Deracemisation of aromatic β-hydroxy esters using immobilised whole cells of Candida parapsilosis ATCC 7330 and determination of absolute configuration by 1H NMR

Deracemisation of aryl and substituted aryl β-hydroxy esters using immobilised whole cells of Candida parapsilosis ATCC 7330 yields the corresponding (S)-enantiomer in >99% enantiomeric excess and good yield (up to 68%). The absolute configuration of ethyl 3-(2,4-dichlorophenyl)-3-hydroxy propanoate and ethyl 3-hydroxy-5-phenyl-pent-4-enoate as determined by 1H NMR using MTPA chloride was found to be ‘S’. The chemical shifts of the methoxy groups of the two diastereomeric MTPA esters were used as diagnostic signals to determine the absolute configuration.

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Ethyl (S)-3-hydroxy 3-phenylpropanoateC11H14O3Ee: 99%[α]D25=-50.1 (c 1.5, CHCl3)Source of chirality: microbial deracemisationAbsolute configuration: (3S)

Ethyl (S)-3-hydroxy 3-(p-methylphenyl)propanoateC12H16O3Ee: 98%[α]D25=-44.6 (c 1.2, CHCl3)Source of chirality: microbial deracemisationAbsolute configuration: (3S)

Ethyl (S)-3-hydroxy 3-(p-chlorophenyl)propanoateC11H13O3ClEe: 99%[α]D25=-43.7 (c 1.38, CHCl3)Source of chirality: microbial deracemisationAbsolute configuration: (3S)

Ethyl (S)-3-hydroxy 3-(p-nitrophenyl)propanoateC11H13NO5Ee: 99%[α]D25=-59.5 (c 1.5, CHCl3)Source of chirality: microbial deracemisationAbsolute configuration: (3S)

Ethyl (S)-3(o,p-dichlorophenyl)-hydroxypropanoateC11H12O3Cl2Ee: 82%[α]D25=-39.8 (c 1.5, CHCl3)Source of chirality: microbial deracemisationAbsolute configuration: (3S)

Ethyl (S)-3-hydroxy-5-phenyl-pent-4-enoateC13H16O3Ee: >99%[α]D25=-2.6 (c 2.7, CHCl3)Source of chirality: microbial deracemisationAbsolute configuration: (3S)