反应详情

Several patents report synthetic routes using enantiomeric separation, however, the synthetic routes result in low yields of the enantiomerically pure product. Optically pure levalbuterol was synthesized by the borane-methylsulfide reduction of the enantiomerically pure precursor (Formula 2) as described in U.S. Pat. No. 5,399,765. The reaction dissolved a mixture of enantiomers of methyl 5-[2-[(1,1-dimethylethyl)amino]-1-hydroxyethyl]-2-hydroxybenzoate and a chiral acid selected from (−)-di-toluoyl-L-tartaric acid and (+)-di-toluoyl-D-tartaric acid in methanol, upon cooling one stereoisomer crystallized, which was separated, and recrystallized as a diastereomer from methanol, the diastereomer was separated, treated with base, and upon reduction formed optically active levalbuterol.

1. customseparation
2. customhowever, the synthetic routes result
3. customin low yields of the enantiomerically pure product
4. dissolutionThe reaction dissolved
5. temperatureupon cooling one stereoisomer crystallized, which
6. customwas separated
7. customrecrystallized as a diastereomer from methanol
8. customthe diastereomer was separated
9. additiontreated with base