- A Three-Dimensional Predictive Active Site Model for Lipase from
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A three-dimensional active site model of lipase from Pseudomonas cepacia - one of the most popular lipases in organic synthesis - was developed on the basis of the kinetic resolution of 3-(aryloxy)propan-2-ols. Size and shape of both hydrophobic binding pockets of the active site of this lipase were determined by substrate mapping in combination with molecular modeling for substrates and nonsubstrates. This model explains and predicts whether a compound is accepted as a substrate or not and allows to assess the enantiomer selectivity of the lipase-catalyzed reaction.
- Lemke, Karin,Lemke, Michael,Theil, Fritz
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- Lipase-catalysed kinetic resolution of phenylethan-1,2-diol by sequential transesterification - the influence of the solvent
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The enantiomer selectivity of the kinetic resolution of phenylethan-1,2-diol [(RS)-1] by sequential acetylation with vinyl acetate in the presence of lipase from Pseudomonas cepacia (Armano PS) was investigated for dependence on the solvent. Optimal conditions for the resolution of (RS)-1 are presented.
- Lemke, Karin,Theil, Fritz,Kunath, Annamarie,Schick, Hans
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- 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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- Enantioselective Deuteration of β-Substituted α,β-Unsaturated Esters by Rhodium-1,2-Bis(2,5-diphenylphospholano)ethane
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We report an efficient method for the synthesis of a chiral C-CHD-CHD-C unit in threo form, which enables the asymmetric conformational analysis of straight alkyl chains. The vicinal dideuterated compound was constructed by enantioselective catalytic deut
- Lethu, Sébastien,Ano, Hikaru,Murata, Michio,Matsuoka, Shigeru
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supporting information
p. 235 - 239
(2018/01/27)
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- Enantioselective Vicinal Diacetoxylation of Alkenes under Chiral Iodine(III) Catalysis
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A procedure for the intermolecular enantioselective dioxygenation of alkenes under iodine(III) catalysis has been developed. This protocol employs Selectfluor as the terminal oxidant together with a defined C 2-symmetric aryl iodide as the organocatalyst. This enantioselective reaction proceeds under mild conditions and converts a series of terminal and internal styrenes into the corresponding vicinal diacetoxylation products with up to 96% ee.
- W?ste, Thorsten H.,Mu?iz, Kilian
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p. 816 - 827
(2016/03/15)
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- Palladium-catalyzed asymmetric hydrogenation of α-acyloxy-1- arylethanones
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First hand: The first example of a palladium-catalyzed asymmetric hydrogenation of α-acyloxy ketones (1) was accomplished to give the hydrogenated products 2 with by far the highest catalytic efficiency in up to quantitative conversions and excellent enantioselectivities. The hydrogenated products could serve as important intermediates for the preparation of many drug candidates. TFE=2,2,2-trifluoroethanol. Copyright
- Chen, Jianzhong,Liu, Delong,Butt, Nicholas,Li, Chao,Fan, Dongyang,Liu, Yangang,Zhang, Wanbin
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p. 11632 - 11636
(2013/11/06)
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- Chemoenzymatic synthesis of enantiomerically pure 1,2-diols employing immobilized lipase in the ionic liquid [bmim]PF6
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Significantly enhanced enantioselectivity in the enzymatic kinetic resolution of 1,2-diols employing immobilized lipase from Pseudomonas cepacia (PS-C, 'Amano') results from the use of the ionic liquid [bmim]PF6 as reaction medium.
- Kamal, Ahmed,Chouhan, Gagan
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p. 8801 - 8805
(2007/10/03)
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- Chemoenzymatic synthesis of enantiomerically pure terminal 1,2-diols
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A new practical method for the enzymatic synthesis of 1,2-diols has been developed by employing a lipase catalyzed one-pot transesterification protocol. A series of substituted α-acetoxyphenylethanones 3a-g have been reduced to the corresponding alcohols under mild conditions employing sodium borohydride and moist neutral alumina, and further subjected for lipase catalyzed irreversible transesterification in the same pot to give mono- and diacetate diols (R)-4 and (S)-5, which on hydrolysis afforded terminal 1,2-diols, (R)- and (S)-6 in high enantiomeric excess.
- Kamal, Ahmed,Sandbhor, Mahendra,Ahmed, Kaleem,Adil,Shaik, Ahmad Ali
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p. 3861 - 3866
(2007/10/03)
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- Microbial transformation of 2-hydroxy and 2-acetoxy ketones with Geotrichum sp.
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Biotransformation of a series of o-, m- and p-substituted α-hydroxy- and α-acetoxyphenylethanones 1a-h and 9a-g with Geotrichum sp. led to the corresponding 1,2-diols 2 and/or monoacetates 10 in moderate to excellent enantiomeric excesses. α-Hydroxy- and α-acetoxyphenylethanones and their m- and p-derivatives gave preponderantly the S-configuration products while in the case of the o-derivatives R-alcohol was provided as the major enantiomer. The results of stereoselectivity were discussed. (C) 2000 Elsevier Science Ltd.
- Wei, Zhi-Liang,Lin, Guo-Qiang,Li, Zu-Yi
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p. 1129 - 1137
(2007/10/03)
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- Kinetic resolution of acyclic 1,2-diols using a sequential lipase- catalyzed transesterification in organic solvents
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A method for the kinetic resolution of 3-(aryloxy)-1,2-propanediols rac- 1a-n without additional protection-deprotection steps using a lipase- catalyzed sequential transesterification with lipase amano PS has been developed. In the first step of this one-pot procedure the racemic 1,2-diols are acylated regioselectively at the primary hydroxy group without enantioselection. The subsequent acylation at the secondary hydroxy group of the formed primary monoacetate is responsible for high enantioselection. The enantioselectivity of this transformation depends significantly on the substitution pattern of the aryl ring and the organic solvent used. 3- (Aryloxy)-1,2-propanediols with substituents in the para-position show a much higher enantioselectivity than the corresponding derivatives with ortho- substituents. Among other substrates, the pharmaceuticals Mephenesin, Guaifenesin, and Chlorphenesin have been resolved. The replacement of the aryloxy by an alkyl substituent causes a dramatic decrease of enantioselectivity.
- Theil,Weidner,Ballschuh,Kunath,Schick
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p. 388 - 393
(2007/10/02)
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- Kinetic resolution of aliphatic 1,2-diols by a lipase-catalyzed sequential acetylation
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The kinetic resolution of 13 racemic aliphatic 1,2-diols (rac-1a-m) by means of a lipase-catalyzed sequential acetylation was investigated. The enantioselectivity of the 3-aryloxy-propane-1,2-diols rac-1a-k depends on the substitution pattern at the aryl ring.
- Theil, Fritz,Weidner, Judith,Ballschuh, Sibylle,Kunath, Annamarie,Schick, Hans
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p. 305 - 306
(2007/10/02)
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- Baker's Yeast Mediated Bioreduction. A New Procedure Using Ethanol as an Energy Source
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A practical procedure using ethanol as an energy source was developed on the bakers's yeast mediated bioreduction of prochiral ketones.
- Kometani, Tadashi,Kitatsuji, Eitaro,Matsuno, Ryuichi
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p. 1465 - 1466
(2007/10/02)
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- ASYMMETRIC REDUCTION OF PROCHIRAL HYDROXY KETONES WITH A CHIRAL REDUCING AGENT PREPARED FROM TIN(II) CHLORIDE, A CHIRAL DIAMINE, AND DIISOBUTYLALUMINUM HYDRIDE
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Asymmetric reduction of prochiral α- and β-hydroxy ketones with a reagent, generated from tin(II) chloride, a chiral diamine, and diisobutylaluminum hydride, afforded the corresponding dihydroxy compounds in good chemical and optical yields.Optical yields depended on the nature of the protective groups of hydroxyl function.
- Mukaiyama, Teruaki,Tomimori, Koji,Oriyama, Takeshi
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p. 1359 - 1362
(2007/10/02)
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- Chiral Recognition of Natural Products on Optically Active Polysiloxanes
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Polysiloxanes with chiral peptide side chains have been synthesized and used as stationary phases in gas chromatography.With these phases amino acid enantiomers can be separated as N-acyl esters.Due to temperature stability up to 230 deg C all protein amino acids can be separated and the racemization of synthetic biologically active peptides controlled.The phases can be used to assign the absolute configuration of amino acids.A variety of other classes of compounds can be separated into their enantiomers using the chiral polysiloxanes, like hydroxy acids, sulfoxides, phosphorous compounds, glycols, atrop isomers, amines and alcohols.Various applications of these phases are described including investigations of enantiomer selectivity in nature. - Key words: Polysiloxanes, Enantiomers, Racemization
- Bayer, Ernst
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p. 1281 - 1291
(2007/10/02)
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