- Evaluation of gem-Diacetates as Alternative Reagents for Enzymatic Regio-and Stereoselective Acylation of Alcohols
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Geminal diacetates have been used as sustainable acyl donors for enzymatic acylation of chiral and nonchiral alcohols. Especially, it was revealed that geminal diacetates showed higher reactivity than vinyl acetate for hydrolases that are sensitive to acetaldehyde. Under optimized conditions for enzymatic acylation, several synthetically relevant saturated and unsaturated acetates of various primary alcohols were obtained in very high yields up to 98% without E/Z isomerization of the double bond. Subsequently, the acyl donor was recreated from the resulting aldehyde and reused constantly in acylation. Therefore, the developed process is characterized by high atomic efficiency. Moreover, it was shown that acylation using geminal diacetates resulted in remarkable regioselectivity by discriminating among the primary and secondary hydroxyl groups in 1-phenyl-1,3-propanediol providing exclusively 3-acetoxy-1-phenyl-propan-1-ol in good yield. Further, enzymatic kinetic resolution (EKR) and chemoenzymatic dynamic kinetic resolution (DKR) protocols were developed using geminal diacetate as an acylating agent, resulting in chiral acetates in high yields up to 94% with enantiomeric excesses exceeding 99%.
- Koszelewski, Dominik,Brodzka, Anna,Madej, Arleta,Trzepizur, Damian,Ostaszewski, Ryszard
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p. 6331 - 6342
(2021/05/06)
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- Free and immobilized lecitase ultra as the biocatalyst in the kinetic resolution of (E)‐4‐arylbut‐3‐en‐2‐yl esters
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The influence of buffer type, co‐solvent type, and acyl chain length was investigated for the enantioselective hydrolysis of racemic 4‐arylbut‐3‐en‐2‐yl esters using Lecitase Ultra (LU). Immobilized preparations of the Lecitase Ultra enzyme had
- Chojnacka, Anna,Drozd, Rados?aw,G?adkowski, Witold,Le?niarek, Aleksandra,Szymańska, Magdalena
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- Continuous-Flow Dynamic Kinetic Resolution of Racemic Alcohols by Lipase–Oxovanadium Cocatalysis
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A continuous-flow dynamic kinetic resolution of racemic secondary alcohols was carried out using a single column reactor packed with a mixture of immobilized lipase and an immobilized oxovanadium species, VMPS4. As a result, optically pure esters were produced in 88–92 % yields. Problems encountered in this study were overcome by using fillers that efficiently maintained the initial distribution of the catalysts in the reactor and by using a packing method in which the mixing ratio of the two catalysts was varied in a stepwise fashion. The flow process led to an increased turnover number of each catalyst compared to those of batch reactions.
- Adebar, Niklas,Akai, Shuji,Gr?ger, Harald,Higashio, Koichi,Kühn, Franziska,Katsuragi, Satoko,Kundu, Dhiman,Plass, Carmen
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supporting information
p. 1961 - 1967
(2020/04/09)
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- Base-Free Dynamic Kinetic Resolution of Secondary Alcohols with a Ruthenium-Lipase Couple
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We report the dynamic kinetic resolution (DKR) of various secondary alcohols by the combination of a ruthenium catalyst and an anionic surfactant-activated lipoprotein lipase. The DKR reactions performed under totally base-free conditions at room temperature provided the products of excellent enantiopurities (91-99% ee or greater) in high yields (92-99%). More importantly, the DKR of α-arylallyl alcohols was achieved for the first time with high yields (87-91%).
- Yun, Inyeol,Park, Jin Yong,Park, Jaiwook,Kim, Mahn-Joo
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p. 16293 - 16298
(2019/12/27)
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- Stereoselective Modification of N-(α-Hydroxyacyl)-glycinesters via Palladium-Catalyzed Allylic Alkylation
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N-(α-Hydroxyacyl)-glycinesters can be used as excellent nucleophiles in Pd-catalyzed allylic alkylation. The method allows for the stereoselective introduction of a wide range of side chains, including highly functionalized ones. Both diastereomers can be accessed through variation of the reaction conditions. Furthermore, the use of stannylated carbonates introduces vinylstannane motifs, which are eligible for subsequent C-C coupling reactions.
- Horn, Alexander,Kazmaier, Uli
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supporting information
p. 4595 - 4599
(2019/06/27)
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- Enhanced activity and modified substrate-favoritism of Burkholderia cepacia lipase by the treatment with a pyridinium alkyl-PEG sulfate ionic liquid
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Three types of pyridinium salts, i.e., 1-ethylpyridin-1-ium cetyl-PEG10 sulfate (PYET), 1-butylpyridin-1-ium cetyl-PEG10 sulfate (PYBU), and 1-(3-methoxypropyl)pyridin-1-ium cetyl-PEG10 sulfate (PYMP), have been prepared and evaluated for their activation property of Burkholderia cepacia lipase by comparison to the control IL-coated enzymes, 1-butyl-2,3-dimethylimidazolium cetyl-PEG10 sulfate-coated lipase PS (IL1-PS). Among the tested pyridinium salt-coated lipases, the PYET-coated lipase PS (PYET-PS) exhibited the best results; the transesterification of 1-(pyridin-2-yl)ethanol, 1-(pyridin-3-yl)ethanol, 1-(pyridin-4-yl)ethanol, or 4-phenylbut-3-en-2-ol proceeded faster than those of the IL1-PS-catalyzed reaction while maintaining an excellent enantioselectivity (E > 200). This improved efficiency was found to be dependent on the increased Kcat value.
- Kadotani, Shiho,Nokami, Toshiki,Itoh, Toshiyuki
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p. 441 - 447
(2019/01/04)
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- Enantioselective NiH/Pmrox-Catalyzed 1,2-Reduction of α,β-Unsaturated Ketones
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The enantioselective 1,2-reduction of α,β-unsaturated ketones was achieved using a NiH catalyst in the presence of pinacolborane. This mild process represents a general method to access a wide variety of structurally diverse α-chiral allylic alcohols in excellent yields and enantioselectivity, as well as very high levels of ambidoselectivity for 1,2- over 1,4-reduction. Furthermore, for reactions on a 10 mmol scale, catalyst loadings as low as 0.5 mol % could be employed to deliver product without any detrimental effect on the yield, enantio-, or ambidoselectivity.
- Chen, Fenglin,Zhang, Yao,Yu, Lei,Zhu, Shaolin
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p. 2022 - 2025
(2017/02/15)
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- Remarkably improved stability and enhanced activity of a: Burkholderia cepacia lipase by coating with a triazolium alkyl-PEG sulfate ionic liquid
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Three types of triazolium cetyl-PEG10 sulfate ionic liquid were synthesized and their activation of Burkholderia cepacia lipase was investigated; both the reaction rate and enantioselectivity depended on the cationic part of the coating ILs and 1-butyl-3-methyl-1,2,3-triazolium cetyl-PEG10 sulfate (Tz1)-coated lipase PS, which is especially suitable for the transesterification of 1-(pyridin-2-yl)ethanol, 1-(pyridin-3-yl)ethanol, and 1-(pyridin-4-yl)ethanol, among 12 types of tested secondary alcohol. The most important result was obtained when these enzymes were stored in an IL ([N221MEM][Tf2N]) solvent: Tz1-PS showed an amazing stability and it exhibited an excellent activity after 2 years when the enzyme was stored in [N221MEM][Tf2N].
- Nishihara,Shiomi,Kadotani,Nokami,Itoh
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supporting information
p. 5250 - 5256
(2017/11/09)
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- Synergetic activation of lipase by an amino acid with Alkyl-PEG sulfate ionic liquid
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The synergetic effect of amino acids and an ionic liquid, 1-butyl-2,3-dimethylimidazolium α-cetylpolyoxyethylene(10) ether sulfate (IL1), as coating materials on lipase was discovered: coating on lipase PS using a certain amino acid with IL1 was found to
- Yoshiyama, Kazuhide,Abe, Yoshikazu,Hayase, Shuichi,Nokami, Toshiki,Itoh, Toshiyuki
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supporting information
p. 663 - 665
(2013/07/27)
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- A mesoporous-silica-immobilized oxovanadium cocatalyst for the lipase-catalyzed dynamic kinetic resolution of racemic alcohols
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V for resolution: A new oxovanadium catalyst (V-MPS; see scheme) immobilized in the pores of mesoporous silica has been developed. The combined use of V-MPS and lipases achieved the dynamic kinetic resolution of a wide range of racemic alcohols (1 or 2) t
- Egi, Masahiro,Sugiyama, Koji,Saneto, Moriaki,Hanada, Ryosuke,Kato, Katsuya,Akai, Shuji
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supporting information
p. 3654 - 3658
(2013/04/23)
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- Highly enantioselective synthesis of 3-substituted furanones by palladium-catalyzed kinetic resolution of unsymmetrical allyl acetates
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Resolving the issue: A near-perfect Pd-catalyzed kinetic resolution of 1,3-disubstituted unsymmetrical allylic acetates uses silyl enol ethers as nucleophiles to access the important 3-substituted-furanone scaffold (see scheme; DACH=diaminocyclohexyl, dba=dibenzylideneacetone). The reaction proceeds under mild conditions and provides the desired products with excellent chemo-, regio-, and enantioselectivity. Copyright
- Mao, Bin,Ji, Yining,Fananas-Mastral, Martin,Caroli, Giuseppe,Meetsma, Auke,Feringa, Ben L.
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p. 3168 - 3173
(2012/05/05)
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- Dynamic kinetic resolution of a wide range of secondary alcohols: Cooperation of dicarbonylchlorido(pentabenzylcyclopentadienyl)ruthenium and CAL-B
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The substrate scope in the dynamic kinetic resolution ofsecondary alcohols was studied by using 31 structurallydifferent alcohols and isopropenyl acetate in the presence ofdicarbonylchlorido(pentabenzylcyclopentadienyl)rutheniumand Candida antarctica lipase B (Novozym 435, CAL-B) in toluene. The enzyme and the ruthenium complex were shown to function in a highly compatible manner allowing the conversion of the racemic alcohols into the (R)-acetates in practically theoretical yields and, in most cases, ee values exceeding 99%. The results are fully comparable to those published previously by using earlier reported, state-of-the-art ruthenium-based catalysts for the alcohol racemization. A clear benefit of the dicarbonylchlorido(pentabenzylcyclopentadienyl)ruthenium system, when compared to other (cyclopentadienyl)ruthenium racemization catalysts, is its simple and cost-efficient preparation. The substrate scope of 31 secondary alcohols was studied in the dynamic kinetic resolution by utilizing dicarbonylchlorido(pentabenzylcyclopentadienyl)rutheniumand Candida antarctica lipase B (CAL-B) in the acylation with isopropenyl acetate in toluene at room temperature. The secondary alcohols were transformed into highly enantiopure (R)-acetates (in most cases ee > 99%) in close to quantitative isolatedyields. Copyright
- Paeivioe, Mari,Mavrynsky, Denys,Leino, Reko,Kanerva, Liisa T.
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supporting information; experimental part
p. 1452 - 1457
(2011/04/22)
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- One-pot synthesis of optically active allyl esters via lipase-vanadium combo catalysis
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The combination of vanadium-oxo compounds (3 or 4) with a lipase produced the regio- and enantioconvergent transformation of racemic allyl alcohols (1 or 2) into optically active allyl esters. In this system, the vanadium compounds catalyzed the continuous racemization of the alcohols along with the transposition of the hydroxyl group, while the lipase effected the chemo- and enantioselective esterification to achieve the dynamic kinetic resolution.
- Akai, Shuji,Hanada, Ryosuke,Fujiwara, Noboru,Kita, Yasuyuki,Egi, Masahiro
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supporting information; experimental part
p. 4900 - 4903
(2011/01/12)
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- Enantioselective synthesis of α-methyl carboxylic acids from readily available starting materials via chemoenzymatic dynamic kinetic resolution
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An enantioselective method for the synthesis of α-methyl carboxylic acids starting from trans-cinnamaldehyde, a readily available and inexpensive compound, has been developed. Allylic alcohol 1 was obtained via a standard Grignard addition to trans-cinnamaldehyde. Dynamic kinetic resolution was applied to allylic alcohol 1 utilizing a ruthenium catalyst and either an (R)-selective lipase or an (S)-selective protease to provide the corresponding allylic esters in high yield and high ee. A copper-catalyzed allylic substitution was then applied to provide the corresponding alkenes with inversion of stereochemistry. Subsequent C-C double bond cleavage afforded pharmaceutically important α-methyl substituted carboxylic acids in high ee and overall yields of up to 76%.
- Thalen, Lisa K.,Sumic, Anna,Bogar, Krisztian,Norinder, Jakob,Persson, Andreas K. Ae.,Baeckvall, Jan-E.
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body text
p. 6842 - 6847
(2010/11/24)
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- A rational design of phosphonium salt type ionic liquids for ionic liquid coated-lipase catalyzed reaction
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A rational design of phosphonium ionic liquid for ionic liquid coated-lipase (IL1-PS)-catalyzed reaction has been investigated, and very rapid transesterification of secondary alcohols accomplished when IL1-PS was used as catalyst in 2-methoxyethoxymethyl(tri-n-butyl)phosphonium bis(trifluoromethanesulfonyl)amide ([P444MEM][NTf2]) as solvent while perfect enantioselectivity was maintaining. Increased K cat value was suggested to be the most important factor in IL1-PS working the best in [P444MEM][NTf2] solvent. The Royal Society of Chemistry 2010.
- Abe, Yoshikazu,Yoshiyama, Kazuhide,Yagi, Yusuke,Hayase, Shuichi,Kawatsura, Motoi,Itoh, Toshiyuki
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experimental part
p. 1976 - 1980
(2011/02/23)
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- Chiral spiroaminoborate ester as a highly enantioselective and efficient catalyst for the borane reduction of furyl, thiophene, chroman, and thiochroman-containing ketones
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Prochiral heteroaryl ketones containing furan, thiophene, chroman, and thiochroman moieties were successfully reduced in the presence of 1-10 mol % of spiroaminoborate ester 1 with different borane sources to afford non-racemic alcohols in up to 99% ee. In addition, modest enantioselectivity, around 80% ee, was achieved in the reduction of linear α,β-unsaturated heteroaryl ketones.
- Stepanenko, Viatcheslav,De Jesus, Melvin,Correa, Wildeliz,Bermudez, Lorianne,Vazquez, Cindybeth,Guzman, Irisbel,Ortiz-Marciales, Margarita
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experimental part
p. 2659 - 2665
(2010/04/29)
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- Enzymatic resolution of chlorohydrins for the synthesis of enantiomerically enriched 2-vinyloxiranes
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A series of vinylchlorohydrins are resolved by enzymatic kinetic resolution. The resulting R-alcohols, obtained in up to 99% ee, are stereoselectively converted into vinyloxiranes in high yield. The S-acetates, obtained in up to 99% ee were either deprotected to S-alcohols, or cyclized directly to vinyl oxiranes under basic conditions, with moderate to no loss in ee. The results are consistent with a racemization mechanism involving reversible migration of the acetate during deprotection. Georg Thieme Verlag Stuttgart.
- McCubbin, J. Adam,Maddess, Matthew L.,Lautens, Mark
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p. 289 - 293
(2008/12/21)
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- An enantioselective route to α-methyl carboxylic acids via metal and enzyme catalysis
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Dynamic kinetic resolution of allylic alcohols to allylic acetates followed by copper-catalyzed allylic substitution gave alkenes in high yields and high optical purity. Subsequent oxidative C-C double bond cleavage afforded pharmaceutically important α-methyl substituted carboxylic acids in high ee.
- Norinder, Jakob,Bogar, Krisztian,Kanupp, Lisa,Baeckvall, Jan-E.
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p. 5095 - 5098
(2008/03/28)
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- Chemoenzymatic dynamic kinetic resolution of allylic alcohols: A highly enantioselective route to acyloin acetates
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Dynamic kinetic resolution (DKR) of a series of sterically hindered allylic alcohols has been conducted with Candida antarctica lipase B (CALB) and ruthenium catalyst 1. The optically pure allylic acetates obtained were subjected to oxidative cleavage to
- Bogar, Krisztian,Vidal, Pilar Hoyos,Alcantara Leon, Andres R.,Baeckvall, Jan-E.
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p. 3401 - 3404
(2008/02/12)
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- Increased enantioselectivity and remarkable acceleration of lipase-catalyzed transesterification by using an imidazolium PEG-Alkyl sulfate ionic liquid
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Several types of imidazolium salt ionic liquids were prepared derived from poly(oxyethylene)alkyl sulfate and used as an additive or coating material for lipase-catalyzed transesterification in an organic solvent. A remarkably increased enantioselectivity was obtained when the salt was added at 3-10 mol % versus substrate in the Burkholderia cepacia lipase (lipase PS-C)-catalyzed transesterification of 1-phe nylethanol by using vinyl acetate in diisopropyl ether or a hexane solvent system. In particular, a remarkable acceleration was accomplished by the ionic liquid coating with lipase PS in an iPr2O solvent system while maintaining excellent enantioselectivity; it reached approximately 500- to 1000-fold acceleration for some substrates with excellent enantioselectivity. A similar acceleration was also observed for IL1-coated Candida rugosa lipase. MALDITOF mass spectrometry experiments of the ionic-liquid-coated lipase PS suggest that ionic liquid binds with lipase protein.
- Itoh, Toshiyuki,Matsushita, Yuichi,Abe, Yoshikazu,Han, Shi-Hui,Wada, Shohei,Hayase, Shuichi,Kawatsura, Motoi,Takai, Shigeomi,Morimoto, Minoru,Hirose, Yoshihiko
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p. 9228 - 9237
(2007/10/03)
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- Novel immobilization method of enzymes using a hydrophilic polymer support
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A novel immobilization of an enzyme with a hydrophilic polymer support in organic solvents has been developed utilizing the "polymer-incarcerated (PI) method", which has been used to immobilize metal catalysts; the kinetic resolution of secondary alcohols
- Kobayashi, Juta,Mori, Yuichiro,Kobayashi, Shu
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p. 4227 - 4229
(2007/10/03)
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- Preparation of novel hydrophobic fluorine-substituted-alkyl sulfate ionic liquids and application as an efficient reaction medium for lipase-catalyzed reaction
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Various types of differently fluorinated-alkyl sulfate ionic liquids have been prepared; the hydrophobicity was dependent on the content ratio of the fluorine on the alkyl sulfate anion and 2,2,3,3,4,4,5,5-octafluoropentyl sulfate salts showed hydrophobic properties. Melting point and viscosity were also dependent on the fluorine contents of the anionic part, while conductivity was determined by the cationic part and not influenced by the fluorine contents. Efficient lipase-catalyzed transesterification was demonstrated using hydrophobic 1-butyl-3-methylimidazolim 2,2,3,3,4,4,5,5-octafluoropentyl sulfate ([bmim][C5F8]) as solvent.
- Tsukada, Yasuhiro,Iwamoto, Kazuhisa,Furutani, Hiroyuki,Matsushita, Yuichi,Abe, Yoshikazu,Matsumoto, Kei,Monda, Keishi,Hayase, Shuichi,Kawatsura, Motoi,Itoh, Toshiyuki
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p. 1801 - 1804
(2007/10/03)
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- Palladium-catalyzed asymmetric synthesis of allylic alcohols from unsymmetrical and symmetrical racemic allylic carbonates featuring C-O-bond formation and dynamic kinetic resolution
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Described is the asymmetric synthesis of the allylic alcohols 11 (85% ee), 15 (99% ee), 17 (93% ee), 19 (61% ee), and 21 (69% ee) through a Pd-catalyzed reaction of the unsymmetrical carbonates rac-10, rac-12, rac-14, rac-16, rac-18, and rac-20, respectively, with KHCO3 and H2O in the presence of bisphosphane 6. Similarly the allylic alcohols 23 (99% ee) and 25 (97% ee) have been obtained from the symmetrical carbonates rac-22 and rac-24, respectively. Reaction of the meso-biscarbonate 26 with H2O and Pd(0)/6 afforded alcohol 27 (96% ee), which was converted to the PG building block 32. The unsaturated bisphosphane 33 showed in the synthesis of alcohols 36, 37, and 39 a similar high selectivity as 6. The formation of alcohols 11, 15, and 17 involves an efficient dynamic kinetic resolution.
- Gais, Hans-Joachim,Bondarev, Oleg,Hetzer, Ralf
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p. 6279 - 6283
(2007/10/03)
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- Asymmetric transesterification of secondary alcohols catalyzed by feruloyl esterase from Humicola insolens
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A new asymmetric transesterification of secondary alcohols catalyzed by feruloyl esterase from Humicola insolens has been found. Although alcohols are not the natural substrates for this enzyme, a high R enantioselectivity was observed. Stereochemical studies showed that variations in substrate structure lead to strong variations in enantioselectivity. The highest enantioselectivities are obtained when the β-carbon of the secondary alcohol is tertiary or quaternary.
- Hatzakis, Nikos S.,Smonou, Ioulia
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p. 325 - 337
(2007/10/03)
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- A systematic strategy for preparation of uncommon sugars through enzymatic resolution and ring-closing metathesis
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A systematic synthetic strategy has been developed for producing uncommon sugars. This method involved kinetic resolution allylic alcohol followed by ring-closing-metathesis (RCM) to generate optical pure lactones as the common precursors. After further d
- Zhu, Lizhi,Kedenburg, James P.,Xian, Ming,Wang, Peng George
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p. 811 - 813
(2007/10/03)
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- Combined ruthenium(II) and lipase catalysis for efficient dynamic kinetic resolution of secondary alcohols. Insight into the racemization mechanism
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Pentaphenylcyclopentadienyl ruthenium complexes (3) are excellent catalysts for the racemization of secondary alcohols at ambient temperature. The combination of this process with enzymatic resolution of the alcohols results in a highly efficient synthesis of enantiomerically pure acetates at room temperature with short reaction times for most substrates. This new reaction was applied to a wide range of functionalized alcohols including heteroaromatic alcohols, and for many of the latter, enantiopure acetates were efficiently prepared for the first time via dynamic kinetic resolution (DKR). Different substituted cyclopentadienyl ruthenium complexes were prepared and studied as catalysts for racemization of alcohols. Pentaaryl-substituted cyclopentadienyl complexes were found to be highly efficient catalysts for the racemization. Substitution of one of the aryl groups by an alkyl group considerably slows down the racemization process. A study of the racemization of (S)-1-phenylethanol catalyzed by ruthenium hydride η5-Ph5CpRu(CO) 2H (8) indicates that the racemization takes place within the coordination sphere of the ruthenium catalyst. This conclusion was supported by the lack of ketone exchange in the racemization of (S)-1-phenylethanol performed in the presence of p-tolyl methyl ketone (1 equiv), which gave 1% of 1-(p-tolyl)ethanol. The structures of ruthenium chloride and iodide complexes 3a and 3c and of ruthenium hydride complex 8 were confirmed by X-ray analysis.
- Martin-Matute, Belen,Edin, Michaela,Bogar, Krisztian,Kaynak, F. Betuel,Baeckvall, Jan-E.
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p. 8817 - 8825
(2007/10/03)
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- The nucleophilic addition of α-metallated 1,3-dioxanes to planar chiral cationic η3-allylmolybdenum complexes. Synthesis of (2E,5S,6R,7E)-6-methyl-8-phenylocta-2,7-dienoic acid methyl ester, a key component of the Cryptophycins
-
Two adjacent stereogenic centres and a pendant alkene were constructed via nucleophilic addition of a 1,3-dioxan-4-ylcopper(I) reagent to a cationic η3-allylmolybdenum complex as part of a synthesis of (2E,5S,6R,7E)-6-methyl-8-phenylocta-2,7-di
- Cooksey, John,Gunn, Andrew,Kocienski, Philip J.,Kuhl, Alexander,Uppal, Sukhjinder,Christopher, John A.,Bell, Richard
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p. 1719 - 1731
(2007/10/03)
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- Asymmetric hydrogenation of an α,β-unsaturated ketone by diamine(ether-phosphine)ruthenium(II) complexes and lipase-catalyzed kinetic resolution: A consecutive approach
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The RuCl2(η1-Ph2PCH2CH 2OCH3)2(diamine) complexes 2L1-2L5 have been prepared in high yields from the reaction of equimolar amounts of RuCl2(η2-Ph2PCH2CH 2OCH3)2 1 with various kinds of chelating diamines L1-L5 to form five-membered chelates with ruthenium. These novel ruthenium(II) complexes have been used as catalysts in the asymmetric hydrogenation of the prochiral ketone trans-4-phenyl-3-butene-2-one 3, using 2-propanol and different types of cocatalysts. Whereas complexes with achiral diamines afforded the racemic alcohols, complexes with chiral diamines (R,R or S,S) allowed the formation of the corresponding enantiomerically enriched secondary alcohol (S or R) with ee values of 45%. In order to obtain the secondary alcohol with ee of >99%, the kinetic resolution of enantiomerically enriched trans-4-phenyl-3-butene-2-ol 3 was performed in a consecutive approach using either the lipase-catalyzed enantioselective transesterification of the alcohol with isopropenyl acetate as the acyl donor in toluene or the enantioselective hydrolysis of the corresponding acetate in buffer. The determination of the enantiomeric excess (ee) of the resulting enantiomerically enriched secondary alcohols was performed by gas chromatography using heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin as the chiral stationary phase.
- Lindner, Ekkehard,Ghanem, Ashraf,Warad, Ismail,Eichele, Klaus,Mayer, Hermann A.,Schurig, Volker
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p. 1045 - 1053
(2007/10/03)
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- Lipase-catalyzed access to enantiomerically pure (R)- and (S)-trans-4-phenyl-3-butene-2-ol
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The enzymatic kinetic resolution of (RS)-trans-4-phenyl-3-butene-2-ol was investigated by screening a range of lipases both for enantioselective transesterification and for enantioselective hydrolysis of its acetate. The lipase from Pseudomonas cepacia immobilized on diatomaceous earth (PSL-D)-catalyzed asymmetric transesterification was performed on gram scale using isopropenyl acetate as an innocuous acyl donor in organic media affording the (S)-alcohol in high enantiomeric excess (>99% ee) and enantiomeric ratio E >150. The lipase (Candida antarctica B, CAL-B)-catalyzed asymmetric hydrolysis of the racemic acetate was performed on gram scale in phosphate buffer affording the (R)-alcohol in high enantiomeric excess (>99% ee) and enantiomeric ratio E >150. The investigation demonstrates that the transesterification of the racemic alcohol in organic solvent was faster than the hydrolysis of the corresponding acetate in phosphate buffer. A GC method was developed to achieve an effective analytical separation of the enantiomers of both substrate and product in one analysis using the chiral stationary phase heptakis(2,3-di-O-methyl-6-O-tert-butyldimethylsilyl)-β-cyclodextrin.
- Ghanem, Ashraf,Schurig, Volker
-
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- Using a lipase as a high-throughput screening method for measuring the enantiomeric excess of allylic acetates
-
This report describes a high-throughput method for measuring the enantiomeric excess of allylic acetates. Such methods are useful tools for screening libraries of potential catalysts for enantioselective reactions. This technique, which is called EMDee fo
- Onaran, M. Burak,Seto, Christopher T.
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p. 8136 - 8141
(2007/10/03)
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- Enantioselective synthesis of benzylic stereocentres via Claisen rearrangement of enantiomerically pure allylic alcohols: Preparation of (R)- and (S)-3-methyl-2-phenylbutylamine
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The Johnson-Claisen rearrangement of enantiopure allylic alcohols in triethylorthopropionate is the key step for the preparation of chiral molecules with benzylic stereogenic carbon atoms bearing an isopropyl moiety. The synthetic procedure is applied to the preparation of (R)- and (S)-3-methyl-2-phenylbutylamine.
- Brenna, Elisabetta,Fuganti, Claudio,Gatti, Francesco G.,Passoni, Massimo,Serra, Stefano
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p. 2401 - 2406
(2007/10/03)
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- One-pot synthesis and resolution of chiral allylic alcohols
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Substituted α,β-unsaturated ketones were selectively reduced to the corresponding allylic alcohols under mild reaction conditions. The allylic alcohols thus obtained were kinetically resolved by lipase catalyzed transesterification in the same pot to affo
- Kamal, Ahmed,Sandbhor, Mahendra,Shaik, Ahmad Ali,Sravanthi
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p. 2839 - 2844
(2007/10/03)
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- Chelated enolates of amino acid esters - New and efficient nucleophiles for isomerization-free, stereoselective palladium-catalyzed allylic substitutions
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Chelated amino acid ester enolates were found to be suitable nucleophiles for palladium-catalyzed allylic alkylations. Unlike stabilized soft nucleophiles, the chelated enolates react under very mild reaction conditions, even at -78 °C. If TFA protected a
- Kazmaier, Uli,Zumpe, Franz L.
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p. 4067 - 4076
(2007/10/03)
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- Chemical-enzymatic synthesis of azasugar phosphonic acids as glycosyl phosphate surrogates
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Starting from achiral materials two stereoisomeric phosphonylated dihydroxypyrrolidines containing four stereogenic centers were synthesized enantioselectively employing a combination of enzymatic and transition-metal-mediated methods. Both compounds contain features of the transition state of the enzyme-catalyzed fucosyl transfer reaction and represent building blocks of potential inhibitors against this class of enzymes.
- Schuster, Matthias,He, Wei-Fang,Blechert, Siegfried
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p. 2289 - 2291
(2007/10/03)
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- Molybdenum(0) and tungsten(0) catalysts with enhanced reactivity for allylic substitution: Regioselectivity and solvent effects
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The binuclear Mo(II) and W(II) complexes 28a,b and 29a,b have been developed as pre-catalysts for allylic substitution with β-dicarbonyl nucleophiles. These complexes are reduced in situ to Mo(0) and W(0) catalytic species 30a,b and 31a,b by excess of NaH, employed to generate sodiomalonate nucleophiles, or by DIBAL-H. 1,3-Dioxolane and 1,4-dioxane, when used as solvents, substantially accelerate the reaction. These new catalysts exhibit "traditional" Mo regiochemistry, i.e., the nucleophilic attack occurring preferentially at the more substituted carbon (5 → 9; 37 → 38), unless an additional factor, such as further coordination to another moiety of the allylic electrophile takes part (41), as in the case of the geranyl-type substrates (32 or 33 → 36).
- Malkov,Baxendale,Mansfield,Kocovsky
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p. 1234 - 1240
(2007/10/03)
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- Dynamic kinetic resolution of allylic alcohols mediated by ruthenium- and lipase-based catalysts.
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An enzyme-metal combo reaction has been developed for the dynamic kinetic resolution of allylic alcohols in which racemic substrates are transformed by a lipase and a ruthenium complex in the presence of an acyl donor to allylic acetates of high optical purity in over 80% yield.
- Lee,Huh,Kim,Jung,Koh,Park
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p. 2377 - 2379
(2007/10/03)
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- The kinetic resolution of allylic alcohols by a non-enzymatic acylation catalyst; application to natural product synthesis
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A planar-chiral DMAP derivative is shown to serve as an effective catalyst for the kinetic resolution of allylic alcohols; to illustrate its practical utility, the catalyst is applied to the resolution of two alcohols that have been employed as intermedia
- Bellemin-Laponnaz, Stephane,Tweddell, Jennifer,Ruble, J. Craig,Breitling, Frank M.,Fu, Gregory C.
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p. 1009 - 1010
(2007/10/03)
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- Process for the production of chiral unsaturated alcohols in high optical purity
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The catalytic asymmetric hydrogenation of enol esters with a vinyllic or acetylenic substituent proceeds with extremely high enantioselectivity using a Rhodium-chiral bisphosphine catalyst. This is at variance with the hydrogenation of enol esters bearing a saturated substituent, which are hydrogenated with only marginal enantioselectivity under the same conditions.
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- Asymmetric hydrogenation of acyclic enol esters
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High enantioselectivity has been observed for the catalytic asymmetric hydrogenation of enol esters bearing a vinylic (≤94% ee) or acetylenic (>97% ee) substituent using a rhodium-chiral bisphosphine catalyst. This is at variance with the hydrogenation of enol esters bearing a saturated substituent, which are hydrogenated with only moderate enantioselectivity under the same conditions.
- Boaz, Neil W.
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p. 5505 - 5508
(2007/10/03)
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- Enantioselective esterifications of unsaturated alcohols mediated by a lipase prepared from Pseudomonas sp.
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Competition experiments and measurements of enantioselectivities were used to develop a simple active-site model (Figure 1) for resolutions of β-hydroxy-α-methylene carbonyl compounds III via acyl transfers mediated by lipase from Pseudomonas sp. (AK). Further experiments were used to test and refine this model with respect to resolutions of allylic, propargylic, homopropargylic, and other alcohols (Tables I-IV, respectively). The model proved extremely reliable for predicting the sense of the asymmetric induction, and the combined data collected in this paper give an indication of what structural features of the substrates can be correlated with high enantioselectivities in these resolutions. Furthermore, the results account for the conspicuous reversal of enantioselectivity previously observed in resolutions of γ-hydroxy-α,β-unsaturated esters 35. Kinetic resolutions of two substrates (allenol 14 and dienol 9) via asymmetric epoxidations were performed for comparison with the methodology presented in this paper.
- Burgess, Kevin,Jennings, Lee D.
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p. 6129 - 6139
(2007/10/02)
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