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•Essential oils from commercial VB and wild GH Geranium macrorrhizum populations.•Antifedant effects of essential GH oil against the aphid Rhopalosiphum padi.•Larvicidal effects GH ...essential oil against the hard tick Hyalomma lusitanicum.•Isolation of germacrone and β-elemenone from GH essential oil.•The activity of the essential oil correlated with germacrone and thymol.
The insecticidal and acaricidal effects of the essential oils (EO) from two populations of Geranium macrorrhizum L (ornamental variety Bevan, VB and wild population from Hungary, GH) have been studied against several insect pests of economic importance in agriculture (Spodoptera littoralis, Myzus persicae and Rhopalosiphum padi), and the hard tick Hyalomma lusitanicum. The oil from the wild population (GH) was characterized by its content in β-elemenone (30.53%), thymol (18.52%) and germacrone (15.54%), while the oil from the commercial variety (VB) had linalool (26.45%) and linalyl acetate (25.11%) as major components. S.litoralis and R. padi were significantly affected by the wild population oil (GH-EO). The oil from the commercial variety VB was less effective against insects. The ixodicidal effects of these oils were strong, being the wild population (GH-EO) the most effective. To correlate the composition of these oils with their activity, the essential oil major components have been isolated (germacrone and β-elemenone) and tested (linalool, thymol, germacrone and β-elemenone). The insect antifeedant and ixodicidal effects of thymol and germacrone explained the bioactivity of the GH essential oil. Therefore, the wild variety of G. macrorrhizum has been selected for domestication given its potential as a source of bioactive extracts and metabolites.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Currently, the use of synthetic pesticides is the main method of plant protection applied in agri- and horticulture. However, its excessive use leads to the development of pesticide resistance, a ...contamination of the environment, toxicity to non-target organisms, and risks for human health. With the ultimate aim of contributing to the develop of a more sustainable pest management, we used the natural product germacrone (
), reported to possess significant insecticidal activity, as starting material for the generation of molecular diversity (
-
). Some of the generated derivatives are natural compounds, such as 1,10-epoxygermacrone (
), 4,5-epoxygermacrone (
), gajutsulactone A (
), germacrol (
), isogermacrone (
), 9-hydroxyeudesma-3,7(11)dien-6-one (
), eudesma-4,7(11),dien-8-one (
), eudesma-3,7(11)-dien-8-one (
) and eudesma-4(15),7(11)-dien-8-one (
). Compounds, 7,11-9,10-diepoxigermacr-4,5-en-8-ol (
, 7,11-epoxieudesma-4,7(11)-dien-8-one (
) and 7,11-epoxieudesma-3,7(11)-dien-8-one (
) are described for the first time. The biocidal activity of most of these compounds was assayed against the tick
The acaricidal effects of compound
were four times higher than that of germacrone (
). Compound
is an insect antifeedant a thousand times more potent than germacrone against
, which makes this substance a promising selective antifeedant against this cereal pest.
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The biomimetic formal synthesis of the antibiotic platensimycin for the treatment of infection by multidrug-resistant bacteria was accomplished starting from either ent-kaurenoic acid or ...grandiflorenic acid, each of which is a natural compound available in multigram scale from its natural source. Apart from the natural origin of the selected precursors, the keys of the described approach are the long-distance functionalization of ent-kaurenoic acid at C11 and the efficient protocol for the A-ring degradation of the diterpene framework.
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Many terpenoids are biosynthesized after a cascade of cyclizations and rearrangements of carbocations mediated by terpenoid synthases, as exemplified in the biosynthesis of lanosterol. Although ...several reports of organisms or purified enzymes catalyzing this cascade of reactions in the laboratory have been described, the development of chemical transformations capable of mimicking such tandem cyclizations and rearrangements constitute a formidable challenge for organic chemists. From the very early works of Van Tamelen in the 1960s to our time, we present the Lewis or Brønsted acids-mediated cyclization–rearrangements of carbocations cascades aimed to mimic the action of enzymes. From all the achievements herein presented, the hypothesis of minimal enzymatic participation is reinforced, and this, if confirmed, promises new achievements in this area in the next future.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OBVAL, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Communic acids are diterpenes with labdane skeletons found in many plant species, mainly conifers, predominating in the genus Juniperus (fam. Cupresaceae). In this review we briefly describe their ...distribution and different biological activities (anti- bacterial, antitumoral, hypolipidemic, relaxing smooth muscle, etc.). This paper also includes a detailed explanation of their use as chiral building blocks for the synthesis of bioactive natural products. Among other uses, communic acids have proven useful as chirons for the synthesis of quassinoids (formal), abietane antioxidants, ambrox and other perfume fixatives, podolactone herbicides, etc., featuring shorter and more efficient processes.
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We have proven that the biomimetic-like synthesis of cannabinoids from citral and the corresponding phenolic counterpart may well be carried out using water as a solvent. The influence of different ...additives such as surfactants was also analyzed. Rationalization of the reaction mode and regiochemistry of the processes were provided in terms of “on water” and “in water” reactions. The same reactions were conducted in organic media using Ga(III) salts as catalysts. Worthy of being underlined, an unprecedented formal 2+2+2 process was found to occur between two citral molecules and the corresponding phenolic species in both aqueous and organic environments. Computational studies were performed in order to gain a comprehensive mechanistic and energetic understanding of the different steps of this singular process. Finally, the influence of SDS micelles in the chemical behavior of olivetol and citral was also pursued using PGSE diffusion and NOESY NMR studies. These data permitted to tentatively propose the existence of a mixed micelle between olivetol and SDS assemblies.
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A detailed experimental and theoretical study corroborates that the reductive deoxygenation of activated (allylic or benzylic) alcohols with excess Ti(III) proceeds via an allyl(benzyl)-radical and ...allyl(benzyl)-Ti, which is protonated, regioselectively in the case of allylic derivatives. The H atom of the newly formed C-H bond in the product originates from the -OH group of the starting material. The deoxygenation of lithium alkoxides or alcohols by using 1.0 mol of Ti(III) leads to the corresponding dimerization products in good yields. An excellent agreement with the experimental data was obtained by using a reaction kinetics simulator to discriminate between competing reactions.
The search for new compounds with biocidal potential was carried out, focusing on the longipinenes 1–7 from the plant species Santolina viscosa Lag. Compounds 1, 2, and 5 showed remarkable molecular ...diversity when treated in acidic reaction conditions. Protonic, Lewis, and heterogeneous compounds were used in the treatment. Three main models of reaction have been observed: isomerization of the double bond (8–10); rearrangements to longibornane-based skeleton (11–15) and ring-opening to himachalane-based skeleton (16–18). Secolongibornane aldehydes 23 and 24 were obtained after epoxide opening under the same reaction conditions. The elucidation of the structures of the new compounds was carried out using spectroscopic data and was supported by computational theoretical calculations of 13C NMR spectra. Additionally, high-resolution mass spectrometry and single-crystal X-ray diffraction analysis were employed for certain compounds. Natural longipinenes 4–7, methyl esters 1–3 of corresponding natural carboxylic acids and the isomerized and derivatives compounds 8–19 exhibit moderate to high insecticidal activity against R. padi and M. persicae insects. Longipinene 5 shows potent inhibition against the root growth of the plants L. perenne and L. sativa, as well as compound 2 on the leaves of L. perenne. Furthermore, significant ixocidal and nematicidal activity was found for this latter compound.
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Naturally occurring nootkatone, with reported insecticidal and acaricidal properties, has been used as a lead to generate molecular diversity and, consequently, new insect antifeedant and ixodicidal ...compounds. A total of 22 derivatives were generated by subjecting this molecule to several reactions including dehydrogenation with the iodine/DMSO system, oxidation with SeO
, epoxidation with
CPBA, oxidation or carbon homologations of the α-carbonyl position with TMSOTf (trimethylsilyl trifluoromethanesulfonate) followed by Rubottom and Dess Martin periodane oxidations, condensation with formaldehyde using Yb(OTf)
as catalyst and dehydroxilation using the Grieco protocol. The insect antifeedant (against
and
) and ixodicidal (against the tick
) activities of these compounds were tested. Compound
was the most active substance against
and
, and twice more efficient than nootkatone in the antitick test.
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Investigations detailed herein, including density functional theory (DFT) calculations, demonstrate that the formation of either alkoxy− or hydroxy−Ti(III) complexes considerably decreases the energy ...of activation for C−O bond homolysis. As a consequence of this observation, we described two new synthetic applications of Nugent’s reagent in organic chemistry. The first of these applications is an one-step methodology for deoxygenation−reduction of alcohols, including benzylic and allylic alcohols and 1,2-dihydroxy compounds. Additionally, we have also proved that Ti(III) is capable of mediating carbonyl coupling−olefination. In this sense, and despite the fact that for over 35 years it has been widely accepted that either Ti(II) or Ti(0) was the active species in the reductive process of the McMurry reaction, the mechanistic evidence presented proves the involvement of Ti(III) pinacolates in the deoxygenation step of the herein described Nugent’s reagent-mediated McMurry olefination. This observation sheds some light on probably one of the mechanistically more complex transformations in organic chemistry. Finally, we have also proved that both of these processes can be performed catalytically in Cp2TiCl2 by using trimethylsilyl chloride (TMSCl) as the final oxygen trap.
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