Dynamic Kinetic Resolution of α‐Aminonitriles to Form Chiral α‐Amino Acids

Abstract

Abstract:We have succeeded in the enzymatic synthesis of (R)-a-aminobutyric acid from racemic aaminobutyronitrile. This has been demonstrated by the use of non-stereoselective nitrile hydratase (NHase) from Rhodococcus opacus 71D, d-aminopeptidase from Ochrobactrum anthropi C1-38 and a-amino-e-caprolactam (ACL) racemase from Achromobacter obae. Racemic a-aminobutyronitrile was completely converted in 6 h at 30 8C to (R)-aaminobutyric acid whose optical purity was more than 99%. (S)-a-Aminobutyric acid was also synthesized from a-aminobutyronitrile by NHase, ACL racemase and l-amino acid amidase from Brevundimonas diminuta TPU 5720. In a similar manner, other (R)-or (S)-a-amino acids with more than 97.5% ee could be synthesized from the corresponding a-aminonitriles. This is the first report on the dynamic kinetic resolution (DKR) of a-aminonitriles to form chiral a-amino acids. The key enzyme in this DKR is non-stereoselective NHase, which had been newly screened from soil samples, and its gene cloned.

Enzymes for pharmaceutical and therapeutic applications

“…Dynamic kinetic resolution of α-aminonitriles to produce chiral α-amino acids (adopted from Ref. [54])…”

Overview on Multienzymatic Cascades for the Production of Non-canonical α-Amino Acids

“…The Amidase Process has been further expanded by including non-stereoselective nitrile hydratase (NHase, EC 4.2.1.84) for the production of different highly enantio-enriched and enantiopure D-and L-α-AAs ( Figure 3E; Yasukawa et al, 2011;Yasukawa and Asano, 2012). A MEC using purified nitrile hydratase from Rhodococcus opacus (RoNHAse), D-aminopeptidase from Ochrobactrum anthropi and ACLR from Achromobacter obae allowed total conversion of racemic α-aminobutyronitrile in 6 h and 30 • C to D-ABA (e.e., >99%) ( Figure 16, Yasukawa et al, 2011). D-Phe was also produced afterward using the same strategy (Yasukawa and Asano, 2012).…”

“…D-Phe was also produced afterward using the same strategy (Yasukawa and Asano, 2012). L-ABA was synthesized by combination of RoNHAse, ACLR from Achromobacter obae and L-amino acid amidase from Brevundimonas diminuta (e.e., >99%) (Yasukawa et al, 2011). Other different D-and L-α-AAs were produced with these systems (> 99% Yield, e.e.…”

“…Other different D-and L-α-AAs were produced with these systems (> 99% Yield, e.e. 97 to >99%; Figure 3E, Yasukawa et al, 2011). Remarkably, RoNHase and ACLR were reported to suffer inhibition by the substrate α-amino nitrile, and thus, substrate concentrations need to be taken into account if using this MEC combination (Yasukawa and Asano, 2012).…”

“…(E) Expansion of the Amidase Process by inclusion of a nitrilase. Enantioselective nitrilase (NHase), coupled to ACLR from Achromobacter obae, D-aminopeptidase from Ochrobactrum anthropi or L-amino acid amidase from Brevundimonas diminuta allowed the production of D-or L-α-AA (Yasukawa et al, 2011;Yasukawa and Asano, 2012).…”