Fatty acids enantioselective esterification

C. cylindracea AOT Brij Esterification of aliphatic alcohols by fatty acids Enantioselective synthesis of ibuprofen esters Transesterification of triglycerides by fatty acids Esterification of DL-menthol [113-117]... 

Hydrolytic enzymes can also catalyzed the esterification of alcohols or acids with hetero atoms.1617 Some examples for the reactions of phosphorous and sulfur compounds by lipases are shown in Figure 16. By the repeated enantioselective acylation and hydrolysis of a hydroxyl phosphonate and its acetate with lipase AH, phosphonic acid analogue of carnitine (essential cofactor of fatty acid metabolism), (A)-phosphocarniiine, and its enantiomer were synthesized as shown in Figure 16 (b). 

W/O microemulsions have also been shown to be an effective system for the lipase-catalyzed enantioselective esterifications of racemic substrates [115,117]. It has been reported that the reaction rate for the esterification of the (-)-enantiomer of menthol with fatty acids catalyzed by P. simplicissimum lipase in AOT-based systems is seven times faster than the esterification rate of the (H-)-enantiomer... 

Scheme 9 Enantioselective esterifications with fatty acids.

The reactivity of lactic acid as an acyl donor and an alcohol nucleophile was investigated in detail by Adlercreutz and coworkers [72]. The esterificahon of lactic acid with a variety of alcohols in hexane was very promising when employing Novozym 435 as the biocatalyst. Moreover, it was found that in the esterification of (rocj-lactic acid, both enantiomers showed similar reactivity, which suggested that CALB is not enantioselective when the substituent is placed at the carbonyl side. Interestingly, no formation of lactic acid oligomers was observed, even if an excess of lactic acid was used, suggesting that the secondary alcohol is rather unreactive. This was corroborated when fatty acids were employed as acyl donor in an esterification of lactic acid, and no ester formahon was observed. Apparently,... 

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