Industrial Biotransformations

3.9 Carboxylic Acids
Other approches include the use of thioesters to increase the acidity of the a-proton
[25], or aryl acetic esters [26].
A reversible Michael reaction can also be used to design dynamic resolution [27].
Ar
iPrO O
N O
lipase
Ar
iPrO O
N O
+
Ar
iPrO O
N O
The internal low stability of hemiacetols has been explored for the dynamic resolution
of 6-acetyloxy-2H-pyran-3(6H)-one [28].
O
O
OH
lipase
vinyl acetate
O
OH
Microbial deracemization has been reported for 2-methyl carboxylic acids via a CoA
intermediate [29]. The use of thioesters is known to facilitate racemization of the a-chiral
center [30].
acyl-CoA synthetase
O
O
O
OAc
arylpropionyl CoA
epimerase
R COOH R COOH
R COSCoA
b-Ketohydrolases can convert diketones into keto acids [31].
O
R
O
OH
ß-ketohydrolases
O
+
R
O
O
O
OH
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