- Baker's yeast-mediated reduction of α-hydroxy ketones and derivatives: The steric course of the biotransformation
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The results from the baker's yeast-mediated reduction of the acetates 3a- d and the methyl ethers 5a-d were compared with the same biotransformation which converts the α-hydroxy ketones 1a-d into the (R)-diols 2a-d (90- 98%ee); the acetates 3a-d afford the (S)-monoacetates 4a-d (72-94% ee) and the methyl ethers 5a-d are reduced to the (R)-monoethers 6a-d (64-76% ee).
- Ferraboschi, Patrizia,Grisenti, Paride,Manzocchi, Ada,Santaniello, Enzo
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- Enantioselective ring-opening reaction of epoxides with MeOH catalyzed by homochiral metal-organic framework
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Two new copper metal-organic frameworks containing 2,2′-dihydroxy-1, 1′-binaphthalene-5,5′-dicarboxylic acid (5,5′-H 2BDA) and 2,2′-dihydroxy-1,1′-binaphthalene-4,4′- dicarboxylic acid (4,4′-H2BDA) have been prepared. X-ray structure determination of [Cu2(5,5′-BDA)2(H 2O)2]·MeOH·2H2O (MOF-1) and [Cu2(4,4′-BDA)2(H2O)2] ·4H2O (MOF-2) revealed similar 2D sheet structures, containing square-grid coordination networks, but differences in the stacking motif. The desolvated MOF-1 and -2 were used as Lewis acid catalysts in the asymmetric ring-opening reaction of epoxides with MeOH.
- Tanaka, Koichi,Otani, Ken-Ichi,Murase, Takanori,Nishihote, Shyota,Urbanczyk-Lipkowska, Zofia
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experimental part
p. 709 - 714
(2012/08/08)
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- Activation of pig liver esterase in organic media with organic polymers. Application to the enantioselective acylation of racemic functionalized secondary alcohols
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Pig liver esterase (PLE) shows practically no activity in acylation of alcohols with vinylic esters in organic solvents. However, addition of methoxypoly(ethylene glycol) (MPEG), bovine serum albumin (BSA), TentaGelAmino resin (TGA), or aminomethyl polystyrene (AMPS) confers activity to PLE in acylation of alcohols with vinyl propionate in organic solvents of low water content. Polymer-activated PLE showed high enantioselectivities (E > 100) in the acylation of racemic 1-alkoxy-, 1-ethylsulfanyl-, and 1-fluoro-3-aryl-2-propanols as well as racemic 1-phenoxy-2-propanol and racemic 1-methoxy-2-phenoxy-2-propanol. The synthetic utility of polymer-activated PLE has been demonstrated by the gram-scale resolution of 1-methoxy-3-phenyl-2-propanol, 1-ethylsulfanyl-3-phenyl-2-propanol, 1-methoxy-3-p-methoxyphenyl-2-propanol, 1- fluoro-3-phenyl-2-propanol, and 1-methoxy-3-phenoxy-2-propanol. In PLE-catalyzed acylation of alcohols with vinyl propionate, acetaldehyde and propionic acids, both being detrimental to the enzyme, are formed as byproducts. In addition, the water content of the system, which is critical for the activity of pig liver esterase, is lowered because of a competing enzymatic hydrolysis of the acyl donor. The polymers TGA, BSA, and AMPS not only scavenge the aldehyde and the acid through imine formation and neutralization, respectively, but replenish at least in part also the water consumed in the competing hydrolysis of the acyl donor. A recovery of PLE together with the polymer was achieved without major loss of activity through their immobilization on a water-saturated polyaramide membrane, which occurs spontaneously in organic solvents.
- Gais,Jungen,Jadhav
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p. 3384 - 3396
(2007/10/03)
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- Zinc triflate-bis-oxazoline complexes as chiral catalysts: Enantioselective reduction of α-alkoxy-ketones with catecholborane
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A new methodology for the catalytic enantioselective reduction of α- alkoxy-ketones is described. The procedure employs Zn(OTf)2-bis-oxazoline complexes (8-10 mol%) as catalysts and catecholborane as the reducing agent. The reaction, carried ou
- Bandini, Marco,Cozzi, Pier Giorgio,De Angelis, Meri,Umani-Ronchi, Achille
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p. 1601 - 1605
(2007/10/03)
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- Application of pig liver esterase catalyzed transesterification in organic media to the kinetic resolution of glycerol derivatives
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The PLE/MPEG catalyzed transesterification of the glycerol ketals rac-1a and rac-1d-f with vinyl propionate in toluene proceeded with good selectivities (E=24-34) and gave the enantiomerically enriched S-alcohols 1a and 1d-f, and the S-esters 2a and 2d-f. High selectivities (E=99 and E≥200) were observed in the transesterification of the glycerol ether rac-3 and its desoxy analog rac-5, both having a secondary hydroxy group, with PLE/MPEG. In transesterifications in organic media PLE exhibited a much higher enantioselectivity than in hydrolysis in water.
- Jungen, Manfred,Gais, Hans-Joachim
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p. 3747 - 3758
(2007/10/03)
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