Hydrochloric Acid → Levalbuterol Hydrochloride

Beteiligte Stoffe

Reaktionsschritte

A mixture of (R)-4-benzyl albuterol from Example-3 (6.6 g, 20 mmol) and 10% Pd/C (1.32 g) in 50 mL of ethanol (denatured with 5 vol % 2-propanol) is shaken on a Parr-hydrogenator under 50 psi of hydrogen at room temperature for 2-3 hours. The catalyst is removed by filtration and the filtrate is concentrated to give crude (R)-albuterol (compound IIIa). The crude albuterol (20 mmol) is dissolved in 20 mL of ethanol and treated with anhydrous HCl in ether (1.0M, 19 mL, 0.95 eq) at 0°-5° C. After 30 min at room temperature, 20 mL of methyl t-butyl ether (MTBE) is added to the mixture and the resulting mixture is stirred at room temperature for 30 min and at 0°-5° C. for 2 hours. The white solid (R)-albuterol hydrochloride (compound IIIb) is collected by filtration and recrystallized from 52 mL of ethanol and 26 mL of MTBE to give pure (R)-albuterol hydrochloride as a white powder (4.6 g, 83.5% yield, 99.6% ee, 99.3% purity).

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