Enzyme catalyzed reaction Porcine pancreatic lipase

Kinetic resolutions by means of the selective formation or hydrolysis of an ester group in enzyme-catalyzed reactions proved to be a successful strategy in the enantioseparation of 1,3-oxazine derivatives. Hydrolysis of the racemic laurate ester 275 in the presence of lipase QL resulted in formation of the enantiomerically pure alcohol derivative 276 besides the (23, 3R)-enantiomer of the unreacted ester 275 (Equation 25) <1996TA1241 >. The porcine pancreatic lipase-catalyzed acylation of 3-(tu-hydroxyalkyl)-4-substituted-3,4-dihydro-2/7-l,3-oxazines with vinyl acetate in tetrahydrofuran (THF) took place in an enantioselective fashion, despite the considerable distance of the acylated hydroxy group and the asymmetric center of the molecule <2001PAC167, 2003IJB1958>. 

Porcine pancreatic lipase catalyzes the transesterification reaction between tribu-tyrin and various primary and secondary alcohols in a 99% organic medium (Zaks, 1984). Upon further dehydration, the enzyme becomes extremely thermostable. Not only can the dry lipase withstand heating at 100 °C for many hours, but it exhibits a high catalytic activity at that temperature. Reduction in water content also alters the substrate specificity of the lipase in contrast to its wet counterpart, the dry enzyme does not react with bulky tertiary alcohols. 

To find a suitable enzyme to catalyze the transesterification reaction (methyl ester to glycerol ester) under mild conditions, we screened a number of lipases and esterases. We found two lipases (Candida cylindracea lipase and porcine pancreatic lipase) to exhibit catalytic activity for this reaction. The reaction conditions entailed elevated temperatures, with the use of glycerol as the solvent and an acyl acceptor. The enzyme catalyzed the esterification of the carboxyl group of the pectin to the Cl (primary) alcohol of the glycerol to form the monoester. No substantial glycerol... 

Much of the current interest in making simple derivatives of (+ )-castanospermine (239) can be traced to a seminal publication in 1989, which showed that the alkaloid s anti-HIV activity could be increased by as much as twenty times upon esterification (216). Positionally selective acylation procedures usually involve sequential protection, acylation, and deprotection steps e.g. the preparation of esters at the C-6 and C-7 (217) or the C-8 hydroxy groups (218). Also of interest are procedures that take advantage of enzyme-catalyzed transesterification with activated esters, e.g. the use of subtilisin for ester formation at C-1, pancreatic porcine lipase for preferential reaction at C-6 and C-7 (219-221), and cross-linked enzyme crystals (CLECs) of subtilisin for making the potentially valuable antitumor agent 1-0-butanoylcastanospermine (222). A cautionary note was sounded, however, when it was observed that 6-0-acyl castanospermine esters could equilibrate to a mixture of... 

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