- Total Synthesis of (-)-Coriolin
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The first total synthesis of the diterpene coriolin in the enantiomerically pure (-)-form is described.The key step is the photocemical generation of the 3,3,6-trimethyltricyclo2,8>octane-4,7-dione building blocks (-)-12a and (-)-12b in solutions of exceptionally high concentrations (>/=20 percent).It involves the site selective oxadi-?-methane rearrangement of one β,γ-enone partial chromofore of the β,γ-unsaturated ε-diketones (-)-9a and (-)-9b which are obtained from bicyclooct-7-ene-2,5-dione, (+/-)-7, by optical resolution, in multigram batch preparations, via the tartarate monoacetals followed by trimethylation. (-)-coriolin is thus accessible in 14 steps from (+/-)-7.
- Demuth, Martin,Ritterskamp, Peter,Weigt, Eva,Schaffner, Kurt
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- Synthesis and Chiroptical Properties of 5,7-Dioxobicyclooct-2-ene and Bicyclooctane-2,5-dione
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5,7-Dioxobicyclooct-2-ene (5) and its dihydro derivative 9 were obtained in racemic from by sequential Diels-Alder addition of maleic anhydride to hydroquinone, hydrolysis of the adduct to diacid 7, oxidative decarboxylation of 7 with lead tetraacetete, and catalytic hydrogenation.Partial resolution of 7 with brucine or quinine afforded (-)-5 in 80-86percent enantiomeric purity.Katalization of (+/-)-5 with diethyl (R,R)-(+)-tartrate and subsequent chromatographic separation of the diastereomeric monoketals gave optically pure samples of both antipodes of the enedione.This substance was found to interact powerfully with plane and circularly polarized light.The Cotton effects observed in the ORD and CD spectra of (-)-5 indicate that its absolute configuration is 1S,4S when analyzed by the generalized octant rule.It follows that (-)-9, its hydrogenation product, is 1R,4R.
- Hill, Richard K.,Morton, Gerald H.,Peterson, John R.,Walsh, James A.,Paquette, Leo A.
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- LOW-MOLECULAR COMPOUND, POLYMER, MATERIAL FOR ELECTRONIC DEVICES, COMPOSITION FOR ELECTRONIC DEVICES, ORGANIC ELECTROLUMINESCENT ELEMENT, ORGANIC SOLAR CELL ELEMENT, DISPLAY AND LIGHTING EQUIPMENT
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A subject for the invention is to provide compounds where a film formation can be made by a wet film formation method, a heating temperature at the film formation is low, the film formed therefrom has high stability, and the other layers can be laminated thereon by a wet film formation method or another method. The compounds are usable as a material for electronic device which decreases little in charge transport efficiency or luminescent efficiency and which have excellent driving stability. The invention resides in a compound and a polymer which are characterized by having a elimination group of a specific structure and in an organic compound characterized by having a elimination group having a low elimination temperature.
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- Efficient bioreduction of bicyclo[2.2.2]octane-2,5-dione and bicyclo[2.2.2]oct-7-ene-2,5-dione by genetically engineered Saccharomyces cerevisiae
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A screening of non-conventional yeast species and several Saccharomyces cerevisiae (baker's yeast) strains overexpressing known carbonyl reductases revealed the S. cerevisiae reductase encoded by YMR226c as highly efficient for the reduction of the diketones 1 and 2 to their corresponding hydroxyketones 3-6 (Scheme 1) in excellent enantiomeric excesses. Bioreduction of 1 using the genetically engineered yeast TMB4100, overexpressing YMR226c, resulted in >99% ee for hydroxyketone (+)-4 and 84-98% ee for (-)-3, depending on the degree of conversion. Baker's yeast reduction of diketone 2 resulted in >98% ee for the hydroxyketones (+)-5 and (+)-6. However, TMB4100 led to significantly higher conversion rates (over 40 fold faster) and also a minor improvement of the enantiomeric excesses (>99%). The Royal Society of Chemistry 2006.
- Friberg, Annika,Johanson, Ted,Franzen, Johan,Gorwa-Grauslund, Marie F.,Frejd, Torbjoern
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p. 2304 - 2312
(2008/03/13)
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- Ketonization equilibria of phenol in aqueous solution
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The two keto tautomers of phenol (1), cyclohexa-2,4-dienone (2) and cyclohexa-2,5-dienone (3), were generated by flash photolysis of appropriate precursors in aqueous solution, and the pH-rate profiles of their enolization reactions, 2 → 1 and 3 → 1, were measured. The rates of the reverse reactions, 1 → 2 and 1 → 3, were determined from the rates of acid-catalyzed hydron exchange at the ortho- and para-positions of 1; the magnitude of the kinetic isotope effect was assessed by comparing the rates of hydrogenation of phenol-2t and -2d. The ratios of the enolization and ketonization rate constants provide the equilibrium constants of enolization, pKE(2, aq, 25°C) = -12.73 ± 0.12 and pKE(3, aq, 25°C) = -10.98 ± 0.15. Combination with the acidity constant of phenol also defines the acidity constants of 2 and 3 through a thermodynamic cycle. These ketones are remarkably strong carbon acids: pKa(2) = -2.89 ± 0.12 and pKa(3) = -1.14 ± 0.15. They disappear by proton transfer to the solvent with lifetimes, τ(2) = 260 μs and τ(3) = 13 ms, that are insensitive to pH in the range from 3-10.
- Capponi, Marco,Gut, Ivo G.,Hellrung, Bruno,Persy, Gaby,Wirz, Jakob
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p. 605 - 613
(2007/10/03)
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- Synthesis and Chiroptical Properties of (1S)-2H2>Bicycloocta-2,5,7-triene (2,5-Dideuteriobarrelene)
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(1S)-2H2>Bicycloocta-2,5,7-triene (1) (2,5-dideuteriobarrelene) was prepared from (1R)-bicyclooct-7-ene-2,5-dione by LiAlD4 reduction followed by pyrolysis of the bis ester of the resulting dideuter
- Lightner, David A.,Paquette, Leo A.,Chayangkoon, Paochai,Lin, Ho-Shen,Peterson, John R.
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p. 1969 - 1973
(2007/10/02)
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- Epoxidation of Barrelene: Preparation and Properties of Oxahomobarrelenes
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A four-step synthesis makes barrelene (1) readily accessible on a 1-2 g scale.Upon epoxidation with KHCO3-buffered m-chloroperbenzoic acid 1 yields the mono- (2b), both the endo,exo- and exo,exo-isomeric bis- (3b and 4b) as well as the trisepoxide 5b.In the presence of traces of acid 2b very rapidly rearranges to cycloheptatriene-7-carbaldehyde (15), 5b undergoes a facile acid-catalyzed rearrangement to 4,7,11-trioxatrishomocubane (16).Under basic and neutral conditions 5b is stable towards virtually any nucleophile, its three epoxide rings can only be opened underreductive conditions with solvated electrons.On the other hand, endo,exo-dioxadihydrobishomobarrelene 20 and oxatrishomobarrelene 23 are readily attacked at the oxirane rings by lithium iodide/disodium hydrogen phosphate.
- Weitemeyer, Christian,Preuss, Thomas,Meijere, Armin de
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p. 3993 - 4005
(2007/10/02)
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