- 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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- Asymmetric reduction of ketones using recombinant E. coli cells that produce a versatile carbonyl reductase with high enantioselectivity and broad substrate specificity
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The gene encoding a versatile biocatalyst that shows high enantioselectivity for a variety of ketones, SCR (Saccharomyces cerevisiae carbonyl reductase), has been identified, cloned, and expressed in Escherichia coli. Two types of expression systems with high NADPH-regenerating capacities have been constructed. One is the tandem system, where the genes encoding SCR and GDH (glucose dehydrogenase) are located in the same plasmid, and the other is the two-plasmid system, where each of the SCR and GDH genes is located in separate plasmids that can coexist in one E. coli cell. Asymmetric reduction of ketones with the recombinant E. coli cells gave synthetically useful 20 alcohols, 11 of which were enantiomerically pure. The productivity of one of these products was as high as 41 g/L.
- Ema, Tadashi,Yagasaki, Hideo,Okita, Nobuyasu,Takeda, Masahiro,Sakai, Takashi
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- Asymmetric reduction of a variety of ketones with a recombinant carbonyl reductase: Identification of the gene encoding a versatile biocatalyst
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The gene encoding a versatile biocatalyst that shows high enantioselectivity for a variety of ketones, SCR (Saccharomyces cerevisiae carbonyl reductase), has been identified, cloned, and expressed in E. coli. Recombinant E. coli co-producing SCR and GDH (glucose dehydrogenase) is an easy-to-use, synthetically useful biocatalyst, and 8 out of the 16 alcohols obtained had enantiomeric purities of >98% ee.
- Ema, Tadashi,Yagasaki, Hideo,Okita, Nobuyasu,Nishikawa, Kumiko,Korenaga, Toshinobu,Sakai, Takashi
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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 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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supporting information
p. 11632 - 11636
(2013/11/06)
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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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- The baker's yeast reduction of 1-acetoxy-2-alkanones in the presence of a sulfur compound
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Improved enantioselectivity was achieved in the baker's yeast reduction of the 1-acetoxy-2-alkanone derivatives by the addition of a sulfur compound such as L-cysteine and phenyl vinyl sulfide. The reaction rate of the baker's yeast reduction was accelerated using a sulfur compound as an additive. The migration of the acetyl group and the hydrolysis of the acetoxy group of the substrate was suppressed using a sulfur compound.
- Hayakawa, Ryuuichirou,Shimizu, Makoto,Fujisawa, Tamotsu
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p. 3201 - 3204
(2007/10/03)
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- Asymmetric Reduction of 1-Acetoxy-2-alkanones with Baker's Yeast: Purification and Characterization of α-Acetoxy Ketone Reductase
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An α-acetoxy ketone reducing enzyme has been purified and characterized from the cell-free extract of bakers' yeast (Saccharomyces cerevisiae). Only one NADPH-dependent dehydrogenase that catalyzed the reduction of α-acetoxy ketone was found in bakers' yeast. The molecular weight of the enzyme was estimated to be 36 kDa by SDS-polyacrylamide gel electrophoresis. The enzyme was composed of a single polypeptide chain. The enzyme had reducing activity for both aliphatic and aromatic α-acetoxy ketones, although no reducing activity toward α-chloro ketones and α-hydroxy ketones was found. The enzyme catalyzed the reduction of not only α-acetoxy ketones, but also β-keto esters. Studies on the chromatographic behavior and stereospecificity indicated that the enzyme was identical with one of the β-keto ester reductases purified from bakers' yeast.
- Ishihara, Kohji,Nakajima, Nobuyoshi,Tsuboi, Sadao,Utaka, Masanori
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p. 3314 - 3319
(2007/10/02)
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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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- 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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