Stereoselective Esterifications of Racemic Carboxylic Acids

The enantioselective esterification of (R,S)-2-phenylpropanoic acid in organic solvent was studied by using dry myceUa of A. oryzae MIM and R. oryzae CBS 

The two micro-organisms were enantiocomplementary since A. oryzae MIM showed preference for the formation of the S-ester, while R. oryzae CBS 

07 preferentially gave the R-ester. As shown in Table 6.5, the highest enanti-oselectivity was obtained with both strains when the esterification was carried out with ethanol a suitable combination of solvent and temperature allows for high enantioselectivily. 

Flurbiprofen is a cyclooxygenase (COX)-inhibiting non-steroidal anti-inflammatory drug (NSAID). The COX-inhibiting activity resides primarily in the (S)-enantiomer whereas the (R)-enantiomer has scarce COX activity. (R)-Flurbiprofen has been found to inhibit tumor growth in various animal models. In vitro experiments have shown that this effect is based on the induction of a cell cycle block and apoptosis [21]. 

At 50 °C the maximum conversion (about 55%) was achieved with 84% e.e. of the unreacted (S)-flurbiprofen. It is noteworthy that molar conversion was complete, although during the direct esterification some water was produced. 

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Stereoselective Esterifications of Racemic Carboxylic Acids 85 IPG butyrate —IPG... 

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