/ , 11-epoxy-3,7-diethyl-1 l-methyl-2,6-tridecadienoate, and 4-methyl JH I have been isolated from embryos of the tobacco homworm, Manduca sexta JH 0 has also been isolated from males of the silkworm, Hylophora cecropia [17, 18, 19]. In higher Diptera (flies), a unique JH bisepoxide, methyl-6,7,10,1 l-bisepoxy-3,7,11-trimethyl 2 -dodecenoate, has been isolated and appears to be the principle JH of some species in this order [20]. 

In addition to pheromones (vide infra), we were interested in juvenile hormones (JHs), and synthesized ( )-juvabione [12] and (-t-)-juvabione [13-14]. JH mimics were later found to be useful as practical insect growth regulators (IGRs). We synthesized ( )-JH I [15], (-i-)-JH I [16] and unnatural (-)-JH I [17]. The naturally occurring (-i-)-JH I was 1.2 x lO times more active than (-)-JH I. Chirality plays an important role at JH receptor sites. 

At the same time, several new compounds which would appear to be homoterpenoids have been discovered. Presumably the extra methyl groups present in compounds of this type are inserted into a terpenoid precursor in an analogous way to the in vivo elaboration of the ergostane-type and stigmastane-type side chains in various plant sterols from the cholestane-type side chain [96, 97]. A probable example of the homoterpenoid group is the juvenile hormone (I) of the giant silkworm moth, where, formally at least, two additional methyl groups would appear to have been added to the famesane skeleton. 

The hydroxy ketones 5 and 6 [35] were the key building blocks in the synthesis of enantiomerically pure insect juvenile hormones [27,35] as shown in Fig. 6. In the case of the synthesis of (+)-4-methyl juvenile hormone I, the half ester 7 was also employed as the building block [36]. 

Kelada, N.L., I.A. Gaaboub, and I.A. Rawash. 1980. A comparison of the juvenilizing effect of six juvenile hormone-like activity compounds on Egyptian Culexpipiens L. Jour. Agricul. Sci. 95 203-312. 

Recently, the biological role of precocene I (132) and II (133) and their conversion into the epoxides has been studied. Precocene II suppresses juvenile hormone (79MI22301, 79CC920) and this has stimulated interest in synthetic analogues (80JHC1377). 

Exercise 30-9 The synthesis of Cecropia juvenile hormone outlined below was designed by E. J. Corey and co-workers. Draw in the structure of the product (as i, ii, etc.) at each stage where this has been omitted, and write above the arrows the reagents and conditions necessary to accomplish reactions where these have been omitted. (To save space, the abbreviation R and R are used to designate parts of the structure that do not change in later steps.)... 

Sreng L., Leoncini I. and Clement J. L. (1999) Regulation of sex pheromone production in the male Nauphoeta cinerea cockroach role of brain extracts, corpora allata (CA), and juvenile hormone (JH). Arch. Insect Biochem. Physiol. 40, 165-172. 

Jeffrey pine beetle, Dendroctonus jeffreyi Hopkins, which had been previously treated with juvenile hormone III (JH III, 2.2 pg/beetle in acetone) and then placed in an aeration tube for 25 to 30 h. Ips paraconfusus and I. pini were each injected with 0.2 pCi of sodium [1-14C]acetate prior to placement in cut pine logs and volatile collection, while D. jeffreyi were each injected with 3.8 (male) and 3.7 (female) pCi of sodium [1-14C]acetate 6.4 (male) and 10.7 (female) h after JH application. (G) The role of the mevalonate pathway in frontalin biosynthesis is supported by the incorporation of radiolabel from [2-14C]mevalonolactone into frontalin by male D. jeffreyi (2.2 pg JH 11 l/beetle in acetone, 10 h incubation and volatile collection, 1.1 pCi of [2 14C] mevalonolactone injected, 20 h volatile collection). Figures adapted from Seybold et al. (1995b) and Barkawi (2002). 

Feyereisen R. (1985) Regulation of juvenile hormone titer synthesis. In Comprehensive Insect Physiology Biochemistry and Pharmacology, eds G. A. Kerkut and L. I. Gilbert pp. 391 —429. Pergamon Press, Oxford. 

Gilbert L. I., Granger N. A. and Roe R. M. (2000) The juvenile hormones historical facts and speculations on future research directions. Insect Biochem. Molec. Biol. 30, 617— 644. 

Rondot I., Quennedey B., Courrent A., Lemoine A. and Delachambre J. (1996) Cloning and sequencing of a cDNA encoding a larval-pupal-specific cuticular protein in Tenebrio molitor (Insecta, Coleoptera). Developmental expression and effect of a juvenile hormone analogue. Eur. J. Biochem. 235, 138-143. 

Rogers, I. H., Manville, J. F., and Sahota, T. (1974). Juvenile hormone analogs in conifers. II. Isolation, identification, and biological activity of c/s-4-[r(R)-5 -dimethyl-3 -oxohexyl]-cyclohexane-1-carboxylicacidand(+)-4(R)-[l (R)-5 -dimethyl-3 -oxohexyl]-1-cyclohex-ene-1-carboxylic acid from Douglas-fir wood. Can. ). Chem. 52, 1192-1199. 

The existence of a cytosolic epoxide hydrolase was first indicated by its ability to hydrolyze analogs of insect juvenile hormone not readily hydrolyzed by microsomal epoxide hydrolase. Subsequent studies demonstrated a unique cytosolic enzyme catalytically and structurally distinct from the microsomal enzyme. It appears probable that the cytosolic enzyme is peroxisomal in origin. Both enzymes are broadly nonspecific and have many substrates in common. It is clear, however, that many substrates hydrolyzed well by cytosolic epoxide hydrolase are hydrolyzed poorly by microsomal epoxide hydrolase and vice versa. For example, l-(4 -ethylphenoxy)-3,7-dimethy I -6,7-epoxy-//7//i,v-2-octene, a substituted geranyl epoxide insect juvenile hormone mimic, is hydrolyzed 10 times more rapidly by the cytosolic enzyme than by the microsomal one. In any series, such as the substituted styrene oxides, the trans configuration is hydrolyzed more rapidly by the cytosolic epoxide hydrolase than is the cis isomer. At the same time, it should remembered that in this and other series,... 

The three major, known insect juvenile hormones (JH I, JH II and JH III) (Figure 6) are all methyl esters of terminally epoxi-dized homologs of farnesoic acid. They are present in varying amounts in different insects at different stages of development and it has been suggested, though not determined, that they may play different hormonal roles. 

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