Biocatalytic cascade reactions for asymmetric synthesis of aliphatic amino acids in a biphasic reaction system

Eul Soo Park, Jong Shik Shin

Research output: Contribution to journalArticlepeer-review

15 Citations (Scopus)

Abstract

Abstract Enantiopure aliphatic amino acids, including l-3-hydroxyadamantylglycine (l-Hag), l-tert-leucine (l-Tle) and l-norvaline, are essential chiral building blocks for a number of pharmaceutical drugs. Here, we developed cascade enzyme reactions in an extractive biphasic system using a branched-chain amino acid transaminase (BCTA) and an (S)-selective ω-transaminase (ω-TA) for asymmetric synthesis of the aliphatic amino acids from achiral α-keto acid precursors. The extractive cascade reactions enabled equilibrium shift of the BCTA reaction by recycling an amino acid cosubstrate as well as acceleration of the ω-TA reaction by removing an inhibitory ketone product from an aqueous phase. Starting with 20 mM α-keto acid, 4 mM rac-homoalanine and 50 mM rac-α-methylbenzylamine (rac-α-MBA), the biphasic cascade reactions afforded synthesis of four unnatural amino acids (i.e., l-Tle, l-Hag, l-norvaline and l-norleucine) and two natural amino acids (i.e., l-valine and l-Leucine) with >92% conversion yield and >99.9% ee. To demonstrate the industrial feasibility of the extractive cascade reaction, preparative-scale synthesis of l-Hag was performed in a reaction mixture consisting of 300 mL hexane and 50 mL aqueous solution (50 mM phosphate buffer, pH 7.0) charged with 50 mM keto acid substrate, 5 mM l-homoalanine, 120 mM rac-α-MBA, 2 U/mL BCTA and 16 U/mL ω-TA. Conversion yield of l-Hag reached 92% with >99.9% ee at 70 h. Product isolation led to 0.32 g white solid of l-Hag (62 % isolation yield).

Original languageEnglish
Article number3203
Pages (from-to)9-14
Number of pages6
JournalJournal of Molecular Catalysis B: Enzymatic
Volume121
DOIs
Publication statusPublished - 2015 Aug 11

Bibliographical note

Funding Information:
This work was supported by the Advanced Biomass R&D Center (ABC-2011-0031358) through the National Research Foundation of Korea and the R&D grant ( S2173394 ) funded by the Small and Medium Business Administration of Korea.

All Science Journal Classification (ASJC) codes

  • Catalysis
  • Bioengineering
  • Biochemistry
  • Process Chemistry and Technology

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