Racemic ibuprofen esterification water

Table 9 influence of the Lyophilization and the Presence of Water on the Esterification of Racemic Ibuprofen, Catalyzed by Immobilized Lipase from C. rugosa in Isooctane... 

Table 10 Influence of Water on the Enantioselectivity of Native and Immobilized Lipt e from C. cylindracea in the Esterification of Racemic Ibuprofen with n-Propanol...

The functions of chiral drugs in human body are closely related to their configurations. It has been reported that the R- and S-isomers of ibuprofen have quite different biological activities and toxicides. So it is imperative to prepare enan-tiomerically pure ibuprofen. Song el al. conducted a study on the lipase-catalyzed esterification of racemic ibuprofen with octanol in AOT reverse micelles [108,109] and found that the esterification is enantioselective and the main product is the corresponding S (-H)-ibuprofen ester, with the conversion yield and the enantiomer excess being about 36% and 0.9732, respectively. The water content and the concentration of AOT in the medium affected the conversion yield, but they had little influence on the enantiomeric excess (Table 15.7). Also, it was found that the chain lengths of alcohols affected both the rate of the reaction and the enantiomeric excess of the products. 

Another approach for the enzymatic preparation of 5-ibuprofen has been demonstrated by de Zoete et al. [229]. The enantioselective ammonolysis of ibuprofen 2-chlo-roethyl ester by Candida antarctica lipase (lipase SP435) gave the remaining ester 5-(+) enantiomer in 44% yield and 96% e.e. The enantioselective enzymatic esterification of racemic ibuprofan has also been demonstrated using lipase from Candida cylindraceae [230]. The reaction was carried out in a water-in-oil microemulsion [bis(2-ethyl-hexyl)sulfosuccinate (AOT)/isooctane). The lipase showed high preference for the S-(+) enantiomers of ibuprofen which was esterified and R-(—) enantiomer remained unreacted. The reaction yield of 35% was obtained using n-propanol in the reaction mixture as nucleophile. 

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