The Discovery of Imine Reductases and their Utilisation for the Synthesis of Tetrahydroisoquinolines

Abstract

Imine reductases (IREDs) are NADPH-dependent enzymes with significant biocatalytic potential for the synthesis of primary, secondary, and tertiary chiral amines. Their applications include the reduction of cyclic imines and the reductive amination of prochiral ketones. In this study, twenty-nine novel IREDs were revealed through genome mining. Imine reductase activities were screened at pH 7 and 9 and in presence of either NADPH or NADH; some IREDs showed good activities at both pHs and were able to accept both cofactors. IREDs with Asn and Glu at the key 187 residue showed preference for NADH. IREDs were also screened against a series of dihydroisoquinolines to synthesise tetrahydroisoquinolines (THIQs), bioactive alkaloids with a wide range of therapeutic properties. Selected IREDs showed high stereoselectivity, as well high THIQ yields (> 90 %) when coupled to a glucose-6-phosphate dehydrogenase for NADPH cofactor recycling.

Biocatalytic reductive aminations with NAD(P)H-dependent enzymes: enzyme discovery, engineering and synthetic applications

“…Targeting THβCs and THIQs, further discovery and engineering work has revealed the powerful potential of IREDs to catalyze this class of stereoselective synthesis of the sterically demanding molecules (Table 3, entries 38–40). 157–159…”

“…Targeting THbCs and THIQs, further discovery and engineering work has revealed the powerful potential of IREDs to catalyze this class of stereoselective synthesis of the sterically demanding molecules (Table 3, entries 38-40). [157][158][159] Fig. 17 In 2022, Li et al reported the two-step sequence employing the EREDs and IREDs for the production of N-substituted g-amino esters and g-lactams using cyclopropylamine as the amine partner (Table 3, entry 31).…”

Enzymatic Oxy‐ and Amino‐Functionalization in Biocatalytic Cascade Synthesis: Recent Advances and Future Perspectives

“…To broaden the enzyme toolbox, novel IREDs were identified and characterized by Cárdenas-Fernández et al for the reduction of dihydroisoquinolines in the synthesis of tetrahydroisoquinolines (THIQs). [90] In the context of expanding the substrate scope of IREDs acting as reductive aminases, Zheng and coworkers reported an IRED from Penicillium camemberti (PcIRED) able to accept a variety of challenging stericallyhindered amines. [91] The authors also performed protein engineering via iterative saturation mutagenesis guided by an AlphaFold2 model of the PcIRED wild type.…”

Introduction of chirality at C1 position of 1-substituted-3,4-dihydroisoquinoline by its enantioselective reduction: synthesis of chiral 1-substituted-1,2,3,4-tetrahydroisoquinoline – a review

“…Cárdenas-Fernández et al reduced 51a, 51k, and 51r with pQR2595, pQR2600, pQR2601, and pQR2612 which are four D187 subgroup of IREDs (Scheme 64). 76 pQR2600 produced 93% ee of (R)-52a, 84% and 21% yield with and without glucose-6-phosphate dehydrogenase (G6PDH) respectively. Similarly, pQR2601 had shown >99% ee of (R)-52a, 98% and 23% yield with and without G6PDH respectively.…”

“…Cárdenas-Fernández et al reduced 51a, 51k, and 51r with pQR2595, pQR2600, pQR2601, and pQR2612 which are four D187 subgroup of IREDs ( Scheme 64 ). 76 …”