A Safe, Efficient, and Cost-Effective Industrial Process for the Highly Stereoselective Synthesis of Levalbuterol Hydrochloride

A novel industrial process for the synthesis of levalbuterol hydrochloride has been developed, involving five key chemical reactions integrated into four steps: α-bromination of the carbonyl group, nucleophilic substitution of the α-bromo carbonyl with an amine, ester hydrolysis, debenzylation, and asymmetric carbonyl reduction. The process affords levalbuterol hydrochloride in an overall yield of 43% with >99.8% enantiomeric excess (ee). Continuous-flow synthesis suppresses dibrominated impurities and improves operational safety. High selectivity for debenzylation and asymmetric reduction is achieved using a formic acid/triethylamine hydrogen-donor system in combination with appropriate catalysts. This process overcomes the limitations of poor stereoselectivity in conventional routes and provides a safe, high-quality, and cost-effective approach for the industrial production of levalbuterol hydrochloride.