合成路线1

2-(4-Hydroxyphenyl)ethanol (I) was protected at the aliphatic hydroxyl group by the following sequence. Reaction of (I) with methoxymethyl chloride and NaH blocked the phenolic hydroxyl as the methoxymethyl ether (II), which was subsequently treated with benzyl bromide to produce the fully protected compound (III). Further hydrolysis of the methoxymethyl ether using trifluoroacetic acid gave rise to 4-(2-benzyloxyethyl)phenol (IV). Condensation of phenol (IV) with 1,1,1-trichloro-2-methyl-2-propanol (V) under basic conditions generated the 2-(aryloxy)isobutyric acid (VI). After esterification of (VI) with SOCl2 in EtOH to give (VII), its O-benzyl protecting group was removed by catalytic hydrogenation to produce (VIII). Alcohol (VIII) was then converted into alkyl bromide (IX) by using CBr4 and PPh3. Alkylation of (-)-4'-hydroxynorephedrine (X) with bromide (IX) in hot DMF afforded the secondary amine (XI). The ethyl ester group of (XI) was finally hydrolyzed with NaOH to the title carboxylic acid.