Academic literature on the topic 'Kettle Point Formation'
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Journal articles on the topic "Kettle Point Formation"
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Bingham-Koslowski, Nikole, Cameron Tsujita, Jisuo Jin, and Karem Azmy. "Widespread Late Devonian marine anoxia in eastern North America: a case study of the Kettle Point Formation black shale, southwestern Ontario." Canadian Journal of Earth Sciences 53, no. 8 (August 2016): 837–55. http://dx.doi.org/10.1139/cjes-2015-0227.
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The Kettle Point Formation of southwestern Ontario consists of intervals of organic-rich interlaminated black shale interbedded with organic-poor greyish green mudstones and rare red beds, separated by metre-scale sequences of non-interlaminated black shale. The formation shows a largely consistent background value for the black shales around −20‰ δ34S, punctuated by a substantial positive excursion of ∼32‰ (up to +12.87‰) that coincides with a significant interval of greyish green mudstone and red beds. Lithological and geochemical data indicate that the black shales were deposited during periods of anoxia, with thick intervals of non-interlaminated black shales recording the peak of anoxia, whereas the greyish green mudstones record deposition in more oxygenated environments. Relative water depth is interpreted as the key control on the vertical and lateral distribution of the Kettle Point lithofacies. Interbedded black shales and greyish green mudstones were deposited in relatively shallow waters, where minor, short-lived falls in relative sea level promoted dysoxic to oxic conditions and the deposition of organic-poor lithologies. Non-interlaminated black shales are indicative of substantial rises in relative sea level, resulting in widespread anoxia and the deposition of thicker and more laterally extensive packages of organic-rich sediment. The formation of black shales in relatively shallow waters in southwestern Ontario implies that the extensive deposition of organic-rich sediment across eastern North America during the Late Devonian was a product of widespread anoxia related to restricted circulation in intracratonic and foreland basin depositional centers.
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CARR, ROBERT K., and WILLIAM J. HLAVIN. "Two new species of Dunkleosteus Lehman, 1956, from the Ohio Shale Formation (USA, Famennian) and the Kettle Point Formation (Canada, Upper Devonian), and a cladistic analysis of the Eubrachythoraci (Placodermi, Arthrodira)." Zoological Journal of the Linnean Society 159, no. 1 (May 2010): 195–222. http://dx.doi.org/10.1111/j.1096-3642.2009.00578.x.
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Abu Bakar, Ahmad Fauzi, Hadariah Bahron, and Karimah Kassim. "Synthesis, Characterization and Neurotoxicity Screening of Schiff Base Ligands and their Complexes." Advanced Materials Research 554-556 (July 2012): 938–43. http://dx.doi.org/10.4028/www.scientific.net/amr.554-556.938.
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Two ligands and four complexes are successfully synthesized by reacting 1,8-diaminonapthelene with aldehyde/ketone derivatives in ratio amine:aldehyde/ketone (1:2) for ligands formation and 1:1 ratio (ligand:metals) for complexes formation. The compounds were characterized through CHNS elemental analysis, IR spectroscopy, 1H NMR spectroscopy, melting point determination, and magnetic susceptibility determination. The neurotoxicity screening of compounds was screened using neuroblastoma SH-SY5Y cell lines and it was indicate the cells were non-toxic either for ligands and complexes after 24 hours exposure.
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Boussada, Hallouma, and Jean-Marie De Ketele. "L'évaluation de la qualité de la formation et du système d'évaluation universitaire: le point de vue des diplômés." Avaliação: Revista da Avaliação da Educação Superior (Campinas) 13, no. 1 (March 2008): 39–61. http://dx.doi.org/10.1590/s1414-40772008000100003.
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Les recherches sur l'évaluation des acquis professionnels des jeunes diplômés (ROMAINVILLE, 2002 ; DE KETELE, 1997, 1999, 2000; FRANCE, 2003) ; Avis du Haut Conseil de l'Evaluation de l'Ecole, 2003) gravitent autour de quatre thèmes : les compétences des étudiants à l'entrée des études, leur perception des compétences acquises à la sortie, leurs compétences méthodologiques et les effets généraux de l'enseignement supérieur. Cependant, peu d'études fournissent des indicateurs précis sur les compétences professionnelles mesurées et sur les critères exigés par le marché de l'emplois. Cette étude porte sur une évaluation rétrospective de la qualité de formation universitaire par des diplômés ayant une expérience de la vie professionnelle. Les résultats par questionnaire sur un échantillon de 158 étudiants, montrent la difficulté de l'université à mettre en œuvre des évaluations pertinentes et valides qui favorisent le développement des compétences nécessaires au devenir professionnel.
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Couture, Philippe, Manal El-Saidi, and John Warkentin. "Ketene acetals from thermolysis of aryloxy methoxy oxadiazolines. Evidence for carbonyl ylide intermediates." Canadian Journal of Chemistry 75, no. 3 (March 1, 1997): 326–32. http://dx.doi.org/10.1139/v97-037.
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Thermolysis of oxadiazolines (5) in benzene at 110 °C leads to ketene acetals (11) as minor products. Carbonyl ylide intermediates (6), and oxiranes (7), presumably in equilibrium with those ylides, are implicated as unstable precursors of the ketene acetals although none of the oxiranes (carbonyl protected α-lactones) were isolable and only one of the ketene acetals was isolable in pure form. The evidence points to the two-step sequence of thermolysis of oxadiazolines, namely, initial cycloreversion to N2 and carbonyl ylide (6), rather than concerted fragmentation to N2, acetone, and carbene (12). The first-formed ylide does fragment to carbene and acetone in a second step that competes with oxirane formation. A tentative mechanism for reaction of 7 with 12, to afford 11, is advanced. Keywords: carbonyl ylide, dioxy oxirane, ketene acetal, oxadiazoline.
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Dan, Vu Ngoc, and V. F. Novikov. "Study of the sorption properties of solvents in thinlayer and column chromatography." Power engineering: research, equipment, technology 22, no. 2 (May 15, 2020): 19–26. http://dx.doi.org/10.30724/1998-9903-2020-22-2-19-26.
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Much attention is paid to the consideration of the causes of transformer oil aging under the influence of technogenic and natural factors. The paper insulation destruction mechanism is considered, as a result of which furan compounds are formed that enter the transformer oil and worsen its dielectric characteristics. The characteristics of the domestic transformer oil grade GK-1 obtained using the technology of hydrocracking in a hydrogen medium are given. Furan compounds are formed in used transformer oil, which are monitored using chromatographic analysis methods according to standard procedures. The group composition of transformer oil was determined using thin layer chromatography. As a solvent used n. Hexane. To extract furan compounds from transformer oil, various organic solvents are used, the physicochemical properties of which are given in this work. It was found that the retention time of the studied sorbates corresponds to an increase in their boiling points for ethyl acetate, methyl ethyl ketone and dodecane. In the case of isopropanol, which has a close boiling point with ethyl acetate and methyl ethyl ketone, a significant increase in retention time is observed, which is associated with the formation of an intermolecular hydrogen bond. The dependence of the spot diameter of furan substances on their concentration was established under conditions of thin-layer chromatography on Sorbfil plastics. Moreover, the most effective separation is characteristic of furfural. In this case, the chromatographic spots are small in size with good fidelity. The ascending mode of column liquid chromatography was used to determine the dependence of the retention time of standard sorbates on the length of the Silyochrome S-80 sorption layer, which is parabolic. It was found that the highest retention times are characteristic of ethoxyethanol and isopropanol, which is consistent with the known theoretical principles of liquid chromatography. Histograms of the effect of the retention time of standard sorbates on their nature and boiling point, where isopropanol and 2-ethoxyethanol are extreme, are presented. In this case, isopropanol having a lower boiling point than 2-Ethoxyethanol is retained on the sorbent more strongly, which is associated with the formation of intermolecular hydrogen bonds with surface silanol groups of the sorbent.
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Wicaksono, Yudi, Dwi Setyawan, and Siswandono Siswandono. "Formation of Ketoprofen-Malonic Acid Cocrystal by Solvent Evaporation Method." Indonesian Journal of Chemistry 17, no. 2 (July 31, 2017): 161. http://dx.doi.org/10.22146/ijc.24884.
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The purpose of this work was to explore the formation of ketoprofen-malonic acid cocrystal by solvent evaporation method. Early detection of cocrystal formation was conducted by hot stage microscopy and solid-liquid phase diagram. Cocrystal were prepared by solvent evaporation method by using isopropyl alcohol as solvent. Characterization of cocrystal was done by Powder X-Ray Diffractometry (PXRD), Differential Scanning Calorimetry (DSC), Fourier Transform Infrared (FTIR) Spectroscopy and Scanning Electron Microscopy (SEM). The results of hot stage microscopic and solid-liquid phase diagram indicated formation of ketoprofen-malonic acid cocrystal. PXRD and DSC measurements showed stoichiometric ratio of cocrystal ketoprofen-malonic acid (2:1). The ketoprofen-malonic acid cocrystal had melting point at 86.2 °C and unique peaks of PXRD pattern at 2θ of 6.1°, 17.8°, 23.2° and 28.6°. FTIR spectra indicated the formation of cocrystal due to interaction of C=O ketone group of ketoprofen with MA molecule. SEM images show that ketoprofen-malonic acid cocrystal have multi-shaped particles with rough surfaces.
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Cao, Xu yan, Fei Huang, and Songlin Zhang. "An Example of Ketone Olefination via Praseodymium-Mediated Barbier Reaction in the Presence of Diethyl Phosphite." Synlett 30, no. 12 (June 25, 2019): 1437–41. http://dx.doi.org/10.1055/s-0039-1690096.
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The first example of carbon double-bond formation via praseodymium-mediated Barbier type reaction of ketones and allyl halides in the presence of diethyl phosphite is reported. The reaction is highly α-regioselective and conveniently carried out under mild conditions in a one-pot fashion. From a synthetic point of view, a series of conjugated alkenes were obtained in moderate to good yields in this one-pot reaction with practical reaction conditions.
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Guthrie, J. Peter, and Zhi Liu. "The enols of acetic acid and methyl acetate." Canadian Journal of Chemistry 73, no. 9 (September 1, 1995): 1395–98. http://dx.doi.org/10.1139/v95-173.
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We have determined the heat of formation of 1,1-dimethoxyethene, ΔHf(l) = −75.56 ± 0.87 kcal mol−1, by measuring the heat of hydrolysis. The heat of vaporization, 8.47 ± 0.10 kcal mol−1, was estimated from the boiling points at various pressures. The standard entropy of gaseous 1,1-dimethoxyethene, 82.02 ± 2. cal deg−1 mol−1, was calculated using frequencies obtained by MO calculations at the 6-31G** level. The free energy of transfer, 1.02 ± 1, was estimated by additivity with allowance for a distant polar interaction. Thus the free energy of formation in aqueous solution, ΔGf(aq) = −37.07 ± 1.48 kcal mol−1, could be calculated. The free energies of hydrolysis for enol ethers appear to be insensitive to structure; we used an average value and so calculated the values of the free energies of formation of the enols of acetic acid and methyl acetate, −67.90 ± 1.67 and −52.48 ± 1.53 kcal mol−1, respectively. These values are in good agreement with other recent evaluations. This method should be applicable to related enols. Keywords: enols, thermodynamics, heat of formation, entropy, ketene acetal.
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Khudheyer Jawad Kadem. "Synthesis and Characterization of New Heterocyclic Compounds from Calix [4] arene Derivative." International Journal of Research in Pharmaceutical Sciences 11, no. 3 (July 6, 2020): 3143–50. http://dx.doi.org/10.26452/ijrps.v11i3.2427.
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In this work, a new heterocyclic compounds derived from Calix[4]arene Derivative had been synthesized. The characterization of the produced compounds was performed using melting point, FT-IR spectroscopy and some of them with 1H-NMR spectroscopy. The spectral data confirm the formation of these compounds. This research includes the following two parts:- Part 1: Synthesis of Calix[4]arane Derivative from reaction Calix[4]arane with 4- Aminobutyric acid to produce ester compound this part4-Aminobutyric acid reaction with freshly distilled thinly chloride , the produce final was purified via distillation below pressure reduced. The product was purified by repeated recrystallization. In this step Converted the substituted carboxylic acid to substituted acid chloride included to obtained good leaving group the compound product containing primary amine and the reaction of Calix[4]arane Derivative with compounds containing carbonyl group(aldehyde or ketone) the carbonyl group of aldehyde or ketone react with primary amine to produce imine compounds(Schiff bases. Part 2: Reaction of produced Schiff base compounds with mercaptoacetic acid (thioglycolic acid) or maleic anhydride to synthesized new heterocyclic compounds Compounds with heterogeneous ring are characterized by having many biological activitiesWhich attracts the attention of researchers, and accordingly various derivatives containing sulfur or oxygen were prepared for heterocyclic compounds, these prepared compounds can have inhibitory activity for some bacteria, fungi, and viruses.
Book chapters on the topic "Kettle Point Formation"
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Taber, Douglass F. "The Johnson Synthesis of Paspaline." In Organic Synthesis. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190646165.003.0105.
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Paspaline 3, isolated from the ergot fungus Claviceps paspali, is a Maxi-K channel antagonist, and so a potential lead for the treatment of Alzheimer’s disease. The selective C–H functionalization that converted 1 to 2 was a key step in the synthesis of 3 reported (J. Am. Chem. Soc. 2015, 137, 4968; J. Org. Chem. 2015, 80, 9740) by Jeffrey S. Johnson of the University of North Carolina. The prochiral diketone 4 was the starting point for the assembly of 1. Selective reduction with a commercial strain of yeast set both the relative and the absolute configuration of 5. The ketone interfered with the subsequent acid-catalyzed cyclization of the epoxy alcohol, so it was protected as the tosylhydrazone 6. This set the stage for the direct Bamford– Stevens conversion to the fully-substituted alkene 7. Ireland–Claisen rearrangement of the isobutyrate derived from 7 proceeded with substantial preference for the equatorial diastereomer 8. This was carried on to the methyl ketone 9. Hydroboration of 9 showed substantial axial preference, to deliver, after oxidation, the equatorial aldehyde 10. Intramolecular aldol condensation to 11 followed by hydrogenation and benzyl oxime formation then completed the preparation of 1. Intramolecular Pd-catalyzed acetoxylation has been extensively studied by Sanford (Org. Lett. 2010, 12, 532). The Sanford conditions, carried out on a gram scale, converted 1 into the equatorial diastereomer 2 with remarkable diastereoselectivity. The final carbocyclic ring was then added by vinyl Grignard addition to the derived keto aldehyde 12. Grubbs cyclization gave 13, that on exposure to acid rearranged to the enone 14. Reduction of the ketone occurred from the open face to give an alcohol that then directed hydrogenation from the opposite face, leading to the desired trans-fused ketone. Sulfenylation then completed the synthesis of the ketone 15. At this point, the authors followed Smith (J. Am. Chem. Soc. 1985, 107, 1769) in using the Gassman protocol (J. Am. Chem. Soc. 1974, 96, 5495) to construct the indole. Amination of the sulfur of 15 with N-chloroaniline gave the sulfonium salt, that on exposure to Et3N rearranged to 16. Reductive desulfurization followed by cyclization completed the synthesis of paspaline 3.
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Taber, Douglass F. "The Harran Synthesis of (+)-Roseophilin." In Organic Synthesis. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190200794.003.0107.
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Ansa-bridged prodiginines include (+)-roseophilin B 3 and streptorubin B. The observation that streptorubin B potentiated apoptopic signaling in cell culture led to the development of obatoclax, currently being evaluated for the treatment of leukemia. Patrick G. Harran of UCLA devised (J. Am. Chem. Soc. 2013, 135, 3788) what promises to be a general route to the prodiginines, a key step of which was the cyclization of 1 to 2. In planning the synthesis of 1, the authors took advantage of the relative inertness of a monosubstituted alkene. Friedel-Crafts acylation of 5 proceeded smoothly without affecting the distal double bond. Reduction then completed the preparation of 7. The preparation of 1 continued from the pyrrole 9, prepared from the pyridine 8. Addition of the derived enoate to the aldehyde 10 proceeded smoothly, to give, after oxidation and acid-mediated rearrangement, the furan 12. Selective metalation followed by carboxylation gave the acid 13, which was combined with 7 to give 15. Deprotonation of 15 gave an intermediate that reacted primarily on the pyrrole N. This intermediate was then reacted with diethylchlorophosphite to give, after oxidation, the phosphoramide 16. Advantage was then taken of the organometallic reactivity of the monosubstituted alkene of 16, as Ru-mediated cross metathesis with 17 followed by reduction completed the preparation of 1. The diheteroaryl ketone of 1 is not enolizable. On exposure to KHMDS, the dialkyl ketone will be deprotonated reversibly. Either enolate could add to the diheteroaryl ketone, but only the adduct from deprotonation of the methylene could go on to alkene formation. This net dehydration may likely be driven by phosphoryl transfer to the intermediate alkoxide. The enone 2 is prochiral. Hydrogenation with an enantiopure catalyst proceeded with high de and 67% ee. Remediated intramolecular Friedel-Crafts addition of the dialkyl ketone to the pyrrole followed by acid-mediated rearrangement then delivered (+)-roseophilin 3. There are several points along this synthesis at which diversity could be introduced. This should enable detailed structure–activity studies of the prodiginines.
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Taber, Douglass F. "The Sato/Chida Synthesis of Paclitaxel (Taxol®)." In Organic Synthesis. Oxford University Press, 2017. http://dx.doi.org/10.1093/oso/9780190646165.003.0104.
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Paclitaxel (Taxol®) 3 is widely used in the clinical treatment of a variety of cancers. Takaaki Sato and Noritaka Chida of Keio University envisioned (Org. Lett. 2015, 17, 2570, 2574) establishing the central eight-membered ring of 3 by the SmI2-mediated cyclization of 1 to 2. The starting point for the synthesis was the enantiomerically-pure enone 5, prepared from the carbohydrate precursor 4. Conjugate addition to 5 proceeded anti to the benzyloxy substituent to give, after trapping with formaldehyde and protection, the ketone 6. Reduction and protection followed by hydroboration led to 7, that was, after protection and deprotection, oxidized to 8. The second ring of 3 was added in the form of the alkenyl lithium derivative 9, prepared from the trisylhydrazone of the corresponding ketone. Hydroxyl-directed epoxidation of 10 proceeded with high facial selectivity, leading, after reduction and protection, to the cyclic carbonate 11. Allylic oxidation converted the alkene into the enone, while at the same time oxidizing the benzyl protecting group to the benzoate, to give 12. Reduction of the ketone 12 led to a mixture of diastereomers. In practice, only one of the diastereomers of 1 cyclized cleanly to 2, as illustrated, so the undesired diastereomer from the NaBH4 reduction was oxidized back to the enone for recycling. For convenience, only one of the diastereomers of 2 was carried forward. To establish the tetrasubstituted alkene of 3, the alkene of 2 was converted to the cis diol and on to the bis xanthate 13. Warming to 50°C led to the desired tetrasubstituted alkene, sparing the oxygenation that is eventually required for 3. For convenience, to intercept 16, the intermediate in the Takahashi total synthesis, both xanthates were eliminated to give 14. Hydrogenation removed the disubstituted alkene, and also deprotected the benzyl ether. Oxidation followed by Peterson alkene formation led to 15, that was carried on to the Takahashi intermediate 16 using the now-standard protocol for oxetane construction. It is a measure of the strength of the science of organic synthesis that Masahisa Nakada of Waseda University also reported (Chem. Eur. J. 2015, 21, 355) an elegant synthesis of 3 (not illustrated).
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Taber, Douglass F. "The Williams Synthesis of (-)-4-Hydroxydictyolactone." In Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0083.
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(-)-4-Hydroxydictyolactone 3, representative of the cyclononene xenicanes isolated from the Dictyotacae algae, readily isomerizes thermally to the more stable ( Z )- 6,7-isomer. Attempts to directly form this strained ring system appeared to be fraught with difficulty. David R. Williams of Indiana University envisoned (J. Am. Chem. Soc. 2009, 131, 9038) that use of Suzuki coupling might ameliorate some of the strain, since at the point of commitment to bond formation, the Pd center would be included in the forming ring. This analysis led specifically to the trans ether 1, as cyclization of the trans ether appeared likely to be more facile than would cyclization of the alternative cis diastereomer. The first challenge was the assembly of the array the four contiguous alkylated stereogenic centers of 1. To this end, the Z secondary ester 7 was prepared from the acetonide 4 , available from mannitol, and ( R )-(+)-citronellic acid, prepared by oxidation of the commercial aldehyde. Addition of 7 to LDA led to decomposition, but inverse addition of LDA to a mixture of the ester, TMSCl, and Et3 N smoothly delivered the ketene silyl acetal. On warming, Ireland-Claisen rearrangement of the ketene silyl acetal led to the acid 8 with remarkable diastereocontrol. The last alkylated stereogenic center of 1 was installed by reductive cyclization of the formate ester 9. Again, the cyclization proceeded with remarkable diastererocontrol. Although the intramolecular reaction of in situ prepared allyl metals is well precedented, the addition to a formate ester had not previously been reported. Although 11 appears to be ready for the long-awaited Suzuki coupling, in fact the TIPS protecting group substantially slowed hydroboration. The free alcohol/methyl acetal was the best substrate for hydroboration, but the free alcohol entered into other side reactions. After extensive experimentation, a happy medium was found with the methyl acetal/TBS ether 1. Selenylation of the lactone 12 followed by oxidative elimination of the selenide delivered the expected Z alkene. Removal of the silyl protecting group had to precede introduction of the second alkene, as the product 3 deteriorated rapidly on exposure to the alkaline conditions of TBAF cleavage.
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Taber, Douglass F. "The Nicolaou/Li Synthesis of Tubingensin A." In Organic Synthesis. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780190200794.003.0095.
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The complex indole diterpene alkaloids, isolated both from Aspergillus sp. and from Eupenicillium javanicum, display a wide range of physiological activity. K.C. Nicolaou of Scripps/La Jolla and Ang Li, now at the Shanghai Institute of Organic Chemistry, conceived (J. Am. Chem. Soc. 2012, 134, 8078) a divergent strategy for the assembly of these alkaloids that enabled syntheses of both anominine (not illustrated) and tubingensin A 3. A key step in the assembly of the carbocyclic skeleton of both alkaloids was the radical cyclization of 1 to 2, establishing the second of the two alkylated quaternary centers of 3. The starting point for the preparation of 1 was commercial pulegone 4. Methylation followed by acid-mediated retro aldol condensation delivered the enantiomerically pure 2,3-dimethyl cyclohexanone 5. To maximize yield, the subsequent Robinson annulation was carried out over three steps, formation of the silyl enol ether, condensation of the enol ether with methyl vinyl ketone 6, and base-mediated cyclization and dehydration of the 1,5-diketone to give 7. The secondary hydroxyl group was introduced by exposure to Oxone of the methyl dienol ether derived from 7. The mixture of diastereomers from the radical Ueno-Stork cyclization of 1 was equilibrated to the more stable 2 by exposure to acid. The authors took advantage of the regioselective enolization of 2, preparing the silyl enol ether, which could then be condensed with formaldehyde to give 10. This hydroxy ketone was carried onto 11 over four steps, commencing with silylation and proceeding through Wittig condensation, desilylation, and oxidation. The addition of the Grignard reagent 12 to the aldehyde 11 gave a secondary alcohol, which was readily dehydrated to the diene 13. The diene resisted thermal cyclization, but on exposure to CuOTf at room temperature it was smoothly cyclized and oxidized to 14. The elaboration of the sidechain had already been worked out in the anominine synthesis. The free lactol derived from 14 resisted many nucleophiles, but vinyl magnesium bromide did add. Bis acetylation of the resulting diol followed by Pd-mediated ionization and reduction of the allylic acetate, and reductive removal of the residual acetate, delivered the terminal alkene 15. Metathesis with isobutylene gave 16, which was deprotected to give tubingensin A 3.
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Taber, Douglass. "The Paquette Synthesis of Fomannosin." In Organic Synthesis. Oxford University Press, 2011. http://dx.doi.org/10.1093/oso/9780199764549.003.0096.
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The compact sesquiterpene ( + )-fomannosin 3, isolated from the pathogenic fungus Fomes annonsus, presents an interesting set of challenges for the organic synthesis chemist, ranging from the strained cyclobutene to the easily epimerized cyclopentanone. In the synthesis of 3 developed (J. Org. Chem . 2008, 73, 4548) by Leo A. Paquette of Ohio State University, the cyclopentane was constructed by ring-closing metathesis of 1. The real challenge of the synthesis was the enantiospecific preparation of 1 from D-glucose. The starting point for the preparation of 1 was the glucose derivative 4. Selective acetonide hydrolysis followed by oxidative cleavage gave the ester 5, which on base treatment followed by hydrogenation delivered the endo ester 6. Condensation of the enolate of 6 with formaldehyde proceeded with high diastereoselectivity, to give, after protection, the ester 7. Conversion of the ester to the vinyl group, exposure to methanolic acid and ether formation completed the preparation of 9. The construction of the cyclobutane of 1 was effected by an interesting application of the Negishi reagent (Cp2ZrCl2/2 x BuLi). Complexation of Cp2Zr with the alkene followed by elimination generated an allylic organometallic 11, which added to the released aldehyde to give the cyclobutanes 12 and 13 in a 2.4:1 diastereomeric ratio. Homologation of the aldehyde 13 and subsequent oxidation were straightforward, but subsequent methylenation of the hindered carbonyl was not. At last, it was found that Peterson olefination worked well. Metathesis then delivered the cyclopentene 2. The last carbons of the skeleton were added by intramolecular aldol cyclization of the thioester 16. The seemingly simple task of converting the alkene of 17 into a ketone proved challenging. Eventually, dihydroxylation followed by oxidation, and then SmI2 reduction, completed the transformation. This still left the challenge of controlling the cyclopentane stereogenic center. Remarkably, dehydration and epimerization led to (+)-Fomannosin 3 as a single dominant diastereomer.
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Taber, Douglass F. "The Ma Synthesis of (-)-GB 13." In Organic Synthesis. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199965724.003.0098.
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An investigation of the activity of the Galbulimima alkaloids, exemplified by (-)- GB 13, led to the development of a series of potent thrombin receptor antagonists. Dawei Ma of the Shanghai Institute of Organic Chemistry devised (Angew. Chem. Int. Ed. 2010, 49, 5887) a concise route to 3 based on the coupling of the chirons 1 and 2. The starting point for the preparation of 1 was the unsaturated ester 4. Cyclization using the chiral enamine protocol developed by d’Angelo delivered the keto ester 6. Reduction with NaBH4 proceeded with substantial diastereocontrol to give an intermediate alcohol, which cyclized under acidic conditions to the lactone 1. The preparation of 2 began with dihydroresorcinol 7. Condensation with the enantiomerically pure amine 8 gave the enamine, that was converted to the bromide and cyclized to 9. Hydrogenation with substantial facial control set the ring fusion. Oxidation with 2-iodoxybenzoic acid (IBX) in DMSO introduced unsaturation with high regioselectivity, to give 2. The ketene silyl acetal 10 derived from the lactone 1 added under Mukaiyama conditions across the open face of 2, to give the adduct 11. The same IBX oxidation protocol was used to introduce unsaturation, and the product was equilibrated to give 12. Hydrogenation, again across the open face of the bicyclic enone, set the last stereogenic center of 13. To construct the cyclohexenone 15, it was necessary to oxidize the diol 14 to the keto aldehyde. Others had found that the Swern modification of the Pfitzner-Moffatt oxidation worked well in such cases, minimizing competing lactone formation. Even more useful was the Boger protocol, which returned to the original Pfitzner-Moffatt conditions, activating DMSO with TFAA. Use of DBU in place of the more typical Et3 N then cleanly delivered the aldol product, which was dehydrated and deprotected to give the enone 15. The final ring closure was effected by reduction of the enone with SmI2. The initially formed 16 was partially reduced to the diol under the reaction conditions, necessitating reoxidation with the Dess-Martin reagent. The introduction of unsaturation with the Nicolaou IBX protocol was again successful, even in this more complex and fragile system.
Conference papers on the topic "Kettle Point Formation"
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Bennett, Yvonne, D. Jeffrey Over, and Sarah Hackett. "CONODONTS, MAGNETIC SUSCEPTIBILITY, AND THE FRASNIAN-FAMENNIAN BOUNDARY IN THE KETTLE POINT FORMATION, UPPER DEVONIAN, SUBSURFACE OF WESTERN ONTARIO, CANADA." In GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-333767.
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Kendall, Brian, Jieying Wang, Liyan Xing, Wang Zheng, and Jian Liu. "COUPLED URANIUM AND MOLYBDENUM ISOTOPE INSIGHTS ON LOCAL AND GLOBAL OCEAN REDOX CONDITIONS DURING DEPOSITION OF THE FRASNIAN-FAMENNIAN KETTLE POINT FORMATION, ONTARIO, CANADA." In GSA Annual Meeting in Indianapolis, Indiana, USA - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018am-320161.
Full textReports on the topic "Kettle Point Formation"
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Hamblin, A. P. Detailed outcrop and core measured sections of the Kettle Point formation, southwestern Ontario, with reference to shale gas potential. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2010. http://dx.doi.org/10.4095/285564.
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