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inhibition of ecdysteroid and juvenile hormone synthesis by …

Compare Woodward's and Corey's syntheses, with their cyclic precursors, resolutions and huge lists of coauthors to, for example, the recent , accomplished entirely using acyclic stereocontrol by a single coworker. I wonder what we'll be doing in another 30 years...

Juvenile Hormone Biosynthesis in Insects: What Is New, What Do We Know, and What Questions Remain?

We further confirmed the significant role of JH in Vg gene regulation by exogenous hormone applications. We selected two- day-old female beetles when Vg mRNA levels are very low. Application of JH III showed induction of Vg2 mRNA levels by nearly 10-fold, while the injection of 20E reduced Vg2 mRNA levels (4-fold less) when compared to the Vg2 mRNA levels in the respective control beetles. Similar opposite action of 20E and JH has been reported in an endoparasitic wasp, Pteromalus puparum (). In this wasp, Vg gene regulation is under the control of 20E; injection of 20E induced Vg gene expression while exogenous application of JH III suppressed the Vg gene expression. In the present study, we also used a JH analog, hydroprene, to confirm the effects of JH III. The application of Hydroprene induced Vg2 expression levels and also partially rescued Vg2 mRNA levels in hydroprene treated JHAMT RNAi beetles during the previtellogenic stage. The regulation of Vg gene expression by JH or JH analogues has been described in many insect species including some beetles (; , ; ; ; ). However, hydroprene application to JHAMT RNAi insects did not restore Vg2 mRNA levels similar to those observed in hydroprene-treated control insects injected with malE dsRNA. This may be due to the function of JH during previtellogenic stage to prepare fat body for Vg synthesis during vitellogenic stage. Since JHAMT RNAi insects are depleted of JH during previtellogenic stage, the fat body would have not become completely competent and therefore hydroprene was not able to induce Vg synthesis to the maximum levels observed in control insects.

EFFECT OF JUVENILE HORMONE ON THE SYNTHESIS …

Sharpless, Enantioselective Synthesis of Juvenile Hormone III in Three Steps from Methyl Farnesoate, , 8, 777 (1993).

The microarray analysis of gene expression in the whole body of female beetles during 1–4 days PAE showed up-regulation of several genes. Among them, Vg mRNA levels increased dramatically after day 3 PAE, indicating that the previtellogenic phase covers 0–3 days PAE and the vitellogenic cycle starts after day 3 PAE. Also, the microarray analysis showed up-regulation of several genes coding for proteins such as JHAMT, Kr-h1, JHE, JHEH, and JHIPs involved in the JH biosynthesis, metabolism and signaling. However, the expression levels of genes coding for proteins involved in ecdysteroid signaling did not change significantly during this stage. Based on the data from the microarray and qRT-PCR analyses and measurement of hormone titers the following conclusions could be drawn: 1) JH levels are high during the previtellogenic stage in the female beetles while ecdysteroid titers decline to low levels; 2) the expression of genes involved in JH biosynthesis and action increase during the previtellogenic stage while the expression of genes involved in ecdysteroid biosynthesis and action decrease or do not change during 1–5 days PAE; and 3) the expression levels of the selected genes determined by qRT-PCR confirmed the changes among the time-points observed in the microarray analysis. Hormone titers and expression profiles of genes involved in biosynthesis and action of these two hormones showed that JH but not ecdysteroids plays key roles in preparing the fat body for Vg synthesis.

In the final figure of the synthesis the first structure has the wrong configuration of the carbamate N (compare to last structure of previous figure).
Did the cladinose (C-3 sugar) really invert to the opposite enantiomer in the final step?
In the juvenile hormone I synthesis what was the purpose of treating with Li & EtNH2 before the Raney Nickel?

Details - JUVENILE HORMONE AND VITELLOGENIN SYNTHESIS …

Synthesis of the (±)-Juvenile Hormone of the Giant Silkworm Moth Hyalophora cecropia L

Most people know that insecticides kill insects. However, the way in which these chemicals work is a mystery to most of us. How an insecticide works is called its mode of action. A complete understanding of the mode of action of an insecticide requires knowledge of how it affects a specific target site within an organism. The target site is usually a critical protein or enzyme in the insect, but some insecticides affect broader targets. For example, silica aerogels affect the entire lipid layer on the insect cuticle. Although most insecticides have multiple biological effects, toxicity is usually attributed to a single major effect. This fact sheet is intended to explain what insecticides do in insects to cause toxicity and death (Table 1).

Pyrethroids are synthetic chemicals whose structures mimic the natural insecticide pyrethrin. Pyrethrins are found in the flower heads of plants belonging to the family Compositae (e.g., chrysanthemums). These insecticides have a unique ability to knock down insects quickly. Synthetic pyrethrins (also known as pyrethroids) have been chemically altered to make them more stable Pyrethroids are axonic poisons (they poison the nerve fiber). They bind to a protein in nerves called the voltage-gated sodium channel. Normally, this protein opens causing stimulation of the nerve and closes to terminate the nerve signal. Pyrethroids bind to this gate and prevent it from closing normally which results in continuous nerve stimulation. This explains the tremors exhibited by poisoned insects. They lose control of their nervous system and are unable to produce coordinated movement.

Synthesis of Radiolabeled Juvenile Hormone Analogs and Chiral Homologs, ..
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Control of juvenile hormone synthesis in corpora allata

Heating this thioester in refluxing toluene gave the desired macrocycle in an excellent 70% yield. From this point only deprotection, attachment of the sugars, and oxidation of the amine to the ketone were required for the completion of the synthesis. First of all, the two cyclic protecting groups were removed, but in order to stop the amine messing up the glycosylation it was protected with the somewhat uncommon p-phenylbenzamide group. After a lot of model studies and optimisation it was determined that there was a marked difference in the reactivities of the three secondary hydroxyl groups now exposed, and this could be exploited to allow attachment of the sugar motifs without the use of any more protecting group chemistry. Although the yields are a bit poor here, I think the directness of this approach is appealing and elegant. Finally, the amide was cleaved under reductive conditions with sodium amalgam. As expected, the amine could then easily be oxidised to the imine in the presence of the three secondary alcohols and this was hydrolysed to give the natural product!

David J Hart (2011) Olefin Synthesis and Cecropia Juvenile Hormone

1. Despite appearing online back in July it's still in the ASAPs (DOI: ). This methodology has proved surprisingly popular and contributed to the synthesis of good number of natural products in the decades following the untimely demise of RBW. The review was written by a former Woodward postdoc who worked on the erythromycin project, Dale E. Ward.

Olefin Synthesis and Cecropia Juvenile Hormone …

dsRNAs were synthesized using the Ambion MEGAscript transcription kit (Ambion, Austin, TX). Cognate primers designed based on the sequences available in the Beetlebase () with T7 polymerase promoter sequence added at their 5′ ends were used in PCR reactions to amplify 300–500 bp fragments of each gene. The resultant PCR products were used in transcription reaction using the kit following the methods described in the instruction manual. The dsRNAs were injected into the pupae/adult on the ventral side of the first abdominal segment using a aspirator tube assembly (Sigma Chemical Co. St. Louis, MO) fitted with 3.5″ glass capillary tube, pulled by a needle puller (Model P-2000, Sutter Instruments Co.). Injected pupae/adults were reared under standard conditions until use. dsRNA injection of all the candidate genes, except for the genes coding for proteins involved in ecdysteroid biosynthesis and action, were injected into the two-day-old pupae. Since injection of dsRNA of genes coding for proteins involved in ecdysteroid biosynthesis and action blocked pupal-adult metamorphosis, these dsRNAs were injected into adults less than 24 h old. The dsRNA of Escherichia coli malE gene was used as the control.

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