- Synthesis of optically active 2-hydroxy monoesters via-kinetic resolution and asymmetric cyclization catalyzed by heterometallic chiral (salen) Co complex
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The binuclear chiral (salen) Co complexes bearing Lewis acids of Al and Ga catalyze regio- and enantioselective ring opening of terminal epoxides with carboxylic acids. The ring opened product of epichlorohydrin with carboxylic acids followed by cyclization step in the presence of catalyst and base represent straightforward, efficient methods for the synthesis of enatiomerically enriched (>99% ee) valuable terminal epoxides. Strong synergistic effects of different Lewis acid of Co-Al and Co-Ga were exhibited in the catalytic process.
- Li, Wenji,Thakur, Santosh Singh,Chen, Shu-Wei,Shin, Chang-Kyo,Kawthekar, Rahul B.,Kim, Geon-Joong
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- Ketoreductases: Stereoselective catalysts for the facile synthesis of chiral alcohols
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The results of a reduction of a wide range of ketones using 31 commercially available isolated ketoreductases (KREDs) are presented. All enzymes accepted a wide substrate range. The stereoselectivity of each enzyme was measured for the reduction of benzoyl-hydroxyacetone and ethyl-3-oxobutanoate, and in each case, enzymes which produce enantiomerically pure (R)- and (S)-alcohols were found. The preparative scale reactions were investigated using two ketones with different hydrophobicities (benzoyl-hydroxyacetone and α-tetralone) and using enzymes with varying specific activities for their reduction. Regardless of the hydrophobicity of the substrate, high titers of ketone (0.75-1.4 M) were reduced in high yield using catalytic amounts of enzyme (1-7% g/g relative to substrate) and cofactor (0.1-0.2% equiv. relative to ketone) within 4-24 h. The cofactor was efficiently regenerated in situ via the oxidation of glucose by glucose dehydrogenase, an enzyme that has also been cloned and over-expressed. These results show that isolated ketoreductases can be quickly and easily screened against target ketones, and the reactions can be scaled to produce preparative amounts of chiral alcohols. Ketoreductase enzymes should become a standard addition to the organic chemists toolbox of asymmetric catalysts for stereoselective ketone reduction.
- Kaluzna, Iwona A.,David Rozzell,Kambourakis, Spiros
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- Kinetic Resolution of 1,2-Diols via NHC-Catalyzed Site-Selective Esterification
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A kinetic resolution of 1,2-diols bearing both a secondary and a primary alcohol motif through an N-heterocyclic carbene-catalyzed oxidative acylation reaction has been developed. A site- and enantioselective esterification reaction is involved for this process. Both the monoacylated diols obtained and the remaining enantioenriched 1,2-diols are versatile building blocks for the preparation of functional molecules with proven biological activities.
- Liu, Bin,Yan, Jiekuan,Huang, Ruoyan,Wang, Weihong,Jin, Zhichao,Zanoni, Giuseppe,Zheng, Pengcheng,Yang, Song,Chi, Yonggui Robin
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supporting information
p. 3447 - 3450
(2018/06/26)
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- Kinetic resolution of 1,2-diols using nitrogen-tethered bisimidazoline-copper(I) catalyzed benzoylation
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Nitrogen-tethered bisimidazoline (Nb-imidazoline) ligand was utilized in the Cu(I)-catalyzed benzoylation of 1,2-diols. With the assistance of i-Pr2NEt, the reaction of rac-1,2-diols with o-methylbenzoyl chloride was smoothly catalyzed by Nb-imidazoline-CuCl in CH2Cl2 to give the corresponding o-methylbenzoylated secondary alcohols in up to 79% ee.
- Arai, Takayoshi,Mizukami, Tomoe,Mishiro, Asami,Yanagisawa, Akira
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experimental part
p. 995 - 1000
(2009/06/28)
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- LEVODOPA PRODRUGS, AND COMPOSITIONS AND USES THEREOF
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Prodrugs of levodopa, methods of making prodrugs of levodopa, methods of using prodrugs of levodopa, and compositions of prodrugs of levodopa are disclosed. Wherein Q is selected from X-CO-, and -CO-X-; X is selected from-O-, and -NR6-; n is an
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Page/Page column 52
(2008/06/13)
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- Lipase-catalyzed selective benzoylation of 1,2-diols with vinyl benzoate in organic solvents
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Lipases from Mucor miehei (MML) and Candida antarctica (CAL) are able to catalyze the benzoylation of the primary hydroxy group of 1,2-diols with vinyl benzoate in organic solvents. We have studied the MML-catalyzed benzoylation that proceeds with high re
- Ciuffreda, Pierangela,Alessandrini, Laura,Terraneo, Giancarlo,Santaniello, Enzo
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p. 3197 - 3201
(2007/10/03)
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