INSIGHTS INTO THE STEREOSELECTIVE SYNTHESIS OF (1S)-NOR(PSEUDO)EPHEDRINE VIA A TWO-STEP BIOCATALYTIC PROCESS WITH IMMOBILIZED ENZYMES

Nor(pseudo)ephedrines (N(P)Es) are amino alcohols known for their sympathomimetic properties. Their conventional asymmetric chemical synthesis is a complex multi-step process which poses challenges in achieving both high yield and optical purity.[1] To address this issue, a biocatalytic two-step cascade was developed for the synthesis of (1S)-N(P)Es and their analogues. This approach combines an acyloin condensation, catalyzed by the (S)-selective acetoin:dichlorophenolindophenol oxidoreductase (Ao:DCPIP OR) from Bacillus licheniformis, with a subsequent transamination step mediated by an amine transaminase ((S)- or (R)-ATA).[2] Building on this strategy, we later immobilized both Ao:DCPIP OR and selected ATAs (Sbv333-ATA and the ATA from Aspergillus terreus) to enhance enzyme stability and reusability within the cascade. The immobilized enzymes were evaluated for their activity recovery, operational stability during recycling, and storage stability. The two-step process was then applied to the semi-preparative synthesis of (1S,2S)-NPE and (1S,2R)-NE, resulting in good to excellent yields and high optical purity.[3]