- Enzymatic synthesis of optically active lactones via asymmetric bioreduction using ene-reductases from the old yellow enzyme family
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In contrast to the widely studied asymmetric bioreduction of α,β-unsaturated carboxylic acid esters catalyzed by ene-reductases, the reaction applied to lactones remains unexplored. A broad set of ene-reductases was found to reduce various α-, β- and γ-substituted α,β-unsaturated butyrolactones to yield the corresponding saturated non-racemic lactones. Substitution patterns greatly influenced activities and stereoselectivities and lactone products were obtained in moderate to excellent yields; importantly, enzyme-based stereocontrol allowed access to both enantiomers in up to >99% ee. Chiral recognition of a distant γ-center led to kinetic resolution with remarkable enantioselectivities (E values up to 49). An unprecedented case of dynamic kinetic resolution was observed with 3-methyl-5-phenylfuran-2(5H)-one, whereby spontaneous racemization of the substrate furnished the product in up to 73% conversion and >99% ee and 96% de.
- Turrini, Nikolaus G.,Hall, Mélanie,Faber, Kurt
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p. 1861 - 1871
(2015/06/02)
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- Catalytic oxidation of furan and hydrofuran compounds 8. Synthesis of 5-ethoxycarbonyl-4-hydroxy-3-oxo-2(3H)-furanone by the oxidation of furfural in the system aqueous H2O2-VOSO4-ethanol
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The special features of the oxidation of furfural by aqueous hydrogen peroxide in the presence of vanadyl sulfate and ethanol has been studied for the first time. It has been established that this reaction proceeds with the formation of previously unknown
- Poskonin
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experimental part
p. 295 - 300
(2009/04/03)
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- Catalytic oxidation of furan and hydrofuran compounds. 5. Hydroxy- and ethoxydihydrofurans and ethoxyfuran - New products from the reaction of furan with hydrogen peroxide
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It was established for the first time by chromato-mass spectrometry that 2-X-5-Y-2,5-dihydrofurans (X, Y = OH, OEt) and 2-ethoxyfuran are formed during the oxidation of furan by hydrogen peroxide in a mixture of water and ethanol in the presence of VOSO4. Stable tautomeric forms of 2-hydroxy- and 2,5-dihydroxyfurans - 2(5H)-furanone and 5-ethoxy-2(5H)-furanone respectively - were isolated from the reaction mixture. A probable scheme for the main reaction paths is proposed. 1999 Kluwer Academic/Plenum Publishers.
- Poskonin,Badovskaya,Povarova
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p. 900 - 906
(2007/10/03)
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- Stereospecific radical addition of isopropanol and n-butanal to (5R)-(l-menthyloxy)furan-2(5H)-one
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The radical addition of PriOH and n-butanal to (5R)-5-(l-menthyloxy)furan-2(5H)-one occurs regio- and diastereospecifically at position 4 of the furanone ring. - Keywords: diastereoselectivity, regioselectivity, radical addition, (5R)-5-(l-menthyloxy)furan-2(5H)-one, 2-propanol, n-butanal, (1)H, (13)C NMR spectra
- Belokon', Yu. N.,Kochetkov, K. A.,Moskalenko, M. A.,Raevsky, N. I.,Savel'eva, T. F.,et al.
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p. 517 - 519
(2007/10/02)
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- HYPERVALENT IODINE OXIDATION: SYNTHESIS OF 5-SUBSTITUTED-2(5H)-FURANONES USING IODOSOBENZENE
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Hypervalent iodine oxidation of 2-(trimethylsilyloxy)furan with iodosobenzene: boron trifluoride etherate in the presence of various nucleophiles yields 5-substituted-2(5H)-furanones.
- Moriarty, Robert M.,Vaid, Radhe K.,Hopkins, Thomas E.,Vaid, Beena K.,Tuncay, Atilla
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p. 3019 - 3022
(2007/10/02)
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- THE SERIES OF SUBSTITUTED BUTANOLIDES AND BUTENOLIDES. V. SYNTHESIS OF 4-HYDROXY-2-BUTEN-4-OLIDE AND ITS DERIVATIVES ON THE BASIS OF THE REACTION OF FURFURAL WITH HYDROGEN PEROXIDE
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New methods were developed for the synthesis of 4-hydroxy-2-buten-4-olide and its derivatives on the basis of the reaction of furfural with hydrogen peroxide in the presence of the compounds of group VI elements and vanadium.The dependence of the yield of 4-hydroxy-2-buten-4-olide on the type of catalyst was established, and the optimum conditions for its production were determined.
- Poskonin, V. V.,Badovskaya, L. A.,Gavrilova, S. P.,Kul'nevich, V. G.
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p. 1535 - 1539
(2007/10/02)
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- Photo-oxygenation des derives de l'hydroxymethyl-5 furfural-2
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Photosensitized oxygenations in alcoholic solution of the furfural compounds 1,6-9 and the furanic compounds 10-17 yield the hydroxybutenolides 2a, 1, 20, 21, 22, the alkoxybutenolides 5, 19, 23, 24 and the unsaturated compounds 25 and 26.With rose bengal fixed on the polysaccharide resin Sephadex A 25 as sensitizer, the quantum yields of singlet oxygen formation in methanol or ethanol are higher (19 to 116percent) than those obtained with the commercial resin Sensitox.Kinetic results for these photo-oxygenations show the electronic influence of the substitution on C2 or C5.Depending on these substituants, several reaction pathways can be envisaged in order to explain the formation of the products.
- Cottier, Louis,Descotes, Gerard,Nigay, Henri,Parron, Jean-Claude,Gregoire, Veronique
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p. 844 - 850
(2007/10/02)
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- SINGLET OXYGEN PHOTOOXYGENATION OF FURANS. ISOLATION AND REACTIONS OF (4+2)-CYCLOADDITION PRODUCTS (UNSATURATED SEC.-OZONIDES)
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Tetraphenylporphin-photosensitized oxygenations of furan (19), 2-methylfuran (26), 2-ethylfuran (39), furfurylalcohol (24), 2-acetylfuran (40), 2-methoxyfuran (42), 2,5-dimethylfuran (30), furfural (25) and 5-methylfurfural (41) in non-polar aprotic solvents yield the corresponding monomeric unsaturated secondary ozonides due to a (4+2)-cycloaddition of singlet oxygen to these furans.With the exception of the ozonide derived from 25, the ozonides were isolated and characterized (1H- and 13NMR spectra, etc.).In non-polar aprotic solvents, the ozonides derived from 19, 26 and 39 undergo thermal rearrangements to the corresponding cis-diepoxides and epoxylactones.Ozonide 31, derived from 30, however, dimerizes; only above about 60 deg is a cis-diepoxide formed from either 31 or its dimer.Rose bengal-photosensitized oxygenations of the furans in alcohols (MeOH, EtOH, i-PrOH) also produce the corresponding ozonides as the primary products of (4+2)-cycloadditions of singlet oxygen to these furans.However, reactions of the alcohols with the ozonides are too fast to allow the ozonides to be isolated.Instead, the same products are obtained as are isolated from reactions carried out by dissolving the ozonides in the alcohols.Depending on the structure of the ozonide, three pathways are available to ozonide/alcohol (ROH) interactions: (1) addition of ROH to yield alkoxy hydroperoxides; one out of several possible isomers is formed in a completely stereoselective and regiospecific reaction; (2) elimination of a bridgehead proton by ROH as a base, as observed with the ozonide derived from 19 to give hydroxy butenolide (78) in yields between 20 and 60percent; and (3) ROH-attack on a carbonyl side-chain under elimination of the corresponding alkyl ester, as observed with furfural photooxygenation which yielded hydroxy butenolide (78) in high yields (>95percent).Interaction of ozonide 31 with tert.-butyl alcohol (t-BuOH) yields quantitatively cis-3-oxo-1-butenylacetate (81) by a Baeyer-Villiger-type rearrangement with vinyl group migration.Hydrogen-bonding between the alcohol and the peroxy group of the ozonides assist the heterolysis of the C-O bonds in the ozonides; the most stabilized cation develops.Front-attack of ROH on this cation explains the stereoselectivity as well as the regiospecificity of the alkoxy hydroperoxide formation; with a bulky alcohol like t-BuOH, ROH-attack on the cation is sterically hindered thus allowing a rearangement to occur. 1,3-Dipolar cycloaddition of p-nitrophenyl azide to ozonide 31 proceeds stereoselectively to one of the isomers 87a/87b.Finally, kinetic results of furan photooxygenation in methanol show the following order of furan-reactivity towards singlet oxygen: 30> 42> 26> 19> 41> 25, with absolute rate constants ranging from 1.8E8(with 30)to 8.4E4 M-1 s-1 (with 25).
- Gollnick, Klaus,Griesbeck, Axel
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p. 2057 - 2068
(2007/10/02)
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- The Synthesis of a Cyclopropane Amino Acid, trans-α-(Carboxycyclopropyl)glycine, found in Ackee Seed
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trans-α-(Carboxycyclopropyl)glycine, a constituent of ackee seed (Blighia sapida), has been synthesized via the key intermediate ethyl (E)-4,4-diethoxybut-2-enoate.
- Landor, Stephen R.,Landor, Phyllis, D.,Kalli, Michael
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p. 2921 - 2926
(2007/10/02)
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- A facile two synthon approach to the camptothecin skeleton
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A synthesis of deethyldesoxycamptothecin via the reaction of two readily accessible synthons is described. One of the synthons constitutes the ABC ring system of camptothecin, while the second provides all the C atoms of the rings D and E. The synthetic approach is suited for the total synthesis of camptothecin analogues.
- Walraven,Pandit
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p. 321 - 327
(2007/10/02)
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