Now showing 1 - 7 of 7
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    Biocatalytic deracemisation of aliphatic β-hydroxy esters: Improving the enantioselectivity by optimisation of reaction parameters
    (01-02-2015)
    Venkataraman, Sowmyalakshmi
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    Optically pure aliphatic β-hydroxy esters were prepared from their racemates by deracemisation using the biocatalyst Candida parapsilosis ATCC 7330. High optical purity (up to >99 %) and good yields (up to 71 %) of the product secondary alcohols were obtained. This study highlights the importance of optimization of reaction conditions using ethyl-3-hydroxybutanoate as the model substrate to improve the enantioselectivity (enantiomeric excess from 9 to 98 %). The present study emphasises the broad substrate scope of the biocatalyst towards deracemisation. This is the first report of Candida parapsilosis ATCC 7330-mediated deracemisation of various alkyl-3-hydroxybutanoates to produce either the (R)-enantiomers (methyl, ethyl, propyl, butyl, t-butyl, allyl-3-hydroxybutanoates) or (S)-enantiomers (pentyl, iso-amyl and iso-propyl-3-hydroxybutanoates).
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    Publication
    Microbial deracemisation of aromatic β-hydroxy acid esters
    (21-06-2004)
    Padhi, Santosh Kumar
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    Pandian, N. Ganesh
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    Aromatic β-hydroxy acid esters were found to undergo deracemisation using whole cells of Candida parapsilosis. The conditions for the deracemisation reaction were optimised where ∼75% isolated yield and >95% enantiomeric excess of the product was achieved. The effect of electron donating as well as electron withdrawing groups present in the standard substrate, ethyl 3-hydroxy 3-phenyl propionate was studied to establish the generality of the reaction. The enantiomeric excess of the product remains high (>95%) irrespective of the different substituents in the para position but substitution at the ortho position obstructs the process. Similarly, ethyl and methyl esters of the standard substrate undergo deracemisation reaction giving high ee of the product, but the benzyl ester of the standard substrate did not undergo deracemisation. © 2004 Elsevier B.V. All rights reserved.
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    Publication
    Deracemisation of aryl substituted α-hydroxy esters using Candida parapsilosis ATCC 7330: Effect of substrate structure and mechanism
    (26-12-2005)
    Baskar, B.
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    Pandian, N. G.
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    Priya, K.
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    Candida parapsilosis ATCC 7330 was found to be an efficient biocatalyst for the deracemisation of aryl α-hydroxy esters (65-85% yield and 90-99% ee). A variety of aryl and aryl substituted α-hydroxy esters were synthesized to reflect steric and electronic effects on biocatalytic deracemisation. The mechanism of this biocatalytic deracemisation was found to be stereoinversion. © 2005 Elsevier Ltd. All rights reserved.
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    Candida parapsilosis ATCC 7330 can also deracemise 1-arylethanols
    (01-12-2011)
    Kaliaperumal, Tarjan
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    Candida parapsilosis ATCC 7330 grown using different culture conditions (inoculum size 4% (v/v), inoculum age 12 h, and harvest time 14 h) from those previously reported (inoculum size 2% (v/v), inoculum age 24 h, and harvest time 44 h) successfully deracemised racemic 1-arylethanols and 4-phenyl-2-butanol to the (R)-enantiomer (ee up to >99%). The deracemisation of racemic 1-aryl ethanol proceeds via (i) enantioselective oxidation of (S)-enantiomer followed by (ii) reduction of the ketone formed to give the racemic alcohol which gets kinetically resolved thus enriching for the (R)-enantiomer from the racemate. This is the first report on the deracemisation of 1-arylethanols using Candida parapsilosis ATTC 7330 via dynamic kinetic resolution. © 2011 Informa UK, Ltd.
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    Publication
    Deracemisation of β-hydroxy esters using immobilised whole cells of Candida parapsilosis ATCC 7330: substrate specificity and mechanistic investigation
    (22-05-2006)
    Padhi, Santosh Kumar
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    Titu, D.
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    Pandian, N. Ganesh
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    Deracemisation of aryl substituted β-hydroxy esters by immobilised whole cells of Candida parapsilosis ATCC 7330 gave >99% ee and up to 75% yield of their corresponding (S)-enantiomers. Mechanistic investigation of the deracemisation reaction carried out using a deuterated substrate, ethyl 3-deutero-3-hydroxy-3-phenyl propanoate revealed that while the (S)-enantiomer remains unreacted the (R)-enantiomer undergoes enantioselective oxidation to its corresponding ketoester, which on complementary enantiospecific reduction gives the (S)-enantiomer in high yield and % ee. © 2006 Elsevier Ltd. All rights reserved.
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    Preparation of optically pure alkyl 3-(hetero-2-yl)-3-hydroxypropanoates by Candida parapsilosis ATCC 7330 mediated deracemisation
    (01-06-2008)
    Titu, D.
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    Deracemisation of racemic alkyl 3-(hetero-2-yl)-3-hydroxypropanoates using whole cells of Candida parapsilosis ATCC 7330 resulted in the formation of the 'S' enantiomer in high enantiomeric excess (up to >99% ee) and isolated yields (up to 75%). © 2007 Elsevier B.V. All rights reserved.
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    Preparation of enantiomerically enriched (S)-ethyl 3-hydroxy 4,4,4-trifluorobutanoate using whole cells of Candida parapsilosis ATCC 7330
    (01-01-2015)
    Venkataraman, Sowmyalakshmi
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    Optically pure (S)-ethyl 3-hydroxy 4,4,4-trifluorobutanoate was prepared using the biocatalyst Candida parapsilosis ATCC 7330 by deracemisation of the racemic alcohol ester in high optical purity (96%) and yield (65%) and by asymmetric reduction from its prochiral ketone (ee up to 84% and yield 60%) under different reaction conditions. This study highlights the possibility of using the same biocatalyst to produce (S)-ethyl 3-hydroxy 4,4,4-trifluorobutanoate using different strategies.