Anju Chadha

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).

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.

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.