- Highly Selective Asymmetric Intramolecular Selenocyclisation
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Asymmetric intramolecular selenocyclisation of alkenoic acids, alkenols and olefinic urethanes using chiral ferrocenylselenenyl cations proceeds smoothly to give the corresponding lactones, cyclic ethers and nitrogen-heterocyclic compounds, respectively, in moderate yields with very high diastereoselectivities.
- Nishibayashi, Yoshiaki,Srivastava, Sanjay Kumar,Takada, Hiroya,Fukuzawa, Shin-ichi,Uemura, Sakae
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- A FACILE SYNTHESIS OF OPTICALLY PURE VALEROLACTONE AND β-HYDROXY VALEROLACTONE FROM A COMMON SUGAR-DERIVED PRECURSOR
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Both title compounds were obtained in four steps from 2R, 3R-dihydroxy-4R-valerolactone 5 readily available from D-ribonolactone.
- Papageorgiou, Christos,Benezra, Claude
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- Carboxyl Group-Directed Iridium-Catalyzed Enantioselective Hydrogenation of Aliphatic ?-Ketoacids
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Although the transition metal-catalyzed asymmetric hydrogenation of aromatic ketones has been extensively explored, the enantioselective hydrogenation of aliphatic ketones remains a challenge because chiral catalysts cannot readily discriminate between the re and si faces of these ketones. Herein, we report a carboxyl-directing strategy for the asymmetric hydrogenation of aliphatic ?-ketoacids. With catalysis by iridium complexes bearing chiral spiro phosphino-oxazoline ligands, hydrogenation of aliphatic ?-ketoacids afforded chiral ?-hydroxylacids with high enantioselectivity (up to 99% ee). Mechanistic studies revealed that the carboxyl group of the substrate directs hydrogen transfer and ensures high enantioselectivity. Density functional theory calculations suggested the occurrence of chiral induction involving a hydrogen-hydrogen interaction between a hydride on the iridium atom and the substituent on the oxazoline ring of the ligand, and on the basis of the calculations, we proposed a catalytic cycle involving only Ir(III), which differs from the Ir(III)/Ir(V) catalytic cycle that operates in the hydrogenation of α,β-unsaturated carboxylic acids.
- Li, Mao-Lin,Li, Yao,Li, Yi-Hao,Pan, Jia-Bin,Song, Song,Zhou, Qi-Lin,Zhu, Shou-Fei
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p. 10032 - 10039
(2020/10/18)
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- Iridium-Catalyzed Asymmetric Hydrogenation of ?- A nd ?-Ketoacids for Enantioselective Synthesis of ?- A nd ?-Lactones
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A highly efficient asymmetric hydrogenation of ?- A nd ?-ketoacids was developed by using a chiral spiro iridium catalyst (S)-1a, affording the optically active ?- A nd ?-hydroxy acids/lactones in high yields with excellent enantioselectivities (up to >99% ee) and turnover numbers (TON up to 100000). This protocol provides an efficient and practical method for enantioselective synthesis of Ezetimibe.
- Hua, Yun-Yu,Bin, Huai-Yu,Wei, Tao,Cheng, Hou-An,Lin, Zu-Peng,Fu, Xing-Feng,Li, Yuan-Qiang,Xie, Jian-Hua,Yan, Pu-Cha,Zhou, Qi-Lin
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supporting information
p. 818 - 822
(2020/02/15)
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- Chiron approach towards optically pure γ-valerolactone from alanine
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A concise synthesis of both enantiomers of γ-valerolactone has been developed from commercially available Alanine. The key steps in the synthesis of these γ-Lactones are DIBAL-H reduction of ester (9) followed by in situ Wittig reaction with EtO2CCH = PPh3 ylide (13) (Z/E = 1: 3.5) and one pot lactonization triggered by deprotection of O-TBS ether (14).
- Datrika, Rajender,Kallam, Srinivasa Reddy,Katta, Rambabu,Siddaiah, Vidavalur,Pratap
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p. 2801 - 2808
(2018/12/04)
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- Facile Synthesis of Optically-Active Γ-Valerolactone from Levulinic Acid and Its Esters Using a Heterogeneous Enantio-Selective Catalyst
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Abstract: Optically-active γ-valerolactone was synthesized by the enantio-selective hydrogenations of levulinic acid and its esters. A tartaric acid-NaBr-modified nickel catalyst produced the optically-active γ-valerolactone with a 60% enantiomeric excess (ee), almost quantitative conversion and chemoselectivity. The synthesis of the optically-active γ-valerolactone using the enantio-selective heterogeneous catalyst would be promising for the large-scale industrial production from levulinic acid and its esters, which can be obtained by the acid-catalyzed dehydration of cellulosic fraction of biomass. Graphical Abstract: [Figure not available: see fulltext.].
- Osawa, Tsutomu,Tanabe, Yuya
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p. 824 - 830
(2018/01/27)
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- Combination of Metal-Catalyzed Cycloisomerizations and Biocatalysis in Aqueous Media: Asymmetric Construction of Chiral Alcohols, Lactones, and γ-Hydroxy-Carbonyl Compounds
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The combination of the metal-catalyzed cycloisomerization of alkynes containing a tethered nucleophile as substituent in aqueous media (followed by the spontaneous hydrolysis, hydroalkoxylation, or aminolysis of the transiently formed five-membered heterocycles) with the subsequent enantioselective ketone bioreduction (mediated by KREDs) has been achieved. The overall transformations, which formally involve a three-step one-pot reaction, provide a variety of enantiopure valuable molecules (e.g., 1,4-diols, lactones, and γ-hydroxy-carbonyl compounds (carboxylic acids, esters, and amides)) with high conversions and enantioselectivities and under mild reaction conditions, disclosing the concept of integrated metal-catalyzed cycloisomerizations of alkynes and enzymatic catalysis in water.
- Rodríguez-álvarez, María J.,Ríos-Lombardía, Nicolás,Schumacher, S?ren,Pérez-Iglesias, David,Morís, Francisco,Cadierno, Victorio,García-álvarez, Joaquín,González-Sabín, Javier
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p. 7753 - 7759
(2017/11/10)
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- Sodium Ion as the Most Essential and Effective Element for the Enantio-Differentiating Hydrogenation of Prochiral Ketones over Tartaric Acid Modified Ni Catalyst
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Abstract: In order to investigate the role of metal ions on a tartaric acid modified nickel catalyst, the enantio-differentiating hydrogenations of methyl acetoacetate and methyl levulinate were carried out. The effects of the addition of 17 metal salts of acetic acid on the enantio-selectivity and the hydrogenation rate were investigated during the hydrogenation of methyl acetoacetate. Among the examined metal salts, the addition of NaBr caused the great increase in the enantio-selectivity and the hydrogenation rate during the hydrogenations of both methyl acetoacetate and methyl levulinate. Based on the strength of the interaction between the metal salts of tartaric acid and the substrate, the sodium salts would have the strongest interaction with the substrate, hence, this would be attributed to the highest enantio-selectivity and hydrogenation rate for the sodium salts of tartaric acid. Graphical Abstract: [Figure not available: see fulltext.]
- Osawa, Tsutomu,Tanabe, Yuya,Fujiwara, Manabu
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p. 686 - 692
(2017/03/08)
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- Stability of gamma-valerolactone under neutral, acidic, and basic conditions
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Dry gamma-valerolactone (GVL) is stable for several weeks at 150?°C and its thermal decomposition only proceeds in the presence of appropriate catalysts. Since GVL does not react with water up to 60?°C for several weeks, it could be used as a green solvent at mild conditions. At higher temperatures, GVL reacts with water to form 4-hydroxyvaleric acid (4-HVA) and reaches the equilibrium in a few days at 100?°C. Aqueous solutions of acids (HCl and H2SO4) catalyze the ring opening of GVL even at room temperature, which leads to the establishment of an equilibrium between GVL, water, and 4-HVA. Although the 4-HVA concentration would be below 4?mol% in the presence of acids, it could be higher than the concentration of a reagent or a catalyst precursor, not to mention a catalytically active species. The latter could be especially worrisome as 4-HVA could be an excellent bi- or even a tri-dentate ligand for transition metals. Aqueous solution of bases (NaOH and NH4OH) also catalyzes the reversible ring opening of GVL. While in the case of NaOH, the product is the sodium salt of 4-hydroxyvalerate, the reversible reaction of GVL, with NH4OH results in the formation of 4-hydroxyvaleric amide. The reversible ring opening of (S)-GVL in the presence of HCl or NaOH has no effect on the stability of the chiral center.
- Wong, Claire Yuet Yan,Choi, Alex Wing-Tat,Lui, Matthew Y.,Fridrich, Bálint,Horváth, Attila K.,Mika, László T.,Horváth, István T.
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p. 423 - 429
(2017/02/23)
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- Stereoselective synthesis of (R)-(?) and (S)-(+)-phoracantholide I from (R)-(+)-γ-valerolactone
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A concise total synthesis of (R)-(?)-phoracantholide I 1 and (S)-(+)-phoracantholide I 2 has been developed from (R)-(+)-γ-valerolactone 6. The key steps in the synthesis of these macrolides involved enzymatic reduction of Levulinic ester 4 by asymmetric dehydrogenase, Z-selective Wittig reaction of (4-carboxybutyl)triphenylphosphonium ylide 11 with lactol 7, and cyclization of seco-acid 8 using either a Yamaguchi lactonization protocol or a Mitsunobu protocol to afford (R)-(?)-phoracantholide I and (S)-(+)-phoracantholide I respectively.
- Datrika, Rajender,Kallam, Srinivasa Reddy,Khobare, Sandip R.,Gajare, Vikas S.,Kommi, Muralikrishna,Rama Mohan,Siddaiah, Vidavalur,Pratap
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p. 603 - 607
(2016/07/11)
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- Application of homochiral alkylated organic cages as chiral stationary phases for molecular separations by capillary gas chromatography
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Molecular organic cage compounds have attracted considerable attention due to their potential applications in gas storage, catalysis, chemical sensing, molecular separations, etc. In this study, a homochiral pentyl cage compound was synthesized from a condensation reaction of (S,S)-1,2-pentyl-1,2-diaminoethane and 1,3,5-triformylbenzene. The imine-linked pentyl cage diluted with a polysiloxane (OV-1701) was explored as a novel stationary phase for high-resolution gas chromatographic separation of organic compounds. Some positional isomers were baseline separated on the pentyl cage-coated capillary column. In particular, various types of enantiomers including chiral alcohols, esters, ethers and epoxides can be resolved without derivatization on the pentyl cage-coated capillary column. The reproducibility of the pentyl cage-coated capillary column for separation was investigated using nitrochlorobenzene and styrene oxide as analytes. The results indicate that the column has good stability and separation reproducibility after being repeatedly used. This work demonstrates that molecular organic cage compounds could become a novel class of chiral separation media in the near future.
- Xie, Shengming,Zhang, Junhui,Fu, Nan,Wang, Bangjin,Hu, Cong,Yuan, Liming
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- Direct asymmetric reduction of levulinic acid to gamma-valerolactone: synthesis of a chiral platform molecule
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Levulinic acid was directly converted to optically active (S)-gamma-valerolactone, a proposed biomass-based chiral platform molecule. By using a SEGPHOS ligand-modified ruthenium catalyst in methanol as a co-solvent, eventually, 100% chemoselectivity, and 82% enantioselectivity were achieved. The effect of the catalyst composition and reaction parameters on the activity and selectivity was investigated in detail. The conversion of a "real" biomass derived levulinic acid to optically active GVL without decreasing the enantioselectivity was also demonstrated.
- Tukacs, József M.,Fridrich, Bálint,Dibó, Gábor,Székely, Edit,Mika, László T.
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p. 5189 - 5195
(2015/12/05)
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- P-Stereogenic pincer iridium complexes: Synthesis, structural characterization and application in asymmetric hydrogenation
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P-Stereogenic PNP type pincer iridium complexes PNPtBuMeIrH2Cl (3) and PNPtBuMeIrH3 (4) were synthesized in reasonable yields and characterized by 1H NMR, 13C NMR, 31P NMR, HRMS and/or single crystal X-ray diffraction. The ORTEP diagram shows that the coordination geometry around the iridium center of complex 3 is approximately octahedral. The chlorinated iridium complex (3) and/or the trihydride iridium complex (4) were used as catalysts in the asymmetric hydrogenation of ketones, olefins and quinoline to provide the desired products with up to 17% enantioselectivity.
- Yang, Zehua,Wei, Xuan,Liu, Delong,Liu, Yangang,Sugiya, Masashi,Imamoto, Tsuneo,Zhang, Wanbin
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- Stereodivergent preparation of valuable γ- Or δ-hydroxy esters and lactones through one-pot cascade or tandem chemoenzymatic protocols
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A series of enantiopure hydroxy esters and lactones has been synthesized in a chemodivergent manner via alcohol dehydrogenase (ADH) reduction of the corresponding keto esters by means of cascade or tandem protocols. Thus, ADH from Rhodococcus ruber (ADH-A) or Lactobacillus brevis (LBADH) afforded both antipodes in a very selective way when dealing with small derivatives. With bulkier substrates, ADH from Ralstonia sp. (RasADH) was successfully employed to achieve the synthesis of enantioenriched γ- or δ-hydroxy esters. To isolate the corresponding lactones, two different approaches were followed: a cascade reaction by spontaneous cyclization of the hydroxy ester intermediate, or a one-pot two-step tandem protocol. Moreover, a chemoenzymatic route was designed to obtain a chiral brominated lactone, which enabled further modifications in a sequential fashion by Pd-catalyzed reactions, affording relevant functionalized lactones.
- Diaz-Rodriguez, Alba,Borzeicka, Wioleta,Lavandera, Ivan,Gotor, Vicente
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p. 386 - 393
(2014/03/21)
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- Biocatalytic oxidation of 1,4-diols and γ-lactols into γ-lactones: Application to chemoenzymatic synthesis of drospirenone
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Oxidation of 1-alkyl-1,4-butanediols with Acetobacter aceti MIM 2000/28 gave the corresponding γ-lactones in good yields. The biotransformation occurred with intermediate formation of γ-lactols, which are also substrates for oxidation with Acetobacter aceti MIM 2000/28, as validated by selective biotransformation of 6β,7β;15β,16β-dimethylene-3- oxo-17α-pregn-4-en-21,17-carbolactol to drospirenone.
- Romano, Diego,Contente, Martina,Granato, Tiziana,Remelli, William,Zambelli, Paolo,Molinari, Francesco
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p. 735 - 737
(2013/07/26)
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- Access to lactone building blocks via horse liver alcohol dehydrogenase-catalyzed oxidative lactonization
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The oxidative lactonization of 1,4-, 1,5-, and 1,6-diols using horse liver alcohol dehydrogenase (HLADH) is reported. Molecular oxygen was used as terminal electron acceptor by utilization of the laccase-mediator concept to regenerate the oxidized nicotinamide cofactor and producing water as sole byproduct. Spontaneous hydrolysis of the lactone products was identified as a major limiting factor toward preparative application of the system, which can be alleviated by using a two liquid phase approach to extracting the product into an organic solvent.
- Kara, Selin,Spickermann, Dominik,Schrittwieser, Joerg H.,Weckbecker, Andrea,Leggewie, Christian,Arends, Isabel W. C. E.,Hollmann, Frank
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p. 2436 - 2439
(2013/11/19)
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- Convergent syntheses of 3,6-dihydroxydec-4-enolides
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The total syntheses of the 3,6-dihydroxydecanolide from Cordyceps militaris and the novel C-3 epimer are reported using a diastereoselective Nozaki-Hiyama-Kishi reaction in the key cyclization to generate the 6R stereocenter.
- Killen, Jonathan C.,Axford, Lorraine C.,Newberry, Sarah E.,Simpson, Thomas J.,Willis, Christine L.
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supporting information; experimental part
p. 4194 - 4197
(2012/10/08)
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- Synthesis of optically active γ-valerolactone and γ-nonanolactone via optical resolution using chiral amine derived from amino acid
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Optically active γ-valerolactone and γ-nonanolactone have been synthesized via optical resolution using a newly developed chiral amine derived from L-phenylalanine. Both racemic γ-lactones were transformed to corresponding diastereomeric amides by amidation with the optical resolution agent. Fractional crystallization of diastereomeric amides, recrystallization of each diastereomer, and subsequent hydrolysis gave optically active γ-valerolactone and γ-nonanolactone with sufficient enantiomeric excess and isolated yield. The optical resolution agent was recovered after hydrolysis.
- Yumoto, Kenichi,Hasegawa, Morifumi,Toshima, Hiroaki
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experimental part
p. 421 - 431
(2010/09/05)
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- A convenient route to chiral γ-lactones via asymmetric hydrogenation of γ-ketoesters using the RuCl3-BINAP-HCl catalytic system
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A convenient one-step synthesis of chiral γ-lactones has been performed. The method is based on enantioselective hydrogenation of γ-ketoesters using the RuCl3-BINAP-HCl catalytic system. Chiral γ-lactones (91-99% ee) have been isolated in 57-88% yield.
- Starodubtseva, Eugenia V.,Turova, Olga V.,Vinogradov, Maxim G.,Gorshkova, Lilia S.,Ferapontov, Vladimir A.,Struchkova, Marina I.
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experimental part
p. 11713 - 11717
(2009/04/11)
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- Tellurium/lithium exchange reactions in the synthesis of spiroketals and 1,6-dioxygenated systems
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1,4-C,O-dianions have been generated through concomitant acid/base and tellurium/lithium exchange reactions. The di-lithium salts were transmetallated with cerium chloride to the corresponding di-cerium salts and subsequently reacted with lactones and carboxylic acid anhydrides to yield the respective spiroketals. The di-lithium entities were also converted into the corresponding cyanocuprates that add in a 1,4-manner to 2-cyclohexen-1-one to form 1,6-dioxygenated compounds.
- Dos Santos, Alcindo A.,Princival, Jefferson L.,Comasseto, Jo?o V.,de Barros, Simone M.G.,Neto, José E. Brainer
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p. 5167 - 5172
(2008/02/01)
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- Enantioselective hydrogenation of levulinic acid esters in the presence of the RuII-BINAP-HCl catalytic system
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The rate of hydrogenation of γ-ketoesters MeCOCH2CH 2COOR (R = Et, Pri, But) in the presence of the chiral RuII-BINAP catalyst (BINAP is 2,2′- bis(diphenylphosphino)-1,1′-binaphthyl) greatly increases upon the addition of 5-10 equivalents of HCl with respect to ruthenium. In the hydrogenation of ethyl levulinate, the optically active γ-hydroxy ester initially formed would cyclize by ~95% to give γ-valerolactone with optical purity of 98-99% ee. When the Ru(COD)(MA)2-BINAP-HCl catalytic system is used (COD is 1,5-cyclooctadiene, MA is 2-methylallyl), complete conversion of the ketoester (R = Et) in EtOH is attained in 5 h at 60°C under an H2 pressure of 60-70 atm.
- Starodubtseva,Turova,Vinogradov,Gorshkova,Ferapontov
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p. 2374 - 2378
(2007/10/03)
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- Kinetic resolution and chemoenzymatic dynamic kinetic resolution of functionalized γ-hydroxy amides
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(Chemical Equation Presented) An efficient kinetic resolution of racemic γ-hydroxy amides 1 was performed via Pseudomas cepacia lipase (PS-C)-catalyzed transesterification. The enzyme PS-C tolerates both variation in the chain length and different functionalities giving good to high enantioselectivity (E values of up to >250). The combination of enzymatic kinetic resolution with a ruthenium-catalyzed racemization led to a dynamic kinetic resolution. The use of 2,4-dimethyl-3-pentanol as a hydrogen source to suppress ketone formation in the dynamic kinetic resolution yields the corresponding acetates in good yield and good to high enantioselectivity (ee's up to 98%). The synthetic utility of this procedure was illustrated by the practical synthesis of the versatile intermediate γ-lactone (R)-5-methyltetrahydrofuran-2-one.
- Fransson, Ann-Britt L.,Boren, Linnea,Pamies, Oscar,Baeckvall, Jan-E.
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p. 2582 - 2587
(2007/10/03)
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- Process-scale preparation of enantiomerically pure γ-lactones by asymmetric hydrogenation of γ-ketoesters and comparative tests of the sensory properties of some antipodes
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A reliable methodology, applicable on a process-scale level, for producing enantiomerically pure chiral γ-lactones by enantioselective hydrogenation of γ-ketoesters, followed by cyclisation of the resulting γ-hydroxyesters, has been developed. The multi-step procedure was transformed into a one-pot reaction. A very efficient chiral Ru-complex, based on the biheteroaromatic diphosphine ligand tetraMe-BITIOP, was developed as a catalyst, capable of coupling fast kinetics with high stereoselection levels. Its structure was fully elucidated through 31P NMR, EPR and X-ray single-crystal analyses. The optimal experimental conditions are as follows: hydrogen pressure=30psi, S/C ratio=2000, 30% in weight substrate concentration. Yields are quantitative and enantiomeric excesses in the range 98-99.9%. Sensorial tests on the antipodes of two γ-lactones demonstrated the very different properties of the enantiomers.
- Benincori, Tiziana,Rizzo, Simona,Pilati, Tullio,Ponti, Alessandro,Sada, Mara,Pagliarini, Ella,Ratti, Simona,Giuseppe, Celentano,De Ferra, Lorenzo,Sannicolo, Franco
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p. 2289 - 2297
(2007/10/03)
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- Enzymatic Resolution of 5-Phenylselanyltetrahydro-2-furanone. Enantioselective Preparation of (R) and (S)-γ-Valerolactone
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Lipase-catalyzed lactonization of (2) provides both (R) and (S) enantiomers of 5-phenylselenyltetrahydro-2-furanone (1) in good enantiomeric excess. The kinetic resolution was examined using PPL (Porcine pancreatic lipase), PSL (Amano PS, Pseudomonas sp. lipase), MML (Mucor miehei lipase), CRL (Candida rugosa lipase), CAL-B (Candida Antarctica lipase, type B) and Novozym 435 (immobilized C. antarctica lipase type B) in different solvents. A tributyltin hydride reduction of enantiomerically enriched 1 gave both (R) and (S) enantiomers of S-4-pentanolide (γ-valerolactone).
- Clososki, Giuliano C.,Costa, Carlos E.,Missio, Lauri J.,Cass, Quezia B.,Comasseto, Joao V.
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p. 817 - 828
(2007/10/03)
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- A convenient route to optically active γ-substituted γ-lactones
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Sodium borohydride reduction of 4-substituted (-)-menthyl/ (-)-bornyl-4-oxobutanoates followed by simple trituration in acidic medium at low temperature resulted in the formation of optically active γ-substituted γ-lactones.
- Karnik, Anil V.,Patil, Sudhir T.,Patnekar, Subodh S.,Semwal, Abha
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p. 1420 - 1422
(2007/10/03)
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- Preparation of synthetically useful chiral building blocks - 5-alkylated γ-lactones via catalytic asymmetric hydrogenation of 4-oxo esters
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Asymmetric hydrogenation of 4-oxo esters, catalyzed by cationic BINAP-Ru(II) complexes, afforded in a good overall yield and with excellent enantioselectivity (> 98% ee), the respective 5-alkylated γ-lactones, useful intermediates for the preparation of pheromones.
- Juszkiewicz,Asztemborska,Jurczak
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p. 1707 - 1711
(2007/10/03)
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- Development of an effective chiral auxiliary for hydroxyalkyl radicals
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The development of an effective chiral auxiliary for hydroxyalkyl radicals is delineated. Both the 2-tetrahydropyranyl (THP) and tri-O-benzyl-2-deoxy-α-D-glucopyranosyl (GLU) auxiliaries resulted in diastereoselective radical additions to methyl acrylate at -78°C (ds = 6/1 and 11/1, respectively). The developing stereochemistry at the radical center was completely under auxiliary control. Correlation experiments showed that the D-GLU auxiliary led to attack on the radical Si-face. The selectivity of these radical additions dropped-off considerably when the more reactive 2-nitropropene trap was employed. Computational studies suggested that the observed facial selectivity was due primarily to entropic factors in the transition state but that a smaller temperature-dependent enthalpic contribution was also involved. It was hypothesized that incorporation of a quaternary center at C-6 (THP numbering) would restore the facial selectivity with more reactive radical traps by restricting the orientations available to the incoming alkene. In the event, the trans-6-tert-butyltetrahydropyranyl (tBu-THP) auxiliary resulted in very good diastereoselection with 2-nitropropene (ds = 35/1 at -78°C, 15/1 at 0°C, and 8/1 at RT) as did the tri-O-benzyl-6,6-dimethyl-2-α-D-deoxyglucopyranosyl (diMe-GLU) auxiliary during additions to ethyl α-trifluoroacetoxyacrylate (ds = 10/1 at 0°C). A protocol for recovery of the sugar-derived chiral auxiliaries was also established. This work sets the stage for the development of a novel approach to 1, 3, 5...(2n + 1) polyols based on iterative radical homologation as well as the application of these pyranosidic auxiliaries to other synthetically important reactions.
- Garner, Philip,Anderson, James T.,Cox, Philip B.,Klippenstein, Stephen J.,Leslie, Ray,Scardovi, Noemi
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p. 6195 - 6209
(2007/10/03)
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- Convenient enantioselective synthesis of new 1,4-sulfanylalcohols from γ-lactones
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A synthetic strategy based upon three basic reactions - enzymatic resolution, oxygen-sulfur exchange, reduction - allowed us to carry out an easy and useful synthesis of a series of new 1,4-sulfanylalcohols from aliphatic γ-lactones. Final products have been obtained in good yields with enantiomeric excesses in a 66-91% range.
- Filippi, Jean-Jacques,Fernandez, Xavier,Lizzani-Cuvelier, Louisette,Loiseau, André-Michel
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p. 6267 - 6270
(2007/10/03)
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- Dynamic kinetic resolution of γ-hydroxy acid derivatives
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Enzymatic resolution and dynamic kinetic resolution of γ-hydroxy acid derivatives 1 have been investigated. Efficient kinetic resolution was obtained using Pseudomonas cepacia lipase in toluene (E value ~400). The combination of enzymatic kinetic resoluti
- Runmo, Ann-Britt L,Pàmies, Oscar,Faber, Kurt,B?ckvall, Jan-E
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p. 2983 - 2986
(2007/10/03)
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- Selective reductions. 59. Effective intramolecular asymmetric reductions of α-, β-, and γ-keto acids with diisopinocampheylborane and intermolecular asymmetric reductions of the corresponding esters with B-chlorodiisopinocampheylborane
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A comparison of the stereochemistry of the products obtained from the intramolecular asymmetric reduction of a series of keto acids with (-)-diisopinocampheylborane and intermolecular asymmetric reduction of the corresponding series of keto esters with (-)-B-chlorodiisopinocampheylborane ((-)-DIP-Chloride) has been made. The stereochemistry of the hydroxy acids from the reduction of keto acids is dependent only on the enantiomer of the reagent used. The stereochemistry of the products from the reduction of keto esters is also consistent, except those of aliphatic α-keto esters. α-, β-, and γ-keto acids provide the corresponding hydroxy acids in 77-98% ee, and the α- and γ-keto esters afford the hydroxy esters in 82-≥99% ee. β-Keto esters do not undergo reduction. Although the reduction of δ-keto acids does not proceed under the same reaction conditions, the reduction of δ-keto esters is facile. All of the products from the reduction of γ-keto acids and esters and δ-keto esters were converted to the corresponding lactones. This study revealed that DIP-Chloride is an efficient reagent for the reduction of α-keto esters at low temperatures.
- Ramachandran, P. Veeraraghavan,Pitre, Sangeeta,Brown, Herbert C.
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p. 5315 - 5319
(2007/10/03)
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- Efficient intramolecular asymmetric reductions of α-, β-, and γ-keto acids with diisopinocampheylborane1
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(equation presented) α-, β-, and γ-Keto acids are reduced with diisopinocampheylborane at room temperature to the corresponding hydroxy acids with predictable stereochemistry in very high ee. The γ-hydroxy acids produced were conveniently cyclized to the corresponding lactones. This provides a simple synthesis of 4-hexanolide, a component of the pheromone secreted by the female dermestid beetle Trogoderma glabrum.
- Veeraraghavan Ramachandran,Brown, Herbert C.,Pitre, Sangeeta
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- Asymmetric hydrosilylation of ketones using trans-chelating chiral peralkylbisphosphine ligands bearing primary alkyl substituents on phosphorus atoms
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Asymmetric hydrosilylation of simple ketones with diphenylsilane proceeded at -40 °C in the presence of a rhodium complex (0.001 - 0.01 molar amount) coordinated with a trans-chelating chiral bisphosphine ligand bearing linear alkyl substituents on the phosphorus atoms, (R,R)-(S,S)-Et-, Pr-, or BuTRAP, giving the corresponding optically active (S)- secondary alcohols with up to 97% ee. The asymmetric hydrosilylation using TRAP ligands with bulkier P-substituents resulted in much lower enantioselectivities. The EtTRAP-rhodium catalyst was also effective for asymmetric hydrosilylation of keto esters with a coordination site for a rhodium atom (up to 98% ee). Optically active symmetrical diols were obtained with up to 99% ee from the corresponding diketones via the asymmetric reduction using 2.5 molar amounts of diphenylsilane.
- Kuwano, Ryoichi,Sawamura, Masaya,Shirai, Junya,Takahashi, Masatoshi,Ito, Yoshihiko
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p. 485 - 496
(2007/10/03)
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- Catalytic enantioselective hydrosilylation of ketones with rhodium- phosphite complexes containing a TADDOLate and a dihydrooxazole unit
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New types of chiral phosphorus/nitrogen ligands, capable of forming six- membered-ring metal chelates have been prepared from α,α,α',α'-tetraaryl- 1,2-dioxolane-4,5-dimethanols (TADDOLs), PCl3, and dihydrooxazole alcohols (from amino acids) (7 in Scheme 1). The X-ray crystal structure of a Rh complex of one of these ligands, 8b, has been determined (Scheme 2 and Fig.). Enantioselective hydrosilylations of dialkyl and aryl alkyl ketones with Ph2SiH2/0.01 equiv. Rh1·7 have been studied and found to provide secondary alcohols in enantiomer ratios of up to 97:3 (Scheme 3 and Table). The ligand prepared from (R,R)-TADDOL and the (R)-valine-derived (R)-α,α- dimethyl-4-isopropyl-4,5-dihydrooxazole-2-methanol gives better results than the (R,R,S)-isomer (7d vs. 7c in Scheme 3), and an i-Pr group on the 4,5- dihydrooxazole ring gives rise to a slightly better selectivity than a Ph group. With the (R,R,R)-ligands the hydrogen transfer occurs from the Re face of the oxo groups (Scheme 4).
- Heldmann, Dieter K.,Seebach, Dieter
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p. 1096 - 1110
(2007/10/03)
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- Asymmetric electrophilic methoxyselenenylations and cyclizations with 3- camphorseleno derivatives
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A series of novel 3-camphor-based diselenides, differing in substitution at C-2, was prepared. The corresponding allyl selenides were used as protecting groups for the diselenide moieties in several subsequent transformations. The diastereoselective methoxyselenenylation of alkenes was achieved with methanolic selenenyl triflates derived from the camphor diselenides, of which the 2-keto analogue proved the most effective. Diastereoselective electrophilic cyclizations of unsaturated alcohols, carboxylic acids and amides were most effectively performed with the corresponding selenenyl chloride, containing a spiro-oxazolidinone moiety at C-2 of the camphor residue. The absolute configurations of several products were determined by reductive deselenization.
- Back, Thomas G.,Dyck, Brian P.,Nan, Siqiao
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p. 3191 - 3208
(2007/10/03)
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- Asymmetric hydrogenation of substituted 2-pyrones
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Various substituted 2-pyrones have been hydrogenated with high enantioselectivity (up to 97% ee) to the corresponding 5,6-dihydropyrones using cationic ruthenium catalysts containing the (6,6'-dimethoxybiphenyl- 2,2'diyl)bis[3,5-di(tert-butyl)phenylphosphine] ligand. When substituents at position 3 are absent, 5,6-dihydropyrones are further hydrogenated to the fully saturated δ-lactones. In the case of 4,6-dimethyl-2H-pyran-2-one, the diastereoselectivity of the second hydrogenation step was determined by the chirality of the applied catalyst, while for the 4,5,6-trimethyl-2H-pyran2- one a double asymmetric induction effect was observed. Other cyclic substrates with endo- or exocyclic double bonds were hydrogenated, although with substantially lower enantioselectivity with respect to the 2-pyrones.
- Fehr, Matthias J.,Consiglio, Giambattista,Scalone, Michelangelo,Schmid, Rudolf
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p. 5768 - 5776
(2007/10/03)
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- A facile synthesis of optically active lactones using benzyl-3,6-anhydro glucofuranoside as chiral auxiliary
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A highly enantioselective synthesis of γ- and δ-lactones using an anhydrofuranoside derived from D-glucose as chiral auxiliary is described.
- Nair, Vijay,Prabhakaran, Jaya,George, Tesmol G.
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p. 15061 - 15068
(2007/10/03)
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- Yeast-mediated synthesis of optically active diols with C2-symmetry and (R)-4-pentanolide
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Reduction of some diketones and a keteacid with yeast, Pichia farinosa IAM 4682 was examined. The reduction of carbonyl groups proceeded highly selectively with an anti-Prelog fashion to give (R)-alcohols. (2R,5R)2,5- Hexanediol (83% yd., >99% e.e., 95% d.e.), (2R,4R)-2,4-pentanediol (94% yd., >99% e.e., 98% d.e.), and (R)-4-pentanolide (67% yd., >99% e.e.) were highly efficiently obtained from the corresponding ketones. Effect of the structure of substrate on the stereochemical course as well as the selectivity were discussed.
- Ikeda,Sato,Sugai,Ohta
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p. 8113 - 8122
(2007/10/03)
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- Asymmetric induction using novel chiral auxiliaries derived from D-glucose
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Asymmetric synthesis of lactones 15a-16b, using the novel auxiliaries 1 and 2 readily available from D-glucose, is described.
- Nair, Vijay,Prabhakaran, Jaya
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p. 593 - 594
(2007/10/03)
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- Synthesis of all the four possible stereoisomers of acaterin, naturally occurring ACAT inhibitor, and the determination of its absolute configuration
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Enantioselective synthesis of all the possible stereoisomers of acaterin 1, naturally occurring ACAT inhibitor with acetogenin-type skeleton, was accomplished starting from both the enantiomers of ethyl 3-hydroxy butanoate 3. Stereochemistry of synthetic samples 1 and pseudo-1 was unambiguously assigned by converting to the authentic compound. The absolute configuration of natural acaterin was determined as (4R, 1'R) by careful comparison of TLC behavior and spectral and optical data.
- Ishigami, Ken,Kitahara, Takeshi
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p. 6431 - 6442
(2007/10/02)
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- Asymmetric Hydrogenation of Olefins with Aprotic Oxygen Functionalities Catalyzed by BINAP-Ru(II) Complexes
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Cyclic α,β-unsaturated ketones, alkylidene lactones, and alkenyl ethers have been hydrogenated in high enantiomeric excesses by use of BINAP-Ru(II) complexes (BINAP = 2,2'-bis(diphenylphosphino)-1,1'-binaphthyl) as catalysts. 2-Alkylidenecyclopentanones were hydrogenated in the presence of Cl, Ru2Cl4(BINAP)2(NEt3), or Ru(OCOCH3)2(BINAP) in up to 98percent ee, while in the case of 2-benzylidene- and 2-(3-phenylpropylidene)cyclopentanones, enantiomeric excesses of the hydrogenation were below 50percent under the same conditions.The sense of asymmetric induction as well as the enantioselectivity (95percent ee) obtained in the hydrogenation of (E)-2-propylidene-γ-butyrolactone were the same as those of the (Z)-isomer.Lactones, 2- and 4-alkylidene-γ-butyrolactones, were converted to the corresponding saturated γ-butyrolactones in 95percent ee.Hydrogenation of diketene with the catalytic system derived from (benzene)>Cl and triethylamine or complex Ru2Cl42(NEt3) established a new synthetic route to (R)-4-methyl-2-oxetanone, a promising monomer of biodegradable polymers, in up to 97percent selectivity and 92percent ee.Alkenyl ethers, 2-methylenetetrahydrofuran, and 2-methyl-3,4-dihydrofuran have also been hydrogenated to give 2-methyltetrahydrofuran in 91 and 87percent ee, respectively.
- Ohta, Tetsuo,Miyake, Tsutomu,Seido, Nobuo,Kumobayashi, Hidenori,Takaya, Hidemasa
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p. 357 - 363
(2007/10/02)
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- Chiral synthesis via organoboranes. 39. A facile synthesis of γ- substituted-γ-butyrolactones in exceptionally high enantiomeric purity
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Optically active homoallylic alcohols of exceptionally high enantiomeric purity (98-≥99% ee) readily available via asymmetric allylboration were converted into p-nitrobenzoate esters and subjected to hydroboration followed by oxidation with CrO3 in aqueous acetic acid (10% H2O) to obtain the corresponding carboxylic acids with the same number of carbon atoms. The protecting ester group was hydrolyzed and the product lactonized in situ to the γ-substituted γ-butyrolactones 5 (R = Me, Pr, i-Pr, t-Bu, Ph, (E)- CH=CHCH3) usually without racemization and in good yields. The method is convenient and potentially valuable for the synthesis of highly functionalized γ-butyrolactones in high optical purity.
- Brown,Kulkarni,Racherla
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p. 365 - 369
(2007/10/02)
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- A simple enantioselective synthesis of γ-valerolactone
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The readily available biopolymer, poly-(R)-3-hydroxybutyrate was converted to (R)-(+)-γ-valerolactone in 32% overall yield in a simple 4 stage procedure.
- O'Neill,Lindell,Simpson,Willis
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p. 117 - 118
(2007/10/02)
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- Asymmetric hydrogenation of unsaturated carbonyl compounds catalyzed by BINAP-Ru(II) complexes. Enantioselective synthesis of γ-butyrolactones and cyclopentanones
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Asymmetric hydrogenation of 2- and 4-alkylidene-γ-butyrolactones and 2-alkylidenecyclopentanones catalyzed by BINAP-Ru(II) complexes affords the corresponding γ-butyrolactones and cyclopentanones in 94-98% ee. Hydrogenation of (E)- and (Z)-2-propylidene-γ-butyrolactone catalyzed by the same catalyst gave the products with the same absolute configuration and in almost equal enantioselectivities, which shows that olefin geometry does not affect the stereochemistry and enantioselectivity.
- Ohta,Miyake,Seido,Kumobayashi,Akutagawa,Takaya
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p. 635 - 638
(2007/10/02)
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- A one-pot synthesis of racemic and enantiomeric γ-butyrolactones
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Borinate esters 4, derived from the hydroboration of homoallylic alcohols 2 were oxidized with chromic acid to provide a one-pot synthesis of the racemic and enantiomeric γ-butyrolactones (2-oxotetrahydrofurans) 3.
- Mandal,Mahajan
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p. 311 - 313
(2007/10/02)
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- Enantiospecific Preparation of the Lactone Fragment of Murisolin
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Both enantiomers (R) and (S) of the functionalized unsaturated γ-lactone moiety of the acetogenin murisolin have been enantiospecifically synthezised from L and D-glutamic acid respectively.
- Harmange, Jean-Christophe,Figadere, Bruno,Hocquemiller, Reynald
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p. 347 - 350
(2007/10/02)
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- Lipase-Catalyzed Preparation of Optically Active γ-Butyrolactones in Organic Solvents
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Lipases in anhydrous organic solvents catalyze the lactonization of esters of γ-hydroxy carboxylic acids with a high degree of stereospecifity.Under these conditions the lipases exhibit both enantioselectivity and prochiral selectivity.We exploited the enzymes' enantioselectivity for synthesis of chiral lactones from racemic γ-hydroxy esters and their prochiral stereospecifity, i.e. the ability to discriminate between enantiotopic groups of a prochiral molecule, for the enantioconvergent lactonization of symmetrical γ-hydroxy diesters.This approach was used to develop a convenient, high yielding, and stereoselective route to several optically active γ-substituted γ-butyrolactones.
- Gutman, Arie L.,Zuobi, Kheir,Bravdo, Tamar
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p. 3546 - 3552
(2007/10/02)
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- Bakers' Yeast Reductions of Alkyl Levulinates: Synthesis of (R)-(+) and (S)-(-) 4-Methylbutyrolactones
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The bakers' yeast reduction of a number of alkyl levulinates occurs in good to moderate yields to give the corresponding (S) alcohols in >98percent ee.The (S) alcohol 1a has been converted to synthetically useful (S)- or (R)-4-methylbutyro-lactone and (S)-(+)-1,4-pentanediol in good yields.
- Jacobs, Hollie,Berryman, Kent,Jones, Joel,Gopalan, Aravamudan
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p. 999 - 1010
(2007/10/02)
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- OXIRANE RINGS: STUDIES AND APPLICATIONS OF A NEW CHEMO AND REGIO SELECTIVE REDUCTIVE OPENING OF EPOXIDES
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The straightforward reductive opening of 1,2 epoxides to alcohols was studied and applied to several significant compounds.The reaction, which proceeds via the nucleophilic opening of the oxirane ring and the subsequent free radical dehalogenation, shows an excellent chemical yield as well as chemo and regioselectivity.This reaction was also applied to a chiral α,β-epoxyester.
- Bonini, Carlo,Fabio, Romano Di,Sotgiu, Giovanni,Cavagnero, Silvia
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p. 2895 - 2904
(2007/10/02)
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- KINETIC RESOLUTION OF RACEMIC β,γ-EPOXY ESTERS WITH PIG LIVER ESTERASE (PLE, E.C. 3.1.1.1.)
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The β,γ-epoxy esters (+/-)-2 to (+/-)-6 were synthetisized.The E-values of kinetic resolution of 2, 3, 4, and 6 with PLE and the absolute configuration of the products of the hydrolysis were determined by the conversion to known compounds.
- Mohr, Peter,Roesslein, Lukas,Tamm, Christoph
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p. 2513 - 2516
(2007/10/02)
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