Hydrogen Albuterol

The second way differs little from the previous, and consists of the initial formation of 4-hydroxy-3-acetoxybromoacetophenone (11.1.27) by acylation of methyl ester salicylic acid using bromoacetyl chloride. This is also reacted with iV-benzyl-tcrt-buty-lamine, and the resulting product (11.1.28) is completely hydrolyzed by lithium aluminum hydride into the (V-benzyl substituted albuterol (11.1.29), the benzyl group of which is removed by hydrogen over a palladium catalyst to give the desired albuterol (11.1.26) [31]. 

A mixture of (R)-4-benzyl albuterol as a free base (3.2 g, 9.73 mmol) and 10% Pd/C (0.64 g) in 24 mL of ethanol (denatured with 5 vol % 2-propanol) is shaken on a Parr-hydrogenator under 50 psi of hydrogen at room temperature for 3 hours. The catalyst is removed by filtration and the filtrate is concentrated to ca. 9 mL in volume containing crude (R)-albuterol and treated with anhydrous HCI in ether (1.0 M, 9.5 mL, 0.98 eq) at 0°-5°C. After 30 min at room temperature, 9 mL of methyl t-butyl ether (MTBE) is added, 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 is collected by filtration and recrystallized from 25 mL of ethanol and 12.5 mL of MTBE to give pure (R)-albuterol hydrochloride (2.17 g, 80.9% yield, 99.6% purity), white powder. 

Albuterol, shown here, is a commonly prescribed asthma medication. For either enantiomer of albuterol, draw a three-dimensional formula using dashes and wedges for bonds that are not in the plane of the paper. Choose a perspective that allows as many carbon atoms as possible to be in the plane of the paper, and show all unshared electron pairs and hydrogen atoms (except those on the methyl groups labeled Me). Specify the R,S) configuration of the enantiomer you drew. 

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