- Bridging racemic lactate esters with stereoselective polylactic acid using commercial lipase catalysis
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A productive and enantioselective hydrolysis of racemic mixtures of lactate esters with commercial Candida rugosa lipase was performed. This step contributes to a novel envisioned route for stereoselective PLA production by combining recent chemocatalytic developments with this biocatalytic contribution, foreseeing two separate l- and d-lactate enantiomer streams. A study of the hydrolysis kinetics identified an unexpected rate determining step at the origin of an unprecedented ester reactivity order.
- Van Wouwe, Pieter,Dusselier, Michiel,Basic, Aurelie,Sels, Bert F.
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supporting information
p. 2817 - 2824
(2013/10/08)
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- Enantioselectivity of haloalkane dehalogenases and its modulation by surface loop engineering
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In the loop: Engineering of the surface loop in haloalkane dehalogenases affects their enantiodiscrimination behavior. The temperature dependence of the enantioselectivity (lnE versus 1/T) of β-bromoalkanes by haloalkane dehalogenases is reversed (red data points) by deletion of the surface loop; the selectivity switches back when an additional single-point mutation is made. This behavior is not observed for -bromoesters.
- Prokop, Zbynek,Sato, Yukari,Brezovsky, Jan,Mozga, Tomas,Chaloupkova, Radka,Koudelakova, Tana,Jerabek, Petr,Stepankova, Veronika,Natsume, Ryo,Van Leeuwen, Jan G. E.,Janssen, Dick B.,Florian, Jan,Nagata, Yuji,Senda, Toshiya,Damborsky, Jiri
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supporting information; experimental part
p. 6111 - 6115
(2010/11/05)
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- Asymmetric hydrolysis of 2-hydroxy-carboxylic esters using recombinant Escherichia coli
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Optically active 2-hydroxy-carboxylates are important compounds for their use as intermediates in the synthesis of pharmaceuticals and stereoblock polymers. Enterobacter sp. DS-S-75 and the recombinant Escherichia coli harbouring the 4-chloro-3-hydroxybutyrate (CHB) hydrolase gene from the strain DS-S-75 showed asymmetric hydrolytic activity towards 2-hydroxy-carboxylates, as well as towards CHB. It was discussed that the hydroxyl group in the substrate was particularly important for the asymmetric hydrolytic activity of the CHB hydrolase, and as such, it was re-designated to EnHCH (hydroxy-carboxylic ester hydrolase derived from Enterobacter sp.). Using the recombinant cell, both the reaction rate and the concentration of the substrates were significantly improved upon when compared to that of DS-S-75. Optically active 2-hydroxy-carboxylates could be synthesized on a practical basis for industrial production in this report.
- Nakagawa, Atsushi,Kato, Ko,Shinmyo, Atsuhiko,Suzuki, Toshio
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p. 2394 - 2398
(2008/03/13)
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- Enantiomeric inclusion of α-hydroxy esters by (R)-(1-naphthyl)glycyl- (R)-phenylglycine and the crystal structures of the inclusion cavities
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A simple dipeptide, (R)-(1-naphthyl)glycyl-(R)-phenylglycine [(R,R)-1], formed inclusion compounds with several α-hydroxy esters (2) with high enantioselectivity. By crystallization of a mixture of the dipeptide [(R,R)- 1] and racemic 2a [MeCH(OH)COOMe] from methanol, asymmetric recognition occurred to give an inclusion compound that contains the S form of 2a in 89% ee. X-ray crystallographic study of the inclusion compound elucidated that the dipeptide molecules arrange in a 'folded antiparallel' β-sheetlike structure to accommodate the α-hydroxy ester in the pocket-type cavity surrounded by naphthyl and phenyl groups on the sheet. Similarly, 2b [MeCH(OH)-COOEt] and 2f [dihydro-3-hydroxy-4,4-dimethyl-2(3H)-furanone] were included with high enantioselectivity of the S form. When bulkier 21 [t- BuCH(OH)COOMe] was used as a guest molecule, the arrangement of dipeptide molecules changed to an 'extended antiparallel' mode, where the naphthyl and phenyl groups arranged in a 'parallel stacked and displaced' mode and a channel-type cavity was constructed. The guest molecules were accommodated via hydrogen bonding in the channel-type cavity with high enantioselectivity of the S form (82% ee). In the case of 2k [i-PrCH-(OH)COOMe], optically pure (S)-2k formed the dipeptide sheet with the 'folded antiparallel' structure by cocrystallization with (R,R)-1, while the 'extended antiparallel' structure appeared in the inclusion of racemic 2k.
- Akazome,Takahashi,Ogura
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p. 2293 - 2300
(2007/10/03)
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