- Large-scale synthesis of enantio- and diastereomerically pure (R,R)-formoterol
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(R,R)-Formoterol (1) is a long-acting, very potent β2-agonist, which is used as a bronchodilator in the therapy of asthma and chronic bronchitis. Highly convergent synthesis of enantio- and diastereomerically pure (R,R)-formoterol fumarate is achieved by a chromatography-free process with an overall yield of 44%. Asymmetric catalytic reduction of bromoketone 4 using as catalyst oxazaborolidine derived from (1R, 2S)-1-amino-2-indanol and resolution of chiral amine 3 are the origins of chirality in this process. Further enrichment of enantio- and diastereomeric purity is accomplished by crystallizations of the isolated intermediates throughout the process to give (R,R)-formoterol (1) as the pure stereoisomer (ee, de >99.5%).
- Hett, Robert,Fang, Qun K.,Gao, Yun,Wald, Stephen A.,Senanayake, Chris H.
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