A Continuous-Flow Cascade Reactor System for Subtilisin A- Catalyzed Dynamic Kinetic Resolution of N-tert-Butyloxycarbonylphenylalanine Ethyl Thioester with Benzylamine

Péter Falus, Lorenzo Cerioli, Gabriella Bajnóczi, Zoltán Boros, Diána Weiser, József Nagy, Davide Tessaro, Stefano Servi, L. Poppe

Research output: Contribution to journalArticle

19 Citations (Scopus)

Abstract

Alcalase® (Subtilisin A) was immobilized by simple hydrophobic adsorption onto various surface-grafted macroporous silica gels resulting in easy-to-prepare and stable biocatalysts enabling the efficient kinetic resolution (KR) and dynamic kinetic resolution (DKR) of racemic N-Boc-phenylalanine ethyl thioester with benzylamine. The immobilized Alcalase biocatalysts, which retained their activity and selectivity when stored at 4°C for more than a year, were tested in enzymatic aminolysis in batch and continuous-flow KRs resulting in (S)-N-Boc-phenylalanine benzylamide in high enantiomeric purity. In KR of the racemic thioester by Alcalase-catalyzed aminolysis in a continuous-flow reactor, the productivity (specific reaction rate, rflow) and enantiomeric ratio (E) were studied in the 0-100°C range. The effect of the temperature on base-catalyzed racemization of the non-transformed (R)-thioester in a continuous-flow reactor was also investigated in the 0-150°C range. The continuous-mode DKR of the racemic thioester in a serial cascade system of six biocatalyst-filled columns at 50°C for KR and five grafted silica gel-filled columns at 150°C for racemization resulted in the formation of the (S)-benzylamide in 79% conversion, 8.17gL-1h-1 volumetric productivity and 98% ee. This is the first example of a dynamic kinetic resolution of an amino acid derivative in continuous-flow mode using an alternating cascade of packed-bed enzyme reactors and racemization reactors kept at different temperatures.

Original languageEnglish
JournalAdvanced Synthesis and Catalysis
DOIs
Publication statusAccepted/In press - 2016

Keywords

  • Amino acid amides
  • Biocatalysis
  • Continuous-flow biotransformation
  • Dynamic kinetic resolution
  • Enantioselectivity
  • Subtilisin A
  • Supported catalysts

ASJC Scopus subject areas

  • Catalysis
  • Organic Chemistry

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