Scalability of U-Shape Magnetic Nanoparticles-Based Microreactor–Lipase-Catalyzed Preparative Scale Kinetic Resolutions of Drug-like Fragments

The production of active pharmaceutical ingredients (APIs) and fine chemicals is accelerating due to the advent of novel microreactors and new materials for immobilizing customized biocatalysts that permit long-term use in continuous-flow reactors. This work studied the scalability of a tunable U-shape magnetic nanoparticles (MNPs)-based microreactor. The reactor consisted of a polytetrafluoroethylene tube (PTFE) of various inner diameters (ID = 0.75 mm, 1.50 mm, or 2.15 mm) and six movable permanent magnets positioned under the tube to create reaction chambers allowing the fluid reaction mixture to flow through and above the enzyme-loaded MNPs anchored by permanent magnets. The microreactors with various tube sizes and MNP capacities were tested with the preparative scale kinetic resolution of the drug-like alcohols 4-(3,4-dihydroisoquinolin-2(1H)-yl)butan-2-ol (±)-1a and 4-(3,4-dihydroquinolin-1(2H)-yl)butan-2-ol (±)-1b, utilizing Lipase B from Candida antarctica immobilized covalently onto MNPs, leading to highly enantioenriched products [(R)-2a,b and (S)-1a,b]. The results in the U-shape MNP flow reactor were compared with reactions in the batch mode with CaLB-MNPs using similar conditions. Of the three different systems, the one with ID = 1.50 mm showed the best balance between the maximum loading capacity of biocatalysts in the reactor and the most effective cross-section area. The results showed that this U-shaped tubular microreactor might be a simple and flexible instrument for many processes in biocatalysis, providing an easy-to-set-up alternative to existing techniques.