One-step eantioselective bioresolution for (S)-2-chlorophenylglycine methyl ester catalyzed by the immobilized Protease 6SD on multi-walled carbon nanotubes in a triphasic system

Abstract

(S)-2-chlorophenylglycine methyl ester ((S)-1) is a key chiral building block of clopidogrel, which is a widely administered antiaggregatory and antithrombotic drug. Herein, Protease 6SD was covalently immobilized on multi-walled carbon nanotubes (MWCNT), and the as-prepared immobilizate P-6SD@NH₂-MWCNT was applied in the enantioselective resolution of (R,S)-1 to yield (S)-1. In order to overcome the poor solubility of (R,S)-1 in aqueous solution, a novel triphasic reaction system constituting P-6SD@NH₂-MWCNT, aqueous phase and methyl tert-butyl ether (MTBE) as the organic phase was constructed, which simultaneously improved the substrate solubility and the immobilizate recyclability. Under the optimized reaction conditions, P-6SD@NH₂-MWCNT catalyzed 10 mM (R,S)-1 for 2 h, yielding optically pure (S)-1 (>99.0 % ee_s) with 70.74 % conversion of the (R,S)-1. Moreover, P-6SD@NH₂-MWCNT can be reused for 15 batches, displaying an exquisite recycling performance. It is for the first time that enantiomerically pure (S)-1 was successfully synthesized by protease-catalyzed one-step resolution.

Keywords: (S)-2-chlorophenylglycine methyl ester; Enantioselective bioresolution; Immobilization; Protease; Triphasic system.