Continuous production of aprepitant chiral intermediate by immobilized amidase in a packed bed bioreactor

To develop a highly efficient method for aprepitant chiral intermediate (S)-4-fluorophenylglycine, a continuous reaction system was established in packed bed bioreactor using amidase covalently immobilized on epoxy resin as biocatalyst. The epoxy resin was firstly modified by metal-chelate method and functional groups (Cu²⁺-IDA) generated were able to rapidly adsorb amidases, which were further covalently bound onto the modified resin with 90.1% immobilization yield and 80.2% activity recovery. The immobilized amidase exhibited excellent thermal stability with the longest half-life of 1456.8 h at 40 °C ever reported. (S)-4-fluorophenylglycine was continuously produced using the reaction system with 49.9% conversion, 99.9% ee, and an outstanding space-time yield of 5.29 kg L^-1 d^-1. Moreover, the efficient reaction system exhibited a high operational stability and retained 86.3% catalytic activity after 25-day continuous operation. This efficient continuous bioprocess presents great industrial potential for large-scale production of (S)-4-fluorophenylglycine.