Antifeedant , production

The thiophene analogue (51) of the natural antifeedant product tonghaosu has been prepared <96TL893>. Several acetylenic thiophene derivatives including 52 have been isolated from Blumea obliqua and characterized <96MI733>. 

A SN reaction-based domino route to clerodane diterpenoid tanabalin (2-488) [258] has been described by Watanabe s group (Scheme 2.111) [259]. This natural product is interesting as it exhibits potent insect antifeedant activity against the pink bollworm, Pectinophora gossypiella, a severe pest of the cotton plant The domino sequence towards the substituted trans-decalin 2-487 as the key scaffold is induced by an intermolecular alkylation of the (5-ke toes ter 2-484 with the iodoalkane 2-483 followed by an intramolecular Michael addition/aldol condensation (Robin-... 

In 1987, Vaultier and coworkers [27] developed a combination of a [4+2] cycloaddition of a bora-1,3-diene to provide an allylborane, which then reacts with an aldehyde to give a highly functionalized alcohol. The Lallemand group, as well as Hall and colleagues, has recently used this procedure. In an approach for the synthesis of the antifeedant natural product clerodin (4-83), Lallemand and coworkers performed a three-component domino reaction of 4-80, 4-81 and methyl acrylate to give 4-82 (Scheme 4.18) [28]. 

A more detailed understanding of the biochemical pathways and enzymes involved in saponin biosynthesis will facilitate the development of plants with altered saponin content. In some cases, enhanced levels of saponins or the synthesis of novel saponins may be desirable (for example, for drug production 4 or improved disease resistance3,5,6), while for other plants, reduction in the content of undesirable saponins would be beneficial (for example, for legume saponins that are associated with antifeedant properties in animal feed7). This chapter is concerned with recent progress that has been made in the characterization of the enzymes and genes involved in the synthesis of these complex molecules and focuses on triterpenoid saponins. 

Panacene (61) is a metabolite of the sea hare Aplysia brasiliana and acts as a fish antifeedent [61]. The synthesis of the racemic natural product, published by Feldman et al. [77] in 1982, takes advantage of the anti-selective SN2 -substitution of the propargylic mesylate 67 with LiCuBr2 (Scheme 18.21). In contrast, the later attempted biomimetic synthesis by treatment of the enyne 68 with NBS or 2,4,4,6-tetrabromocyclohexadienone did not proceed stereoselectively and led to a 1 1 mixture of the target molecule 61 together with its allenic epimer [78]. 

Table 1. Bioactive fungal products from endophytic fungi in recent literature reviews. The compounds include antifungal, antibacterial, antimycobacterial, antiviral, nematicidal, cytotoxic, antineoplastic, antioxidant, antiinsectant, antifeedant, antidiabetic, herbicidal, algicidal, specific en mie inhibitory, and immunomodulatory activities. 

Acetylnimbandiol was insectidical (EI50 = 21 ppm) when fed to the larvae of II. vlrescens, while the structurally related salannin, which lacks the A-ring ketone (Figure 13), was not (Table VII) (57). Nakanishi (58) has pointed out that natural products with electrophilic moieties tend to be cytotoxic and insect antifeedant. Possibly the growth-Inhibitory activity of the limonoids may also be attributed to a nonspecific electrophilic effect. 

Chimyl alcohol (Structure 7.79), isolated from the mantle tissues of the nudibranch Tritoniella belli,44 caused rejection by O. validus of shrimp-treated disks at natural tissue-level concentrations. T. belli sequesters this defensive chemistry from its diet, the stoloniferan coral Clavularia franklin-iana. Sequestration of chimyl alcohol from the diet, however, seems to be opportunistic, and T. belli also provisions its mucus with other yet undescribed deterrent natural products.49 Chimyl alcohol is reported from other non-Antarctic molluscs209 and has been demonstrated to function as an antibacterial and a fish antifeedant at levels found in the tissues of the dorid nudibranchs Archidoris montereyensis and Aldisa sanguinea cooperi.210... 

The Brassica family produces a wide range of glucosinolate compounds, anionic glycosides produced by the plant as antifeedant protective chemicals. As significant amounts of these compounds are left in the oilseed rape meals that remain after oil extraction, there is currently interest in exploiting these materials as crop-protection products for control of soil-borne diseases (Palmieri, 2003). 

Nutmeg oil has strong antifeedant activity, fumigant toxicity and contact toxicity against the stored product insects, Tribolium castaneum and Sitophilus zeamis. The... 

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