Ethyl bromoacetate

L-Carvone, chitosan (medium viscous, 200~400 mPa·s), and aryl aldehydes were purchased from Energy Chemical (Shanghai, China). 4-Methyl-thiosemicarbazide was provided by TCI (Tokyo, Japan). Ethyl bromoacetate, 5-amino-1,3,4-thiadiazole-2-thiol, chloroacetyl chloride, and other reagents/solvents were obtained from Macklin (Shanghai, China).

PA from Bacillus megaterium (PGA-750) covalently immobilized on polymethacrylate resin was purchased from Shunfeng Haider Co. Ltd. (Zhejiang, China). PAs from Escherichia coli (PGA-II) and from Achromobacter sp. (PGA-IV) immobilized on polyacrylate resin were kindly donated by Shijiazhuang Pharmaceutical Group Co. Ltd. (Hebei, China). PAs (SIPA-III, SIPA-IV, and SIPA-V) from E. coli immobilized on polystyrene resin were purchased from Hunan Flag Biotech Co. Ltd. (Hunan, China). All the PAs used in this work were penicillin G acylases. 7-ACA and N-bromoacetyl-7-ACA were kindly provided by Baiyunshan Chemical Pharmaceutical Factory (Guangzhou, China). Methyl bromoacetate, ethyl bromoacetate, penicillin G potassium salt (PGK), and p-dimethylaminobenzaldehyde (PDAB) were obtained from Macklin Biochemical Co. Ltd. (Shanghai, China). 6-APA was purchased from Aladdin Industrial Co. (Shanghai, China). All other reagents were of analytical grade and obtained from commercial sources.