Highly Enantioselective Hydrolysis of (R,S)-Phenylalanine Isopropyl Ester by Subtilisin Carlsberg. Continuous Synthesis of (S) -Phenylalanine in a Hollow Fiber/Liquid Membrane Reactor
The resolution of racemic phenylalanine esters with esterases has been reexamined in relation to the development of a continuous process based on the use of hollow fiber/liquid membrane (SLM) reactors. The requirement for high enantioselectivity was met by phenylalanine isopropyl ester, whose (R)‐en...
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Published in | Biotechnology progress Vol. 8; no. 3; pp. 197 - 203 |
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Main Authors | , , , |
Format | Journal Article |
Language | English |
Published |
USA
American Chemical Society
01.05.1992
American Institute of Chemical Engineers |
Subjects | |
Online Access | Get full text |
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Summary: | The resolution of racemic phenylalanine esters with esterases has been reexamined in relation to the development of a continuous process based on the use of hollow fiber/liquid membrane (SLM) reactors. The requirement for high enantioselectivity was met by phenylalanine isopropyl ester, whose (R)‐enantiomer was found refractory to the action of subtilisin Carlsberg, in water, pH 7.5, at 25 °C. The continuous feeding of (R, S)‐Phe‐O‐iPr‐HCl at 2 mm/h to 0.7 g/L subtilisin resulted in steady‐state reaction conditions that gave (S)‐Phe‐OH of 95% enantiomeric excess (ee) at the theoretical rate. The unreacted (R)‐Phe‐O‐iPr, which permeated out continuously, had 80% ee and was racemized quantitatively by heating with a salicylaldehyde catalyst in refluxing toluene. Doubling the feeding rate (4 mm/h) created excessive accumulation of (R)‐Phe‐O‐iPr in the reactor, which inhibited the enzyme through nonproductive binding, lowering the (S)‐Phe‐OH resolution rate to 68% of the theoretical rate. Similar experiments with (R, S)‐Phe‐OMe‐HCl gave (S)‐Phe‐OH of 9–48% ee, due to the enzymatic hydrolysis of (R)‐Phe‐OMe experienced during the runs. When α‐chymotrypsin was used for the continuous hydrolysis of (R, S)‐Phe‐O‐iPr, the isolated (S)‐Phe‐OH showed 67% ee, indicating that substantial hydrolysis of the (‐R)‐ester had occurred. |
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Bibliography: | ark:/67375/WNG-1GRKRN4W-F istex:88FA86D5A72EB09BC2A84852685F55477CEBF6A9 ArticleID:BTPR5420080305 ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23 |
ISSN: | 8756-7938 1520-6033 |
DOI: | 10.1021/bp00015a004 |