Veterinary drug florfenicol has been exclusively licensed in food producing animal species for its outstanding effectiveness and safety, and the annual demand reaches around 4000 tons. The industrial production of florfenicol mainly using copper sulfate causes severe environmental pollution. Moreover, this process produces a pair of diastereomers, only one of which can be directly converted into florfenicol. Although the other isomer can be converted to florfenicol, the process is very complicated. Therefore, several enzymatic approaches to the chiral intermediate of florfenicol based on aldolase or transaldolase have been developed. However, to convert the intermediate to florfenicol, esterification and reduction are required to convert the terminal carboxyl group into hydroxyl group.

In a new study that appears in ACS Catalysis, Prof. Shuangjun Lin’s group from Shanghai Jiao Tong University created a novel route using engineered transketolase and transaminase to design and construct a simplified one-pot method to synthesize the hydroxyl-terminated chiral intermediate from the industrial raw materials of florfenicol.

On the basis of the understanding of the catalytic mechanism and protein structure of the transketolase (TK) and transaminase (TA), the researchers established an enzyme-substrate binding model by molecular docking and designed a semi-rational mutation strategy. The enantioselectivity of TK, the enantiopreference and ketone/aldehyde substrate selectivity of TA were successfully inverted through enzymatic engineering. Using the engineered TK and TA, (1R,2R)-p-methylsulfonyl phenylserinol was enzymatically synthesized in high yield (76%) with high stereoselectivity (96% de and > 99% ee), which provided the most direct chiral intermediate for the preparation of florfenicol.

 The study, “One-Pot Asymmetric Synthesis of an Aminodiol Intermediate of Florfenicol Using Engineered Transketolase and Transaminase,” is authored by Prof. Lin Shuangjun and the laboratory colleagues. Prof. Lin Shuangjun is the corresponding author. Liu Qi, a PhD student of the School of Life Sciences and Technology, is the first author.

This research was funded by the National Key Research and Development Program (2018YFA0901900) and the National Natural Science Foundation of China (21632007, 3142001).

Full text link：https://pubs.acs.org/doi/10.1021/acscatal.1c01229